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Effect of Betulinic Acid on Anticancer Drug-Resistant Colon Cancer Cells
Abstract
Primary or acquired resistance of tumours to established chemotherapeutic regimens is a major concern in oncology. Attempts to improve the survival of cancer patients largely depend on strategies to prevent tumour cell resistance. 5-Fluorouracil (5-FU)-based chemotherapy with a combination of other drugs such as irinotecan (IRT) and oxaliplatin (OXT) has been reported to be effective, even though an optimal regimen has yet to be defined due to the relatively high toxicity of the procedure. The aim of this study was to examine the effect of betulinic acid (BetA) as a chemosensitizer for anticancer drug treatment in chemoresistant colon cancer cell lines. A chemoresistant cell line to 5-fluorouracil (SNU-C5/5FU-R), irinotecan (SNU-C5/IRT-R) and oxaliplatin (SNU-C5/OXT-R) treatment were derived from the wild-type colon adenocarcinoma cell line (SNU-C5/WT). The effect of BetA or a combination of anticancer drugs and BetA on the multidrug resistance-related genes, caspases, Bcl-2, Bad and cell death in the SNU-C5/WT and SNU-C5/R cell lines was analysed. BetA alone was an effective chemotherapeutic drug for the SNU-C5/WT, SNU-C5/5FU-R and SNU-C5/OXT-R cells. The combination of BetA with IRT or OXT was effective against SNU-C5/5FU-R cells, and the combination of BetA with 5-fluorouracil, IRT or OXT was effective against SNU-C5/OXT-R cells. BetA induced cancer cell death by apoptosis through the mitochondrial pathway. These findings indicate that the use of BetA as a chemosensitizer may be a new strategy to enhance the efficacy of chemotherapy. However, further studies will be needed for confirmation.
... SNU-C5 colon cancer cells contain two missense mutations in the p53 gene, resulting in the complete loss of normal p53 function (Rand et al., 1996), and have been used in many studies, including multidrug resistance and anti-cancer drug screening studies (Ku and Park, 2005). An OXT-resistant colon cancer cell line (SNU-C5/OXTR) has been derived from a parental wild-type colon cancer cell line (SNU-C5) via chronic exposure to OXT (Jung et al., 2007). A few studies have evaluated OXT resistance using SNU-C5/OXTR cells. ...
... A few studies have evaluated OXT resistance using SNU-C5/OXTR cells. The combined application of betulinic acid, a chemosensitizer, and OXT induces apoptosis of SNU-C5/OXTR via the mitochondrial pathway (Jung et al., 2007), and co-treatment with OXT and melatonin increases ER stress and apoptosis in SNU-C5/ OXTR cells . ...
Few studies have evaluated the role of autophagy in the development of oxaliplatin (OXT) resistance in colon cancer cells. In this study, we compared the role of autophagy between SNU-C5 colon cancer cells and OXT-resistant SNU-C5 (SNU-C5/OXTR) cells. At the same concentration of OXT, the cytotoxicity of OXT or apoptosis was significantly reduced in SNU-C5/OXTR cells compared with that in SNU-C5 cells. Compared with SNU-C5 cells, SNU-C5/OXTR cells exhibited low levels of autophagy. The expression level of important autophagy proteins, such as autophagy-related protein 5 (Atg5), beclin-1, Atg7, microtubule-associated proteins 1A/1B light chain 3B I (LC3-I), and LC3-II, was significantly lower in SNU-C5/OXTR cells than that in SNU-C5 cells. The expression level of the autophagy-essential protein p62 was also lower in SNU-C5/OXTR cells than in SNU-C5 cells. In SNUC5/ OXTR cells, the production of intracellular reactive oxygen species (ROS) was significantly higher than that in SNU-C5 cells, and treatment with the ROS scavenger N-acetylcysteine restored the reduced autophagy levels. Furthermore, the expression of antioxidant-related nuclear factor erythroid 2-related factor 2 transcription factor, heme oxygenase-1, and Cu/Zn superoxide dismutase were also significantly increased in SNU-C5/OXTR cells. These findings suggest that autophagy is significantly reduced in SNU-C5/OXTR cells compared with SNU-C5 cells, which may be related to the production of ROS in OXT-resistant cells.
... Betulinic acid has been well known to inhibit proliferation and induce apoptosis in various cancer cell lines, including those of the breast, prostate, brain, colon, and leukemia [40][41][42][43][44]. It has recently been reported that betulinic acid induces apoptosis by stabilizing p53 and by downregulating the NF-κB pathway in human prostate cancer cells, irrespective of the androgen association [45]. ...
... Another interesting study revealed that betulinic acid can induce apoptosis in cisplatin-resistant ovarian cancer cells and Puma activation plays a critical role in mediating betulinic acid-induced apoptosis in cisplatin-resistant ovarian cancer cells [58]. Biomolecules 2019, 9, x 9 of 13 Betulinic acid has been well known to inhibit proliferation and induce apoptosis in various cancer cell lines, including those of the breast, prostate, brain, colon, and leukemia [40][41][42][43][44]. It has recently been reported that betulinic acid induces apoptosis by stabilizing p53 and by downregulating the NF-κB pathway in human prostate cancer cells, irrespective of the androgen association [45]. ...
Ovarian cancer is one of the leading causes of cancer deaths worldwide in women, and the most malignant cancer among the different gynecological cancers. In this study, we explored potentially anticancer compounds from Cornus walteri (Cornaceae), the MeOH extract of which has been reported to show considerable cytotoxicity against several cancer cell lines. Phytochemical investigations of the MeOH extract of the stem and stem bark of C. walteri by extensive application of chromatographic techniques resulted in the isolation of 14 compounds (1–14). The isolated compounds were evaluated for inhibitory effects on the viability of A2780 human ovarian carcinoma cells and the underlying molecular mechanisms were investigated. An 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay was employed to assess the anticancer effects of compounds 1–14 on A2780 cells, which showed that compound 11 (betulinic acid) reduced the viability of these cells in a concentration-dependent manner and had an half maximal (50%) inhibitory concentration (IC50) of 44.47 μM at 24 h. Nuclear staining and image-based cytometric assay were carried out to detect the induction of apoptosis by betulinic acid. Betulinic acid significantly increased the condensation of nuclei and the percentage of apoptotic cells in a concentration-dependent manner in A2780 cells. Western blot analysis was performed to investigate the underlying mechanism of apoptosis. The results indicated that the expression levels of cleaved caspase-8, -3, -9, and Bax were increased in A2780 cells treated with betulinic acid, whereas those of Bcl-2 were decreased. Thus, we provide the experimental evidence that betulinic acid can induce apoptosis in A2780 cells through both mitochondria-dependent and -independent pathways and suggest the potential use of betulinic acid in the development of novel chemotherapeutics for ovarian cancer therapy.
... In addition, the combination of 5-FU and betulinic acid has been shown to induce apoptosis in 5-FU resistant cells and this occurred similarly with a co-treatment of betulinic acid and oxaliplatin in the oxaliplatin-resistant line. These results imply that combination therapy has succeeded in bypassing the obtained chemoresistance [128]. ...
... with cisplatin inhibits cell growth and induces apoptosis Induces cell apoptosis, upregulates Tnf a and b SW480, DLD-1 Induces apoptosis, higher effect by TRAIL co-treatment[111] Quercetin SW-620, HT-29, Caco-2 Sensitizes cells against TRAIL, causing apoptosis, generating of ROS[113] [114] Colo-205, Colo-320HSR, Colo-201, LS-174 and WiDrInhibits expression of RASA1[112] in vivo CT26 model decreased lung metastasis, migration and invasion[115] Artesunate HCT116 induces cell cycle arrest in the G1 phase, in comb. With cisplatin creates ROS[116] FU/oxaliplatin resistant SNU-C5 Induces apoptosis in 5-FU and oxaliplatin resistants[128] Lycopene SW480Acts anti-inflammatory suppresses the expression of PCNA and b-catechins ...
... concern in the treatment of cancer. A study conducted by Jung et al. (2007) demonstrated that this resistance could be overcome by supplementation of betulinic acid where it acts as a chemosensitizer. An adenocarcinoma wild-type derived cell line (SNU-C5/WT) chemoresistant of 5-fluorouracil (SNU-C5/5FU-R), irinotican (SNU-C5/ IRT-R) & oxaliplatin (SNU-C5/OXT-R) respectively were treated with betulinic acid. ...
... ↓% of cells in G0/G1 and S phase and ↑ % of cells in G2/ M; ↑PARP cleavage; ↓ Sp1, ↓ Sp3, ↓ Sp4, ↓sp regulated genes viz., EGFR, p65 subunit of NFκB, PTTG1 and cyclin D1. ↓ Tumor burden; ↓ Sp1, ↓ Sp3, ↓ Sp4; ↓ Tumor burden. Rzeski et al., 2006;Jung et al. 2007;Chintharlapalli et al., 2011;Mullauer et al., 2011. ...
Multistep model of colon carcinogenesis has provided the framework to advance our understanding of the molecular basis of colon cancer. This multistage process of carcinogenesis takes a long period to transform from a normal epithelial cell to invasive carcinoma. Thus, it provides enough time to intervene the process of carcinogenesis especially through dietary modification. In spite of the in-depth understanding of the colon cancer etiology and pathophysiology and its association with diet, colon cancer remains a major cause of cancer mortality worldwide. Phytochemicals and their derivatives are gaining attention in cancer prevention and treatment strategies because of cancer chemotherapy associated adverse effects. Being the largest group of phytochemicals traditionally used for medicinal purpose in India and China, terpenoids are recently being explored as anticancer agents. Anticancer properties of terpenoids are associated with various mechanisms like counteraction of oxidative stress, potentiating endogenous antioxidants, improving detoxification potential, disrupting cell survival pathways and inducing apoptosis. This review gives a comprehensive idea of naturally occurring terpenoids as useful agents for the prevention of colon cancer with reference to their classes, sources and molecular targets. Based on the explored molecular targets further research in colon cancer chemoprevention is warranted.
... Blanco et al. determined that a combination of betulinic acid and 5-fluorouracil reverted apoptosis induction in the 5-fluorouracil-resistant cells [19]. A parallel reversion activity was found with a combination of betulinic acid and oxaliplatin in oxaliplatin-resistant cells [60]. Some authors described that oleanolic acid is an inhibitor of efflux transporters, including Pglycoprotein, and in combination with paclitaxel may enhance the intracellular concentration of chemotherapeutic drugs [61]. ...
Cancer cells’ resistance to anticancer drugs represents a major clinical problem and the most important failure of treatment. Combination chemotherapy is more effective than monotherapy due
to additive or synergistic effects. The aim of our research was to assess the effects of the combinations of apple extract’s triterpenic compounds, individual triterpenic acids, and doxorubicin (DOX) on
human colon adenocarcinoma (HT-29) and human glioblastoma (U-87) cell lines in 2D and 3D cultures. The effect of the combination of apple extracts, the triterpenic standards, and DOX against
HT-29 and U-87 cell viability was tested by the MTT and spheroid growth assays.
... Other promising natural compounds have been proposed in combination with oxaliplatin, such as betulinic acid, alanolactone, or piperlongumine, with promising results but yet only scarce research available. In oxaliplatin-resistant CRC cells treated with betulinic acid, Bcl-2 anti-apoptotic protein was down-regulated, whereas pro-apoptotic Bad was up-regulated [67]. Furthermore, alantolactone, a sesquiterpene lactone extracted from the roots of Inula helenium L., a Chinese herbal remedy, enhanced the effect of oxaliplatin on colorectal cancer HCT-116 cells through induction of ROS, activation of JNK and p38 MAPK apoptotic pathways [68]. ...
Acquired drug resistance represents a major clinical problem and one of the biggest limitations of chemotherapeutic regimens in colorectal cancer. Combination regimens using standard chemotherapeutic agents, together with bioactive natural compounds derived from diet or plants, may be one of the most valuable strategies to overcome drug resistance and re-sensitize chemoresistant cells. In this review, we highlight the effect of combined regimens based on conventional chemotherapeutics in conjunction with well-tolerated plant-derived bioactive compounds, mainly curcumin, resveratrol, and EGCG, with emphasis on the molecular mechanisms associated with the acquired drug resistance.
... They can induce apoptosis through the mitochondrial pathway via releasing cytochrome C and/or caspase activation. They cause the formation of an apoptosis-inducing factor (AIF) [43]. Some of these compounds can induce the production of pro-apoptotic protein caspase-3 and BAX and inhibit anti-apoptotic factors [44]. ...
Colon cancer is the third most predominant cancer caused by genetic, environmental and nutritional factors. Plant-based compounds are very well known to regress colon cancer in many ways, like delaying tumor growth, managing chemotherapy and radiation therapy side-effects, and working at the molecular levels. Medicinal plants contain many bioactive phytochemicals such as flavonoids, polyphenol compounds, caffeic acid, catechins, saponins, polysaccharides, triterpenoids, alkaloids, glycosides, phenols, quercetin, luteolin, kaempferol and luteolin glycosides, carnosic acid, oleanolic acid, rosmarinic acid, emodin, and eugenol and anthricin. These bioactive compounds can reduce tumor cell proliferation via several mechanisms, such as blocking cell cycle checkpoints and promoting apoptosis through activating initiator and executioner caspase. Traditional medicines have been used globally to treat cancers because of their anti-cancer effects, antioxidant properties, anti-inflammatory properties, anti-mutagenic effects, and anti-angiogenic effects. In addition, these medicines effectively suppress early and intermediate stages of carcinogenesis when administered in their active and pure form. However, traditional medicine is not very popular due to some critical challenges. These include poor solubility and absorption of these compounds, intellectual property-related issues, involvement of drug synergism, absence of drug-likeness, and unsure protocols for their extraction from the plant source. Using bioactive compounds in colon cancer has equal advantages and limitations. This review highlights the benefits and challenges of using bioactive compounds derived from plants for colon cancer. We have also discussed using these compounds to target cancer stem cell self-renewal, its effects on cancer cell metabolism, safety parameters, easy modulation, and their bioavailability.
... Moreover, BA has been demonstrated to suppress cancer growth (Fulda 2009). It has been exhibited anticancer curative effect in human cancers, such as brain tumors, cervical cancer, head and neck squamous carcinoma, leukemia, neuroectodermal tumors (Gomath et al., 2014), breast carcinoma (Tiwari et al., 2014), colorectal carcinoma (Jung et al., 2007), glioblastoma (Jeremias et al., 2004), lung carcinoma (Hsu et al., 2012), melanoma (Jeremias et al., 2004) and prostrate carcinoma (Rabi et al., 2008). However, the effect of BA on human cholangiocarcinoma cells has not formerly been determined. ...
Background:
Betulinic acid (BA), a pentacyclic triterpene glycoside extract from guava (Psidium guajava Linn.) leaves, displays a variety of biological activities which exhibit cancer therapeutic properties associated with cancer growth inhibition in various kinds of human cancer cells including brain, breast, colorectal, cervical, lung and prostate gland. However, the effects on human cholangiocarcinoma cells have not previously been reported. Current study, we evaluated the activity of BA against human cholangiocarcinoma (HuCCA) cells.
Methods:
The cytotoxicity analysis was measured by using MTT assay on HuCCA and BHK-21 cells. Analysis of apoptosis was evaluated by using staining with Hoechst 33342 and quantitative real-time PCR.
Results:
The BA (50-800 µg/mL) significantly reduced the viability of HuCCA cells in a dose-dependent action with 50% inhibitory concentration (IC50) of 92.45 µg/mL at 24 h. It also induced apoptosis signaling pathway, such as nuclear chromatin condensation and fragmentation. Quantitative real-time PCR analysis demonstrated that BA increased p53, Bax and caspase-3 expression whilst it decreased Bcl-2 expression in the HuCCA cells in a dose dependent manner.
Conclusion:
BA can inhibit the HuCCA cell viability and induce apoptosis of neoplastic cells. This study indicates that BA has effective treatment for cholangiocarcinoma in vitro. Consequently, BA may be used as a novel therapeutic agent for the treatment of cholangiocarcinoma in the future.
... This further confirmed that synergistic interaction occurred when the two agents were used together. It was interesting that BA was also confirmed to be highly related to cytotoxic activity against MDR cell lines (Jung et al., 2007;Saeed et al., 2018), whereas this does not necessarily mean that the processing was P-gp relevant. As reported, the inhibition of autocrine motility factor receptor (AMFR) activity should be the mechanism of BA to decrease MDR (Saeed et al., 2018). ...
Betulinic acid (BA) and 23-Hydroxybetulinic acid (23-HBA) are natural products with similar structures, which show a range of biological effects including cytotoxicity activity. The aim of current research was to investigate and evaluate the combinational cytotoxicity of BA and 23-HBA with chemotherapeutic agents in vitro, and to clarify the potential interaction and related mechanism with P-gp. Instead of BA, 23-HBA could increase cytotoxicity of MCF-7/ ADR cells to adriamaycin (ADR) and vincristine (VCR). The intracellular accumulation of ADR/ VCR in MCF-7/ADR cells was obviously increased in the presence of 23-HBA. Furthermore, 23-HBA could show dose-dependent increase on the transport of VCR and digoxin, which are typical P-gp substrates, in both MDCK-MDR1 and Caco-2 cells. However, the transport of BA and 23-HBA was not influenced by P-gp inhibition in MDCK-MDR1 cells. MDR1 shift assay and molecular docking model suggested that both compounds showed interaction with P-gp, yet the binding affinity and sites are different. In conclusion, 23-HBA could strongly improve the efficacy of anti-tumor agents in multidrug resistance (MDR) cells, which was related to P-gp inhibition. The MDR1 shift assay and molecular docking study further revealed that 23-HBA and BA showed different interaction modes with P-gp.
... Betulinic has shown synergistic effects with [74]: ...
Cancer still remains a leading cause of death despite improvements in diagnosis, drug discovery and therapy approach. Therefore, there is a strong need to improve methodologies as well as to increase the number of approaches available. Natural compounds of different origins (i.e., from fungi, plants, microbes, etc.) represent an interesting approach for fighting cancer. In particular, synergistic strategies may represent an intriguing approach, combining natural compounds with classic chemotherapeutic drugs to increase therapeutic efficacy and lower the required drug concentrations. In this review, we focus primarily on those natural compounds utilized in synergistic approached to treating cancer, with particular attention to those compounds that have gained the most research interest.
... Cell lines resistant to 5-fluorouracil (5-FU) (SUN-C5/5FU-R), IRT (SUN-C5/IRT-R) and OXT (SUN-C5/OXT-R) were isolated from the wild-type colon cancer cell line (SUN-C5/WT), and BA alone was effective against wild type, 5FU-R and OXT-R. BA combined with OXT was capable of inducing the apoptosis of the SNU-C5/OXT-R cell [69]. Aisha et al. [70] not only found that BA inhibited the growth of colon cancer cell HCT116 in a dose-dependent manner but also that the combination of 2.5 µg/mL α-mangostin and BA could significantly increase the cytotoxicity of BA. ...
Betulinic acid, a pentacyclic triterpene, is distributed in a variety of plants, such as birch, eucalyptus and plane trees. It shows a wide spectrum of biological and pharmacological properties, such as anti-inflammatory, antibacterial, antiviral, antidiabetic, antimalarial, anti-HIV and antitumor effects. Among them, the antitumor activity of betulinic acid has been extensively studied. However, obtaining betulinic acid from natural resources can no longer meet the needs of medicine and nutrition, so methods such as chemical synthesis and microbial biotransformation have also been used to prepare betulinic acid. At the same time, with the development of synthetic biology and genetic engineering, and the elucidation of the biosynthetic pathways of terpenoid, the biosynthesis of betulinic acid has also been extensively researched. This article reviews the preparation of betulinic acid and its pharmacological activities, in order to provide a reference for the research and utilization of betulinic acid.
... It has been tested in combination with curcumin, resveratrol, Ganoderma lucidum polysaccharides, genistein, geraniol, betulinic acid, gossypol, and protopanaxadiol. In addition, a combination of geraniol, protopanaxadiol, and 5-FU has been shown to reduce tumor volume in in vivo models [10][11][12][13][14][15][16][17]. In all cases, combination treatment synergistically induced apoptosis in colon cancer cells. ...
Combination therapy is based on the beneficial effects of pharmacodynamic interaction (synergistic or additive) between combined drugs or substances. A considerable group of candidates for combined treatments are natural compounds (e.g., isothiocyanates) and their analogs, which are tested in combination with anticancer drugs. We tested the anticancer effect of the combined treatment of isothiocyanate 2-oxohexyl isothiocyanate and 5-fluorouracil in colon and prostate cancer cell lines. The type of interaction was described using the Chou-Talalay method. The cytostatic and cytotoxic activities of the most promising combined treatments were investigated. In conclusion, we showed that combined treatment with 5-fluorouracil and 2-oxohexyl isothiocyanate acted synergistically in colon cancer. This activity is dependent on the cytostatic properties of the tested compounds and leads to the intensification of their individual cytotoxic activity. The apoptotic process is considered to be the main mechanism of cytotoxicity in this combined treatment.
... We determined cytochrome C release at 12 h after etoposide treatment since it is well known from other cell lines that it induced caspase-9 activation at 12 h and earlier [32]. Activation of effector caspases after administration of betulinic acid has also been reported as early as 12 h after administration of 5 µg/ml betulinic acid [33]. ...
Renal cell carcinomas (RCCs) exhibit a marked resistance towards apoptosis. Although most apoptotic stimuli converge at the level of the mitochondria, little is known about the mitochondrial apoptosis pathway in renal cell carcinomas. The aim of the present study, therefore, was to investigate the functionality of the mitochondrial apoptosis pathway in renal cell carcinoma cell lines by exposure to TRAIL, etoposide, HA14-1 and betulinic acid activating the mitochondria by different mechanisms. Sensitivity to TRAIL-induced apoptosis correlated with cleavage of the initiator caspase-8, but the mitochondrial apoptosis pathway was not induced. Similarly, etoposide and betulinic acid could not induce mitochondrial damage. In contrast, HA14-1 was able to activate mitochondrial apoptosis, thereby demonstrating functionally inducible signalling pathways downstream of the mitochondria. The intactness of the pathways upstream of the mitochondria was shown by pretreatment of TRAIL-sensitive cell lines with HA14-1, which could reconstitute TRAIL-induced mitochondrial damage and resulted in a synergistic apoptosis induction.
Our results demonstrate that the apoptotic pathways upstream and downstream of the mitochondria are intact and inducible in renal cell carcinoma cell lines. However, resistance towards mitochondrial apoptosis is located on the level of the mitochondria themselves.
... Wogonin and betulinic acid obstruct PI3K/Akt signaling and downregulate protein expression of HIF1α-induced glycolytic genes [210,211]. Betulinic acid seems to be a very effective chemosensitizer for anticancer drug treatment in chemoresistant cell lines [212,213]. Curcumin and esculetin induce apoptosis by inhibiting EGFR-directed signaling of PI3K pathway [214,215]. Dioscin has been shown to induce autophagy by diminishing PI3K/Akt/mTOR pathway [216]. ...
The metabolism of cancer is remarkably different from that of normal cells and confers variety of benefits including the promotion of other cancer hallmarks. As the rewired metabolism is a near-universal property of cancer cells, efforts are underway to exploit metabolic vulnerabilities for therapeutic benefit. In the continued search for a safer and effective ways of cancer treatment, structurally diverse plant-based compounds have gained substantial attention. Here, we present an extensive assessment of the role of phytocompounds in modulating cancer metabolism and make a case for the use of plant-based compounds in targeting metabolic vulnerabilities of cancer. We discuss the interactions of phytocompounds with major metabolic pathways and evaluate the role of phytochemicals in the regulation of growth signaling and transcriptional programs involved in metabolic transformation of cancer. Lastly, we examine the potential of these compounds in clinical management of cancer along with limitations and challenges
... For example, apigenin sensitized the colon cancer cells to ABT-263 via the downregulation of pro-survival protein-induced myeloid leukemia cell differentiation protein (Mcl-1) expression and inhibition of the Akt/ERK signaling pathway in both in vitro and in vivo settings [152]. In 2007, Jung et al. [153] reported that betulinic acid significantly reversed chemoresistance in SNU-C5/5FU-R cells, in combination with irinotecan (IRT) or OXP, and in SNU-C5/ OXP-R cells, in combination with IRT or OXP or 5-FU. Similarly, cardamonin was found to chemosensitize HCT116/5-FU cells to 5-FU via caspase mediated apoptosis, activation of TSP50 and inhibition of cyclin E and NF-κB [154]. ...
Despite significant advancements made in the treatment of cancer during the past several decades, it remains one of the leading causes of death worldwide killing approximately 9.6 million people annually. The major challenge for therapeutic success is the development of chemoresistance in cancer cells against conventional chemotherapeutic agents via modulation of numerous survival and oncogenic signaling pathways. Therefore, sensitization of cancer cells to conventional drugs using multitargeted agents that suppress the survival and oncogenic pathways, in single or in combination, is an emerging strategy to overcome drug-resistance. During the last couple of decades phytochemicals such as curcumin, resveratrol, tocotrienol and quercetin have emerged as potential chemosensitizing agents in cancer cells due to their less toxic and multitargeted properties. Numerous preclinical and clinical studies enumerated their potential to prevent drug resistance and sensitize cancer cells to chemotherapeutic agents by modulating several genes/proteins or pathways that regulate the key factors during the growth and progression of tumors such as inhibition of anti-apoptotic proteins, activation of pro-apoptotic proteins, reduced expression of different transcription factors, chemokines, enzymes, cell adhesion molecules, protein tyrosine kinases and cell cycle regulators. Therefore, natural chemosensitizing agents will have a special place in cancer treatment in the near future. This comprehensive review summarizes data obtained from various in vitro, in vivo and clinical studies to provide a new perspective for the application of agents obtained from “Mother Nature” as potential chemosensitizers for further cancer drug research and development.
... Due to drug resistance, the response rate of oxaliplatin is only 50-60% in standard-of-care first-line therapy [3]. 5-FU is another base analogue used for CRC thermotherapy [4,5]. However, 5-FU resistance is frequent in CRC patients, which impedes the clinical outcomes [6,7]. ...
Colorectal cancer (CRC) remains one of the leading causes of cancer-related deaths in the world. Chemotherapy has been used to treat CRC patients in order to improve prognosis. Oxaliplatin and 5-Fluorouracil (5-FU) based chemotherapy is a first line treatment for locally advanced and metastatic CRC. For patients with wild-type KRAS metastatic CRC, cetuximab (an EGFR monoclonal antibody) is a commonly used targeted therapy. CRC is initially sensitive to chemotherapy and targeted therapy. However, drug resistance frequently arises, which significantly affect the treatment outcome in these patients. An increasing number of studies have indicated that lncRNAs are implicated in the drug resistance of CRC. This review aims to gain insights into the role and molecular mechanism of lncRNAs in CRC drug resistance.
... What is significant, both discussed compounds could be successfully combined with other cytotoxic forms of cancer treatment. Favourable results were obtained by combining BA and, respectively, vincristine, 5-fluorouracil, doxorubicin, etoposide, actinomycin D, mithramycin A, cisplatin, taxol, oxaliplatin, or irinotecan, as well as ionizing radiation (Sawada et al. 2004;Jung et al. 2007;Gao et al. 2011;Bache et al. 2011;Zhao et al. 2012;Csuk 2014). In turn, a combination of BE and sorafenib, a kinase inhibitor effective against various carcinomas, enhanced the induction of apoptosis in different non-small cell lung cancer lines (Kutkowska et al. 2017). ...
Betulin, a pentacyclic triterpene and a plant pentacyclic triterpene metabolite, can be found in large quantities in the outer bark of the birches (Betula, Betulaceae). Betulinic acid, obtained by betulin oxidation, is also abundantly present in nature. Both compounds show a wide spectrum of biological and pharmacological properties, such as anti-HIV, anti-inflammatory, and, considered the most important, anti-cancer. Although the specific mechanism of action of betulin against malignant cells is still a subject of detailed research, the activity of betulin acid has been linked to the induction of the intrinsic pathway of apoptosis. As this process occurs with the sparing of non-cancer cells, and the induction of apoptosis can occur under conditions in which standard therapies fail, both substances seem as promising experimental anti-cancer drugs. The aim of this review is to comprehensively summarise the potential of betulin and betulinic acid, both in vitro and in vivo. The discovery, structure, organic synthesis and derivatives forming were shortly described. Also, the potential molecular mechanisms of action and numerous medical applications of betulin and betulinic acid were presented, including previous studies of anti-cancer activity of the compounds, with listed cancer cell types susceptible to therapy.
... In addition, achievable in vivo concentration of BA has the ability to stop the colony formation by tumor cells. These evidence indicates the valuable characteristic of BA to be used as a strong therapeutic agent against most of the frequent cancer cell types (Jung et al., 2007). Interestingly BA showed no serious adverse effects such as systemic toxicity and weight loss, when administered in high doses to animals (Chintharlapalli et al., 2007;Mullauer et al., 2010;Mullauer et al., 2011;Udeani et al., 1999). ...
... However, the regulatory effects of betulinic acid on the NF-κB pathway and on Bax or Bak expression are not well clarified [130]. Betulinic acid seems to be a very effective chemosensitizer for anticancer drug treatment in chemoresistant cell lines once it promotes the inhibition of multidrug resistance proteins in vivo and in vitro, as for example in combination with 5-fluorouracil (5-FU) and oxaliplatin [133,137]. These results clearly demonstrate that in some cases, it is possible to circumvent acquired chemoresistance by combination therapy of anticancer drugs with chemosensitizers as betulinic acid. ...
Cancer is a multistage process resulting in an uncontrolled and abrupt division of cells and is one of the leading causes of mortality. The cases reported and the predictions for the near future are unthinkable. Food and Drug Administration data showed that 40% of the approved molecules are natural compounds or inspired by them, from which, 74% are used in anticancer therapy. In fact, natural products are viewed as more biologically friendly, that is less toxic to normal cells. In this review, the most recent and successful cases of secondary metabolites, including alkaloid, diterpene, triterpene and polyphenolic type compounds, with great anticancer potential are discussed. Focusing on the ones that are in clinical trial development or already used in anticancer therapy, therefore successful cases such as paclitaxel and homoharringtonine (in clinical use), curcumin and ingenol mebutate (in clinical trials) will be addressed. Each compound's natural source, the most important steps in their discovery, their therapeutic targets, as well as the main structural modifications that can improve anticancer properties will be discussed in order to show the role of plants as a source of effective and safe anticancer drugs.
... BetA inhibited proliferation and induced apoptosis in various cancer cell lines such as breast, prostate, brain, colon, and leukemia (Fulda et al., 1999;Raghuvar Gopal et al., 2005;Chintharlapalli et al., 2007;Jung et al., 2007;Tiwari et al., 2014). Moreover, BetA has shown in vivo anticancer activity in melanoma and prostate xenograft mouse models (Eiznhamer and Xu, 2004;Chintharlapalli et al., 2007). ...
Betulinic acid (BetA) is a naturally occurring pentacyclic triterpene isolated from the outer bark of white-barked birch trees and many other medicinal plants. Here, we studied betulinic acid's cytotoxic activity against drug-resistant tumor cell lines. P-glycoprotein (MDR1/ABCB1) and BCRP (ABCG2) are known ATP-binding cassette (ABC) drug transporters that mediating MDR. ABCB5 is a close relative to ABCB1, which also mediates MDR. Constitutive activation of the EGF receptor is tightly linked to the development of chemotherapeutic resistance. BetA inhibited P-gp, BCRP, ABCB5 and mutation activated EGFR overexpressing cells with similar efficacy as their drug-sensitive parental counterparts. Furthermore, the mRNA expressions of ABCB1, BCRP, ABCB5 and EGFR were not related to the 50% inhibition concentrations (IC50) for BetA in a panel of 60 cell lines of the National Cancer Institute (NCI), USA. In addition to well-established MDR mechanisms, we attempted to identify other molecular mechanisms that play a role in mediating BetA's cytotoxic activity. For this reason, we performed COMPARE and hierarchical cluster analyses of the transcriptome-wide microarray-based mRNA expression of the NCI cell lines panel. Various genes significantly correlating to BetA's activity were involved in different biological processes, e.g., cell cycle regulation, microtubule formation, signal transduction, transcriptional regulation, chromatin remodeling, cell adhesion, tumor suppression, ubiquitination and proteasome degradation. Immunoblotting and in silico analyses revealed that the inhibition of AMFR activity might be one of the mechanisms for BetA to overcome MDR phenotypes. In conclusion, BetA may have therapeutic potential for the treatment of refractory tumors.
... Betulinic acid (BetA), is a pentacyclic triterpenoid extracted from birch trees (Betula pubescens) and selfheal (Prunella vulgaris). Besides anti-retroviral, anti-malarial, and anti-inflammatory properties, recent studies have shown it to exhibit potent anti-cancer activity against several human cancers with no significant effect on normal cells [128][129][130]. Interestingly, it was shown to induce apoptosis in human neuroblastoma cells in vitro and in vivo [131]. ...
Glioblastoma (GBM) is one of the most aggressive malignant tumors with an overall dismal survival averaging one year despite multimodality therapeutic interventions including surgery, radiotherapy and concomitant and adjuvant chemotherapy. Few drugs are FDA approved for GBM, and the addition of temozolomide (TMZ) to standard therapy increases the median survival by only 2.5 months. Targeted therapy appeared promising in in vitro monolayer cultures, but disappointed in preclinical and clinical trials, partly due to the poor penetration of drugs through the blood brain barrier (BBB). Cancer stem cells (CSCs) have intrinsic resistance to initial chemoradiation therapy (CRT) and acquire further resistance via deregulation of many signaling pathways. Due to the failure of classical chemotherapies and targeted drugs, research efforts focusing on the use of less toxic agents have increased. Interestingly, multiple natural compounds have shown antitumor and apoptotic effects in TMZ resistant and p53 mutant GBM cell lines and also displayed synergistic effects with TMZ. In this review, we have summarized the current literature on natural products or product analogs used to modulate the BBB permeability, induce cell death, eradicate CSCs and sensitize GBM to CRT.
... Betulinic acid seems to be a very effective chemosensitizer for anticancer drug treatment in chemoresistant cell lines once it promotes the inhibition of multidrug resistance proteins in vivo and in vitro, as for example in combination with 5-fluorouracil (5-FU) and oxaliplatin [133,137]. These results clearly demonstrate that in some cases, it is possible to circumvent acquired chemoresistance by combination therapy of anticancer drugs with chemosensitizers as betulinic acid. ...
Cancer is a multistage process resulting in an uncontrolled and abrupt division of cells and is one of the leading causes of mortality. The cases reported and the predictions for the near future are unthinkable. Food and Drug Administration data showed that 40% of the approved molecules are natural compounds or inspired by them, from which, 74% are used in anticancer therapy. In fact, natural products are viewed as more biologically friendly, that is less toxic to normal cells. In this review, the most recent and successful cases of secondary metabolites, including alkaloid, diterpene, triterpene and polyphenolic type compounds, with great anticancer potential are discussed. Focusing on the ones that are in clinical trial development or already used in anticancer therapy, therefore successful cases such as paclitaxel and homoharringtonine (in clinical use), curcumin and ingenol mebutate (in clinical trials) will be addressed. Each compound's natural source, the most important steps in their discovery, their therapeutic targets, as well as the main structural modifications that can improve anticancer properties will be discussed in order to show the role of plants as a source of effective and safe anticancer drugs.
... [16][17][18] However, the mechanism of BA-induced antitumor effect has been still on debate. 12,19 In CRC cells, BA could induce apoptosis through the mitochondrial pathway, 20 inhibited cell growth of CRC cells by downregulating Sp transcription factors in SW480 and RKO cells, 21 or by suppressing NF-κB and STAT3 signaling in HT29 cells. 22 It has also been reported that BA can function as NF-κB activator in a number of other cancer cell lines, 23 suggesting that the antitumor mechanisms of BA was dependent on tumor type. ...
Betulinic acid (BA) exhibits cytotoxic activity against some cancer cells. However, the molecular mechanism of BA against CRC cells was little reported. Here, we proved that BA elicited CRC cells' growth inhibition and apoptosis in a dose-dependent manner. In addition, BA treatment induced autophagy via inhibiting the AKT-MTOR signaling pathway. Inhibition of autophagy by either administration of autophagic inhibitor chloroquine or siRNA-mediated knockdown of ATG5 could augment BA-induced apoptotic cell death as well as inhibition of cell proliferation. Moreover, we found that p53 was firstly activated by short exposure to BA and then was rapidly degraded via the ubiquitin-mediated degradation pathway in both wtp53 and mutp53 CRC cells. Notably, more preferential cytotoxicity of BA was obtained in mutp53 cells (IC50 values: HT29, 125 μM; SW480, 58 μM) rather than wtp53 cells (IC50 values: HCT116, 178 μM). Further experiments demonstrated that siRNA-mediated p53 knockdown attenuated BA-induced autophagy, and forced overexpression of p53 augmented BA-induced autophagy, indicating that p53-enhanced BA-induced autophagy. Moreover, BA enhanced the sensitivity of mutp53 cells to chemotherapy drugs such as 5-FU and ADR by degradation of mutp53. Overall, our study proved that BA could induce CRC cell death by inducing apoptosis and reduce the overaccumulation of BA-induced protective autophagy by degrading wtp53 and mutp53 dependent on the ubiquitin-mediated degradation pathway to achieve killer effect, suggesting that BA might serve as a novel desirable drug for mutp53 cancer therapy.
... Betulinic acid (16) (Bet A) is a naturally occurring triterpenoid that is extracted from the bark of several plant species mainly the white birch (Betula pubescens). Bet A has been studied for its cytotoxic effect against various types of malignancies including melanoma cells [119], neuroblastoma tumor cells [120], glioma cells [121], human leukemia HL-60 [122], malignant head and neck squamous cell carcinoma SCC25 and SCC9 cell lines [123], and colon cancer cells [124]. It was found that Bet A induced the cell death in cancer cells through intrinsic apoptotic pathway that lead to cytochrome c release into cytosol followed by activation of caspase cascade and DNA fragmentation [125], in addition to the upregulation of pro-apoptotic Bax, Bak and Mcl-1 family and downregulation of anti-apoptotic Bcl-2 that induce the cell cycle arrest at G1 phase in MCF7 breast cancer cell line [126]. ...
Natural products with immunomodulatory activity are widely used in treatment of many diseases including autoimmune diseases, inflammatory disorders in addition to cancer. They gained a great interest in the last decades as therapeutic agents since they provide inexpensive and less toxic products than the synthetic chemotherapeutic agents. Immunomodulators are the agents that have the ability to boost or suppress the host defense response that can be used as a prophylaxis as well as in combination with other therapeutic modalities. The anticancer activity of these immunomodulators is due to their anti-inflammatory, antioxidant, and induction of apoptosis, anti-angiogenesis, and anti-metastasis effect. These natural immunomodulators such as genistein, curcumin, and resveratrol can be used as prophylaxis against the initiation of cancer besides the inhibition of tumor growth and proliferation. Whereas, immunostimulants can elicit and activate humoral and cell-mediated immune responses against the tumor that facilitate the recognition and destruction of the already existing tumor. This review represents the recent studies on various natural immunomodulators with antitumor effects. We have focused on the relationship between their anticancer activity and immunomodulatory mechanisms. The mechanisms of action of various immunomodulators such as polyphenolic compounds, flavonoids, organosulfur compounds, capsaicin, vinca alkaloids, bromelain, betulinic acid and zerumbone, the affected cancerous cell lines in addition to the targeted molecules and transcriptional pathways have been review and critically analyzed.
... VEGF is known to regulate angiogenesis and vascular permeability; angiogenesis is an important process in tumor growth and development (Goel and Mercurio, 2013), because new blood vessels feed the tumor with oxygen and nutrients, allowing tumor development. Betulinic acid has interesting effects on drug-resistant CRC cells, compared to other standard drugs in CRC therapy such as 5-FU, IRT, and OXT; its mechanism of action suggests that betulinic acid triggers apoptosis since the levels of cleaved caspase 3 are increased (Jung et al., 2007). Autophagy is another process that is induced by an analogue of betulinic acid on HT-29 cells by increasing the level of Beclin 1 (autophagy-related protein) and decreasing levels of p62 (Dutta et al., 2016). ...
In recent times, a great deal of interest has been motivated on plant derived compounds known as nutraceuticals. These compounds exert important beneficial activities that improve people's health status when are consumed regularly, and now they appear as a viable option to explore their possible therapeutic effects against diseases like cancer. Particularly, lupane-type triterpenes have shown great ability to modulate multiple cancer-related signaling pathways and processes, including NF-κB, Wnt/β-catenin, PI3K/Akt, apoptosis, and many other routes related to proliferation or cell death, which are uncontrolled in malignant tumors. These investigations have promoted in vitro and in vivo studies, searching their mechanisms of action; although more research is still needed to prove its potential in human clinical trials. This review focuses on the ability of betulin, betulinic acid and lupeol to show benefits against the most common types of malignant tumors, which are considered a major global threat for public health.
... A similar reversion effect was observed with a combination of betulinic acid plus oxaliplatin in oxaliplatin-resistant cells. These results clearly demonstrate that in some cases it is possible to circumvent acquired chemoresistance by combination therapy of anticancer drugs with chemosensitizers as betulinic acid (Jung et al., 2007). ...
Combination therapy consists in the simultaneous administration of a conventional chemotherapy drug (or sometimes, a radiotherapy protocol) together with one or more natural bioactives (usually from plant or fungal origin) of small molecular weight. This combination of anticancer drugs may be applied to cell cultures of tumor cells, or to an animal model for a cancer type (or its xenograft), or to a clinical trial in patients. In this review, we summarize current knowledge describing diverse synergistic effects on colorectal cancer cell cultures, animal models, and clinical trials of various natural bioactives (stilbenes, flavonoids, terpenes, curcumin, and other structural families), which may be important with respect to diminish final doses of the chemotherapy drug, although maintaining its biological effect. This is important as these approaches may help reduce side effects in patients under conventional chemotherapy. Also, these molecules may exerts their synergistic effects via different cell cycle pathways, including different ones to those responsible of resistance phenotypes: transcription factors, membrane receptors, adhesion and structural molecules, cell cycle regulatory components, and apoptosis pathways.
... BA induces apoptosis through the mitochondrial or intrinsic pathway via caspase-dependent and caspase-independent mechanisms. This induction is independent of p53 status and CD95-L/receptor [71][72][73] (Fig. 2). ...
... Cells were cultured in RPMI 1640 medium containing 10% heat-inactivated fetal calf serum, streptomycin (100 mg/ml), and penicillin (100 units/ml). The SNUC5/5-FUR cell line was obtained from the Research Center for Resistant Cells of Chosun University (Gwangju, Korea) and subcultured twice per week in medium containing 140 mM 5-FU for more than 6 months until a stable cell line was established (Jung et al., 2007). ...
We investigated the role of autophagy in SNUC5/5-FUR, 5-fluorouracil (5-FU) resistant SNUC5 colon cancer cells. SNUC5/5-FUR cells exhibited low level of autophagy, as determined by light microscopy, confocal microscopy, and flow cytometry following acridine orange staining, and the decreased level of GFP-LC3 puncta. In addition, expression of critical autophagic proteins such as Atg5, Beclin-1 and LC3-II and autophagic flux was diminished in SNUC5/5-FUR cells. Whereas production of reactive oxygen species (ROS) was significantly elevated in SNUC5/5-FUR cells, treatment with the ROS inhibitor N-acetyl cysteine further reduced the level of autophagy. Taken together, these results indicate that decreased autophagy is linked to 5-FU resistance in SNUC5 colon cancer cells.
... The cells were exposed to the drugs starting from 1 × IC 50 (5-FU 17.5 μM and OXT 7.14 μM), and the concentrations were escalated at an increasing rate of 50%, and then finally cultured at fixed concentrations over a level of 10 times the IC 50 of 5-FU and OXT, respectively. Cells were cultured in a fixed 5-FU (140 μM) and OXT (7.14 μM) concentration for all subsequent experiments [35]. Human ovarian cancer cells A2780 and its cisplatin resistant derivative A2780/CR were obtained from Sigma-Aldrich Co and were cultured in RPMI-1640 supplemented with 10% FBS and 1% penicillin/streptomycin. ...
We recently reported that DNA demethylase ten-eleven translocation 1 (TET1) upregulates nuclear factor erythroid 2-related factor 2 (Nrf2) in 5-fluorouracil-resistant colon cancer cells (SNUC5/5-FUR). In the present study, we examined the effect of histone modifications on Nrf2 transcriptional activation. Histone deacetylase (HDAC) and histone acetyltransferase (HAT) were respectively decreased and increased in SNUC5/5-FUR cells as compared to non-resistant parent cells. Mixed-lineage leukemia (MLL), a histone methyltransferase, was upregulated, leading to increased trimethylation of histone H3 lysine 4, while G9a was downregulated, leading to decreased dimethylation of histone H3 lysine 9. siRNA-mediated MLL knockdown decreased levels of Nrf2 and HO-1 to a greater extent than did silencing HAT1. Host cell factor 1 (HCF1) was upregulated in SNUC5/5-FUR cells, and we observed interaction between HCF1 and MLL. Upregulation of O-GlcNAc transferase (OGT), an activator of HCF1, was also associated with HCF1-MLL interaction. In SNUC5/5-FUR cells, a larger fraction of OGT was bound to TET1, which recruits OGT to the Nrf2 promoter region, than in SNUC5 cells. These findings indicate that SNUC5/5-FUR cells are under oxidative stress, which induces expression of histone methylation-related proteins as well as DNA demethylase, leading to upregulation of Nrf2 and 5-FU resistance.
... Combination of betulinic acid with irinotecan (IRT) and oxaliplatin (OXT) was effective against SNU-C5/5FU-R cells. Betulinic acid induced cancer cell death by apoptosis through the mitochondrial pathway [54]. The active components of south asian medicinal plants, which have interact with cell surface ABC transporters such as P-gp, ABCG2, and receptor tyrosine kinases including TRIAL-R, FLT3, KIT, VEGFR and EGFR. ...
Cancer is a hyperproliferative disorder that involves transformation, dysregulation of apoptosis, proliferation, invasion, angiogenesis and metastasis. During the last 30 years, extensive research has revealed much about the biology of cancer. Chemotherapy and radiotherapy are the mainstays of cancer treatment, particularly for patients who do not respond to surgical resection. However, cancer treatment with drugs or radiation is seriously limited by chemoresistance and radioresistance. Various approaches and strategies are employed to overcome resistance to chemotherapy and radiation treatment. Many plant-derived phytochemicals have been investigated for their chemo- and radio-sensitizing properties. The peoples of South Asian countries such as India, Pakistan, Sri Lanka, Nepal, Bangladesh and Bhutan have a large number of medicinal plants from which they produce various pharmacologically potent secondary metabolites. The medicinal properties of these compounds have been extensively investigated and many of them have been found to sensitize cancer cells to chemo- and radio-therapy. This review focuses on the role of South Asian medicinal compounds in chemo- and radio-sensitizing properties in drug- and radio-resistant cancer cells. Also discussed is the role of South Asian medicinal plants in protecting normal cells from radiation, which may be useful during radiotherapy of tumors to spare surrounding normal cells.
... Cells were cultured in RPMI-1640 medium (Invitrogen Life Technologies, Grand Island, NY, USA) containing 10% heat-inactivated fetal bovine serum (Sigma-Aldrich, St. Louis, MO, USA) at 37˚C in a 5% CO 2 incubator. A total of 1x10 4 SNU-C5R cells/well were then subcultured at 37˚C in 140 mM 5-FU twice per week for >6 months in order to establish stable drug-resistant cell lines (26). ...
The mechanisms underlying drug resistance in colorectal cancer (CRC) treatment remain to be fully elucidated. Therefore, the present study aimed to investigate the underlying mechanism resistance to a widely used anticancer drug, 5‑Fluorouracil (5‑FU). Nuclear factor‑erythroid 2‑related factor 2 (Nrf2) is an important transcription factor involved in cellular protection. In the present study, it was hypothesized that the epigenetic modification of Nrf2 may be a potential target for 5‑FU resistance in CRC treatment. Protein and messenger RNA levels of Nrf2, heme oxygenase‑1 (HO‑1), DNA methylases and DNA methyltransferases were determined and DNA methylation analysis for the Nrf2 promoter was performed in a human CRC control (SNU‑C5) and resistant (SNU‑C5R) cell line. The results demonstrated that Nrf2 expression levels, nuclear translocation and promoter binding were significantly increased in SNU‑C5R cells compared with SNU‑C5 cells. Elevated levels of activated Nrf2 in SNU‑C5R cells resulted in the increased protein expression and activity of HO‑1. In addition, increased production of reactive oxygen species (ROS) and upregulation of ten‑eleven translocation (TET)1 were observed in SNU‑C5R cells compared with SNU‑C5 cells. Furthermore, methylation analysis revealed Nrf2 promoter cytosine‑phosphate‑guanine island hypomethylation in 5‑FU‑treated cells. In conclusion, the results indicated that 5‑FU‑induced ROS production resulted in the upregulation of TET1 expression and function. In addition, these results indicated that TET‑dependent demethylation of the Nrf2 promoter upregulated Nrf2 and HO‑1 expression, which induced cellular protection mechanisms, ultimately leading to drug resistance.
... Thus, betulinic acid was reported to act in concert with ionizing radiators (Selzer et al. 2000 ;Eder-Czembirek et al. 2010 ;Bache et al. 2011 ) in melanoma cells (Selzer et al. 2000 ) as well as to induce apoptosis and to inhibit clonogenic survival of tumor cells when administered together with several chemotherapeutic drugs, e.g. cis -platin, taxol, doxorubicin, vincristine (Pirnia et al. 2002 ;Basu et al. 2003 ;Jeremias et al. 2004 ;Sawada et al. 2004 ;Zanon et al. 2004 ;Eder-Czembirek et al. 2005 ;Fulda and Debatin 2005 ;Boyle et al. 2006 ;Rieber and Rieber 2006 ;Jung et al. 2007 ;Paffhausen et al. 2007 ;Ammann et al. 2009 ;Surowiak et al. 2009 ;Yamai et al. 2009 ) . ...
Because of their selective cytotoxicity against many different tumor cell and their favorable therapeutic index, betuline, betulinic acid and many of their derivatives are very promising chemotherapeutic agents for the treatment and prevention of several diseases especially of cancer. © 2012 Springer Science+Business Media Dordrecht. All rights are reserved.
... 17,103 BA is also able to enhance the sensitivity of multidrug resistant colon cancer cells toward 5-fluorouracil, irinotecan, and oxaliplatin. 104 In addition, BA in combination with other chemicals such as ginsenoside Rh2, epithelial growth factor receptor tyrosine kinase inhibitor PD153035, mithramycin A, or thalidomide increases cell death in various cancer cell lines. 89,105,106 BA can be used to enhance the efficacy of hyperthermia in low pH adapted melanoma cells DB-1. ...
Betulinic acid (BA) is a lupane-type pentacyclic triterpene, distributed ubiquitously throughout the plant kingdom. BA and its derivatives demonstrate multiple bioactivities, particularly an antitumor effect. This review critically describes the recent research on isolation, synthesis, and derivatization of BA and its natural analogs betulin and 23-hydroxybetulinic acid. The subsequent part of the review focuses on the current knowledge of antitumor properties, combination treatments, and pharmacological mechanisms of these compounds. A 3D-QSAR analysis of 62 BA derivatives against human ovarian cancer A2780 is also included to provide information concerning the structure-cytotoxicity relationships of these compounds.
© 2015 Wiley Periodicals, Inc.
Natural products serve as the single most productive source for the discovery of drugs and pharmaceutical leads. Among the various chemicals derived from microbes, plants, and animals, phytochemicals have emerged as potential candidates for the development of anticancer drugs due to their structural diversities, complexities, and pleiotropic effects. Herein, we discuss betulinic acid (BA), a ubiquitously distributed lupane structured pentacyclic triterpenoid, scrutinized as a promising natural agent for the prevention, suppression, and management of various human malignancies. Ease of availability, common occurrences, cell-specific cytotoxicity, and astonishing selectivity are the important factors that contribute to the development of BA as an anticancer agent. The current review delineates the mechanistic framework of BA-mediated cancer suppression through the modulation of multiple signaling pathways and also summarizes the key outcomes of BA in preclinical investigations.
Thiosemicarbazones have received noteworthy attention due to their numerous pharmacological activities. Various thiosemicarbazone derivatives have been reported to play a key role as potential chemotherapeutic agents for the management of cancer. Herein, we aimed to establish the anticancer efficacy of novel thiosemicarbazone derivative C4 against colon cancer in vitro. The MTT viability assay identified C4 as a promising anticancer compound in a panel of cancer cell lines with the most potent activity against colon cancer cells. Further anticancer potential of C4 was evaluated against HT-29 and SW620 colon cancer cell lines considering the factors like cell adhesion and migration, oxidative stress, cell cycle arrest, and apoptosis. Our results showed that C4 significantly inhibited the migration and adhesion of colon cancer cells. C4 significantly increased the intracellular reactive oxygen species (ROS) and induced apoptotic cell death. Cell cycle analysis revealed that C4 interfered in the cell cycle distribution and arrested the cells at the G2/M phase of the cell cycle. Consistent with these results C4 also down-regulated the Bcl-XL and Bcl-2 and up-regulated the caspase-3 expression. These findings introduced C4 as the potential anticancer agent against colon cancer.
The Glioblastoma Multiforme (GBM; grade IV astrocytoma) exhorts tumors of star-shaped
glial cells in the brain. It is a fast-growing tumor that spreads to nearby brain regions specifically to
cerebral hemispheres in frontal and temporal lobes. The etiology of GBM is unknown, but major risk
factors are genetic disorders like neurofibromatosis and schwannomatosis, which develop the tumor in
the nervous system. The management of GBM with chemo-radiotherapy leads to resistance, and current
drug regimen like Temozolomide (TMZ) is less efficacious. The reasons behind the failure of
drugs are due to DNA alkylation in the cell cycle by enzyme DNA guanidase and mitochondrial dysfunction.
Naturally occurring bioactive compounds from plants referred as phytochemicals, serve as
vital sources for anti-cancer drugs. Some prototypical examples include taxol analogs, vinca alkaloids
(vincristine, vinblastine), podophyllotoxin analogs, camptothecin, curcumin, aloe-emodin, quercetin,
berberine etc. These phytochemicals often regulate diverse molecular pathways, which are implicated
in the growth and progression of cancers. However, the challenges posed by the presence of
BBB/BBTB to restrict the passage of these phytochemicals, culminates in their low bioavailability and
relative toxicity. In this review, we integrated nanotech as a novel drug delivery system to deliver phytochemicals
from traditional medicine to the specific site within the brain for the management of
GBM.
Allergic asthma is a chronic inflammatory disease, which involves many cellular and cellular components. Cataract is a condition that affects the transparency of the lens, which the opacity of the lens caused by any innate or acquired factor degrades its transparency or changes in color. Both of them belong to diseases induced by immune disorders or inflammation. We want to confirm the signaling pathways involved in the regulation of asthma and cataract simultaneously, and provide reference for the later related experiments. So we conducted a scoping review of many databases and searched for studies (Academic research published in Wiley, Springer and Bentham from 2000 to 2019) about the possible relationship between asthma and cataract. It was found that during the onset of asthma and cataract, Rho/Rock signaling pathway, Notch signaling pathway, Wnt/β-catenin signaling pathway, PI3K/AKT signaling pathway, JAK/STAT signaling pathway, MAPK signaling pathway, TGF-β1/Smad signaling pathway and NF-κB signaling pathway are all active, so they may have a certain correlation in pathogenesis. Asthma may be associated with cataract through the eight signaling pathways, causing inflammation or immune imbalance based on allergy that can lead to cataract. According to these studies, we speculated that the three most likely signaling pathway are PI3K/AKT, MAPK and NF-κB signaling pathway.
Background/Aim: Dendropanax morbifera (DM) and Commersonia bartramia (CB) are possible candidates for immunotherapy. In this study, the cytotoxicity and chemical sensitization of DM and CB extracts on gynecologic and colon cancers were evaluated. Materials and Methods: The malignant cell lines were cultured and analyzed for cytotoxicity and chemical sensitization. A mouse model was also constructed to make the condition similar to in vivo. Reverse transcription-polymerase chain reaction was conducted to determine alterations in drug-resistant genes. Results: The extracts from DM and CB showed specific cytotoxicity to malignant cell lines. DM increased chemical sensitivity to cervical and ovarian cancer, while CB showed improved sensitization to endometrial cancer. The effects of the extracts were confirmed using a mouse model. The extracts induced differences in the expression levels of a number of genes related to drug resistance. Conclusion: DM and CB extracts could be novel agents for immunotherapy and chemical sensitization in gynecologic and colon cancers.
Changes in immunological pathways are involved in all stages of cancer. The immune system is composed of cells which are extremely sensitive to environmental changes. Antitumor immune response involves several pathways. The innate immune response is carried out by neutrophils, macrophages, eosinophils, mast cells, and natural killer (NK) cells, while the adaptive immune response is carried out by B-lymphocytes (B-cells) and T-lymphocytes (T-cells). Overall, lymphocytes act through the recognition of specific antigens circulating in the blood or on the cell surface. Connections between the innate and adaptive immune systems are made either by direct cell contact or by release of cytokines. Under normal conditions, inflammatory response is self-limiting because the production of pro-inflammatory cytokines (TH1 cytokines) is followed by generation of anti-inflammatory (TH2) cytokines such as interleukin (IL)-1, IL-10, or IL-13. Under special circumstances and defects in the resolution process or if its underlying factors continue, then inflammation will turn into chronic inflammation linked to increased risk of cancer. Chronic inflammation can increase the risk of cancer through promoting tumor initiation, the rate and extent of cell division, neovascularization, and angiogenesis. In addition, chronic inflammation results in an overload of reactive oxygen species (ROS), which, in turn, may lead to the development and progression of chronic diseases like cancer. Upregulation of cyclooxygenase (COX)-2, which is not expressed in most cells, may contribute to cancer development and progression through the release of prostaglandins (PGs). Signal transduction pathways like nuclear factor-kappa B (NF-κB) promote inducible expression of several proteins, such as cytokines, chemokines, acute-phase response proteins, cell adhesion molecules, antimicrobial peptides, inducible nitric oxide synthase (iNOS), and COX-2. Antitumoral immune response is mainly produced by T-cells to destroy tumor cells. However, immune escape mechanisms are a hallmark of tumor progression. Recent efforts have been devoted to develop small-molecule drugs that stimulate antitumoral immunity. While immunotherapy alone seems not to be sufficient to eradicate tumors, results of adjuvant immunotherapy are becoming ever more convincing. Bioactive dietary components that antagonize immune escape mechanisms would have potential to prevent tumor development or enhance tumor regression.
Cancer is one of the most serious illnesses of our civilization. The
International Agency for Research on Cancer estimated that 14.1 million new cancer
cases were diagnosed and that 8.2 million patients died from this disease worldwide
in 2012 alone. Therefore, there is an urgent need for novel anticancer agents as
well as new treatment strategies. Natural products have been valuable sources of
new therapeutic agents. Thus, the aim of present chapter is to provide an overview
of the anticancer natural compounds highlighting the successful cases with clinical
application such as Taxol, vincristine and omacetaxine mepesuccinate; those
involved in clinical trials such as parthenolide, betulinic acid, ingenol mebutate and
curcumin; and the ones with high degree of activity and safety profile such as resveratrol,
ursolic acid, tetrandrine and triptolide. For each one of these compounds, it
will be presented and discussed its natural origin, cell target, mechanism of action,
pharmacologic aspects as well as the structural modifications that improve its anticancer
properties in order to summarize the recent medicinal advances of natural
anticancer compounds and their analogues. All these aspects aim to draw our readers’
attention to the plants and/or their secondary metabolites therapeutic potential
and in consequence value the plants’ role in anticancer drug discovery.
Background/aim:
Dendropanax morbifera (DM) and Commersonia bartramia (CB) are possible candidates for immunotherapy. In this study, the cytotoxicity and chemical sensitization of DM and CB extracts on gynecologic and colon cancers were evaluated.
Materials and methods:
The malignant cell lines were cultured and analyzed for cytotoxicity and chemical sensitization. A mouse model was also constructed to make the condition similar to in vivo. Reverse transcription-polymerase chain reaction was conducted to determine alterations in drug-resistant genes.
Results:
The extracts from DM and CB showed specific cytotoxicity to malignant cell lines. DM increased chemical sensitivity to cervical and ovarian cancer, while CB showed improved sensitization to endometrial cancer. The effects of the extracts were confirmed using a mouse model. The extracts induced differences in the expression levels of a number of genes related to drug resistance.
Conclusion:
DM and CB extracts could be novel agents for immunotherapy and chemical sensitization in gynecologic and colon cancers.
Background
The SALL4/Sall4 is constitutively expressed in human and mice. SALL4 mRNA could be used as a marker for the diagnosis of different types of cancers. On the other hand, chrysin has diverse biological properties.
Objectives
In the present study, the effect of the chrysin was investigated on the CT26 colon cancer in vitro and in vivo. Furthermore, the expression levels of the stem cell markers; sall4 and Bax was analyzed, as well.
Materials and Methods
The cytotoxic effects and the type of cell death induced by chrysin were evaluated using a number of biological assays. The apoptotic pathway was examined by caspase-3and caspase-9 assay. The in vivo antitumor efficacy of chrysin on transplanted CT26 tumor cells in BALB/c mice was investigated. In addition, mRNA expression of sall4, Bax was analyzed with RT-PCR.
Results
MTT assay and morphological characteristics showed that chrysin exerted a cytotoxic effect on CT26 cells in a dose dependent manner with IC50= 80 μg.mL⁻¹. The biological assays have indicated that chrysin administrated cytotoxicity on colon cancer cells through recruitment of the apoptosis. Caspase-3 and caspase-9 colorimetric assays, in addition to Bax expression analysis, have indicated the involvement of intrinsic apoptotic pathway in the cytotoxic effect of the chrysin. The in vivo assay revealed a remarkable reduction of the colon tumor volume in treated mice (8, 10 mg.kg ⁻¹) as compared to the untreated mice. RT-PCR elucidated that chrysin attenuated tumor volume through down regulation of the sall4 and up-regulation of the Bax.
Conclusions
It was demonstrated that chrysin accomplishes anti-cancer effect on colon cancer cells via induction of the apoptosis and attenuation of the sall4 the expression. These findings introduce chrysin as an efficient apoptosis based therapeutic agent against colon cancer.
Betulinic acid (BA), a lupane-type pentacyclic triterpenoid saponin from tree bark, has the potential to induce the apoptosis of cancer cells without toxicity towards normal cells in vitro and in vivo. The antitumor pharmacological effects of BA consist of triggering apoptosis via the mitochondrial pathway, regulating the cell cycle and the angiogenic pathway via factors, including specificity protein transcription factors, cyclin D1 and epidermal growth factor receptor, inhibiting the signal transducer and activator of transcription 3 and nuclear factor‑κB signaling pathways, preventing the invasion and metastasis of tumor cells, and affecting the expression of topoisomerase I, p53 and lamin B1. In previous years, several studies have shown its antitumor effect, initially applied to malignant melanoma, however, it also has broad efficacies against most solid types of tumor from different regions of the body. There have been few investigations in hematological malignancies, however, this direction may offer potential in such a novel field of research. In this review, the primary pharmacological effects of BA in tumors, particularly in hematological malignancies are discussed.
The present review gives an outline of some oncopharmacological projects focused on the characterization of plant-derived natural products, conducted at the Faculty of Pharmacy at the Medical University of Sofia. These include collaborative phytochemical/pharmacological studies of a) alkaloids, b) saponines with immunomodulatory and anti-cancer effects; c) cytotoxic lignans; iii) phenolic compounds (acylphloroglucinols, benzophenones, xanthones) from Hypericum spp. iv) various volatiles and crude extracts.
An important method of drug discovery is examination of diverse life forms, including medicinal plants and natural products (NPs) or
bioactive compounds isolated from these sources. In cancer research, lead structures of compounds from natural sources can be used
to design novel chemotherapies with enhanced biological properties. Betulinic acid (3β-hydroxy-lup-20(29)-en-28-oic acid or BetA) is
a naturally occurring pentacyclic triterpene with a wide variety of biological activities, including potent antitumor properties.
Nonmalignant cells and normal tissues are not affected by BetA. Because BetA exerts its effects directly on the mitochondrion and
triggers death of cancerous cells, it is an important alternative when certain chemotherapy drugs fail. Mitochondrion-targeted agents
such as BetA hold great promise to circumvent drug resistance in human cancers. BetA is being developed by a large network of
clinical trial groups with the support of the U.S. National Cancer Institute. This article discusses recent advances in research into
anticancer activity of BetA, relevant modes of delivery, and the agent’s therapeutic efficacy, mechanism of action, and future
perspective as a pipeline anticancer drug. BetA is a potentially important agent in cancer therapeutics.
Pentacyclic triterpenoids comprise a largest class of natural products, bearing several biological activities, among them anticancer activity. This chapter strolls through the antitumor properties of betulin, betulinic acid, oleanolic acid, glycyrrhetinic acid, ursolic acid, and their derivatives. Within each section is presented the most relevant properties that contribute to the antitumor activity of the referred natural triterpenoids and their semisynthetic derivatives. These compounds are potential candidates for the development of more efficient anticancer or cancer preventive drugs, and the semisynthetic derivatives produced so far can shed some light on the path to follow to obtain such compounds.
This chapter analyzes the isolation/fractionation of products obtained from plant and marine sources and their therapeutic current uses and discusses the results obtained in some clinical trials. Throughout history, humans have relied on plants for their basic needs such as production of food, clothing, and, medicines. Plants have been the basis of traditional medicines and continue to provide mankind with new remedies. The ocean coastal margins are being extraordinarily rich in species diversity, especially in tropical environments. Combined with the exploration of marine microbial life forms, there have been improvements in various approaches and strategies for interfacing natural products with modern biology and screening platforms. The chapter presents an overview of some plant- or plant/marine-derived compounds with well-known profiles of antidiabetic claims.
The Balkan Region represents one of the Europe's major centres of plant diversity, with an substantial number of endemic genera and species having a wide distribution throughout the diverse ecosystems of the region. Plants remain an unequalled source of biochemical diversity and in the last several decades there is an unprecedented interest towards identifying perspective leads of plant origin. The phytochemical and pharmacological investigation of medicinal plants has long history as corroborated by the large number of facilities located in the Bulgarian Academy of Sciences, Faculty of Pharmacy at Medical University, Sofia or within the Bulgarian pharmaceutical industry. Several examples from our search for new immunomodulatory and/or antineoplastic compounds obtained from Bulgarian plants will be presented to demonstrate the potential and problems of the pharmacological screening of natural products. These include: i) isolation, purification, identification and biological evaluation of saponines with immunomodulatory and anti-cancer effects; ii) phytochemical, biotechnological and pharmacological evaluation of indigenous Linum sp. as sources for cytotoxic podophyllotoxin-like lignans; iii) phytochemical evaluation of the phenolic compounds (acylphloroglucinols, benzophenones, xanthones) from Hypericum sp. and investigation of their antineoplastic, antiangiogenic and myeloprotective effects; iv) investigation of the alkaloid thaliblastin from Thalictrum spp. as modulator of multidrug-resistance in cancer cells.
Different classes of anticancer drugs may trigger apoptosis by acting on different subcellular targets and by activating distinct
signaling pathways. Here, we report that betulinic acid (BetA) is a prototype cytotoxic agent that triggers apoptosis by a
direct effect on mitochondria. In isolated mitochondria, BetA directly induces loss of transmembrane potential independent
of a benzyloxycarbonyl-Val-Ala-Asp-fluoromethyl ketone-inhibitable caspase. This is inhibited by bongkrekic acid, an agent
that stabilizes the permeability transition pore complex. Mitochondria undergoing BetA-induced permeability transition mediate
cleavage of caspase-8 (FLICE/MACH/Mch5) and caspase-3 (CPP32/Yama) in a cell-free system. Soluble factors such as cytochrome
c or apoptosis-inducing factor released from BetA-treated mitochondria are sufficient for cleavage of caspases and nuclear
fragmentation. Addition of cytochromec to cytosolic extracts results in cleavage of caspase-3, but not of caspase-8. However, supernatants of mitochondria, which
have undergone permeability transition, and partially purified apoptosis-inducing factor activate both caspase-8 and caspase-3
in cytosolic extracts and suffice to activate recombinant caspase-8. These findings show that induction of mitochondrial permeability
transition alone is sufficient to trigger the full apoptosis program and that some cytotoxic drugs such as BetA may induce
apoptosis via a direct effect on mitochondria.
Intrinsic and acquired multidrug resistance (MDR) in many human cancers may be due to expression of the multidrug transporter P-glycoprotein (Pgp), which is encoded by the mdr1 gene. There is substantial evidence that Pgp is expressed both as an acquired mechanism (e.g., in leukemias, lymphomas, myeloma, and breast and ovarian carcinomas) and constitutively (e.g., in colorectal and renal cancers) and that its expression is of prognostic significance in many types of cancer. Clinical trials of MDR modulation are complicated by the presence of multiple-drug-resistance mechanisms in human cancers, the pharmacokinetic interactions that result from the inhibition of Pgp in normal tissues, and, until recently, the lack of potent and specific inhibitors of Pgp. A large number of clinical trials of reversal of MDR have been undertaken with drugs that are relatively weak inhibitors and produce limiting toxicities at doses below those necessary to inhibit Pgp significantly. The advent of newer drugs such as the cyclosporin PSC 833 (PSC) provides clinicians with more potent and specific inhibitors for MDR modulation trials. Understanding how modulators of Pgp such as PSC 833 affect the toxicity and pharmacokinetics of cytotoxic agents is fundamental for the design of therapeutic trials of MDR modulation. Our studies of combinations of high-dose cyclosporin (CsA) or PSC 833 with etoposide, doxorubicin, or paclitaxel have produced data regarding the role of Pgp in the clinical pharmacology of these agents. Major pharmacokinetic interactions result from the coadministration of CsA or PSC 833 with MDR-related anticancer agents (e.g., doxorubicin, daunorubicin, etoposide, paclitaxel, and vinblastine). These include increases in the plasma area under the curve and half-life and decreases in the clearance of these cytotoxic drugs, consistent with Pgp modulation at the biliary lumen and renal tubule, blocking excretion of drugs into the bile and urine. The biological and medical implications of our studies include the following. First, Pgp is a major organic cation transporter in tissues responsible for the excretion of xenobiotics (both drugs and toxins) by the biliary tract and proximal tubule of the kidney. Our clinical data are supported by recent studies in mdr-gene-knockout mice. Second, modulation of Pgp in tumors is likely to be accompanied by altered Pgp function in normal tissues, with pharmacokinetic interactions manifesting as inhibition of the disposition of MDR-related cytotoxins (which are transport substrates for Pgp). Third, these pharmacokinetic interactions of Pgp modulation are predictable if one defines the pharmacology of the modulating agent and the combination. The interactions lead to increased toxicities such as myelosuppression unless doses are modified to compensate for the altered disposition of MDR-related cytotoxins. Fourth, in serial studies where patients are their own controls and clinical resistance is established, remissions are observed when CsA or PSC 833 is added to therapy, even when doses of the cytotoxin are reduced by as much as 3-fold. This reversal of clinical drug resistance occurs particularly when the tumor cells express the mdr1 gene. Thus, tumor regression can be obtained without apparent increases in normal tissue toxicities. In parallel with these trials, we have recently demonstrated in the laboratory that PSC 833 decreases the mutation rate for resistance to doxorubicin and suppresses activation of mdr1 and the appearance of MDR mutants. These findings suggest that MDR modulation may delay the emergence of clinical drug resistance and support the concept of prevention of drug resistance in the earlier stages of disease and the utilization of time to progression as an important endpoint in clinical trials. Pivotal phase III trials to test these concepts with PSC 833 as an MDR modulator are under way or planned for patients with acute myeloid leukemias, multiple myeloma, and ovarian carcinoma.
Betulinic acid (BA), a melanoma-specific cytotoxic agent, induced apoptosis in neuroectodermal tumors, such as neuroblastoma, medulloblastoma, and Ewing's sarcoma, representing the most common solid tumors of childhood. BA triggered an apoptosis pathway different from the one previously identified for standard chemotherapeutic drugs. BA-induced apoptosis was independent of CD95-ligand/receptor interaction and accumulation of wild-type p53 protein, but it critically depended on activation of caspases (interleukin 1beta-converting enzyme/Ced-3-like proteases). FLICE/MACH (caspase-8), considered to be an upstream protease in the caspase cascade, and the downstream caspase CPP32/YAMA/Apopain (caspase-3) were activated, resulting in cleavage of the prototype substrate of caspases PARP. The broad-spectrum peptide inhibitor benzyloxycarbonyl-Val-Ala-Asp-fluoromethylketone, which blocked cleavage of FLICE and PARP, also completely abrogated BA-triggered apoptosis. Cleavage of caspases was preceded by disturbance of mitochondrial membrane potential and by generation of reactive oxygen species. Overexpression of Bcl-2 and Bcl-XL conferred resistance to BA at the level of mitochondrial dysfunction, protease activation, and nuclear fragmentation. This suggested that mitochondrial alterations were involved in BA-induced activation of caspases. Furthermore, Bax and Bcl-xs, two death-promoting proteins of the Bcl-2 family, were up-regulated following BA treatment. Most importantly, neuroblastoma cells resistant to CD95- and doxorubicin-mediated apoptosis were sensitive to treatment with BA, suggesting that BA may bypass some forms of drug resistance. Because BA exhibited significant antitumor activity on patients' derived neuroblastoma cells ex vivo, BA may be a promising new agent for the treatment of neuroectodermal tumors in vivo.
Anticancer treatment using cytotoxic drugs is considered to mediate cell death by activating key elements of the apoptosis program and the cellular stress response. While proteolytic enzymes (caspases) serve as main effectors of apoptosis, the mechanisms involved in activation of the caspase system are less clear. Two distinct pathways upstream of the caspase cascade have been identified. Death receptors, eg, CD95 (APO-1/Fas), trigger caspase-8, and mitochondria release apoptogenic factors (cytochrome c, Apaf-1, AIF), leading to the activation of caspase-9. The stressed endoplasmic reticulum (ER) contributes to apoptosis by the unfolded protein response pathway, which induces ER chaperones, and by the ER overload response pathway, which produces cytokines via nuclear factor-kappaB. Multiple other stress-inducible molecules, such as p53, JNK, AP-1, NF-kappaB, PKC/MAPK/ERK, and members of the sphingomyelin pathway have a profound influence on apoptosis. Understanding the complex interaction between different cellular programs provides insights into sensitivity or resistance of tumor cells and identifies molecular targets for rational therapeutic intervention strategies.
The clinical observation of the multidrug resistance (MDR) phenotype is often associated with overexpression of the mdrl gene, in particular with respect to ovarian cancer. However, until now the mdrl-inducing potential of commonly used antineoplastics has been only incompletely explored. We performed short-term cultures of six ovarian cancer cell lines (MZOV4, EF027, SKOV3, OAW42, OTN14, MZOV20) exposed to either blank medium or cisplatin, doxorubicin or paclitaxel at concentrations related to the clinically achievable plasma peak concentration. A highly specific quantitative real-time RT-PCR was used to detect the Mdr1 transcripts. Mdrl mRNA contents were calibrated in relation to coamplified GAPDH mRNA. Mdrl mRNA was detectable in each cell line. In 13 out of 18 assays (72%) the specific anticancer drug being tested induced mdr1 transcription. No decrease in mdr1 mRNA concentration was observed. Our data suggest that mdr1 induction by antineoplastics is one of the reasons for failure of ovarian cancer therapy but may vary individually.
We previously described that betulinic acid (BetA), a naturally occurring pentacyclic triterpenoid, induces apoptosis in tumor cells through the mitochondrial pathway. Here, for the first time, we provide evidence that BetA cooperated with anticancer drugs to induce apoptosis and to inhibit clonogenic survival of tumor cells. Combined treatment with BetA and anticancer drugs acted in concert to induce loss of mitochondrial membrane potential and the release of cytochrome c and Smac from mitochondria, resulting in activation of caspases and apoptosis. Overexpression of Bcl-2, which blocked mitochondrial perturbations, also inhibited the cooperative effect of BetA and anticancer drugs, indicating that cooperative interaction involved the mitochondrial pathway. Notably, cooperation of BetA and anticancer drugs was found for various cytotoxic compounds with different modes of action (e.g., doxorubicin, cisplatin, Taxol, VP16, or actino-mycin D). Importantly, BetA and anticancer drugs cooperated to induce apoptosis in different tumor cell lines, including p53 mutant cells, and also in primary tumor cells, but not in human fibroblasts indicating some tumor specificity. These findings indicate that using BetA as sensitizer in chemotherapy-based combination regimens may be a novel strategy to enhance the efficacy of anticancer therapy, which warrants further investigation.
Recent evidence demonstrates that the anticancer activity of betulinic acid (BetA) can be markedly increased by combination protocols, for example with chemotherapy, ionizing radiation or TRAIL. Since nuclear factor-kappaB (NF-kappaB), a key regulator of stress-induced transcriptional activation, has been implicated in mediating apoptosis resistance, we investigated the role of NF-kappaB in BetA-induced apoptosis. Here, we provide for the first time evidence that BetA activates NF-kappaB in a variety of tumor cell lines. NF-kappaB DNA-binding complexes induced by BetA consisted of p50 and p65 subunits. Nuclear translocation of p65 was also confirmed by immunofluorescence microscopy. BetA-induced NF-kappaB activation involved increased IKK activity and phosphorylation of IkappaB-alpha at serine 32/36 followed by degradation of IkappaB-alpha. Reporter assays revealed that NF-kappaB activated by BetA is transcriptionally active. Interestingly, inhibition of BetA-induced NF-kappaB activation by different chemical inhibitors (proteasome inhibitor, antioxidant, IKK inhibitor) attenuated BetA-induced apoptosis. Importantly, specific NF-kappaB inhibition by transient or stable expression of IkappaB-alpha super-repressor inhibited BetA-induced apoptosis in SH-EP neuroblastoma cells, while transient expression of IkappaB-alpha super-repressor had no influence on BetA-induced apoptosis in two other cell lines. Thus, our findings that activation of NF-kappaB by BetA promotes BetA-induced apoptosis in a cell type-specific fashion indicate that NF-kappaB inhibitors in combination with BetA would have no therapeutic benefit or could even be contraproductive in certain tumors, which has important implications for the design of BetA-based combination protocols.
The management of cancer involves procedures, which include surgery, radiotherapy and chemotherapy. Development of chemoresistance is a persistent problem during the treatment of local and disseminated disease. A plethora of cytotoxic drugs that selectively, but not exclusively, target actively proliferating cells include such diverse groups as DNA alkylating agents, antimetabolites, intercalating agents and mitotic inhibitors. Resistance constitutes a lack of response to drug-induced tumour growth inhibition; it may be inherent in a subpopulation of heterogeneous cancer cells or be acquired as a cellular response to drug exposure. Resistance varies. Although regulatory approval may require efficacy in as few as 20% of trial cohorts, a drug may subsequently be used in unselected patients displaying resistance to the treatment. Principal mechanisms may include altered membrane transport involving the P-glycoprotein product of the multidrug resistance (MDR) gene as well as other associated proteins, altered target enzyme (e.g. mutated topoisomerase II), decreased drug activation, increased drug degradation due to altered expression of drug-metabolising enzymes, drug inactivation due to conjugation with increased glutathione, subcellular redistribution, drug interaction, enhanced DNA repair and failure to apoptose as a result of mutated cell cycle proteins such as p53. Attempts to overcome resistance mainly involve the use of combination drug therapy using different classes of drugs with minimally overlapping toxicities to allow maximal dosages and with narrowest cycle intervals, necessary for bone marrow recovery. Adjuvant therapy with P-glycoprotein inhibitors and, in specific instances, the use of growth factor and protein kinase C inhibitors are newer experimental approaches that may also prove effective in abrogating or delaying onset of resistance. Gene knockout using antisense molecules may be another effective way of blocking drug resistance genes. Conversely, drug resistance may also be used to good purpose by transplanting retrovirally transformed CD34 cells expressing the MDR gene to protect the bone marrow during high-dose chemotherapy.
We examined the involvement of sphingosine kinase-1, a critical regulator of the sphingolipid balance, in susceptibility to antineoplastic agents of either sensitive or multidrug-resistant acute myeloid leukemia cells. Contrary to parental HL-60 cells, doxorubicin and etoposide failed to trigger apoptosis in chemoresistant HL-60/Doxo and HL-60NP16 cells overexpressing MRP1 and MDR1, respectively. Chemosensitive HL-60 cells displayed sphingosine kinase-1 inhibition coupled with ceramide generation. In contrast, chemoresistant HL-60/ Doxo and HL-60/VP16 had sustained sphingosine kinase-1 activity and did not produce ceramide during treatment. Enforced expression of sphingosine kinase-1 in chemosensitive HL-60 cells resulted in marked inhibition of apoptosis that was mediated by blockade of mitochondrial cytochrome c efflux hence suggesting a control of apoptosis at the pre-mitochondrial level. Incubation with cell-permeable ceramide of chemoresistant cells led to a sphingosine kinase-1 inhibition and apoptosis both prevented by sphingosine kinase-1 over-expression. Furthermore, F-12509a, a new sphingosine kinase inhibitor, led to ceramide accumulation, decrease in sphingosine 1-phosphate content and caused apoptosis equally in chemosensitive and chemoresistant cell lines that is inhibited by adding sphingosine 1-phosphate or overexpressing sphingosine kinase-1. F-12509a induced classical apoptosis hallmarks namely nuclear fragmentation, caspase-3 cleavage as well as downregulation of antiapoptotic XIAP, and release of cytochrome c and SMAC/Diablo.
Background and Procedure. We identified BetA as a new cytotoxic agent active against neuroectodermal tumor cells including neuroblastoma, medulloblastoma, glioblastoma and Ewing sarcoma cells, representing the most common solid tumors of childhood. Results. BetA induced apoptosis by a direct effect on mitochondria independent of accumulation of wild-type p53 protein and independent of death-inducing ligand/receptor systems such as CD95. Mitochondrial perturbations on treatment with BetA resulted in the release of soluble apoptogenic factors such as cytochrome c or AlF from mitochondria into the cytosol, where they induced activation of caspases. Overexpression of the anti-apoptotic proteins Bcl-2 or Bcl-X-L that blocked loss of the mitochondrial membrane potential and cytochrome c release from mitochondria also conferred resistance to BetA. Most importantly, BetA exhibited potent antitumor activity on neuroblastoma cells resistant to CD95- or doxorubicin-triggered apoptosis and on primary tumor cells from patients with neuroectodermal tumors. Conclusions. Thus, BetA may be a promising new agent in the treatment of neuroectodermal tumors including neuroblastoma in vivo. (C) 2000 Wiley-Liss, Inc.
Four human colon adenocarcinoma cell lines, SNU-C1, SNU-C4, SNU-C5, and NCI-H716, that are capable of proliferating autonomously in serum-free medium containing no added peptide growth factors were identified. All four cell lines show epidermal growth factor (EGF) receptors (EGFRs), express transforming growth factor alpha (TGF-alpha) messenger RNA, and release anti-TGF-alpha-immunoreactive molecules. The blocking anti-EGFR monoclonal antibody (mAb) 225 blocks autonomous proliferation of SNU-C1 and SNU-C4 cells. In both of these cell lines, the inhibitory effect of mAb 225 is reversible by the addition of EGF, TGF-alpha, or conditioned medium from any of the four cell lines. In contrast, autonomous proliferation of SNU-C5 and NCI-H716 cells is not inhibited by mAb 225 and is not affected by exogenous EGF, TGF-alpha, or conditioned medium. Together, these data confirm the previous finding that anti-EGFR antibodies can inhibit the proliferation of some carcinoma cell lines that coexpress TGF-alpha and EGFR. However, here it is shown that the mechanisms of autonomous proliferation of colon carcinoma cell lines are heterogeneous and not always sensitive to antibody disruption of TGF-alpha/EGFR autocrine interactions.
As a result of bioassay-guided fractionation, betulinic acid, a pentacyclic triterpene, was identified as a melanoma-specific cytotoxic agent. In follow-up studies conducted with athymic mice carrying human melanomas, tumour growth was completely inhibited without toxicity. As judged by a variety of cellular responses, antitumour activity was mediated by the induction of apoptosis. Betulinic acid is inexpensive and available in abundant supply from common natural sources, notably the bark of white birch trees. The compound is currently undergoing preclinical development for the treatment or prevention of malignant melanoma.
Oxaliplatin has shown in vivo cytotoxic activity against colorectal cell lines. Preliminary studies suggest potentiation of fluorouracil (5-FU). To assess this issue, we performed a phase II study in pretreated patients with advanced colorectal cancer (CRC) resistant to leucovorin and 5-FU. The regimen (FOLFOX2) consisted of oxaliplatin 100 mg/m2 as a 2-h infusion on day 1; leucovorin 500 mg/m2 as a 2-h infusion, followed by 5-FU 24-h infusion 1.5-2 g/m2 for two consecutive days every 2 weeks. The initial 5-FU dose was 1.5 g/m2 for two cycles and increased to 2 g/m2 in case of no toxicity > grade 2. 46 patients were treated, all with disease progression on leucovorin and 5-FU therapy for metastatic disease, or relapse less than 6 months after the end of adjuvant therapy. One complete response (CR) and 20 partial responses (PRs) were observed for an overall response rate of 46%. 22 patients had prior documented progression while receiving the same schedule of leucovorin and 5-FU as the one used in the FOLFOX2 regimen, and among them, 10 had PRs (45%). From the start of FOLFOX2, median progression-free survival was 7 months and median survival 17 months. WHO toxicity > or = grade 3 per patient was: peripheral neuropathy 9%, nausea 4%, diarrhoea 9%, mucositis 13%, neutropenia 39%, thrombocytopenia 11%, alopecia 9%, and allergy 2%. Overall, 21 patients (46%) experienced grade 3-4 toxicity. This combination of leucovorin, 5-FU and oxaliplatin achieves a high response rate in pretreated patients with CRC resistant to leucovorin and 5-FU. Limiting toxicities are neutropenia and peripheral neuropathy.
Oxaliplatin, classical [5-fluorouracil (5-FU)] and non-classical (AG337) thymidylate synthase inhibitors have shown promising activity in the treatment of cancer. This study investigates the cytotoxic effects of oxaliplatin in combination with 5-FU and AG337 in cultured human colon (HT29, CaCo2), breast (MCF-7, MDA-MB-231) and ovarian (2008) cancer cell lines, and their derived counterparts selected for their resistance to 5-FU (HT29-5-FU), doxorubicin (MCF-7mdr) or cisplatin (2008C13). Therapeutic experiments were conducted in mice bearing colon-HT29 xenografts and in the GR hormone-independent mammary carcinoma model. In vitro, oxaliplatin shows potent cytotoxic activity in colon (IC50 from 2.1 +/- 1.1 to 5.9 +/- 1.7 microM), ovarian (IC50 = 10 +/- 1.6 microM) and breast cancer cells (IC50 from 7.4 +/- 2.7 to 17.9 +/- 7.1 microM). Oxaliplatin was a potent inhibitor of DNA synthesis and bound to cellular DNA. Surprisingly, the overall amount of oxaliplatin DNA binding was significantly inferior to that induced by isocytotoxic concentrations of cisplatin in HT29 (p=0.026). In vitro, synergistic antiproliferative effects were observed when oxaliplatin was added to 5-FU and AG337. Those synergistic effects of combinations were maintained in colon HT29-5-FU cancer cells. In vivo, 5-FU increased significantly the antitumor activity of oxaliplatin in HT29 xenografts (p=0.0036), and similarly 5-FU and AG337 increased the activity of oxaliplatin in the GR tumor model (p=0.0012). These data may encourage further clinical investigation of oxaliplatin in combination with classical and non-classical thymidylate synthase inhibitors in the treatment of human cancers.
Strictly speaking, multidrug resistance (MDR) describes the experimental observation of cross resistance to various structurally unrelated cytotoxic agents in laboratory models of cancer. These drugs have in common their origin as natural products, and in 1985 the basis of this MDR was established as the over-expression of a membrane glycoprotein, called P-glycoprotein (Pgp), which acts as a drug efflux pump actively depleting intracellular drug concentrations in resistant tumour cells. Since then, MDR has arguably taken on a second meaning, i.e. 'misunderstood drug resistance', through the understandable, but mistaken assumption by many scientists and some clinicians that the clinical observation in cancer patients treated with chemotherapy of resistance to a wide range of cytotoxic drugs (either as a primary or acquired property) inevitably involves the same mechanism. At present, the evidence from clinical studies to support such a notion is clearly lacking, particularly in solid tumours. However, increased Pgp expression has been observed in a number of clinical situations, and its relevance requires further elucidation. Current data indicate that increased Pgp expression represents an adverse prognostic factor, for reasons which may be quite unrelated to developing drug resistance. Experimentally, MDR can be reversed by simultaneous treatment with a number of non-cytotoxic agents which competitively inhibit Pgp function. Despite the reservations outlined, numerous clinical trials of this approach have been conducted. The results have generally been negative in solid tumours, although some have been more promising in haematological cancers. The most recent studies have used more potent modulating agents, such as the cyclosporin analogue, PSC833. Interpretation of data from these trials is complicated by pharmacokinetic interactions between the target cytotoxic drug and the modulating agent. Randomized trials are now underway in a number of tumour types; thus a clearer picture of the clinical relevance of MDR should emerge over the next few years.
Betulinic acid (BA), a pentacyclic triterpene, is an experimental cytotoxic agent for malignant melanoma. Here, we show that BA triggers apoptosis in five human glioma cell lines. BA-induced apoptosis requires new protein, but not RNA, synthesis, is independent of p53, and results in p21 protein accumulation in the absence of a cell cycle arrest. BA-induced apoptosis involves the activation of caspases that cleave poly(ADP ribose)polymerase. Interactions of death ligand/receptor pairs of the CD95/CD95 ligand family do not mediate BA-induced caspase activation. BA enhances the levels of BAX and BCL-2 proteins but does not alter the levels of BCL-xS or BCL-xL. Ectopic expression of BCL-2 prevents BA-induced caspase activation, DNA fragmentation, and cell death. Furthermore, BA induces the formation of reactive oxygen species that are essential for BA-triggered cell death. The generation of reactive oxygen species is blocked by BCL-2 and requires new protein synthesis but is unaffected by caspase inhibitors, suggesting that BA toxicity sequentially involves new protein synthesis, formation of reactive oxygen species, and activation of crm-A-insensitive caspases.
We identified betulinic acid (BetA) as a new cytotoxic agent active against neuroectodermal tumor cells including neuroblastoma, medulloblastoma, glioblastoma and Ewing's sarcoma cells representing the most common solid tumors of childhood. BetA induced apoptosis independent of wild-type p53 protein and accumulation of death inducing ligand/receptor systems such as CD95. BetA had a direct effect on mitochondria resulting in the release of soluble apoptogenic factors such as cytochrome c or AIF from mitochondria into the cytosol where they induced activation of caspases. Over expression of the anti-apoptotic proteins Bcl-2 or Bcl-XL that blocked loss of the mitochondrial membrane potential and cytochrome c release from mitochondria conferred resistance to BetA at the level of mitochondrial dysfunction, protease activation and nuclear fragmentation. Neuroblastoma cells resistant to CD95- or doxorubicin-triggered apoptosis remained sensitive to treatment with BetA suggesting that BetA may bypass some forms of resistance. Moreover, BetA exhibited potent antitumor activity on primary tumor cell cultures from all neuroblastoma (4/4), all medulloblastoma (4/4) and most glioblastoma patients (20/24) ex vivo. These findings suggest that BetA may be a promising new agent in the treatment of neuroectodermal tumors in vivo.
Abbreviations: AIF, apoptosis inducing factor; BetA, betulinic acid; DiOC6(3), 3,3'-dihexyloxacarbocyanide iodide; DTT, Dithiothreitol; ECL, enhanced chemiluminescence; FACS, fluorescence-activated cell-sorting; ICE, interleukin 1β-converting enzyme; ΔYm mitochondrial transmembrane potential; PARP, poly(ADP-ribose) polymerase; zVAD.fmk, benzyloxycarbonyl-Val-Ala-Asp-fluoromethyl ketone.
To estimate the magnitude of benefit of chemotherapy in prolonging survival for patients with metastatic colorectal cancer, a meta-analysis of randomized controlled trial was performed. A systematic search was performed to identify randomized trials comparing chemotherapy with observation or supportive care alone. Trials were assessed for quality of reporting, publication bias and heterogeneity. Relative risks for outcomes from published data were pooled using a random-effects model. Seven trials with 614 patients were included. All trials used fluoropyrimidine-based chemotherapy, through a variety of routes and schedules, including intravenous, intra-portal and hepatic arterial infusion. Compared with the 'no-chemotherapy' arm, chemotherapy significantly reduced 1-year mortality (risk ratio 0.69; 95% confidence interval (CI) 0.60-0.81, P < 0.00001). The mortality at 2 years was not significantly different (risk ratio 0.93; 95% CI 0.87-1.00, P = 0.053). Between-trial comparisons demonstrated benefit with a variety of routes and schedules. Chemotherapy significantly prolongs 1-year survival for patients with metastatic colorectal cancer, and should be offered to those with good performance status.
We identified BetA as a new cytotoxic agent active against neuroectodermal tumor cells including neuroblastoma, medulloblastoma, glioblastoma and Ewing sarcoma cells, representing the most common solid tumors of childhood.
BetA induced apoptosis by a direct effect on mitochondria independent of accumulation of wild-type p53 protein and independent of death-inducing ligand/receptor systems such as CD95. Mitochondrial perturbations on treatment with BetA resulted in the release of soluble apoptogenic factors such as cytochrome c or AIF from mitochondria into the cytosol, where they induced activation of caspases. Overexpression of the anti-apoptotic proteins Bcl-2 or Bcl-X(L) that blocked loss of the mitochondrial membrane potential and cytochrome c release from mitochondria also conferred resistance to BetA. Most importantly, BetA exhibited potent antitumor activity on neuroblastoma cells resistant to CD95- or doxorubicin-triggered apoptosis and on primary tumor cells from patients with neuroectodermal tumors.
Thus, BetA may be a promising new agent in the treatment of neuroectodermal tumors including neuroblastoma in vivo.
Cytotoxic chemotherapy for colorectal cancer has undergone a period of dramatic development over the course of the last 5 years. Four distinct classes of drug with activity in this disease are now available, and the current challenge is to establish the best way to use these agents, either in sequence or in combination, for the benefit of patients. This review aims to summarize the data relating to the newer agents and to propose directions for future research. DRUGS TARGETING THYMIDYLATE SYNTHASE 5-fluorouracil (5-FU) has established single-agent activity in advanced colorectal cancer. Its main intracellular target is thymidylate synthase, which is inhibited by the active metabolite of 5-FU, 5-fluorodeoxyuridine monophosphate (FdUMP) (Figure 1). The lack of alternative agents until recent years has fuelled extensive research into the biochemical modulation of 5-FU and alternative methods of delivery, primarily based on continuous infusion of the drug. Many individual clinical trials have demonstrated enhanced response rates when 5-FU is co-administered with folinic acid (calcium leucovorin). However a significant survival benefit has been more difficult to establish. Indeed a meta-analysis of nine trials showed no survival advantage for folinic acidmodulated 5-FU over 5-FU alone (Advanced Colorectal Cancer Meta-Analysis Project, 1992). Similarly, continuous infusion of 5FU using a variety of different schedules also enhances response rates over bolus delivery. A meta-analysis of seven randomized trials addressing this question showed a small but statistically significant improvement in median survival for 5-FU infusion over 5-FU bolus (12.1 vs 11.3 months, P = 0.039). Haematological toxicity was also significantly less common with 5-FU infusion, underlining the improved therapeutic ratio provided by this approach (Meta-analysis Group In Cancer, 1998). Drawing on the experience gained with 5-FU infusion, two new avenues of drug development have been explored. The direct thymidylate synthase (TS) inhibitors are a group of rationally designed molecules that compete with folinic acid for binding to TS (Figure 1). Intracellular polyglutamation of some of these compounds leads to their retention within the cell, and hence prolonged inhibition of TS. Raltitrexed, the lead agent in this class, has been the subject of extensive clinical evaluation. Its efficacy at the established dose of 3 mg m −2
Human malignant melanoma is notoriously resistant to chemotherapeutic agents. Melanoma-derived cell lines are often markedly chemoresistant, suggesting that cellular mechanisms mediate generation of the multidrug resistance (MDR) phenotype. This phenotype is often due to P-glycoprotein (Pgp) and the MDR-associated protein (MRP), which are drug transporter proteins associated with resistance to a broad spectrum of lipophilic drugs.
To determine the relationships between the expression of the MDR gene MDR-1 (the product of which is Pgp) or the MRP gene, and clinical chemoresistance of malignant melanoma.
We examined changes in the expression of MDR-1 and MRP genes at the mRNA level before and after chemotherapy by reverse transcription-polymerase chain reaction (RT-PCR) analysis using formalin-fixed, paraffin-embedded sections of 18 specimens taken from eight melanoma patients. mRNA expression of the MDR-1 and MRP gene-specific PCR products was quantitatively determined by densitometry and compared with that of an internal standard (beta-actin).
Five of seven primary melanomas were found to express the MRP gene to a certain extent even before chemotherapy. After first and second courses of chemotherapy, six patients had an increased ratio of MRP mRNA to beta-actin mRNA compared with the prechemotherapy levels in the same patients. None of the cases of melanoma expressed MDR-1.
These results suggest that a significant mRNA level of MRP gene was intrinsically present in malignant melanoma even before exposure to chemotherapeutic drugs and increased in its expression after chemotherapy, suggesting that MRP plays a part in increasing the chemoresistance of malignant melanoma during chemotherapy.
Defects in apoptosis underpin both tumorigenesis and drug resistance, and because of these defects chemotherapy often fails. Understanding the molecular events that contribute to drug-induced apoptosis, and how tumors evade apoptotic death, provides a paradigm to explain the relationship between cancer genetics and treatment sensitivity and should enable a more rational approach to anticancer drug design and therapy.
Development of resistance to anticancer drugs is a major concern in clinical oncology and might be particularly involved in the secondary treatment failure frequently seen in ovarian cancer. Clinical observation of the multidrug resistance (MDR) phenotype is often associated with overexpression of the mdr1-gene. However, until now the mdr1-inducing potential of commonly used antineoplastics has been only incompletely explored.
We perfomed short-term cultures of 7 established ovarian cancer cell lines exposed to either blank medium or one of three single anticancer drugs (cisplatin, doxorubicin, paclitaxel) at concentrations related to the clinically achievable plasma peak concentration. Mdr1-transcripts were detected using the highly specific quantitative real time RT-PCR. To calibrate each approach, mdr1-mRNA content was calculated in relation to co-amplified GAPDH-mRNA.
Mdr1-mRNA was detectable in each cell line. In 13 assays (62%) the specific anticancer drug being tested induced mdr1-transcription. No decrease in mdr1-mRNA concentration was observed. The method described here is easy to perform and could be of striking value in predicting the development of tumor chemoresistance.
Our data indicate that mdr1-induction by antineoplastics is one of the reasons for failure of ovarian cancer therapy but may vary from one individual to another.
The mitochondrion plays a crucial role in the process of apoptosis and has thus become one of the targets for the search for potential chemotherapeutic agents. Betulinic acid [3beta-hydroxy-lup-20(19)lupaen-28-carbonic acid], a lupane-type triterpene which is abundant in many plant species, has been shown to exert a direct effect on the mitochondria and subsequent apoptosis in melanoma cells. Chemical synthesis and modification of betulinic acid are being explored to develop more potent derivatives. We present here the apoptotic activity of several natural derivatives of betulinic acid which were isolated from the roots of a Chinese medicinal herb, Pulsatilla chinensis (Bge) Regel [Ye, W., Ji, N.N., Zhao, S.X., Liu, J.H., Ye, T., McKervey, M.A., Stevenson, P., 1996. Triterpenoids from Pulsatilla chinensis. Phytochemistry 42, 799-802]. Of the five compounds tested, 3-oxo-23-hydroxybetulinic acid was the most cytotoxic on murine melanoma B16 cells (IC50=22.5 microg/ml), followed by 23-hydroxybetulinic acid and betulinic acid (IC50=32 and 76 microg/ml, respectively), with lupeol and betulin exhibiting the weakest cytotoxicity (IC50> or =100 microg/ml). Exposure of B16 cells to betulinic acid, 23-hydroxybetulinic acid and 3-oxo-23-hydroxybetulinic acid caused a rapid increase in reactive oxidative species production and a concomitant dissipation of mitochondrial membrane potential in a dose- and time-dependent manner, which resulted in cell apoptosis, as demonstrated by fluorescence microscopy, gel electrophoresis and flow-cytometric analysis. Cell cycle analysis further demonstrated that both 3-oxo-23-hydroxybetulinic acid and 23-hydroxybetulinic acid dramatically increased DNA fragmentation at the expense of G1 cells at doses as low as 12.5 and 25 microg/ml, respectively, thereby showing their potent apoptotic properties. Our results showed that hydroxylation at the C3 position of betulinic acid is likely to enhance the apoptotic activity of betulinic acid derivatives (23-hydroxybetulinic acid and 3-oxo-23-hydroxybetulinic acid) on murine melanoma B16 cells.
Multidrug resistance (MDR) mediated by membrane transporters, such as P-glycoprotein (MDR-1) and MDR-associated protein (MRP), remains a challenge in the therapy of renal cell carcinoma (RCC). Chemotherapy targeted to hormone receptors may provide a new approach to overcome chemoresistance. The cytotoxic analogue of bombesin/gastrin-releasing peptide (GRP), AN-215, consists of a superactive derivative of doxorubicin, AN-201, which is linked to a bombesin analogue carrier: RC-3094.
The authors examined the expression of bombesin/GRP receptors in 3 human RCC cell lines (A-498, ACHN. and 786-0) by using reverse-transcriptase-polymerase chain reaction (RT-PCR) analysis and radioligand-binding assays. They also evaluated the effects of AN-215 and its cytotoxic radical AN-201 in the same RCC models in vivo, and they studied the effects of AN-215 and AN-201 on the expression levels of MDR-1 and subtype 1 of MRP (MRP-1) by using real-time PCR.
A N-215 significantly (P < 0.05) inhibited the growth of A-498, ACHN, and 786-0 RCC xenografted into nude mice by 59.2-67.6%, whereas the cytotoxic radical AN-201 alone had no significant antitumor effects. The efficacy of AN-215 was independent of the expression patterns of MDR-1 and MRP-1 in these RCC cell lines. The induction of MDR-1 by AN-215 was similar (Experiment 2) or weaker (Experiment 1) compared with AN-201. Both AN-215 and AN-201 caused only a minor induction of MRP-1.
The current findings indicated that targeted chemotherapy with cytotoxic bombesin/GRP analogue AN-215 can inhibit the growth of RCC, providing a new treatment modality for patients with advanced RCC.
The intrinsic or acquired resistance to anticancer drugs remains one of the most significant factors impeding the progress of cancer chemotherapy. This phenomenon often involves simultaneous resistance to other anticancer drugs that differ in their chemical structure and mode of action and are not even used in chemotherapy. This phenotype has been called multidrug resistance (MDR). Although the cellular basis underlying MDR is not fully understood, several factors mediating therapy resistance in tumors have been proposed. One of the mechanisms leading to chemoresistance of tumor cells is the increased activity of transporter proteins. The best-characterized transporter protein is MDR1/P-glycoprotein, and a number of clinical investigations have suggested that its intrinsic or acquired overexpression resulted in a poor clinical outcome of chemotherapy. Various types of compounds and techniques for the reversal of MDR1/P-glycoprotein-mediated MDR have been developed, and efforts have concentrated on the inhibition of function and suppression of expression. This review summarizes the current state of knowledge of MDR1/P-glycoprotein and the modulation of MDR by targeting MDR1/P-glycoprotein.
A phase II study of oxaliplatin combined with 5-fluorouracil and leucovorin (Mayo Clinic regimen) in 5-fluorouracil refractory colorectal cancer
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The Authors Journal compilation © 2007 Nordic Pharmacological Society
© 2007 The Authors
Journal compilation © 2007 Nordic Pharmacological Society. Basic & Clinical Pharmacology & Toxicology, 101, 277–285
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- E Raymond
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Parkin DM, Whelan SL, Ferlay J et al. Cancer Incidence in Five
Continents, Vol. VIII. IARC Scientific Publications, Lyon,
France, 2002.