No full-text available
To read the full-text of this research,
you can request a copy directly from the authors.
Role of Breast Cancer Resistance Protein (BCRP, ABCG2) in Cancer Outcomes and Drug Resistance
Abstract
The breast cancer resistance protein (BCRP), formally known as ATP-binding cassette protein G2 (ABCG2), is an efflux transporter that plays a significant role in altering absorption, distribution, metabolism, and excretion (ADME) of most extant and emerging molecular cancer therapeutics. BCRP expressed by neoplastic cells may also contribute to the resistance of these cells to chemotherapeutic agents. Although the expression of BCRP in human cancers has often correlated with adverse outcomes, to date therapeutic strategies utilizing the inhibition of BCRP function to improve the ADME of cancer chemotherapeutics or to sensitize cancer cells that express BCRP to chemotherapy have not been fruitful. This review will examine the most current literature probing BCRP’s role in ADME of cancer therapeutic agents and drug resistance.
... In both situations, the hydrophilic parts protrude toward the bulk solution and protect the particles from interaction with the blood proteins (Blunk 1993). The term "steric stabilization" was introduced by Naper in 1983 (Naper 1983). The major work in this area has been done with liposomes. ...
... 2. A portion of the polymer should extend in the bulk aqueous medium, with optimal extensions and flexibility of the polymer segments that determines the dominance of steric repulsion over the van der Waals attractive forces. Therefore, block copolymers with hydrophilic and hydrophobic chains are more effective than homopolymers (Naper 1983). 3. The surface-modifying polymer should coat the surface completely; any incomplete coverage of the surface may leave it prone to opsonization. ...
... However, there are limited literature reports on the surface modification of nanoparticles using adsorption or incorporation of PEG within the polymer matrix. The other way to protect the surface is to graft a polymer chain onto the surface by covalent bonding to induce "steric stabilization" (Naper 1983). ...
In Chap. 10.1007/978-3-030-54490-4_14, electrospinning has been introduced as a strategy to manipulate the physical properties of a therapeutics-loaded system and to enhance the versatility of drug delivery. In the remaining chapters in Section V, the use of chemical means to manipulate the surface properties of a carrier for more effective systemic drug delivery will be discussed. As a matter of fact, a therapeutic agent must stay in the body as long as it is needed to reach the intended site of action in order to elicit a therapeutic response. To extend the blood retention time of an agent, one commonly used strategy is surface modification. In this chapter, we will first discuss the principles of clearance of particulate drug delivery systems from the body by the mononuclear phagocyte system (MPS), followed by a discussion of the possible use of polymers as modifiers of the surface properties of the particulate systems for enhanced performance in systemic drug delivery. Finally, the applications of surface-modified particulates in non-MPS targeting, including cancer chemotherapy and delivery across the blood–brain barrier, will also be discussed.
... CD133 + cells have certain characteristics of bladder cancer stem cells [15], and the expression of CD133 in tumors has been significantly correlated with urothelial carcinoma grade and stage [16]. Additionally, different stem-like markers and drug-resistant genes, such as OCT-4, SOX2 and ATP Binding Cassette Subfamily G Member 2 (ABCG2), are closely related to spheroid-forming ability and impact bladder tumor formation [17][18][19]. ...
Background
Cancer stem-like capacities are major factors contributing to unfavorable prognosis. However, the associated molecular mechanisms underlying cancer stem-like cells (CSCs) maintain remain unclear. This study aimed to investigate the role of the ubiquitin E3 ligase membrane-associated RING-CH 7 (MARCH7) in bladder cancer cell CSCs.
Methods
Male BALB/c nude mice aged 4–5 weeks were utilized to generate bladder xenograft model. The expression levels of MARCHs were checked in online databases and our collected bladder tumors by quantitative real-time PCR (q-PCR) and immunohistochemistry (IHC). Next, we evaluated the stem-like capacities of bladder cancer cells with knockdown or overexpression of MARCH7 by assessing their spheroid-forming ability and spheroid size. Additionally, we conducted proliferation, colony formation, and transwell assays to validate the effects of MARCH7 on bladder cancer CSCs. The detailed molecular mechanism of MARCH7/NOD1 was validated by immunoprecipitation, dual luciferase, and in vitro ubiquitination assays. Co-immunoprecipitation experiments revealed that nucleotide-binding oligomerization domain-containing 1 (NOD1) is a substrate of MARCH7.
Results
We found that MARCH7 interacts with NOD1, leading to the ubiquitin–proteasome degradation of NOD1. Furthermore, our data suggest that NOD1 significantly enhances stem-like capacities such as proliferation and invasion abilities. The overexpressed MARCH7 counteracts the effects of NOD1 on bladder cancer CSCs in both in vivo and in vitro models.
Conclusion
Our findings indicate that MARCH7 functions as a tumor suppressor and inhibits the stem-like capacities of bladder tumor cells by promoting the ubiquitin–proteasome degradation of NOD1. Targeting the MARCH7/NOD1 pathway could be a promising therapeutic strategy for bladder cancer patients.
... ABC transporters influence the effectiveness of cytotoxic compounds, since ABC transporter overexpression is associated with multidrug resistance (MDR) in cancer cells, which leads to chemotherapy failure [1]. The expression of P-glycoprotein and other ABC transporters has been demonstrated in many cancer types, and high ABC-transporter expression was linked to shorter survival of patients [2][3][4]. The advent of RNA-sequencing and other genome-and transcriptome-wide techniques re-opened new avenues to address this important question in a more comprising fashion than ever before. ...
ATP-binding cassette (ABC) transporters mediate multidrug resistance in cancer. In contrast to DNA single nucleotide polymorphisms in normal tissues, the role of mutations in tumors is unknown. Furthermore, the significance of their expression for prediction of chemoresistance and survival prognosis is still under debate.
We investigated 18 tumors by RNA-sequencing. The mutation rate varied from 27,507 to 300885. In ABCB1, three hotspots with novel mutations were in transmembrane domains 3, 8, and 9. We also mined the cBioPortal database with 11,814 patients from 23 different tumor entities. We performed Kaplan-Meier survival analyses to investigate the effect of ABC transporter expression on survival rates of cancer patients.
Novel mutations were also found in ABCA2, ABCA3, ABCB2, ABCB5, ABCC1-6, and ABCG2. Mining the cBioPortal database with 11,814 patients from 23 different tumor entities validated our results. Missense and in-frame mutations led to altered binding of anticancer drugs in molecular docking approaches. The ABCB1 nonsense mutation Q856* led to a truncated P-glycoprotein, which may sensitize tumors to anticancer drugs. The search for ABC transporter nonsense mutations represents a novel approach for precision medicine..
Low ABCB1 mRNA expression correlated with significantly longer survival in ovarian or kidney cancer and thymoma. In cancers of breast, kidney or lung, ABC transporter expression correlated with different tumor stages and human populations as further parameters to refine strategies for more individualized chemotherapy.
... BCRP is named after its first detection in breast cancer, but later it turned out that it can be expressed in many other tumor types as well. The clinical relevance of BCRP expression regarding response to therapy and survival prognosis in gastrointestinal tumors, breast cancer, lung cancer, head and neck cancer, ovarian cancer, prostate cancer, glioblastoma, leukemia and others has Mahmoud et al. (2018) been reviewed (Natarajan et al. 2015;Nielsen et al. 2017;Hira and Terada 2018). Like BCRP/ABCG2, ABCB5 is a half-transporter that needs to dimerize to constitute functional units. ...
Multidrug resistance is a major factor causing the failure of cancer chemotherapy. Efflux pumps of the ATP-binding cassette (ABC) transporter family expel a large array of diverse anticancer drugs out of tumor cells thereby rendering them unresponsive to drug treatment. During the past 2 decades, we focused on three ABC transporters, i.e. P-glycoprotein (MDR1/ABCB1), breast cancer resistance protein (BCRP/ABCG2), and ABCB5 with the aim to find natural products with activity against multidrug-resistant cells. We investigated more than 102 cytotoxic medicinal plants and more than 228 isolated cytotoxic phytochemicals with defined chemical structures from 16 countries in Africa, Near East, Asia, and Europe for their activity to kill multidrug-resistant cells. A synopsis of these results is given in this review article. ABCB1-, ABCG2- or ABCB5-expressing cells were moderately or strongly cross-resistant to a considerable portion of plant extracts or phytochemicals, making them less suitable for the treatment of multidrug resistant tumors. While another large portion of compounds inhibited sensitive and multidrug-resistant cells with similar efficacy, a small fraction of medicinal plants and phytochemicals (3–8%) suppressed multidrug-resistant cells with even much better efficacy as their drug-sensitive counterparts. This hypersensitivity phenomenon is termed “collateral sensitivity”. These compounds may be exquisitely suited to kill otherwise resistant and refractory tumors. Molecular modes of action of collateral sensitivity as well as possibilities for further drug development, chemical derivatization of natural lead compounds and rationale phytotherapy are discussed.
... ABC transporter overexpression is associated with multidrug resistance (MDR) in cancer cells, possibly leading to chemotherapy failure [1]. The overexpression of ABC transporters is also associated with shorter survival rates of cancer patients [2][3][4]. RNA-sequencing and other genome-and transcriptome-wide techniques paved the way to address the MDR phenomenon and the corresponding influence of ABC transporters in a more comprehensive fashion. ...
The efficiency of chemotherapy drugs can be affected by ATP-binding cassette (ABC) transporter expression or by their mutation status. Multidrug resistance is linked with ABC transporter overexpression. In the present study, we performed rare mutation analyses for 12 ABC transporters related to drug resistance (ABCA2, -A3, -B1, -B2, -B5, -C1, -C2, -C3, -C4, -C5, -C6, -G2) in a dataset of 18 cancer patients. We focused on rare mutations resembling tumor heterogeneity of ABC transporters in small tumor subpopulations. Novel rare mutations were found in ABCC1, but not in the other ABC transporters investigated. Diverse ABCC1 mutations were found, including nonsense mutations causing premature stop codons, and compared with the wild-type protein in terms of their protein structure. Nonsense mutations lead to truncated protein structures. Molecular docking and heat map analyses of ABCC1/MRP1 pointed out that Lys498* appeared in a separate cluster branch due to the large deletion, leading to a massive disruption in the protein conformation. The resulting proteins, which are nonfunctional due to nonsense mutations in tumors, offer a promising chemotherapy strategy since tumors with nonsense mutations may be more sensitive to anticancer drugs than wild-type ABCC1-expressing tumors. This could provide a novel tumor-specific toxicity strategy and a way to overcome drug resistance.
... This leads to the failure of chemotherapy with fatal consequences for cancer patients. The expression of P-gp and other ABC transporters has been demonstrated in many cancer types and high ABC-transporter expression in linked to the shorter survival of patients Roundhill et al., 2015;Natarajan et al., 2015). As ABC transporter expression is a negative prognostic marker for treatment outcome, they are of high clinical relevance . ...
Cancer chemotherapy is frequently hampered by drug resistance. Concepts to combine anticancer drugs with different modes of action to avoid the development of resistance did not provide the expected success in the past, because tumors can be simultaneously non-responsive to many drugs (e.g. the multidrug resistance phenotype). However, tumors may be specifically hypersensitive to other drugs – a phenomenon also termed collateral sensitivity. This seems to be a general biological mechanism, since it also occurs in drug-resistant Escherichia coli and Saccharomyces cerevisiae.
Here, we give a timely and comprehensive overview on hypersensitivity in resistant cancer cells towards natural products and their derivatives. Since the majority of clinically established anticancer drugs are natural products or are in one way or another derived from them, it is worth hypothesizing that natural products may deliver promising lead compounds for the development of collateral sensitive anticancer drugs.
Hypersensitivity occurs not only in classical ABC transporter-mediated multidrug resistance, but also in many other resistance phenotypes. Resistant cancers can be hypersensitive to natural compounds from diverse classes and origins (i.e. mitotic spindle poisons, DNA topoisomerase 1 and 2 inhibitors, diverse phytochemicals isolated from medicinal plants, (semi)synthetic derivatives of phytochemicals, antibiotics, marine drugs, recombinant therapeutic proteins and others).
Molecular mechanisms of collateral sensitivity include (1) increased ATP hydrolysis and reactive oxygen species production by futile cycling during ABC transporter-mediated drug efflux, (2) inhibition of ATP production, and (3) alterations of drug target proteins (e.g. increased expression of topoisomerases and heat shock proteins, inhibition of Wnt/β-catenin pathway, mutations in β-tubulin).
The phenomenon of hypersensitivity needs to be exploited for clinical oncology by the development of (1) novel combination protocols that include collateral sensitive drugs and (2) novel drugs that specifically exhibit high degrees of hypersensitivity in resistant tumors.
... Some of the commonly used PCSCs surface markers include CD44, CD133, α 2 β 1 integrin and ALDH1, among others [15]. [30,31]. Some natural phytochemical compounds, such as metformin, genistein, salinomycin, curcumin, vitamin D and sulforaphane have shown promise against PCSCs [32][33][34][35]. ...
The importance of prostate cancer stemness in prostate tumor recurrence and mortality cannot be overemphasized and shouldn't be trivialized. Intra-tumoral heterogeneity complicated by the presence and enrichment for prostate cancer stem cell (PCSC) population in prostate cancer (PCa) patient or survivors have been implicated in the initiation, progression, aggressiveness, metastasis, treatment failures and recurrence of the disease. More studies are needed to bring clarity to the molecular mechanisms of PCa stem-ness and its role in the development of castration-resistant PCa. In addition, selective and effective therapies are needed to target PCSCs to prevent PCa aggressiveness and recurrence. An overview of the role and molecular mechanisms of PCSCs, as well as some currently proposed diagnostic, prognostic and therapeutic methods for eradicating PCSCs to prevent PCa recurrence and psychological 'fear of recurrence', have been discussed and summarized.
Keywords: Prostate Cancer Stem Cells; Cancer Recurrence; Fear of Cancer Recurrence; Cancer Stemness; Castration-resistant Prostate
Cancer
Background: Carnosic acid (CA) is one of the main constituents in rosemary extract. It possesses valuable pharmacological properties, including anti-oxidant, anti-inflammatory, anti-microbial and anti-cancer activities. Numerous in vitro and in vivo studies investigated the anticancer profile of CA and emphasized its potentiality for cancer treatment. Nevertheless, the role of multidrug-resistance (MDR) related mechanisms for CA's anticancer effect is not yet known.
Purpose: We investigated the cytotoxicity of CA against known mechanisms of anticancer drug resistance (P-gp, ABCB5, BCRP, EGFR and p53) and determined novel putative molecular factors associated with cellular response towards CA.
Study design: Cytotoxicity assays, bioinformatic analysis, flow cytometry and western blotting were performed to identify the mode of action of CA towards cancer cells.
Methods: The cytotoxicity to CA was assessed using the resazurin assays in cell lines expressing the mentioned resistance mechanisms. A pharmacogenomic characterization of the NCI 60 cell line panel was applied via COMPARE, hierarchical cluster and network analyses. Flow cytometry was used to detect cellular mode of death and ROS generation. Changes in proteins-related to apoptosis were determined by Western blotting.
Results: Cell lines expressing ABC transporters (P-gp, BCRP or ABCB5), mutant EGFR or p53 were not cross-resistant to CA compared to their parental counterparts. By pharmacogenomic approaches, we identified genes that belong to different functional groups (e.g. signal transduction, regulation of cytoskeleton and developmental regulatory system). These genes were predicted as molecular determinants that mediate CA tumor cellular responses. The top affected biofunctions included cellular development, cellular proliferation and cellular death and survival. The effect of CA-mediated apoptosis in leukemia cells, which were recognized as the most sensitive tumor type, was confirmed via flow cytometry and western blot analysis.
Conclusion: CA may provide a novel treatment option to target refractory tumors and to effectively cooperate with established chemotherapy. Using pharmacogenomic approaches and network pharmacology, the relationship between cancer complexity and multi-target potentials of CA was analyzed and many putative molecular determinants were identified. They could serve as novel targets for CA and further studies are needed to translate the possible implications to clinical cancer treatment.
Little is known about the optimal clinical use of ABT-888 (veliparib) for treatment of glioblastoma. ABT-888 is a PARP inhibitor undergoing extensive clinical evaluation in glioblastoma, because it may synergize with the standard-of-care temozolomide (TMZ). We have elucidated important factors controlling ABT-888 efficacy in glioblastoma. Experimental design: We used genetically engineered spontaneous glioblastoma mouse models and allograft models that were orthotopically transplanted into wildtype (WT) and Abcb1/Abcg2 deficient (KO) recipients.
ABT-888/TMZ is not efficacious against p53;p16Ink4a/p19Arf;K Rasv12;LucR allografts in WT recipients, indicating inherent resistance. Abcb1/Abcg2 mediated efflux of ABT-888 at the blood-brain barrier (BBB) causes a 5-fold reduction of ABT-888 brain penetration (p<0.0001) that was fully reversible by elacridar. Efficacy studies in WT and KO recipients and/or concomitant elacridar demonstrate that Abcb1/Abcg2 at the BBB and in tumor cells impair TMZ/ABT-888 combination treatment efficacy. Elacridar also markedly improved TMZ/ABT-888 combination treatment in the spontaneous p53;p16Ink4a/p19Arf;K-Rasv12;LucR glioblastoma model. Importantly, ABT-888 does enhance TMZ efficacy in Pten deficient glioblastoma allografts and spontaneous tumors, even in Abcb1/Abcg2 proficient WT mice. Loss of PTEN occurs frequently in glioblastoma (36%) and in silico analysis on glioblastoma patient samples revealed that it is associated with a worse overall survival (310 days vs. 620 days, n=117).
The potential of ABT-888 in glioblastoma can best be demonstrated in patients with PTEN null tumors. Therefore, clinical trials with ABT-888 should evaluate these patients as a separate group. Importantly, inhibition of ABCB1 and ABCG2 (by elacridar) may improve the efficacy of TMZ/ABT-888 therapy in all glioblastoma patients.
A small population of cancer stem cells named the "side population" (SP) has been demonstrated to be responsible for the persistence of many solid tumors. However, the role of the SP in leukemic pathogenesis remains controversial. The resistance of leukemic stem cells to targeted therapies, such as tyrosine kinase inhibitors (TKIs), results in therapeutic failure or refractory/relapsed disease in chronic myeloid leukemia (CML). The drug pump, ATP-binding cassette sub-family G member 2 (ABCG2), is well known as a specific marker of the SP and could be controlled by several pathways, including the PI3K/Akt pathway. Our data demonstrated that compared with wild-type K562 cells, the higher percentage of ABCG2+ cells corresponded to the higher SP fraction in K562/ABCG2 (ABCG2 overexpressing) and K562/IMR (resistance to imatinib) cells, which exhibited enhanced drug resistance along with downregulated phosphatase and tensin homologue deleted on chromosome -10 (PTEN) and activated phosphorylated-Akt (p-Akt). PTEN and p-Akt downregulation could be abrogated by both the PI3K inhibitor LY294002 and the mTOR inhibitor rapamycin. Moreover, in CML patients in the accelerated phase/blastic phase (AP/BP), increased SP phenotype rather than ABCG2 expression was accompanied by the loss of PTEN protein and the up-regulation of p-Akt expression. These results suggested that the expression of ABCG2 and the SP may be regulated by PTEN through the PI3K/Akt pathway, which would be a potentially effective strategy for targeting CML stem cells.
Genistein, the predominant isoflavone found in soy products, has exerted its anticarcinogenic effect in many different tumor types in vitro and in vivo. Accumulating evidence in recent years has strongly indicated the existence of cancer stem cells in gastric cancer. Here, we showed that low doses of genistein (15 µM), extracted from Millettia nitida Benth var hirsutissima Z Wei, inhibit tumor cell self-renewal in two types of gastric cancer cells by colony formation assay and tumor sphere formation assay. Treatment of gastric cancer cells with genistein reduced its chemoresistance to 5-Fu (fluorouracil) and ciplatin. Further results indicated that the reduced chemoresistance may be associated with the inhibition of ABCG2 expression and ERK 1/2 activity. Furthermore, genistein reduced tumor mass in the xenograft model. Together, genistein inhibited gastric cancer stem cell-like properties and reduced its chemoresistance. Our results provide a further rationale and experimental basis for using the genistein to improve treatment of patients with gastric cancer.
The protein kinase C δ interacts and phosphorylates HuR, dictating its functionality. We show here that the genotoxic stimulus induced by doxorubicin triggers PKCδ interaction with HuR and leads to HuR phosphorylation on serine 221 and 318 and cytoplasmic translocation. This series of events is crucial to elicit the death pathway triggered by doxorubicin and is also necessary to promote HuR function in post-transcriptional regulation of gene expression, since genetic ablation of PKCδ brought to HuR inability to bind its target mRNAs, TOP2A included. In in vitro selected doxorubicin resistant human breast cancer cell lines upregulating the multidrug resistance marker ABCG2, PKCδ and HuR proteins were coordinately downregulated together with the doxorubicin target TOP2A protein, whose mRNA is HuR-regulated. Therefore, we show here that PKCδ, HuR and TOP2A constitute a network mediating doxorubicin efficacy in breast cancer cells. The importance of these molecular events in cancer therapy is suggested by their being profoundly suppressed in cells selected for doxorubicin resistance.
Imatinib mesylate (IM) has become a standard of care in chronic myeloid leukemia (CML) therapy. Single nucleotide polymorphisms (SNPs) and altered expression in drug transporter genes may influence IM response. In order to investigate whether mRNA expression and SNPs in drug transporters are associated with IM resistance, we studied 118 chronic-phase CML patients receiving the standard dose of IM (400 mg/day). They were assigned as responders and non-responders according to European LeukemiaNet criteria (2009). mRNA expression in samples at diagnosis (without IM therapy) and outcomes after IM failure were also evaluated in subgroups of patients. Major molecular response (MMR), complete molecular response and primary and secondary resistance were all assessed. BCR-ABL1, ABCB1, ABCG2, SLC22A1 and SLCO1A2 mRNA expression and SNPs in ABCG2 and SLC22A1 genes were analyzed. ABCG2 mRNA expression in the non-responders was higher before and during IM therapy. Furthermore, ABCG2 was overexpressed in those who did not achieve MMR (P = 0.027). In a subgroup of patients who switched to second-generation tyrosine kinase inhibitors, high mRNA expression of ABCG2 was associated with a risk of 24 times that of not achieving complete cytogenetic response (OR 24.00, 95 % CI 1.74-330.80; P = 0.018). In the responder group, patients who achieved MMR (P = 0.009) presented higher mRNA levels of SLC22A1. The SNPs were not associated with mRNA expression of ABCG2 and SLC22A1. Our data suggest that elevated ABCG2 expression (an efflux transporter) could be associated with IM resistance and could impact on second-generation TKI response, whereas high SLC22A1 expression (an influx transporter) may be associated with a successful IM therapy in CML patients.
Either oxaliplatin- or irinotecan-containing regimen could receive a good effectiveness in patients with metastatic colorectal cancer as the first-line chemotherapy, but not all patients would benefit from the treatment they have received. This study was to investigate the role of single nucleotide polymorphisms (SNPs) of methylenetetrahydrofolate reductase (MTHFR) and ATP-binding cassette sub-family G member 2 (ABCG2) in selecting the most appropriate treatment for individual patients. Ninety-two metastatic colorectal cancer patients treated with first-line 5-fluoropyrimidine (5-FU), leucovorin, and oxaliplatin (FOLFOX), capecitabine, and oxaliplatin (XELOX) and sixty-two patients receiving 5-FU, leucovorin, and irinotecan (FOLFIRI) were reviewed. The SNPs of MTHFR and ABCG2 were detected using gene sequencing method after DNA PCR amplification, which was extracted from peripheral blood karyocytes. Clinical characteristics and gene polymorphisms were evaluated in univariate and multivariate analysis as predictive factors for response rate (RR) and progression-free survival (PFS). In patients bearing 2-4 genotypes of MTHFR 677C/C, MTHFR 1298 A/C or C/C, ABCG2 34G/G, and ABCG2 421C/A or A/A, those who received oxaliplatin-based chemotherapy achieved a higher RR (41.7 vs. 18.8 %, P = 0.027) and longer median PFS (mPFS) than irinotecan-based therapy [8.9 vs. 7.1 m, FOLFIRI: hazard ratio (HR) = 1.722, 95 % confidence interval (CI) 1.026-2.892, P = 0.040, compared with FOLFOX/XELOX]; on the contrary, patients carrying 0 or 1 above genotype exhibited better outcomes after receiving FOLFIRI chemotherapy (mPFS: 9.3 vs. 6.4 m, FOLFIRI: HR = 0.422, 95 % CI 0.205-0.870, P = 0.019, compared with FOLFOX/XELOX). Combination of SNPs with MTHFR and ABCG2 may play a role in helping clinicians to select first-line chemotherapy for patients with metastatic colorectal cancer.
In mammals, excess purine nucleosides are removed from the body by breakdown in the liver and excretion from the kidneys. Uric acid is the end product of purine metabolism in humans. Two-thirds of uric acid in the human body is normally excreted through the kidney, whereas one-third undergoes uricolysis (decomposition of uric acid) in the gut. Elevated serum uric acid levels result in gout and could be a risk factor for cardiovascular disease and diabetes. Recent studies have shown that human ATP-binding cassette transporter ABCG2 plays a role of renal excretion of uric acid. Two non-synonymous single nucleotide polymorphisms (SNPs), i.e., 421C>A (major) and 376C>T (minor), in the ABCG2 gene result in impaired transport activity, owing to ubiquitination-mediated proteosomal degradation and truncation of ABCG2, respectively. These genetic polymorphisms are associated with hyperuricemia and gout. Allele frequencies of those SNPs are significantly higher in Asian populations than they are in African and Caucasian populations. A rapid and isothermal genotyping method has been developed to detect the SNP 421C>A, where one drop of peripheral blood is sufficient for the detection. Development of simple genotyping methods would serve to improve prevention and early therapeutic intervention for high-risk individuals in personalized healthcare.
Pharmacogenetic studies in chronic myelogenous leukemia (CML) typically use a candidate gene approach. In an alternative strategy, we analyzed the impact of single nucleotide polymorphisms (SNPs) in drug transporter genes on the molecular response to imatinib, using a DNA chip containing 857 SNPs covering 94 drug transporter genes. Two cohorts of CML patients treated with imatinib were evaluated: an exploratory cohort including 105 patients treated at 400 mg/d and a validation cohort including patients sampled from the 400 mg/d and 600 mg/d arms of the prospective SPIRIT trial (n=239). Twelve SNPs discriminating patients according to cumulative incidence of major molecular response (CI-MMR) were identified within the exploratory cohort. Three of them, all located within the ABCG2 gene, were validated in patients included in the 400 mg/d arm of the SPIRIT trial. We identified an ABCG2 haplotype (define as G-G, rs12505410 and rs2725252) as associated with significantly higher CI-MMR in patients treated at 400 mg/d. Interestingly, we found that patients carrying this ABCG2 "favorable" haplotype in the 400 mg arm reached similar CI-MMR rates that patients randomized in the imatinib 600 mg/d arm. Our results suggest that response to imatinib may be influenced by constitutive haplotypes in drug transporter genes. Lower response rates associated with "non- favorable" ABCG2 haplotypes may be overcome by increasing the imatinib daily dose up to 600 mg/d.
Purine cyclin-dependent kinase inhibitors have been recognized as promising candidates for the treatment of various cancers; nevertheless, data regarding interaction of these substances with drug efflux transporters is still lacking. Recently, we have demonstrated inhibition of breast cancer resistance protein (ABCG2) by olomoucine II and purvalanol A and shown that these compounds are able to synergistically potentiate the antiproliferative effect of mitoxantrone, an ABCG2 substrate. In this follow up study, we investigated whether olomoucine II and purvalanol A are transported by ABCG2 and ABCB1 (P-glycoprotein). Using monolayers of MDCKII cells stably expressing human ABCB1 or ABCG2, we demonstrated that olomoucine II, but not purvalanol A, is a dual substrate of both ABCG2 and ABCB1. We, therefore, assume that pharmacokinetics of olomoucine II will be affected by both ABCB1 and ABCG2 transport proteins, which might potentially result in limited accumulation of the compound in tumor tissues or lead to drug-drug interactions. Pharmacokinetic behavior of purvalanol A, on the other hand, does not seem to be affected by either ABCG2 or ABCB1, theoretically favoring this drug in the potential treatment of efflux transporter-based multidrug resistant tumors. In addition, we observed intensive sulfatation of olomoucine II in MDCKII cell lines with subsequent active efflux of the metabolite out of the cells. Therefore, care should be taken when performing pharmacokinetic studies in MDCKII cells, especially if radiolabeled substrates are used; the generated sulfated conjugate may largely contaminate pharmacokinetic analysis and result in misleading interpretation. With regard to chemical structures of olomoucine II and purvalanol A, our data emphasize that even drugs with remarkable structure similarity may show different pharmacokinetic behavior such as interactions with ABC transporters or biotransformation enzymes.
The efflux transporters ABCB1 and ABCG2 have been demonstrated to interact with tyrosine kinase inhibitors (TKIs) imatinib, nilotinib and dasatinib. However, while some studies conclude that TKIs are substrates of one or both transporters, other studies demonstrate only an inhibitory function. This variation is likely due to differences in the concentration of TKIs assayed and experimental systems utilised. This article examines the evidence for clinically relevant interactions between three currently approved TKIs, and ABCB1/ABCG2.Clinical Pharmacology & Therapeutics (2013); accepted article preview online 9 October 2013 doi:10.1038/clpt.2013.208.
The aim of this study was to investigate the pharmacogenetic determinants of sunitinib-related toxicity and ethnic difference in metastatic renal cell carcinoma (mRCC) among Korean patients.
A pharmacogenetic study was performed in 65 patients with mRCC treated with the standard schedule of sunitinib (50 mg orally once daily for 4 weeks-on/2 weeks-off). Detailed data regarding the toxicity of sunitinib, including thrombocytopenia, neutropenia, anemia, and hand-foot syndrome (HFS), were prospectively collected in a clinical trial program (n = 38) or standard oncology practice (n = 27). Total of 12 genetic polymorphisms in 8 candidate genes (CYP1A1, CYP3A5, ABCB1, ABCG2, PDGFRα, VEGFR2, RET, and FLT3) were analyzed for an association with treatment-related toxicity from sunitinib using Pearson χ (2) test.
Common grade 3 or grade 4 treatment-related toxicities were thrombocytopenia (36.9 %, 24/65), neutropenia (18.4 %, 12/65), anemia (7.7 %, 5/65), and HFS (12.3 %, 8/65). Patients carrying an ABCG2 421 AA genotype developed significantly more grade 3 or grade 4 thrombocytopenia, neutropenia, and HFS adjusted for age, sex, and Eastern Cooperative Oncology Group performance status, and body surface area (odds ratio compared with AC/CC genotypes [OR] 9.90, P = 0.04, thrombocytopenia; OR 18.20, P = 0.02, neutropenia; and OR 28.46, P = 0.01, HFS). In addition, total and surface protein ABCG2 protein expression was decreased in ABCG2 421 AA mutant cells compared to wild type.
Among 12 genetic polymorphisms, polymorphism in the ABCG2 421C>A gene may be mostly associated with the risk of sunitinib-related toxicity in mRCC patients. Considering the high frequency of 421C>A SNP in Asian, this may be related to differential toxicities among ethnic groups.
ABCG2 is a member of the ATP binding cassette (ABC) transmembrane proteins that plays an important role in stem cell biology and drug resistance of cancer cells. In this study, we investigated how expression of human ABCG2 gene is regulated in lung cancer A549 cells. Binding of Sp1 and Sp3 transcription factors to the ABCG2 promoter in vitro and in vivo was elucidated by electrophoretic mobility shift assay and chromatin immunoprecipitation assay. The ABCG2 promoter activity was impaired when Sp1 sites were mutated but was enhanced by over-expression of Sp1 or Sp3 proteins. Knockdown of Sp1 or Sp3 expression by short interfering RNA significantly decreased the expression of ABCG2 mRNA and protein, resulting in attenuated formation of the side population in A549 cells. In addition, Sp1 inhibition in vivo by mithramycin A suppressed the percentage of the side population fraction and sphere forming activities of A549 cells. Moreover, inhibiting Sp1- or Sp3-dependent ABCG2 expression caused chemosensitization to the anticancer drug cisplatin. Collectively, our results demonstrate that Sp1 and Sp3 transcription factors are the primary determinants for activating basal transcription of the ABCG2 gene and play an important role in maintaining the side population phenotype of lung cancer cells.
The overexpression of the serine/threonine specific polo-like kinase 1 (Plk1) has been detected in various types of cancer, and thus has fast become an attractive therapeutic target for cancer therapy. BI 2536 is the first selective inhibitor of Plk1 that inhibits cancer cell proliferation by promoting G2/M cell cycle arrest at nanomolar concentrations. Unfortunately, alike most chemotherapeutic agents, the development of acquired resistance to BI 2536 is prone to present a significant therapeutic challenge. One of the most common mechanisms for acquired resistance in cancer chemotherapy is associated with the overexpression of ATP-binding cassette (ABC) transporters ABCB1, ABCC1 and ABCG2. Here, we discovered that overexpressing of either ABCB1 or ABCG2 is a novel mechanism of acquired resistance to BI 2536 in human cancer cells. Moreover, BI 2536 stimulates the ATPase activity of both ABCB1 and ABCG2 in a concentration-dependent manner, and inhibits the drug substrate transport mediated by these transporters. More significantly, the reduced chemosensitivity and BI 2536-mediated G2/M cell cycle arrest in cancer cells overexpressing either ABCB1 or ABCG2 can be significantly restored in the presence of selective inhibitor or other chemotherapeutic agents that also interact with ABCB1 and ABCG2, such as tyrosine kinase inhibitors nilotinib and lapatinib. Taken together, our findings indicate that in order to circumvent ABCB1 or ABCG2-mediated acquired resistance to BI 2536, a combined regimen of BI 2536 and inhibitors or clinically active drugs that potently inhibit the function of ABC drug transporters, should be considered as a potential treatment strategy in the clinic.
The oral second-generation bis-aryl urea fms-like tyrosine kinase 3 (FLT3) inhibitor quizartinib (AC220) has favorable kinase selectivity and pharmacokinetics. It inhibits mutant and wild-type FLT3 in vivo at 0.1 and 0.5 µM, respectively, and has shown favorable activity and tolerability in phase I and II trials in acute myeloid leukemia, with QT prolongation as the dose-limiting toxicity. Co-administration with chemotherapy is planned. We characterized interactions of quizartinib with the ATP-binding cassette (ABC) proteins ABCB1 (P-glycoprotein) and ABCG2 (breast cancer resistance protein). Its effects on uptake of fluorescent substrates and apoptosis were measured by flow cytometry, binding to ABCB1 and ABCG2 drug-binding sites by effects on [(125)I]iodoarylazidoprazosin ([(125)I]-IAAP) photolabeling and ATPase activity, and cell viability by the WST-1 colorimetric assay. Quizartinib inhibited transport of fluorescent ABCG2 and ABCB1 substrates in ABCG2- and ABCB1-overexpressing cells in a concentration-dependent manner, from 0.1 to 5 µM and from 0.5 to 10 µM, respectively, and inhibited [(125)I]-IAAP photolabeling of ABCG2 and ABCB1 with IC50 values of 0.07 and 3.3 µM, respectively. Quizartinib at higher concentrations decreased ABCG2, but not ABCB1, ATPase activity. Co-incubation with quizartinib at 0.1 to 1 µM sensitized ABCG2-overexpressing K562/ABCG2 and 8226/MR20 cells to ABCG2 substrate chemotherapy drugs in a concentration-dependent manner in cell viability and apoptosis assays. Additionally, quizartinib increased cellular uptake of the ABCG2 substrate fluoroquinolone antibiotic ciprofloxacin, which also prolongs the QT interval, in a concentration-dependent manner, predicting altered ciprofloxacin pharmacokinetics and pharmacodynamics when co-administered with quizartinib. Thus quizartinib inhibits ABCG2 at pharmacologically relevant concentrations, with implications for both chemosensitization and adverse drug interactions. These interactions should be considered in the design of treatment regimens combining quizartinib and chemotherapy drugs and in choice of concomitant medications to be administered with quizartinib.
This Commentary focuses on genetic polymorphisms in membrane transporters. We present two polymorphisms for which there is a compelling body of literature supporting their clinical relevance: OATP1B1 (c.521T>C, p.V174A, rs4149056) and BCRP (c.421C>A, p.Q141K, rs2231142). The clinical evidence demonstrating their role in variation in pharmacokinetics and pharmacodynamics is described along with their allele frequencies in ethnic populations. Recommendations for incorporating studies of transporter polymorphisms in drug development are provided, along with the regulatory implications.
Achievement of complete molecular response in chronic phase chronic myeloid leukemia patients has been recognized as an important milestone in therapy cessation and treatment-free remission; therefore, the identification of predictors of complete molecular response in these patients is important. This study evaluated complete molecular response rates in imatinib-treated chronic phase chronic myeloid leukemia patients with major molecular response by using the international standardization for breakpoint cluster region-Abelson1 quantitative polymerase chain reaction. The correlation of complete molecular response with various clinical, pharmacokinetic, and immunological parameters was determined. Complete molecular response was observed in 75/152 patients (49.3%). In the univariate analysis, Sokal score, median time to major molecular response, ABCG2 421C>A, and regulatory T cells were significantly lower in chronic phase chronic myeloid leukemia patients with complete molecular response than in those without complete molecular response. In the multivariate analysis, duration of imatinib treatment (odds ratio: 1.0287, P=0.0003), time to major molecular response from imatinib therapy (odds ratio: 0.9652, P=0.0020), and ABCG2 421C/C genotype (odds ratio: 0.3953, P=0.0284) were independent predictors of complete molecular response. In contrast, NK cell number, BIM deletion polymorphisms, and plasma trough imatinib concentration were not significantly associated with achieving complete molecular response. Several predictive markers for achieving complete molecular response were identified in this study. According to our findings, some chronic myeloid leukemia patients treated with imatinib may benefit from a switch to second-generation tyrosine kinase inhibitors (ClinicalTrials.gov, UMIN000004935).
Breast cancer resistance protein (Bcrp) is an ATP-dependent efflux drug transporter. It has a diverse spectrum of hydrophilic and hydrophobic substrates ranging from anticancer, antiviral and antihypertensive drugs, to organic anions, antibiotics, phytoestrogens (e.g., genistein, daidzein, coumestrol), xenoestrogens and steroids (e.g., dehydroepiandrosterone sulfate). Bcrp is an integral membrane protein in cancer and normal cells within multiple organs (e.g., brain, placenta, intestine and testis) that maintains cellular homeostasis by extruding drugs and harmful substances from the inside of cells. In the brain, Bcrp is a major component of the blood-brain barrier located on endothelial cells near tight junctions (TJs). However, Bcrp is absent at the Sertoli cell blood-testis barrier (BTB); instead, it is localized almost exclusively to the endothelial TJ in microvessels in the interstitium and the peritubular myoid cells in the tunica propria. Recent studies have shown that Bcrp is also expressed stage specifically and spatiotemporally by Sertoli and germ cells in the seminiferous epithelium of rat testes, limited only to a testis-specific cell adhesion ultrastructure known as the apical ectoplasmic specialisation (ES) in stage VI-early VIII tubules. These findings suggest that Bcrp is equipped by late spermatids and Sertoli cells to protect late-stage spermatids completing spermiogenesis. Furthermore, Bcrp was found to be associated with F (filamentous)-actin and several actin regulatory proteins at the apical ES and might be involved in the organisation of actin filaments at the apical ES in stage VII-VIII tubules. These findings will be carefully evaluated in this brief review.Asian Journal of Andrology advance online publication, 13 May 2013; doi:10.1038/aja.2013.24.
Background:
Current evidence indicates that a stem cell-like sub-population within malignant glioblastomas, that overexpress members of the adenosine triphosphate-binding cassette (ABC) family transporters, is responsible for multidrug resistance and tumour relapse. Eradication of the brain tumour stem cell (BTSC) compartment is therefore essential to achieve a stable and long-lasting remission.
Methods:
Melatonin actions were analysed by viability cell assays, flow cytometry, quantitative PCR for mRNA expression, western blot for protein expression and quantitative and qualitative promoter methylation methods.
Results:
Combinations of melatonin and chemotherapeutic drugs (including temozolomide, current treatment for malignant gliomas) have a synergistic toxic effect on BTSCs and A172 malignant glioma cells. This effect is correlated with a downregulation of the expression and function of the ABC transporter ABCG2/BCRP. Melatonin increased the methylation levels of the ABCG2/BCRP promoter and the effects on ABCG2/BCRP expression and function were prevented by preincubation with a DNA methyltransferase inhibitor.
Conclusion:
Our results point out a possible relationship between the downregulation of ABCG2/BCRP function and the synergistic toxic effect of melatonin and chemotherapeutic drugs. Melatonin could be a promising candidate to overcome multidrug resistance in the treatment of glioblastomas, and thus improve the efficiency of current therapies.
e19156
Background: DNA repair pathway is a crucial molecular mechanism potentially involved in resistance to platinum-based chemotherapy in the unresectable non-small cell lung cancer. Furthermore, single nucleotide polymorphisms (SNPs) and haplotypes in the ERCC2 gene are thought to be associated with the risk of developing lung cancer and clinical outcomes. Methods: We genotyped 8 ERCC2 htSNPs for 129 unresectable NSCLC (stage IIIA, 12; stage III, 36; stage IV, 82) cases treated with first-line platinum-based chemotherapy. Clinical characteristics, treatment outcomes, and predictive value of htSNPs in patient response, survival, and chemotherapy-related adverse events were analyzed according to each ERCC2 htSNP using chi-square test, Kaplan-Meier method, and Cox proportional hazard model. Results: No differences were observed in patient or disease characteristics and response according to ERCC2 htSNPs. In a survival analysis, rs50872 was significantly related to overall survival (OS) (log-rank test, p=0.014). The median survival duration of rs50872 G/G, A/G, and A/A genotypes was 35.75 (95% confidence interval [CI] 21.05-50.45), 36.07 (hazard ratio[HR] 1.02, 95% CI 25.20-46.94), and 16.75 (HR 3.49, 95% CI 5.73-27.77) months, respectively. A significant association was observed between grade 3-4 infections and poor survival: OS in patients with a grade 0-2 infection: 35.75 months (95% CI 28.15-43.35); OS in patients with a grade 3-4 infection: 12.86 months (95% CI 8.99-16.72, HR 3.57) (log-rank test, p<0.001). In a subgroup analysis, rs238405 genotype was significantly related to OS in the taxane-based group. However, rs238416 genotype was significantly associated with OS in the gemcitabine-based group. Conclusions: ERCC2 htSNPs rs50872 (overall), rs238405 (taxane-based group), and rs238416 (gemcitabine-based group) and infection related to first-line chemotherapy were associated with OS in unresectable NSCLC patients treated with first-line platinum-based chemotherapy. However, additional large prospective studies focusing on the role of ERCC2 htSNPs in unresectable NSCLC are needed.
Despite undisputed success of tyrosine kinase inhibitors (TKI) in the therapy of chronic myeloid leukemia (CML), development of drug resistance and inability to cure the disease challenge clinicians and researchers. Additionally, recent reports regarding cardiovascular toxicities of 2(nd) and 3(rd) generation TKIs prove that there is still a place for novel therapeutic combinations in CML. We have previously shown that statins are able to modulate activity of chemotherapeutics or antibodies used in oncology. Therefore, we decided to verify if statins are able to potentiate antileukemic activity of imatinib, still a frontline treatment of CML. Lovastatin, a cholesterol lowering drug, synergistically potentiates antileukemic activity of imatinib in cell lines and in primary CD34+ CML cells from patients in different phases of the disease, including patients resistant to imatinib with no detectable mutations. This effect is related to increased intracellular concentration of imatinib in CD34+ CML cells and cell lines measured using uptake of (14)C-labeled imatinib. Lovastatin does not influence influx but significantly inhibits efflux of imatinib mediated by ABC (ATP-binding cassette) transporters: ABCB1 and ABCG2. The addition of cholesterol completely reverses these effects. Statins do not affect expression of ABCB1 and ABCG2 genes. The effects are drug-class specific as they were also observed with other statins. Our results suggest that statins may offer a valuable addition to imatinib in a selected group of CML patients.
Potent ABCG2 inhibitors were recently identified as asymmetric chromones with different types of substituents. We here synthesized symmetric bis-chalcones, that were differently substituted and screened for their ability to inhibit mitoxantrone efflux from ABCG2-transfected HEK293 cells. Potent bis-chalcone inhibitors were identified, the efficiency depending on both position of the central ketone groups and the number and positions of lateral methoxy substituents. The best derivative, namely 1p, was selective for ABCG2 over P-glycoprotein and MRP1, appeared not to be transported by ABCG2, and was at least as active on various drug-selected cancer cells overexpressing ABCG2. Compound 1p stimulated the ABCG2 basal ATPase activity by contrast to a chromone lead which inhibited, suggesting different mechanisms of interaction. Combination of both types of inhibitors produced synergistic effects, leading to complete inhibition at very low concentrations.
The introduction and success of imatinib mesylate (IM) has become a paradigm shift in chronic myeloid leukemia (CML) treatment. However, the high efficacy of IM has been hampered by the issue of clinical resistance that might due to pharmacogenetic variability. In the current study, the contribution of three common single nucleotide polymorphisms (SNPs) of ABCB1 (T1236C, G2677T/A and C3435T) and two SNPs of ABCG2 (G34A and C421A) genes in mediating resistance and/or good response among 215 CML patients on IM therapy were investigated. Among these patients, the frequency distribution of ABCG2 421 CC, CA and AA genotypes were significantly different between IM good response and resistant groups (P = 0.01). Resistance was significantly associated with patients who had homozygous ABCB1 1236 CC genotype with OR 2.79 (95%CI: 1.217–6.374, P = 0.01). For ABCB1 G2677T/A polymorphism, a better complete cytogenetic remission was observed for patients with variant TT/AT/AA genotype, compared to other genotype groups (OR = 0.48, 95%CI: 0.239–0.957, P = 0.03). Haplotype analysis revealed that ABCB1 haplotypes (C1236G2677C3435) was statistically linked to higher risk to IM resistance (25.8% vs. 17.4%, P = 0.04), while ABCG2 diplotype A34A421 was significantly correlated with IM good response (9.1% vs. 3.9%, P = 0.03). In addition, genotypic variant in ABCG2 421C>A was associated with a major molecular response (MMR) (OR = 2.20, 95%CI: 1.273–3.811, P = 0.004), whereas ABCB1 2677G>T/A variant was associated with a significantly lower molecular response (OR = 0.49, 95%CI: 0.248–0.974, P = 0.04). However, there was no significant correlation of these SNPs with IM intolerance and IM induced hepatotoxicity. Our results suggest the usefulness of genotyping of these single nucleotide polymorphisms in predicting IM response among CML patients.
Methotrexate [MTX] is the cornerstone of chemotherapy for primary CNS lymphoma [PCNSL] yet how blood-brain barrier [BBB] efflux transporters ABCG2 and ABCC4 influence required high-dose therapy is unknown. To evaluate their role we used four mouse strains, C57/B6 [WT], Abcg2-/-, Abcc4-/-, and Abcg2-/-;Abcc4-/-(double knockout, DKO) and conducted brain microdialysis studies following single IV MTX doses of 50 mg/kg. Based on the AUCplasma to assess systemic exposure to MTX the rank order was Abcc4-/- < WT < Abcg2-/- < Abcg2-/-Abcc4-/-, with only the DKO exposure being significantly higher than the WT group (p<0.01), and a reflection of role of Abcg2 -in biliary excretion and Abcc4 in renal excretion. MTX brain interstitial fluid concentrations obtained by microdialysis were used to calculate the AUCbrain that found the rank order of exposure to be WT < Abcc4-/- < Abcg2-/- < Abcg2-/-Abcc4-/- with the largest difference being 4-fold; 286.13 ± 130 ug*min/ml (DKO) vs. 66.85 ± 26 (WT). Since the transporters affected the systemic disposition of MTX, particularly in the DKO group, the ratio of the AUCbrain/AUCplasma or the brain/plasma partition coefficient Kp was calculated and revealed that the double knockout strain had a significantly higher value [0.23 ± 0.09] than the WT strain [0.11 ± 0.05]. Both Abcg2 and Abcc4 limited BBB penetration of MTX, yet only when both drug efflux pumps were negated did the brain accumulation of MTX significantly increase. These findings indicate a contributory role of both ABCG2 and ABCC4 to limit MTX distribution in patients.
MicroRNAs (miRNAs) are a class of small non-coding RNA molecules involved in the regulation of key biological processes. Different miRNAs with pro-oncogenic and anti-oncogenic properties have been identified in glioblastomas. We decided to analyze expression profiles of 10 mature miRNAs (miR-7-1, miR-10а, miR-17, miR-20а, miR-21, miR-23а, miR-26а, miR-137, and miR-222) in post-surgery glioma specimens of different grade in order to find whether the expression level correlates with tumor grades. We also measured expression of six key genes such as PTEN, p21/CDKN1A, MDR1, ABCG2, BAX, and BCL-2 involved in the regulation of critical glioma signaling pathways to establish the effect of miRNAs on these signaling mechanisms.
Using RT-PCR, we performed expression analysis of 25 tumor fresh samples (grade II-IV).
We found gradual increase in miR-21 and miR-23a levels in all tumor grades whereas miR-7 and miR-137 were significantly down-regulated depending on the glioma grade. MDR, ABCG2, and p21/CDKN1A levels were significantly up-regulated while expression of PTEN was down-regulated in tumor samples compared to the normal brain tissue.
These observations provide new insights into molecular pathogenic mechanisms of glioma progression and suggest about a potential value of miRNAs as a putative diagnostic marker of brain tumors.
to investigate the effects of antidiabetic drug metformin on proliferation and apoptosis in human hepatocellular carcinoma cell line Huh-7 cells.
Huh-7 cells were treated with metformin at different concentrations. Cell viability was determined by MTT assay. Cell apoptosis and CD133(+) expression rate were detected by flow cytometery (FCM). Expressions of PTEN, Akt, p-Akt, Bcl-2, Bax proteins in the cells were measured by Western blot. The effect of metformin on the hepatosphere formation was observed in the serum-free suspension culture. Reverse transcription-polymerase chain reaction (RT-PCR) was used to validate the expression levels of stemness marker genes CD133, β-catenin, and ABCG2 mRNA in the hepatospheres.
The proliferation of Huh-7 cells was inhibited by metformin in a dose- and time-dependent manner. The early and late cell apoptosis rates induced by metformin at dose of 10 mmol/L for 48 hrs were (22.29 ± 0.8)% and (13.87 ± 1.2)%, respectively, and 25 mmol/L for 48 hrs (15.28 ± 2.1)% and (25.89 ± 2.3)%, respectively. Western blotting results revealed that the expression of CD133, phosphorylated Akt and the Bcl-2/Bax ratio were downregulated, and PTEN was upregulated in the Huh-7 cells after treated with 25 mmol/L metformin for 48 hrs. Metformin inhibited the formation of hepatospheres. Metformin also downregulated the expression of several cancer stem cells (CSCs)-related genes which are involved in the signaling pathways governing the self-renewal, proliferation and differentiation of CSCs in the hepatospheres.
Metformin inhibits the proliferation of human hepatocellular carcinoma Huh-7 cells and enhances their apoptosis in vitro. It may be related to the downregulation of PI3K/Akt signal pathway and selectively targeting CD133(+) cells.
Oxaliplatin-based chemotherapy (CT), widely used as adjuvant therapy for stage III and selected high-risk stage II colon cancer (CC) patients, is often associated with cumulative peripheral neuropathy. Our aim is to identify single-nucleotide polymorphisms (SNPs) in genes involved in oxaliplatin metabolism, DNA repair mechanisms, cell cycle control, detoxification or excretion pathways to predict severe (grade 2-3) oxaliplatin-induced peripheral neuropathy (OXPN) among CC patients treated with oxaliplatin and fluoropyrimidine-based adjuvant CT.
Genomic DNA was extracted from formalin-fixed-paraffin-embedded peritumoral samples from 206 high-risk stage II and stage III CC patients receiving oxaliplatin-based adjuvant CT from January 2004 to December 2009. Genotyping was carried out for 34 SNPs in 15 genes using MassARRAY (SEQUENOM) technology. A total of 181 stage II-III CC patients treated with the same CT regimens were enrolled as a validation set.
The rs2230641 cyclin H (CCNH) rs2230641 C/C [odd ratio (OR) = 5.03, 95% confidence interval (CI) 1.061-2.41, P = 0.042] and the ATP-binding cassette subfamily G, member 2 (ABCG2) rs3114018 A/A genotypes (OR = 2.67; 95% CI 0.95-4.41; P = 0.059) were associated with a higher risk of severe OXPN. In addition, patients harboring the combination of CCNH C/C and/or the ABCG2 rs3114018 A/A genotypes had a higher risk of grade 2-3 OXPN than those with the CCNH any T and ABCG2 any C genotypes (37.73% versus 19.42%; OR = 2.46; 95% CI 1.19-5.07; P = 0.014) in the logistic regression analysis using age, gender, adjuvant CT regimen and cumulative dose of oxaliplatin as covariates. The ability to predict severe OXPN of this combined analysis was independently validated in the second cohort (58% versus 33.33%; OR = 2.99; 95% CI 1.45-6.13; P = 0.002).
Our results suggest that SNPs in CCNH and ABCG2 can modulate the development of severe OXPN among stage II-III CC patients who received oxaliplatin-based CT, thus enabling the individualization of adjuvant treatment.
One of the major causes of failure in chemotherapy for patients with acute lymphoblastic leukemia (ALL) is the acquisition of multidrug resistance (MDR). Predominant mechanisms for MDR acquisition include the overexpression of efflux pumps. In the present study, the regulation of the expression of two genes that encode efflux pumps, ATP-binding cassette, sub-family B, member 1 (ABCB1) and ABCG2, through mitogen-activated protein kinase (MAPK) pathways was examined.
ABCB1 and ABCG2 mRNAs were quantified in a T-ALL cell line, CCRF-HSB-2 and a B-ALL cell line, YAMN90 using real-time RT-PCR. Changes in the mRNA amounts of these genes were examined after activation or inhibition of MAPK/extracellular signal-regulated kinase (ERK) pathway and c-Jun NH2-terminal kinase (JNK) pathway.
Activation of MAPK/ERK pathway up-regulated ABCB1 expression but down-regulated ABCG2 expression. Activation of JNK pathway up-regulated ABCG2 gene expression.
The expressions of ABCB1 and ABCG2 genes were regulated through MAPK/ERK and JNK pathways in the human ALL cell lines.
The tyrosine kinase inhibitors (TKIs) used in the treatment of chronic myeloid leukemia are substrates for the efflux transport protein ATP-binding cassette subfamily G member 2 (ABCG2). Variations in ABCG2 activity might influence pharmacokinetics and therapeutic outcome of TKIs. The role of ABCG2 single-nucleotide polymorphisms (SNPs) in TKI treatment is not clear and functional in-vitro studies are lacking. The aim of this study was to investigate the consequences of ABCG2 SNPs for transport and efficacy of TKIs [imatinib, N-desmethyl imatinib (CGP74588), dasatinib, nilotinib, and bosutinib].
ABCG2 SNPs 34G>A, 421C>A, 623T>C, 886G>C, 1574T>G, and 1582G>A were constructed from ABCG2 wild-type cDNA and transduced to K562 cells by retroviral gene transfer. Variant ABCG2 expression in cell membranes was evaluated and the effects of ABCG2 SNPs on transport and efficacy of TKIs were measured as the ability of ABCG2 variants to protect against TKI cytotoxicity.
Wild-type ABCG2 had a protective effect against the cytotoxicity of all investigated compounds except bosutinib. It was found that ABCG2 expression provided better protection against CGP74588 than its parent compound, imatinib. ABCG2 421C>A, 623T>C, 886G>C, and 1574T>G reduced cell membrane expression of ABCG2 and the protective effect of ABCG2 against imatinib, CGP74588, dasatinib, and nilotinib cytotoxicity.
These findings show that the ABCG2 SNPs 421C>A, 623T>C, 886G>C, and 1574T>G increase the efficacy of investigated TKIs, indicating a reduced transport function that might influence TKI pharmacokinetics in vivo. Furthermore, the active imatinib metabolite CGP74588 is influenced by ABCG2 expression to a greater extent than the parent compound.
Multidrug resistance is a major barrier against successful chemotherapy, and this has been shown in vitro to be often caused by ATP-binding cassette (ABC) transporters. These transporters are frequently overexpressed in human cancers and confer an adverse prognosis in many common malignancies. The genetic factors, however, that initiate their expression in cancer are largely unknown. Here we report that the major multidrug transporter ABCG2 (BCRP/MXR) is directly and specifically activated by the transcription factor E2F1-a factor perturbed in the majority of human cancers. E2F1 regulates ABCG2 expression in multiple cell systems, and, importantly, we have identified a significant correlation between elevated E2F1 and ABCG2 expression in human lung cancers. We show that E2F1 causes chemotherapeutic drug efflux both in vitro and in vivo via ABCG2. Furthermore, the E2F1-ABCG2 axis suppresses chemotherapy-induced cell death that can be restored by the inhibition of ABCG2. These findings therefore identify a new axis in multidrug resistance and highlight a radical new function of E2F1 that is relevant to tumor therapy.Oncogene advance online publication, 25 November 2013; doi:10.1038/onc.2013.470.
The breast cancer resistance protein (BCRP, ABCG2) is an efflux transporter that removes xenobiotics that cross the placenta back to the maternal circulation, thereby limiting exposure of the fetus to drugs and chemicals. Currently, variability of BCRP expression within the placenta is not known. Ten placentas were collected from healthy women undergoing elective Cesarean sections at term. Villous samples were dissected in defined regions (medial, intermediate, and peripheral) and BCRP mRNA and protein were quantified. There were no regional differences in mRNA expression of housekeeping genes (GAPDH, RPL13a, PRL, 18S). GAPDH had the lowest correlation with BCRP Ct values and was used for BCRP mRNA normalization. No differences in placental BCRP mRNA and protein were observed among the sample sites (<20% variability). Sampling site does not affect the expression of BCRP, supporting the utility of single site sampling protocols to assess the interindividual regulation of this transporter in human placentas.
: Interpatient variability in drug response can be widely explained by genetically determined differences in metabolizing enzymes, drug transporters, and drug targets, leading to different pharmacokinetic and/or pharmacodynamic behaviors of drugs. Genetic variations affect or do not affect drug responses depending on their influence on protein activity and the relevance of such proteins in the pathway of the drug. Also, the frequency of such genetic variations differs among populations, so the clinical relevance of a specific variation is not the same in all of them. In this study, a panel of 33 single nucleotide polymorphisms in 14 different genes (ABCB1, ABCC2, ABCG2, CYP2B6, CYP2C19, CYP2C9, CYP3A4, CYP3A5, MTHFR, NOD2/CARD15, SLCO1A2, SLCO1B1, TPMT, and UGT1A9), encoding for the most relevant metabolizing enzymes and drug transporters relating to immunosuppressant agents, was analyzed to determine the genotype profile and allele frequencies in comparison with HapMap data. A total of 570 Spanish white recipients and donors of solid organ transplants were included. In 24 single nucleotide polymorphisms, statistically significant differences in allele frequency were observed. The largest differences (>100%) occurred in ABCB1 rs2229109, ABCG2 rs2231137, CYP3A5 rs776746, NOD2/CARD15 rs2066844, TPMT rs1800462, and UGT1A9 rs72551330. In conclusion, differences were recorded between the Spanish and other white populations in terms of allele frequency and genotypic distribution. Such differences may have implications in relation to dose requirements and drug-induced toxicity. These data are important for further research to help explain interindividual pharmacokinetic and pharmacodynamic variability in response to drug therapy.
Chemotherapy is one of the major forms of cancer treatment. Unfortunately, tumors are prone to multidrug resistance leading to failure of treatment. Breast cancer resistance protein (BCRP), the second member of ABC transporter subfamily G, has been found to play a major role in drug efflux and hence multidrug resistance. Until now very few potent and selective BCRP inhibitors like Ko143 have been identified. In the search for more potent and selective BCRP inhibitors we synthesized and investigated a series of differently substituted quinazoline compounds. Several variations at positions 2, 4, 6 and 7 of the quinazoline scaffold were carried out to develop a structure-activity-relationship analysis for these compounds. It was found that compounds bearing a phenyl substituent at position 2 of the 4-anilinoquinazoline scaffold were most potent. On the aniline ring at position 4 of the quinazoline moiety substituents like NO2, CN, CF3 led to very high BCRP inhibition potencies. The most potent compounds were further investigated for their intrinsic cytotoxicity and their ability to reverse the multidrug resistance. Compound 20, an anilinoquinazoline bearing a phenyl ring at position 2 and meta-nitro substitution on the 4-anilino ring, was found to have the highest therapeutic ratio. The most active compounds from each variation were also investigated for their effect on BCRP expression. It was found that compound 20 has no significant effect on BCRP expression, while compound 31 decreased the surface BCRP expression. The only difference in the two compounds was the presence of a 3,4-dimethoxyphenyl ring in compound 31 instead of phenyl substitution at position 2 of the quinazoline moiety. From the study of all target compounds, compound 20 was the most prominent compound having inhibitory potency even higher than Ko143, the most potent BCRP inhibitor known. Compound 20 was also found to be selective towards BCRP with a very high therapeutic ratio.
This study quantitatively assessed transport mechanisms that limit the brain distribution of sunitinib, and investigated adjuvant strategies to improve its brain delivery for the treatment of glioblastoma multiforme (GBM). Sunitinib has not shown significant activity in GBM clinical trials, despite positive results seen in preclinical xenograft studies. We performed in vivo studies in transgenic FVB mice: wild-type, Mdr1a/b(-/-), Bcrp1(-/-) and Mdr1a/b(-/-)Bcrp1(-/-) genotypes were examined. The brain-to-plasma AUC ratio after an oral dose (20 mg/kg) was similar to steady-state tissue distribution coefficient (Kp), indicating linear distribution kinetics in mice over this concentration range. Furthermore, the distribution of sunitinib to the brain increased after administration of selective P-glycoprotein (P-gp) or breast cancer resistance protein (Bcrp) pharmacological inhibitors, and a dual inhibitor, elacridar, comparable to that of the corresponding transgenic genotype. The brain-to-plasma ratio after co-administration of elacridar in wild-type was ~12, compared to ~17.3 in Mdr1a/b(-/-)Bcrp1(-/-) mice. Overall, these findings indicate that there is a co-operation at the BBB in restricting the brain penetration of sunitinib and brain delivery can be enhanced by administration of a dual inhibitor. These data indicate that the presence of cooperative efflux transporters, P-gp and Bcrp, in an intact BBB, can protect invasive glioma cells from chemotherapy. Thus, one may consider the use transporter inhibition as a powerful adjuvant in the design of future clinical trials for the targeted delivery of sunitinib to GBM.
The role of ERβ in breast cancer is still under investigation. Various studies have provided evidence that ERβ behaves as a tumor suppressor in breast cancer, whereas some studies of ERα-negative breast cancer reported a positive correlation between high ERβ expression and poor prognostic phenotypes, such as induced proliferation, invasion and metastasis. In the present immunohistochemistry study of 99 ERα-/PR- breast cancer samples, nuclear expression of ERβ was positively associated with membranous expression of breast cancer resistance protein (BCRP), Ki67 (proliferation marker) and tumor size. Moreover, both endogenous and exogenous ERβ upregulated BCRP expression which induced BCRP-mediated drug resistance and enhanced proliferation of ERα-/PR- breast cancer cells in the presence of 17β-estradiol (E2), whereas these effects were reversed by additional use of tamoxifen (TAM). In addition, the regulation of BCRP via specific binding between ERβ and estrogen response element (ERE) was demonstrated in the EMSA assay. Overall, our findings manifest that ERβ might act as a tumor promoter of cell proliferation and BCRP-mediated drug resistance in ERα-/PR- breast cancer. TAM routinely used for patients with ERα+/PR+, ERα+/PR- and ERα-/PR+ breast cancer might also be effective in ERα-/PR- but ERβ+ breast cancer. Therefore, the detection of ERβ in clinic is valuable and should not be neglected in breast cancer, especially for the ERα-/PR- phenotype. This article is protected by copyright. All rights reserved.
Crizotinib is an oral tyrosine kinase inhibitor approved for treating patients with non-small cell lung cancer (NSCLC) containing an anaplastic lymphoma kinase (ALK) rearrangement. We used knockout mice to study the roles of P-glycoprotein (ABCB1) and breast cancer resistance protein (ABCG2) in plasma pharmacokinetics and brain accumulation of oral crizotinib, and the feasibility of improving crizotinib kinetics using coadministration of the dual ABCB1/ABCG2 inhibitor elacridar. In vitro, crizotinib was a good transport substrate of human ABCB1, but not of human ABCG2 or murine Abcg2. With low-dose oral crizotinib (5 mg/kg), Abcb1a/1b(-/-) and Abcb1a/1b;Abcg2(-/-) mice had an ~2-fold higher plasma AUC than wild-type mice, and a markedly (~40-fold) higher brain accumulation at 24 hr. Also at 4 hr, crizotinib brain concentrations were ~25-fold, and brain-to-plasma ratios ~14-fold higher in Abcb1a/1b(-/-) and Abcb1a/1b;Abcg2(-/-) mice than in wild-type mice. High-dose oral crizotinib (50 mg/kg) resulted in comparable plasma pharmacokinetics between wild-type and Abcb1a/1b(-/-) mice, suggesting saturation of intestinal Abcb1. Nonetheless, brain accumulation at 24 hr was still ~70-fold higher in Abcb1a/1b(-/-) than in wild-type mice. Importantly, oral elacridar coadministration increased the plasma and brain concentrations and brain-to-plasma ratios of crizotinib in wild-type mice, equaling the levels in Abcb1a/1b;Abcg2(-/-) mice. Our results indicate that crizotinib oral availability and brain accumulation were primarily restricted by Abcb1 at a non-saturating dose, and that coadministration of elacridar with crizotinib could substantially increase crizotinib oral availability and delivery to the brain. This principle might be used to enhance therapeutic efficacy of crizotinib against brain metastases in NSCLC patients. © 2013 Wiley Periodicals, Inc.
Multidrug resistance (MDR), usually mediated by overexpression of efflux transporters such as P-gp, ABCG2 and/or MRP1, remains a major obstacle hindering successful cancer chemotherapy. There has been great interest in the development of inhibitors towards these transporters to circumvent resistance. However, since the inhibition of transporter is not specific to cancer cells, a decrease in the cytotoxic drug dosing may be needed to prevent excess toxicity, thus undermining the potential benefit brought about by a drug efflux inhibitor. The design of potent MDR modulators specific towards resistant cancer cells and devoid of drug-drug interactions will be needed to effect MDR reversal.
Recent evidence suggests that the PTEN/PI3K/Akt pathway may be exploited to alter ABCG2 subcellular localization, thereby circumventing MDR. Three PPARγ agonists (telmisartan, pioglitazone and rosiglitazone) that have been used in the clinics were tested for their effect on the PTEN/PI3K/Akt pathway and possible reversal of ABCG2-mediated drug resistance.
The PPARγ agonists were found to be weak ABCG2 inhibitors by drug efflux assay. They were also shown to elevate the reduced PTEN expression in a resistant and ABCG2-overexpressing cell model, which inhibit the PI3K-Akt pathway and lead to the relocalization of ABCG2 from the plasma membrane to the cytoplasma, thus apparently circumventing the ABCG2-mediated MDR.
Since this PPARγ/PTEN/PI3K/Akt pathway regulating ABCG2 is only functional in drug-resistant cancer cells with PTEN loss, the PPARγ agonists identified may represent promising agents targeting resistant cells for MDR reversal.
Membrane transporters are widely recognized as important determinants of drug disposition and response, generating increasing interest on the pharmacological implications of their genetic variations. The aim of this study was to elucidate the predictive/prognostic role of ATP-binding cassette (ABC) and solute carrier (SLC) protein polymorphisms on irinotecan (FOLFIRI regimen) outcome.
A total of 250 White metastatic colorectal cancer patients homogenously treated with a first-line FOLFIRI regimen were genotyped for a panel of variants in five transporter genes. The primary study endpoints were the response rate (partial or complete response), overall survival, and time to progression. Toxicity was considered a secondary endpoint. Irinotecan pharmacokinetic data of 71 patients were used for polymorphism functional analysis.
Two variants of the ABCG2 (-15622C>T, rs7699188) gene were found to be predictive (P<0.01) of the response rate. High-order relationships of ABC/SLC markers with previously investigated genetic (UGT1A1 polymorphisms) and nongenetic (primary tumor site) factors that helped determine the response rate were highlighted. A prognostic effect of the ABCB1 rs2032582 variant on patient overall survival emerged (P=0.0074). The ABCG2 rs7699788 variant was also seen to be associated with grade 3-4 nonhematological toxicity (P=0.0012). The ABCG2 (-15622C>T, rs7699188) and ABCB1 (rs2032582) polymorphisms were not found to be associated with pharmacokinetic parameters.
This study showed that ABC/SLC polymorphisms have a crucial contribution toward the FOLFIRI outcome. This could represent a further step toward personalized therapy.
Targeted inhibition of multidrug ABCG2 transporter is believed to improve cancer therapeutics. However, the consequences of ABCG2 inhibition have not been systematically evaluated since ABCG2 is expressed in several organs including the liver. Here, we demonstrate that ABCG2-deficient hepatocytes have increased amounts of fragmental mitochondria accompanied by disruption of mitochondrial dynamics and functions. This disruption was due to ABCG2 knockout elevating intracellular protoporphyrin IX, which led to upregulation of DRP-1-mediated mitochondrial fission. The finding that ABCG2 deficiency can generate dysfunctional mitochondria in hepatocytes raises concerns regarding the systematic use of ABCG2 inhibitor in cancer patients.
Drugs of abuse affect pregnancy outcomes, however, the mechanisms in which cannabis exert its effects are not well understood. The aim of this study was to examine the influence of short-term (1-2h) exposure to cannabidiol (CBD), a major phytocannabinoid, on human placental Breast Cancer Resistance Protein (BCRP) function.
The in vitro effect of short-term exposure to CBD on BCRP in BeWo and Jar cells (MCF7/P-gp cells were used for comparison) was tested with Mitoxantrone (MX) uptake, and Nicardipine was used as positive control. The ex vivo perfused cotyledon system was used for testing the effect of CBD on glyburide transport across the placenta. Glyburide (200ng/ml) was introduced to maternal (M) and fetal (F) compartments through a re-circulating 2h perfusion, and its transplacental transport was tested with [n=8] or without [n=8] CBD.
1) CBD inhibition of BCRP-dependent MX efflux was concentration dependent and of a non-cell type specific nature (p<0.0001); 2) In the cotyledon perfusion assay, the administration of CBD to the maternal perfusion media increased the F/M ratio of glyburide concentrations (1.3±0.1 vs 0.8±0.1 at 120 min. of perfusion, p<0.001).
1) Placental BCRP function is inhibited following even a short term exposure to CBD; 2) the ex vivo perfusion assay emphasize this effect by increased placental penetration of glyburide to the fetal compartment; and 3) these findings suggest that marijuana consumption enhances placental barrier permeability to xenobiotics and could endanger the developing fetus. Thus, the safety of drugs that are BCRP substrates is questionable during cannabis consumption by pregnant women.
Breast cancer resistance protein (BCRP/ABCG2) specifically transports various chemotherapeutic agents and is involved in the development of multidrug resistance (MDR) in cancer cells. MicroRNAs (miRNAs) can play an important role in modulating the sensitivity of cancer cells to chemotherapeutic agents. Therefore, after confirming that BCRP was increased in the mitoxantrone (MX)-resistant MCF-7 breast cancer cell line MCF-7/MX compared with its parental sensitive MCF-7 cell line, we aimed to explore the miRNAs that regulate BCRP expression and sensitize breast cancer cells to chemotherapeutic agents. In the present study, bioinformatic analysis indicated that miR-487a was one of the miRNAs that could bind to the 3' untranslated region (3'UTR) of BCRP. Quantitative RT-PCR (qRT-PCR) analysis demonstrated that the expression of miR-487a was reduced in MCF-7/MX cells, and a luciferase reporter assay demonstrated that miR-487a directly bound to the 3'UTR of BCRP. Moreover, ectopic miR-487a down-regulated BCRP expression at the mRNA and protein levels, increasing the intracellular accumulation and cytotoxicity of MX in resistant MCF-7/MX breast cancer cells. Meanwhile, inhibition of miR-487a increased BCRP expression at the mRNA and protein levels and induced MX resistance in sensitive MCF-7 breast cancer cells. Furthermore, the reduced expression of BCRP and increased antitumor effects of MX were also detected in MCF-7/MX xenograft tumors treated with the miR-487a agmir. Thus, our results suggested that miR-487a can directly regulate BCRP expression and reverse chemotherapeutic drug resistance in a subset of breast cancers.
Low brain accumulation of anticancer drugs due to efflux transporters may limit chemotherapeutic efficacy, necessitating better understanding of the underlying mechanisms. P-glycoprotein (Abcb1a/1b) and breast cancer resistance protein (Abcg2) combination knockout mice often display disproportionately increased brain accumulation of shared drug substrates compared to single transporter knockout mice. Recently developed pharmacokinetic models could explain this phenomenon. To experimentally test these models and their wider relevance for tyrosine kinase inhibitors (TKIs) and other drugs, we selected dasatinib, sorafenib and sunitinib because of their divergent oral availability and brain accumulation profiles: brain accumulation of dasatinib is mainly restricted by Abcb1, that of sorafenib mainly by Abcg2, and that of sunitinib equally by Abcb1 and Abcg2. We analyzed the effect of halving the efflux activity of these transporters at the blood-brain barrier (BBB) by generating heterozygous Abcb1a/1b;Abcg2 knockout mice, and testing plasma and brain levels of the drugs after oral administration at 10 mg/kg. RT-PCR analysis confirmed ~2-fold decreased expression of both transporters in brain. Interestingly, whereas complete knockout of the transporters caused 24- to 36-fold increases in brain accumulation of the drugs, the heterozygous mice only displayed 1.6- to 1.9-fold increases of brain accumulation relative to wild-type mice. These results are well in line with the predictions of the pharmacokinetic models, and provide strong support for their validity for a wider range of drugs. Moreover, retrospective analysis of fetal accumulation of drugs across the placenta in Abcb1a/1b heterozygous knockout pups suggests that these models equally apply to the maternal-fetal barrier.
CYT387 is an orally bioavailable, small molecule inhibitor of Janus family of tyrosine kinases (JAK) 1 and 2. It is currently undergoing Phase I/II clinical trials for the treatment of myelofibrosis and myeloproliferative neoplasms. We aimed to establish whether the multidrug efflux transporters P-glycoprotein (P-gp; MDR1; ABCB1) and breast cancer resistance protein (BCRP;ABCG2) restrict oral availability and brain penetration of CYT387. In vitro, CYT387 was efficiently transported by both human MDR1 and BCRP, and very efficiently by mouse Bcrp1 and its transport could be inhibited by specific MDR1 inhibitor, zosuquidar and/or specific BCRP inhibitor, Ko143. CYT387 (10mg/kg) was orally administered to wild-type (WT), Bcrp1-/-, Mdr1a/1b-/- and Bcrp1;Mdr1a/1b-/- mice and plasma and brain concentrations were analyzed. Over 8hours, systemic exposure of CYT387 was similar between all the strains, indicating that these transporters do not substantially limit oral availability of CYT387. Despite the similar systemic exposure, brain accumulation of CYT387 was increased 10.5- and 56-fold in the Bcrp1;Mdr1a/1b-/- mice compared to the WT strain at 2 and 8h after CYT387 administration, respectively. In single Bcrp1-/- mice, brain accumulation of CYT387 was more substantially increased than in Mdr1a/1b-/- mice, suggesting that CYT387 is a slightly better substrate of Bcrp1 than of Mdr1a at the blood-brain barrier. These results indicate a marked and additive role of Bcrp1 and Mdr1a/1b in restricting brain penetration of CYT387, potentially limiting efficacy of this compound against brain (micro)metastases positioned behind a functional blood-brain barrier.
Breast cancer resistance protein (BCRP)/ATP-binding cassette subfamily G member 2 (ABCG2) mediates multidrug resistance (MDR) in breast cancers. In this study, we aimed to investigate the role of microRNAs in regulation of BCRP expression and BCRP-mediated drug resistance in breast cancer cells. Microarray analysis was performed to determine the differential expression patterns of miRNAs that target BCRP between the MX-resistant breast cancer cell line MCF-7/MX and its parental MX-sensitive cell line MCF-7. MiR-181a was found to be the most significantly down-regulated miRNA in MCF-7/MX cells. Luciferase activity assay showed that miR-181a mimics inhibited BCRP expression by targeting the 3' untranslated region (UTR) of the BCRP mRNA. Overexpression of miR-181a down-regulated BCRP expression, and sensitized MX-resistant MCF-7/MX cells to MX. In a nude mouse xenograft model, intratumoral injection of miR-181a mimics inhibited BCRP expression, and enhanced the antitumor activity of MX. In addition, miR-181a inhibitors up-regulated BCRP expression, and rendered MX-sensitive MCF-7 cells resistant to MX. These findings suggest that miR-181a regulates BCRP expression via binding to the 3'-UTR of BCRP mRNA. MiR-181a is critical for regulation of BCRP-mediated resistance to MX. MiR-181a may be a potential target for preventing and reversing drug resistance in breast cancer.
Abstract We investigated the association of genetic polymorphisms in drug metabolizing enzymes (DMEs) and transporters in patients with docetaxel-induced febrile neutropenia, by a new high-throughput DMEs and transporters (DMETPlus) microarray platform, characterizing 1936 single nucleotide polymorphisms (SNPs) in 225 genes. We recruited 100 Lebanese breast cancer patients from a consecutive cohort of 277 patients who received docetaxel either alone, or in combination with trastuzumab. Out of 100 patients, 18 had developed febrile neutropenia (cases). They were age- and treatment- matched with 18 patients who did not develop febrile neutropenia on docetaxel (controls). We found that 12 SNPs in seven genes (ABCC6, ABCG1, ABCG2, CYP1A2, CYP2D6, FMO2, and FMO3) were significantly associated with febrile neutropenia after docetaxel treatment. Many of these SNPs have not been previously reported to be associated with toxicity due to docetaxel treatment. Interestingly, one SNP in the FMO3 gene (rs909530) was significantly associated with three clinical endpoints: febrile neutropenia, reduced absolute neutrophil count, and hemoglobin reduction. To the best of our knowledge, this is the first study that evaluated the effect of a large array of nearly 2000 polymorphisms in DMEs and transporters on docetaxel toxicity in breast cancer patients, and in a previously understudied population. Additionally, it attests to the feasibility of genomics research in low- and middle-income countries (LMICs). In light of the current global epidemic of noncommunicable diseases (NCDs) such as breast cancer impacting LMICs, we suggest pharmacogenomics is considered as an integral part of the global health research agenda for NCDs and personalized therapeutics.
Background:
Methotrexate (MTX) is a drug used to treat psoriasis due to inducing immune cell apoptosis. However, certain patients show MTX resistant. CD147, highly expressed by psoriatic PBMCs, is assumed to regulate MTX sensitivity. The underlining mechanism is still relatively understudied.
Objective:
To understand the mechanisms of that CD147 promotes MTX resistance in immune cells.
Methods:
The expression of CD147 and ABCG2 in PBMCs from psoriatic patients, cellular apoptosis and intracellular MTX amount were measured. We also checked the cellular drug sensitivity of CHO (Chinese Hamster Ovary) cell lines with introduced CD147 and Jurkat T cells depeleted CD147. By immunoprecipitation, we detected the interaction between CD147 and ABCG2.
Results:
Both ABCG2 and CD147 are highly expressed in psoriatic PBMCs. Cultured in vitro, the PBMCs from psoriatic patients were more resistant to MTX-induced apoptosis comparing to PBMCs from healthy people. Further studies demonstrated that exogenous overexpression of CD147 in CHO cells increased ABCG2 protein level. After MTX treatment, CD147 overexpressing CHO cells showed lower apoptosis rate and lower intracellular MTX concentration. On the contrary, knockdown of CD147 by shRNA in Jurkat T cells decreased ABCG2 expression, as well as increased MTX-induced apoptosis and decreased MTX efflux. Immunoprecipitation experiment revealed that the trans-membrane domain of CD147 conferred its' interaction with ABCG2.
Conclusion:
Our study suggests a role of CD147 in regulating ABCG2 transportation of MTX in immune cells. Strategies involving targeting CD147 could be considered in clinical treatment of psoriatic patients resistant to MTX.