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ABSTRACT: Tumor microenvironment (TME) refers to the dynamic cellular and extra-cellular components surrounding tumor cells at each stage of the carcinogenesis. TME has now emerged as an integral and inseparable part of the carcinogenesis that plays a critical role in tumor growth, angiogenesis, epithelial to mesenchymal transition (EMT), invasion, migration and metastasis. Besides its vital role in carcinogenesis, TME is also a better drug target because of its relative genetic stability with lesser probability for the development of drug-resistance. Several drugs targeting the TME (endothelial cells, macrophages, cancer-associated fibroblasts, or extra-cellular matrix) have either been approved or are in clinical trials.Recently, non-steroidal anti-inflammatory drugs targeting inflammationwere reported to also prevent several cancers. These exciting developments suggest that cancer chemopreventive strategies targeting both tumor and TME would be better and effective towards preventing, retarding or reversing the process of carcinogenesis. Here, we have reviewed the effect of a well established hepatoprotective and chemopreventive agent silibinin on cellular (endothelial, fibroblast and immune cells) and non-cellular components (cytokines, growth factors, proteinases etc.) of theTME. Silibinin targets TME constituents as well as their interaction with cancer cells, thereby inhibiting tumor growth, angiogenesis, inflammation, EMT, and metastasis.Silibinin is already in clinical trials, and based upon completed studies we suggest that its chemopreventive effectiveness should be verified through its effect on biological end points in both tumor and TME. Overall, we believe that the chemopreventive strategies targeting both tumor and TMEhave practical and translational utility in lowering the cancer burden.
Current cancer drug targets 04/2013; · 5.13 Impact Factor
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ABSTRACT: Despite advances in early detection, prostate cancer remains the second highest cancer mortality in American men, and even successful interventions are associated with enormous health care costs as well as prolonged deleterious effects on quality of patient life. Prostate cancer chemoprevention is one potential avenue to alleviate these burdens. It is a regime whereby long-term treatments are intended to prevent or arrest cancer development, in contrast to more direct intervention upon disease diagnosis. Based on this intention, cancer chemoprevention generally focuses on the use of nontoxic chemical agents which are well-tolerated for prolonged usage that is necessary to address prostate cancer's multistage and lengthy period of progression. One such nontoxic natural agent is the flavonoid silibinin, derived from the milk thistle plant (Silybum marianum), which has ancient medicinal usage and potent antioxidant activity. Based on these properties, silibinin has been investigated in a host of cancer models where it exhibits broad-spectrum efficacy against cancer progression both in vitro and in vivo without noticeable toxicity. Specifically in prostate cancer models, silibinin has shown the ability to modulate cell signaling, proliferation, apoptosis, epithelial to mesenchymal transition, invasion, metastasis, and angiogenesis, which taken together provides strong support for silibinin as a candidate prostate cancer chemopreventive agent.
The AAPS Journal 04/2013; · 5.09 Impact Factor
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ABSTRACT: Prognosis of pancreatic cancer is extremely poor, suggesting critical needs for additional drugs to improve disease outcome. Here, we examined efficacy and associated mechanism of a novel agent bitter melon juice (BMJ) against pancreatic carcinoma cells both in culture and nude mice.BMJ anticancer efficacy was analyzed in human pancreatic carcinoma BxPC-3, MiaPaCa-2, AsPC-1 and Capan-2 cells by MTT, cell death ELISA and annexin/PI assays. BMJ effect on apoptosis regulators was assessed by immunoblotting. In vivo BMJ efficacy was evaluated against MiaPaCa-2 tumors in nude mice, and xenograft analyzed for biomarkers by immunohistochemistry (IHC). Results showed that BMJ (2-5% v/v) decreases cell viability in all four pancreatic carcinoma cell lines by inducing strong apoptotic death. At molecular level, BMJ caused caspases activation, altered expression of Bcl2 family members, and cytochrome-c release into the cytosol. Additionally, BMJ decreased survivin and XIAP but increased p21, CHOP and phosphorylated MAPKs (ERK1/2 and p38) levels. Importantly, BMJ activated AMP-activated protein kinase (AMPK); a biomarker for cellular energy status, and an AMPK inhibitor (Compound C) reversed BMJ-induced caspase 3 activation suggesting activated-AMPK involvement in BMJ-induced apoptosis. In vivo, oral administration of lyophilized BMJ (5 mg in 100 µl water/day/mouse) for 6 weeks inhibited MiaPaCa-2 tumor xenograft growth by 60% (p<0.01) without noticeable toxicity in nude mice. IHC analyses of MiaPaCa-2 xenografts showed that BMJ also inhibits proliferation, induces apoptosis and activates AMPK in vivo. Overall, BMJ exerts strong anti-cancer efficacy against human pancreatic carcinoma cells, both in vitro and in vivo, suggesting its clinical usefulness.
Carcinogenesis 03/2013; · 5.70 Impact Factor
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ABSTRACT: Recent studies have demonstrated silibinin efficacy against ultraviolet B (UVB)-induced skin carcinogenesis via different mechanisms in cell lines and animal models; however, its role in regulating interleukin-12 (IL-12), an immunomodulatory cytokine that reduces UVB-induced DNA damage and apoptosis, is not known. Here, we report that UVB irradiation causes caspase 3 and PARP cleavage and apoptosis, and addition of recombinant IL-12 or silibinin immediately after UVB significantly protects UVB-induced apoptosis in JB6 cells. IL-12 antibody-mediated blocking of IL-12 activity compromised the protective effects of both IL-12 and silibinin. Both silibinin and IL-12 also accelerated the repair of UVB-caused cyclobutane-pyrimidine dimers (CPDs) in JB6 cells. Additional studies confirmed that indeed silibinin causes a significant increase in IL-12 levels in UVB-irradiated JB6 cells as well as in mouse skin epidermis, and that similar to cell-culture findings, silibinin topical application immediately after UVB exposure causes a strong protection against UVB-induced TUNEL positive cells in epidermis possibly through a significantly accelerated repair of UVB-caused CPDs. Together, these findings for the first time provide an important insight regarding the pharmacological mechanism wherein silibinin induces endogenous IL-12 in its efficacy against UVB-caused skin damages. In view of the fact that an enhanced endogenous IL-12 level could effectively remove UVB-caused DNA damage and associated skin cancer, our findings suggest that the use of silibinin in UVB-damaged human skin would also be a practical and translational strategy to manage solar radiation-caused skin damages as well as skin cancer. © 2013 Wiley Periodicals, Inc.
Molecular Carcinogenesis 01/2013; · 3.16 Impact Factor
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ABSTRACT: Silybin or silibinin, a flavonolignan isolated from Milk thistle seeds, is one of the popular dietary supplements and has been extensively studied for its antioxidant, hepatoprotective and anti-cancer properties. We have envisioned that potency of silybin could be further enhanced through suitable modification/s in its chemical structure. Accordingly, here, we synthesized and characterized a series of silybin derivatives namely 2,3-dehydrosilybin (DHS), 7-O-methylsilybin (7OM), 7-O-galloylsilybin (7OG), 7,23-disulphatesilybin (DSS), 7-O-palmitoylsilybin (7OP), and 23-O-palmitoylsilybin (23OP); and compared their anti-cancer efficacy using human bladder cancer HTB9, colon cancer HCT116 and prostate carcinoma PC3 cells. In all the 3 cell lines, DHS, 7OM and 7OG demonstrated better growth inhibitory effects and compared to silybin, while other silybin derivatives showed lesser or no efficacy. Next, we prepared the optical isomers (A and B) of silybin, DHS, 7OM and 7OG, and compared their anti-cancer efficacy. Isomers of these three silybin derivatives also showed better efficacy compared with respective silybin isomers, but in each, there was no clear cut silybin A versus B isomer activity preference. Further studies in HTB cells found that DHS, 7OM and 7OG exert better apoptotic activity than silibinin. Clonogenic assays in HTB9 cells further confirmed that both the racemic mixtures as well as pure optical isomers of DHS, 7OM and 7OG were more effective than silybin. Overall, these results clearly suggest that the anti-cancer efficacy of silybin could be significantly enhanced through structural modifications, and identify strong anti-cancer efficacy of silybin derivatives, namely DHS, 7OM, and 7OG, signifying that their efficacy and toxicity should be evaluated in relevant pre-clinical cancer models in rodents.
PLoS ONE 01/2013; 8(3):e60074. · 4.09 Impact Factor
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ABSTRACT: Currently, there are limited therapeutic options against bone metastatic prostate cancer (PCA), which is primarily responsible for high mortality and morbidity in PCA patients. Enhanced osteoclastogenesis is an essential feature associated with metastatic PCA in the bone microenvironment. Silibinin, an effective chemopreventive agent, is in phase II clinical trials in PCA patients but its efficacy against PCA cells-induced osteoclastogenesis is largely unknown. Accordingly, here we examined silibinin effect on PCA cells-induced osteoclastogenesis employing human PCA (PC3MM2, PC3, and C4-2B) and murine macrophage RAW264.7 cells. We also assessed silibinin effect on receptor activator of nuclear factor κB ligand (RANKL)-induced signaling associated with osteoclast differentiation in RAW264.7 cells. Further, we analyzed silibinin effect on osteomimicry biomarkers in PCA cells. Results revealed that silibinin (30-90 µM) inhibits PCA cells-induced osteoclast activity and differentiation in RAW264.7 cells via modulating expression of several cytokines (IGF-1, TGF-β, TNF-α, I-TAC, M-CSF, G-CSF, GM-CSF, etc.) that are important in osteoclastogenesis. Additionally, in RAW264.7 cells, silibinin decreased the RANKL-induced expression and nuclear localization of NFATc1, which is considered the master regulator of osteoclastogenesis. Furthermore, silibinin decreased the RANKL-induced DNA binding activity of NFATc1 and its regulators NF-κB and AP1, and the protein expression of osteoclast specific markers (TRAP, OSCAR, and cathepsin K). Importantly, silibinin also decreased the expression of osteomimicry biomarkers (RANKL, Runx2, osteocalcin, and PTHrP) in cell culture (PC3 and C4-2B cells) and/or in PC3 tumors. Together, our findings showing that silibinin inhibits PCA cells-induced osteoclastogenesis, suggest that silibinin could be useful clinically against bone metastatic PCA. © 2012 Wiley Periodicals, Inc.
Molecular Carcinogenesis 10/2012; · 3.16 Impact Factor
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Shrotriya Sangeeta, Deep Gagan,
Ramasamy Kumaraguruparan,
Raina Komal,
Barbakadze Vakhtang,
Merlani Maia,
Gogilashvili Lali,
Amiranashvili Lela,
Mulkijanyan Karen,
Papadopoulos Kyriakos,
Agarwal Chapla,
Agarwal Rajesh
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ABSTRACT: The major obstacles in human prostate cancer (PCA) treatment are the development of resistance to androgen ablation therapy leading to hormone-refractory state and the toxicity associated with chemotherapeutic drugs. Thus, the identification of additional non-toxic agents that are effective against both androgen-dependent and androgen-independent PCA is needed. In the present study, we investigated the efficacy of a novel phytochemical poly[3-(3, 4-dihydroxyphenyl)glyceric acid] (p-DGA) from Caucasian species of comfrey (Symphytum caucasicum) and its synthetic derivative syn-2, 3-dihydroxy-3-(3, 4-dihydroxyphenyl) propionic acid (m-DGA) against PCA LNCaP and 22Rv1 cells. We found that both p-DGA and m-DGA suppressed the growth and induced death in PCA cells, with comparatively lesser cytotoxicity towards non-neoplastic human prostate epithelial cells. Furthermore, we also found that both p-DGA and m-DGA caused G(1) arrest in PCA cells through modulating the expression of cell cycle regulators, especially an increase in CDKIs (p21 and p27). In addition, p-DGA and m-DGA induced apoptotic death by activating caspases, and also strongly decreased AR and PSA expression. Consistent with in vitro results, our in vivo study showed that p-DGA feeding strongly inhibited 22Rv1 tumors growth by 76% and 88% at 2.5 and 5mg/kg body weight doses, respectively, without any toxicity, together with a strong decrease in PSA level in plasma; and a decrease in PCNA, AR and PSA expression but increase in p21/p27 expression and apoptosis in tumor tissues from p-DGA-fed mice. Overall, present study identifies p-DGA as a potent agent against PCA without any toxicity, and supports its clinical application.
Carcinogenesis 06/2012; 33(8):1572-80. · 5.70 Impact Factor
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ABSTRACT: Head and neck squamous cell carcinoma (HNSCC) is the sixth leading cancer in the world; the main risk factors are alcohol and tobacco use. Advancements in therapies have yet to improve the prognosis of HNSCC. The connection between diabetes and cancer is being recognized, and metformin has been shown to decrease cancer incidence in diabetic patients. Accordingly, here, for the first time, we investigated metformin's efficacy on the growth and viability of human HNSCC FaDU and Detroit cells. Our results show that metformin treatment (5-20 mM) dose-dependently inhibits the growth of both cell lines. In FaDU cells, metformin caused 18-57% and 35-81% growth inhibition after 48 and 72 h treatments, respectively. Similarly, in Detroit 562 cells, 48 and 72 h metformin treatment resulted in 20-57% and 33-82% inhibition, respectively. Mechanistically, metformin caused G 1 arrest, which coincided with a decrease in the protein levels of CDKs (2, 4 and 6), cyclins (D1 and E) and CDK inhibitors (p15, p16, p18 and p27), but no change in p19 and p21. Metformin also decreased the levels of oncogenic proteins Skp2 and β-Trcp. In other studies, metformin decreased the phosphorylation of 4E-BP1 at Ser65, Thr37/46 and Thr70 sites, but drastically increased the phosphorylation of EF2 at Thr56 and AMPK at Thr172, which results in global translational inhibition. In summary, the observed wide spectrum of mechanistic effects of metformin on HNSCC cells provides support for the anticancer capability of the drug and its potential use in future therapies.
Cell cycle (Georgetown, Tex.) 04/2012; 11(7):1374-82. · 5.36 Impact Factor
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ABSTRACT: Head and neck squamous cell carcinoma (HNSCC) accounts for 6% of all malignancies in USA and unfortunately the recurrence of secondary primary tumors and resistance against conventional treatments decrease the overall 5 year survival rate in HNSCC patients. Thus, additional approaches are needed to control HNSCC. Here, for the first time, employing human HNSCC Detroit 562 and FaDu cells as well as normal human epidermal keratinocytes, we investigate grape seed extract (GSE) efficacy and associated mechanism in both cell culture and nude mice xenografts. GSE selectively inhibited the growth and caused cell cycle arrest and apoptotic death in both Detroit 562 and FaDu cells by activating DNA damage checkpoint cascade, including ataxia telangiectasia mutated/ataxia telangiectasia-Rad3-related-checkpoint kinase 1/2-cell division cycle 25C as well as caspases 8, 9 and 3. Consistent with these results, GSE treatment resulted in a strong DNA damage and a decrease in the levels of DNA repair molecules breast cancer gene 1 and Rad51 and DNA repair foci. GSE-caused accumulation of intracellular reactive oxygen species was identified as a major mechanism of its effect for growth inhibition, DNA damage and apoptosis, which was remarkably reversed by antioxidant N-acetylcysteine. GSE feeding to nude mice decreased Detroit 562 and FaDu xenograft tumor growth by 67 and 65% (P < 0.001), respectively. In immunohistochemical analysis, xenografts from GSE-fed groups showed decreased proliferation but increased DNA damage and apoptosis. Together, these findings show that GSE targets both DNA damage and repair and provide mechanistic insights for its efficacy selectively against HNSCC both in cell culture and mouse xenograft, supporting its translational potential against HNSCC.
Carcinogenesis 02/2012; 33(4):848-58. · 5.70 Impact Factor
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ABSTRACT: The role of neo-angiogenesis in prostate cancer (PCA) growth and metastasis is well established, but the development of effective and non-toxic pharmacological inhibitors of angiogenesis remains an unaccomplished goal. In this regard, targeting aberrant angiogenesis through non-toxic phytochemicals could be an attractive angiopreventive strategy against PCA. The rationale of the present study was to compare the anti-angiogenic potential of four pure diastereoisomeric flavonolignans, namely silybin A, silybin B, isosilybin A and isosilybin B, which we established previously as biologically active constituents in Milk Thistle extract. Results showed that oral feeding of these flavonolignans (50 and 100 mg/kg body weight) effectively inhibit the growth of advanced human PCA DU145 xenografts. Immunohistochemical analyses revealed that these flavonolignans inhibit tumor angiogenesis biomarkers (CD31 and nestin) and signaling molecules regulating angiogenesis (VEGF, VEGFR1, VEGFR2, phospho-Akt and HIF-1α) without adversely affecting the vessel-count in normal tissues (liver, lung, and kidney) of tumor bearing mice. These flavonolignans also inhibited the microvessel sprouting from mouse dorsal aortas ex vivo, and the VEGF-induced cell proliferation, capillary-like tube formation and invasiveness of human umbilical vein endothelial cells (HUVEC) in vitro. Further studies in HUVEC showed that these diastereoisomers target cell cycle, apoptosis and VEGF-induced signaling cascade. Three dimensional growth assay as well as co-culture invasion and in vitro angiogenesis studies (with HUVEC and DU145 cells) suggested the differential effectiveness of the diastereoisomers toward PCA and endothelial cells. Overall, these studies elucidated the comparative anti-angiogenic efficacy of pure flavonolignans from Milk Thistle and suggest their usefulness in PCA angioprevention.
PLoS ONE 01/2012; 7(4):e34630. · 4.09 Impact Factor
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ABSTRACT: Better preventive strategies are required to reduce ultraviolet (UV)-caused photodamage, the primary etiological factor for non-melanoma skin cancer (NMSC). Accordingly, here we examined the preventive efficacy of silibinin against UVB-induced photodamage using mouse epidermal JB6 cells and SKH1 hairless mouse epidermis. In JB6 cells, silibinin pretreatment protected against apoptosis and accelerated the repair of cyclobutane pyrimidine dimers (CPD) induced by moderate dose of UVB (50 mJ/cm(2)), which we are at risk of daily exposure. Silibinin also reversed UVB-induced S phase arrest, reducing both active DNA synthesizing and inactive S phase populations. In mechanistic studies, UVB-irradiated cells showed a transient upregulation of both phosphorylated (Ser-15 and Ser-392) and total p53, whereas silibinin pretreatment led to a more sustained upregulation and stronger nuclear localization of p53. Silibinin also caused a marked upregulation of GADD45α, a downstream target of p53, implicated in DNA repair and cell cycle regulation. Importantly, under p53 and GADD45α knockdown conditions, cells were more susceptible to UVB-induced apoptosis without any significant S phase arrest, and protective effects of silibinin were compromised. Similar to the in vitro results, topical application of silibinin prior to or immediately after UVB irradiation resulted in sustained increase in p53 and GADD45α levels and accelerated CPD removal in the epidermis of SKH1 hairless mice. Together, our results show for the first time that p53-mediated GADD45α upregulation is the key mechanism by which silibinin protects against UVB-induced photodamage and provides a strong rationale to investigate silibinin in reducing the risk and/or preventing early onset of NMSC.
Carcinogenesis 12/2011; 33(3):629-36. · 5.70 Impact Factor
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ABSTRACT: For understanding of signaling molecules important in lung cancer growth and progression, IL-1beta effect was analyzed on iNOS expression and key signaling molecules in human lung carcinoma A549 cells and established the role of specific signaling molecules by using specific chemical inhibitors. IL-1beta exposure (10 ng/ml) induced strong iNOS expression in serum starved A549 cells. Detailed molecular analyses showed that IL-1beta increased expression of phosphorylated STAT1 (Tyr701 and Ser727) and STAT3 (Tyr705 and Ser727) both in total cell lysates and nuclear lysates. Further, IL-1beta exposure strongly activated MAPKs (ERK1/2, JNK1/2 and p38) and Akt as well as increased nuclear levels of NF-kappaB and HIF-1alpha in A549 cells. Use of specific chemical inhibitors for JAK1 kinase (piceatannol), JAK2 kinase (AG-490), MEK1/2 (PD98059) and JNK1/2 (SP600125) revealed that IL-1beta-induced iNOS expression involved signaling pathways in addition to JAK-STAT and ERK1/2-JNK1/2 activation. Overall, these results suggested that instead of specific pharmacological inhibitors, use of chemopreventive agents with broad spectrum efficacy to inhibit IL-1beta-induced signaling cascades and iNOS expression would be a better strategy towards lung cancer prevention and/or treatment.
Indian journal of experimental biology 11/2011; 49(11):840-7. · 1.29 Impact Factor
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ABSTRACT: The epithelial-to-mesenchymal transition (EMT) in prostate cancer (PCA) cells is considered prerequisite for acquiring migratory/invasive phenotype, and subsequent metastasis. We hypothesized that promoting the E-cadherin expression in PCA cells by using nontoxic phytochemicals, like silibinin, would prevent EMT and consequently invasiveness. Our results showed that silibinin treatment (5-90 μmol/L) significantly inhibits migratory and invasive potential of advance human PCA PC3, PC3MM2, and C4-2B cells in in vitro assays. Importantly, the antimigratory/antiinvasive efficacy of silibinin was not due to its cytotoxicity toward PCA cells. Molecular analyses showed that silibinin increases E-cadherin level that was localized mainly at cellular membrane as evidenced by subcellular fractional and confocal analyses in PC3 cells, which might be responsible for morphologically observed shift toward epithelial character. Silibinin also decreased the levels of Slug, Snail, phospho-Akt(ser(473)), nuclear β-catenin, phospho-Src(tyr(419)) and Hakai; together they play an important role in regulating E-cadherin expression/function and EMT. Similar silibinin effects on E-cadherin, β-catenin, phospho-Src(tyr(419)), and Hakai levels were also observed in PC3MM2 and C4-2B PCA cells. Selective Src inhibition by dasatinib also showed increased E-cadherin expression in PC3 cells suggesting a possible involvement of Src inhibition in silibinin-caused increase in E-cadherin level. Additional studies in PC3 cells with stable knock-down of E-cadherin expression revealed that antimigratory/antiinvasive efficacy of silibinin is in-part dependent on E-cadherin expression. Together, our results showing antimigratory/antiinvasive effects of silibinin and associated mechanisms suggest that silibinin should be tested further in clinically relevant animal models toward exploiting its potential benefits against metastatic PCA.
Cancer Prevention Research 05/2011; 4(8):1222-32. · 4.91 Impact Factor
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ABSTRACT: Malignant gliomas are one of the most devastating and incurable tumors. Sustained excessive angiogenesis by glioma cells is the major reason for their uncontrolled growth and resistance toward conventional therapies resulting in high mortality. Therefore, targeting angiogenesis should be a logical strategy to prevent or control glioma cell growth. Earlier studies have shown that Asiatic Acid (AsA), a pentacyclic triterpenoid, is effective against glioma and other cancer cells; however, its efficacy against angiogenesis remains unknown. In the present study, we examined the anti-angiogenic efficacy of AsA using human umbilical vein endothelial cells (HUVEC) and human brain microvascular endothelial cells (HBMEC). Our results showed that AsA (5-20 µM) inhibits HUVEC growth and induces apoptotic cell death by activating caspases (3 and 9) and modulating the expression of apoptosis regulators Bad, survivin and pAkt-ser473. Further, AsA showed a dose-dependent inhibition of HUVEC migration, invasion and capillary tube formation, and disintegrated preformed capillary network. AsA also inhibited the VEGF-stimulated growth and capillary tube formation by HUVEC and HBMEC. Next, we analyzed the angiogenic potential of conditioned media collected from human glioma LN18 and U87-MG cells treated with either DMSO (control conditioned media, CCM) or AsA 20 µM (AsA20 conditioned media, AsA20CM). CCM from glioma cells significantly enhanced the capillary tube formation in both HUVEC and HBMEC, while capillary tube formation in both endothelial cell lines was greatly compromised in the presence of AsA20CM. Consistent with these results, VEGF expression was lesser in AsA20CM compared to CCM, and indeed AsA strongly inhibited VEGF level (both cellular and secreted) in glioma cells. AsA also showed dose-dependent anti-angiogenic efficacy in Matrigel plug assay, and inhibited the glioma cells potential to attract HUVEC/HBMEC. Overall, the present study clearly showed the strong anti-angiogenic potential of AsA and suggests its usefulness against malignant gliomas.
PLoS ONE 01/2011; 6(8):e22745. · 4.09 Impact Factor
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ABSTRACT: Earlier, we reported the strong preventive efficacy of silibinin against colorectal cancer (CRC), but its usefulness against established CRC or effect of its withdrawal on CRC growth remained unknown. Present study focused on these important issues by employing two different treatment protocols in advanced human CRC SW480 xenograft in nude mice.
In the first treatment protocol, silibinin was fed for 28 days (200 mg/kg body weight, 5 days/week) to mice with growing SW480 xenograft; thereafter, tumor growth was monitored for additional 3 weeks without silibinin treatment. In the second protocol, silibinin treatment was started after 25 days of SW480 cells injection (established tumors), and tumor growth was studied 4 days, 8 days and 16 days after silibinin treatment.
In both treatment protocols, silibinin had strong and sustained inhibitory effect on xenograft growth. Detailed xenograft analyses showed that silibinin, in both treatment protocols, exerts anti-proliferative, pro-apoptotic and anti-angiogenic effects. Further, silibinin reduced the expression of β-catenin and phospho-GSK3β in xenograft tissues. Silibinin also targeted signaling molecules involved in CRC proliferation and survival (cyclin D1, c-Myc and survivin) as well as angiogenesis regulators (VEGF and iNOS).
Collectively, these findings substantiate silibinin's therapeutic efficacy against CRC, advocating its translational potential.
Pharmaceutical Research 10/2010; 27(10):2085-97. · 4.09 Impact Factor
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ABSTRACT: Prostate cancer (PCA) is the second most malignancy in American men. Advanced stage PCA cells possess unlimited replication potential as well as resistance to apoptosis. Therefore, targeting survival mechanisms and activating apoptotic machinery in PCA cells using nontoxic phytochemicals is suggested as an attractive strategy against this deadly malignancy. In the present study, we assessed the effect of one such botanical agent, namely isosilybin A, on apoptotic machinery and key members of cell survival signaling [Akt, NF-κB, and androgen receptor (AR)] in different PCA cells. Results showed that isosilybin A (90-180 µM) treatment significantly induces apoptotic death by activating both extrinsic (increased level of DR5 and cleaved caspase 8) and intrinsic pathways (caspase 9 and 3 activation) of apoptosis in three different human PCA cell lines namely 22Rv1, LAPC4, and LNCaP. Further, isosilybin A treatment decreased the levels of phospho-Akt (serine-473), total Akt, and the nuclear levels of NF-κB constituents (p50 and p65). Isosilybin A treatment also decreased the AR and PSA level in 22Rv1, LAPC4, and LNCaP cells. Employing pan-caspase inhibitor (Z-VAD.fmk), we confirmed that isosilybin A-mediated decreased AR is independent of caspases activation. Temporal kinetics analysis showed that the primary effect of isosilybin A is on AR, as decrease in AR was evident much earlier (4 h) relative to caspase activation and apoptosis induction (12 h). Overall, our results demonstrated that isosilybin A activates apoptotic machinery in PCA cells via targeting Akt-NF-κB-AR axis; thereby, indicating a promising role for this phytochemical in the management of clinical PCA.
Molecular Carcinogenesis 10/2010; 49(10):902-12. · 3.16 Impact Factor
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ABSTRACT: Cancer is a major health problem around the world. Research efforts in the last few decades have been successful in providing better and effective treatments against both early stage and localized cancer, but clinical options against advanced metastatic stage/s of cancer remain limited. The high morbidity and mortality in most of the cancers are attributed to their metastatic spread to distant organs. Due to its extreme clinical relevance, metastasis has been extensively studied and is now understood as a highly complex biological event that involves multiple steps including acquisition of invasiveness by cancer cells, intravasation into circulatory system, survival in the circulation, arrest in microvasculature, extravasation, and growth at distant organs. The increasing understanding of molecular underpinnings of these events has provided excellent opportunity to target metastasis especially through nontoxic and biologically effective nutraceuticals. Silibinin, a popular dietary supplement isolated from milk thistle seed extracts, is one such natural agent that has shown biological efficacy through pleiotropic mechanisms against a variety of cancers and is currently in clinical trials. Recent preclinical studies have also shown strong efficacy of silibinin to target cancer cell's migratory and invasive characteristics as well as their ability to metastasize to distant organs. Detailed mechanistic analyses revealed that silibinin targets signaling molecules involved in the regulation of epithelial-to-mesenchymal transition, proteases activation, adhesion, motility, invasiveness as well as the supportive tumor-microenvironment components, thereby inhibiting metastasis. Overall, the long history of human use, remarkable nontoxicity, and preclinical efficacy strongly favor the clinical use of silibinin against advanced metastatic cancers.
CANCER AND METASTASIS REVIEW 09/2010; 29(3):447-63. · 9.35 Impact Factor
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ABSTRACT: Colorectal cancer is one of the leading causes of cancer-related morbidity and mortality. The use of nontoxic phytochemicals in the prevention and intervention of colorectal cancer has been suggested as an alternative to chemotherapy. Here we assessed the anticancer efficacy of silibinin against advanced colorectal cancer LoVo cells both in vitro and in vivo. Our results showed that silibinin treatment strongly inhibits the growth of LoVo cells (P < 0.05-0.001) and induces apoptotic death (P < 0.01-0.001), which was associated with increased levels of cleaved caspases (3 and 9) and cleaved poly(ADP-ribose) polymerase. Additionally, silibinin caused a strong cell cycle arrest at G(1) phase and a slight but significant G(2)-M-phase arrest at highest concentration (P < 0.01-0.001). Molecular analyses for cell cycle regulators showed that silibinin decreases the level of cyclins (D1, D3, A and B1) and cyclin-dependent kinases (1, 2, 4, and 6) and increases the level of cyclin-dependent kinase inhibitors (p21 and p27). Consistent with these results, silibinin treatment also decreased the phosphorylation of retinoblastoma protein at Ser(780), Ser(795), and Ser(807)/Ser(811) sites without significantly affecting its total level. In animal studies, oral administration of silibinin for 6 weeks (at 100 and 200 mg/kg/d for 5 days/wk) significantly inhibited the growth of LoVo xenograft (P < 0.001) in athymic nude mice without any apparent toxicity. Analyses of xenograft tissue showed that silibinin treatment inhibits proliferation and increases apoptosis along with a strong increase in p27 levels but a decrease in retinoblastoma phosphorylation. Together, these results suggest the potential use of silibinin against advanced human colorectal cancer.
Molecular Cancer Therapeutics 07/2009; 8(8):2366-74. · 5.23 Impact Factor
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ABSTRACT: Silibinin is currently under phase II clinical trial in prostate cancer patients; however, its antitumor effects and mechanisms are not completely understood. Herein, we studied the efficacy and associated mechanisms of silibinin against orthotopically growing advanced human prostate carcinoma PC-3 tumors.
Athymic male mice were orthotopically implanted with PC-3 cells in prostate and 1 week later after surgical recovery were gavaged daily with silibinin (100 mg/kg body weight) for 7 weeks.
Silibinin treatment reduced the lower urogenital weight (including tumor, prostate, and seminal vesicle) by 40% (P < 0.05) without any toxicity in mice. Silibinin decreased proliferating cell nuclear antigen expression and proliferating cells (P < 0.001) but increased cleaved caspase-3-positive cells (P < 0.01) and apoptotic cells (P < 0.001) and suppressed tumor microvessel density (P < 0.001) and vascular endothelial growth factor expression (P = 0.02). Decreased levels of cyclin-dependent kinases 2, 4, and 6, CDC2, and cyclins D1, D3, E, and A were observed, indicating an inhibitory effect of silibinin on cell cycle progression. Silibinin showed a tremendous increase in extracellular signal-regulated kinase 1/2 phosphorylation but decreased c-Jun NH(2)-terminal kinase 1/2 and p38 mitogen-activated protein kinase phosphorylation. A moderate decrease in phosphorylated and total levels of Akt was also noted. A marked inhibitory effect of silibinin on signal transducers and activators of transcription (STAT) 1 (Tyr(701)), STAT1 (Ser(727)), STAT3 (Tyr(705)), STAT3 (Ser(727)), and STAT5 (Tyr(794)) phosphorylation together with a decrease in their total levels was also observed.
These findings provide evidence for antitumor efficacy of silibinin against orthotopically growing prostate tumor in mice with multitargeted mechanistic insights and support its clinical investigation in prostate cancer.
Clinical Cancer Research 01/2009; 15(2):613-21. · 7.74 Impact Factor
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Cancer Prevention Research 12/2008; 1(6):409-12. · 4.91 Impact Factor
