Gene Summary

Gene:ABCB1; ATP binding cassette subfamily B member 1
Aliases: CLCS, MDR1, P-GP, PGY1, ABC20, CD243, GP170
Summary:The membrane-associated protein encoded by this gene is a member of the superfamily of ATP-binding cassette (ABC) transporters. ABC proteins transport various molecules across extra- and intra-cellular membranes. ABC genes are divided into seven distinct subfamilies (ABC1, MDR/TAP, MRP, ALD, OABP, GCN20, White). This protein is a member of the MDR/TAP subfamily. Members of the MDR/TAP subfamily are involved in multidrug resistance. The protein encoded by this gene is an ATP-dependent drug efflux pump for xenobiotic compounds with broad substrate specificity. It is responsible for decreased drug accumulation in multidrug-resistant cells and often mediates the development of resistance to anticancer drugs. This protein also functions as a transporter in the blood-brain barrier. Mutations in this gene are associated with colchicine resistance and Inflammatory bowel disease 13. Alternative splicing and the use of alternative promoters results in multiple transcript variants. [provided by RefSeq, Feb 2017]
Databases:VEGA, OMIM, HGNC, Ensembl, GeneCard, Gene
Protein:multidrug resistance protein 1
Source:NCBIAccessed: 15 March, 2017


What does this gene/protein do?
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Pathways:What pathways are this gene/protein implicaed in?
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Cancer Overview

Research Indicators

Publications Per Year (1992-2017)
Graph generated 15 March 2017 using data from PubMed using criteria.

Literature Analysis

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Tag cloud generated 15 March, 2017 using data from PubMed, MeSH and CancerIndex

Specific Cancers (6)

Data table showing topics related to specific cancers and associated disorders. Scope includes mutations and abnormal protein expression.

Note: list is not exhaustive. Number of papers are based on searches of PubMed (click on topic title for arbitrary criteria used).

Latest Publications: ABCB1 (cancer-related)

Onishi H, Suyama K, Yamasaki A, et al.
CD24 Modulates Chemosensitivity of MCF-7 Breast Cancer Cells.
Anticancer Res. 2017; 37(2):561-565 [PubMed] Related Publications
The role of cluster of differentiation (CD) 24 in breast cancer remains unclear; previously, we showed that CD24 suppresses malignant phenotypes by inactivating Hedgehog signaling through signal transducer and activator of transcription (STAT) 1 inhibition. In this study, we examined how CD24 affects chemosensitivity in breast cancer cells. The CD44(+)CD24(+) breast cancer cell line MCF-7 was transfected with CD24 with/without STAT1 siRNA, and chemosensitivity to 5-fluorouracil (5-FU) and cis-diamminedichloroplatinum (CDDP) was measured. CD24 inhibition reduced chemosensitivity to 5-FU, while STAT1 inhibition did not affect chemosensitivity to 5-FU in CD24 siRNA-transfected cells. Conversely, CD24 inhibition did not affect chemosensitivity to CDDP, while STAT1 inhibition reduced chemosensitivity to CDDP in CD24 siRNA-transfected cells. STAT1 inhibition, but not CD24 inhibition, reduced expression of the ATP-binding cassette (ABC) transporter genes, ABCB1 and ABCG2. In conclusion, CD24 inhibition may modulate chemosensitivity according to drug type, but ABC transporter expression appears not to contribute to this mechanism. This study contributes to determining the role of CD24 in breast cancer.

Zhang M, Zhuang G, Sun X, et al.
TP53 mutation-mediated genomic instability induces the evolution of chemoresistance and recurrence in epithelial ovarian cancer.
Diagn Pathol. 2017; 12(1):16 [PubMed] Free Access to Full Article Related Publications
BACKGROUND: Genomic instability caused by mutation of the checkpoint molecule TP53 may endow cancer cells with the ability to undergo genomic evolution to survive stress and treatment. We attempted to gain insight into the potential contribution of ovarian cancer genomic instability resulted from TP53 mutation to the aberrant expression of multidrug resistance gene MDR1.
METHODS: TP53 mutation status was assessed by performing nucleotide sequencing and immunohistochemistry. Ovarian cancer cell DNA ploidy was determined using Feulgen-stained smears or flow cytometry. DNA copy number was analyzed by performing fluorescence in situ hybridization (FISH).
RESULTS: In addition to performing nucleotide sequencing for 5 cases of ovarian cancer, TP53 mutations were analyzed via immunohistochemical staining for P53. Both intensive P53 immunohistochemical staining and complete absence of signal were associated with the occurrence of TP53 mutations. HE staining and the quantification of DNA content indicated a significantly higher proportion of polyploidy and aneuploidy cells in the TP53 mutant group than in the wild-type group (p < 0.05). Moreover, in 161 epithelial ovarian cancer patients, multivariate logistic analysis identified late FIGO (International Federation of Gynecology and Obstetrics) stage, serous histotype, G3 grade and TP53 mutation as independent risk factors for ovarian cancer recurrence. In relapse patients, the proportion of chemoresistant cases in the TP53 wild-type group was significantly lower than in the mutant group (63.6% vs. 91.8%, p < 0.05). FISH results revealed a higher percentage of cells with >6 MDR1 copies and chromosome 7 amplication in the TP53 mutant group than in the wild-type group [11.7 ± 2.3% vs. 3.0 ± 0.7% and 2.1 ± 0.7% vs. 0.3 ± 0.05%, (p < 0.05), respectively]. And we observed a specific increase of MDR1 and chromosome 7 copy numbers in the TP53 mutant group upon disease regression (p < 0.01).
CONCLUSIONS: TP53 mutation-associated genomic instability may promote chromosome 7 accumulation and MDR1 amplification during ovarian cancer chemoresistance and recurrence. Our findings lay the foundation for the development of promising chemotherapeutic approaches to treat aggressive and recurrent ovarian cancer.

Palko-Labuz A, Sroda-Pomianek K, Uryga A, et al.
Anticancer activity of baicalein and luteolin studied in colorectal adenocarcinoma LoVo cells and in drug-resistant LoVo/Dx cells.
Biomed Pharmacother. 2017; 88:232-241 [PubMed] Related Publications
Due to the type-specific diversity of cancer cells, an analysis and elucidation of molecular mechanisms responsible for anticancer properties of biologically active compounds are essential. Plant-derived polyphenolic compounds such as flavonoids may be useful in cancer chemoprevention or treatment because they influence diverse molecular pathways in cancer cells. In these studies anticancer activity of natural occurring flavones, baicalein and luteolin was investigated in colon cancer cells LoVo and in their drug resistant subline LoVo/Dx. Inhibitory activity of these flavones on cells growth and their ability to induce apoptosis were observed. A less pronounced influence of studied flavones on proliferation and apoptosis of LoVo/Dx as compared with LoVo cells well correlated with significantly lower cytotoxicity of these compounds in drug-resistant cells. These effects may be related to overexpression of multidrug transporter P-glycoprotein in drug-resistant LoVo/Dx cells. Our studies indicated that baicalein could be a substrate of this drug transporter.

Lu C, Shan Z, Li C, Yang L
MiR-129 regulates cisplatin-resistance in human gastric cancer cells by targeting P-gp.
Biomed Pharmacother. 2017; 86:450-456 [PubMed] Related Publications
Development of multiple drug resistance (MDR) to chemotherapy is the major reason for the failure of gastric cancer (GC) treatment. P-glycoprotein (P-gp), which is encoded by MDR gene 1, as one of the mechanisms responsible for MDR. Mounting evidence has demonstrated that the drug-induced dysregulation of microRNAs (miRNAs) function may mediate MDR in cancer cells. However, the underling mechanisms of miRNA-mediated MDR in GC remain unclear. Here, we found that miR-129 was downregulated in cisplatin-resistant GC tissues/cells. Our results also showed that overexpression of miR-129 decreased cisplatin-resistance in cisplatin-resistant GC cells, and miR-129 knockdown reduced chemosensitivity to cisplatin in cisplatin-sensitive GC cells. Furthermore, miR-129 activated the intrinsic apoptotic pathway via upregulating caspase-9 and caspase-3. Most importantly, we further confirmed that P-gp is the functional target of miR-129 by regulating cisplatin-resistance in GC cells. These results suggested that miR-129 reversed cisplatin-resistance through inhibiting the P-gp expression in GC cells.

Tsuji D, Ikeda M, Yamamoto K, et al.
Drug-related genetic polymorphisms affecting severe chemotherapy-induced neutropenia in breast cancer patients: A hospital-based observational study.
Medicine (Baltimore). 2016; 95(44):e5151 [PubMed] Related Publications
Chemotherapy-induced neutropenia (CIN) is one of the major adverse events that necessitate chemotherapy dose reduction. This study aimed to evaluate the association between grade 4 neutropenia and genetic polymorphisms in breast cancer patients. In this genetic polymorphism association study, peripheral blood samples from 100 consecutive breast cancer outpatients, between August 2012 and September 2014, treated with doxorubicin and cyclophosphamide (AC) combination chemotherapy were genotyped for polymorphisms in adenosine triphosphate-binding cassette subfamily B member 1 (ABCB1), cytochrome P450 (CYP) enzyme-coding genes (CYP2B6 and CYP3A5), glutathione S-transferase (GST), and excision repair cross-complementing 1 (ERCC1). Associations between grade 4 neutropenia and genotypes as well as risk factors were examined using multivariate logistic regression. From 100 patients, 32.0% had grade 4 neutropenia. Multivariate logistic regression analysis revealed that ERCC1 118C > T (odds ratio [OR], 3.43; 95% confidence interval [CI], 1.22-9.69; P = 0.020), CYP2B6*6 (OR, 4.51; 95% CI, 1.21-16.95; P = 0.025), body mass index (BMI) (OR, 6.94; 95% CI, 1.15-41.67; P = 0.035), and baseline white blood cell (WBC) count (OR, 2.99; 95% CI, 1.06-8.40; P = 0.038) were significant predictors of grade 4 neutropenia. ERCC1 and CYP2B6 gene polymorphisms were associated with the extent of grade 4 neutropenia in patients receiving AC chemotherapy. In addition to previously known risk factors, BMI and WBC counts, ERCC1 and CYP2B6 gene polymorphisms were also identified as independent strong predictors of grade 4 neutropenia.

Xiao Y, Jiao C, Lin Y, et al.
lncRNA UCA1 Contributes to Imatinib Resistance by Acting as a ceRNA Against miR-16 in Chronic Myeloid Leukemia Cells.
DNA Cell Biol. 2017; 36(1):18-25 [PubMed] Related Publications
Imatinib (IM) has been applied to the chronic phase of chronic myeloid leukemia (CML) and has great benefit on the prognosis of patients with CML. The function of drug efflux mediated by multidrug resistance protein-1 (MDR1) is considered as a main reason for IM drug resistance in CML cells. However, the exact mechanisms of MDR1 modulation in IM resistance of CML cells remain unclear. In the present study, long noncoding RNA (lncRNA) UCA1 was identified as an important modulator of MDR1 by a model system of leukemia cell lines with a gradual increase of MDR1 expression and IM resistance. Overexpression of UCA1 increased MDR1 expression to promote IM resistance of CML cells. Furthermore, for the first time, we demonstrated that UCA1 functions as a competitive endogenous (ceRNA) of MDR1 through completely binding the common miR-16. UCA1-MDR1 might be a novel target for enhancing the therapeutic efficacy of CML patients with IM resistance.

Choi HS, Cho SG, Kim MK, et al.
SH003 enhances paclitaxel chemosensitivity in MCF-7/PAX breast cancer cells through inhibition of MDR1 activity.
Mol Cell Biochem. 2017; 426(1-2):1-8 [PubMed] Related Publications
Paclitaxel is an anti-cancer drug for treating cancer, but paclitaxel resistance is reported in cancer cells. Multidrug resistance (MDR) is related with the epithelial-to-mesenchymal transition (EMT) mechanism, which plays a key role in cancer metastasis. Moreover, EMT mechanism is connected to tamoxifen resistance in breast cancer cells. Consequently, oncologists are interested in finding new MDR1 inhibitors originating from herbal medicines to have less side-effect. Here, we investigated an inhibition effect of SH003 on MDR1 activity in paclitaxel-resistant MCF-7/PAX breast cancer cells. Our results showed that paclitaxel did not inhibit a proliferation in paclitaxel-resistant MCF-7 breast cancer cells. Paclitaxel-resistant MCF-7 cells showed an increase of MDR1 activity, which was confirmed by measuring an amount of accumulated rhodamine 123 in the cells. Also, qRT-PCR and Western blot assays confirmed that paclitaxel-resistant MCF-7 cells exhibited high MDR1 expression level. Furthermore, paclitaxel-resistant MCF-7 cells showed mesenchymal morphology with alterations of EMT markers, and acquired tamoxifen resistance with a decrease of ERα expression. We also found that a combinatorial treatment of SH003 and paclitaxel in paclitaxel-resistant MCF-7 cells caused apoptosis in synergistic manner, which was due to SH003 inhibition of MDR1 expression. Therefore, SH003 could be a potential agent for overcoming MDR in drug-resistant cancer cells.

Dragoj M, Milosevic Z, Bankovic J, et al.
Targeting CXCR4 and FAK reverses doxorubicin resistance and suppresses invasion in non-small cell lung carcinoma.
Cell Oncol (Dordr). 2017; 40(1):47-62 [PubMed] Related Publications
BACKGROUND: Current high lung cancer mortality rates are mainly due to the occurrence of metastases and therapeutic resistance. Therefore, simultaneous targeting of these processes may be a valid approach for the treatment of this type of cancer. Here, we assessed relationships between CXC chemokine receptor type 4 (CXCR4) and focal adhesion kinase (FAK) gene expression levels and expression levels of the drug resistance-related genes ABCB1 and ABCC1, and tested the potential of CXCR4 and FAK inhibitors to reverse doxorubicin (DOX) resistance and to decrease the invasive capacity of non-small cell lung carcinoma (NSCLC) cells.
METHODS: qRT-PCR was used for gene expression analyses in primary lung tissue samples obtained from 30 NSCLC patients and the human NSCLC-derived cell lines NCI-H460, NCI-H460/R and COR-L23. MTT, flow cytometry, cell death and β-galactosidase activity assays were used to assess the in vitro impact of CXCR4 and FAK inhibitors on DOX sensitivity. In addition, invasion and gelatin degradation assays were used to assess the in vitro impact of the respective inhibitors on metastasis-related processes in combination with DOX treatment.
RESULTS: We found that ABCB1 over-expression was significantly associated with CXCR4 and FAK over-expression, whereas ABCC1 over-expression was associated with increased FAK expression. We also found that CXCR4 and FAK inhibitors strongly synergized with DOX in reducing cell viability, arresting the cell cycle in the S or G2/M phases and inducing senescence. Additionally, we found that DOX enhanced the anti-invasive potential of CXCR4 and FAK inhibitors by reducing gelatin degradation and invasion.
CONCLUSIONS: From our data we conclude that targeting of CXCR4 and FAK may overcome ABCB1 and ABCC1-dependent DOX resistance in NSCLC cells and that simultaneous treatment of these cells with DOX may potentiate the anti-invasive effects of CXCR4 and FAK inhibitors.

Gupta MK, Behara SK, Vadde R
In silico analysis of differential gene expressions in biliary stricture and hepatic carcinoma.
Gene. 2017; 597:49-58 [PubMed] Related Publications
In-silico attempt was made to identify the key hub genes which get differentially expressed in biliary stricture and hepatic carcinoma. Gene expression data, GSE34166, was downloaded from the GEO database, which contains 10 biliary stricture samples (4 benign control and 6 malignant carcinoma), for screening of key hub genes associated with the disease. R packages scripts were identified 85 differentially expressed genes. Further these genes were uploaded in WebGestalt database and identified nine key genes. Using STRING database and Gephi software, the protein-protein interaction networks were constructed and also studied gene ontology through WebGestalt. Finally, we identified four key genes (CXCR4, ADH1C, ABCB1 and ADH1A) are associated with liver carcinoma and further cross-validated with Liverome, Protein Atlas database and bibliography. In addition, transcription factors and their binding sites also studied. These identified hub genes and their transcription factors are the probable potential targets for possible future drug design.

Pavlikova L, Seres M, Imrichova D, et al.
The expression of P-gp in leukemia cells is associated with cross-resistance to protein N-glycosylation inhibitor tunicamycin.
Gen Physiol Biophys. 2016; 35(4):497-510 [PubMed] Related Publications
In P-gp-positive cell variants obtained from L1210 cells either by selection with vincristine (L1210/R) or by transfection with the human gene encoding P-gp (L1210/T), we have previously described cross-resistance to tunicamycin (TNM), a protein N-glycosylation inhibitor. Here we studied whether this cross-resistance also underlies P-gp-positive variants of human acute myeloid leukemia cells (AML) derived from SKM-1 and MOLM-13 cells (SKM-1/VCR, SKM-1/LEN, MOLM-13/VCR) by selection with vincristine (VCR) and lenalidomide (LEN). While SKM-1/LEN cells were P-gp positive, no P-gp was detected in MOLM-13/LEN cells. P-gp-positive cells could be repeatedly passaged in medium containing TNM. In contrast, more than 90% of P-gp-negative cells were entering and progressing through cell death mechanisms after the third passage in medium containing TNM. Combined apoptosis/necrosis cell death was detected in L1210 cells after exposure to TNM. Passaging of P-gp-negative AML cells in medium containing TNM induced preferentially apoptosis. Damage to P-gp-negative cells induced with TNM was associated with arrest in the G1 phase of the cell cycle. P-gp-positive leukemia cells differed from P-gp-negative cells in the composition of plasma membrane glycoproteins, which we monitored with the aid of different lectins. The application of TNM to cells induced additional changes in membrane-linked glycosides.

Ramírez-Pacheco A, Moreno-Guerrero S, Alamillo I, et al.
Mexican Childhood Acute Lymphoblastic Leukemia: A Pilot Study of the MDR1 and MTHFR Gene Polymorphisms and Their Associations with Clinical Outcomes.
Genet Test Mol Biomarkers. 2016; 20(10):597-602 [PubMed] Related Publications
BACKGROUND: Genetic polymorphisms in patients with acute lymphoblastic leukemia (ALL) may influence the toxicity of chemotherapeutic agents. Due to the importance of the transport P-glycoprotein and methylenetetrahydrofolate reductase in the metabolism of chemotherapeutic agents, we analyzed the MDR1 rs1045642 and MTHFR rs1801133 polymorphisms and their associations with clinical outcomes in Mexican childhood ALL patients.
METHODS: A total of 109 patients participated in this study. The clinical evaluation consisted of a physical examination and a laboratory test. Genotyping of MDR1 rs1045642 (3435 C>T) and MTHFR rs1801133 (677 C>T) was performed by polymerase chain reaction/restriction fragment length polymorphism. Statistical analyses were performed using SPSS 14.0. The odds ratios and 95% confidence intervals (CI) were estimated by logistic regression.
RESULTS: Individuals who were CC homozygotes at MDR1 rs1045642 had lower risk of having methotrexate plasma concentrations >1 μM and leukopenia grade I (odds ratio [OR] = 0.30; 95% CI = 0.13-0.72 and OR = 0.32; 95% CI = 0.14-0.72, respectively). Patients who were CC homozygotes at MTHFR rs1801133 had a higher risk of developing mucositis (OR = 3.61; 95% CI = 1.42-9.14).
CONCLUSION: MDR1 rs1045642 and MTHFR rs1801133 should be considered as diagnostic candidates for the identification of pediatric patients with a high risk of suffering adverse events during ALL treatment.

Kobayashi M, Funayama R, Ohnuma S, et al.
Wnt-β-catenin signaling regulates ABCC3 (MRP3) transporter expression in colorectal cancer.
Cancer Sci. 2016; 107(12):1776-1784 [PubMed] Free Access to Full Article Related Publications
We determined the gene expression profiles for 48 ATP binding cassette (ABC) transporters in matched colon cancer and normal colon tissues in order to provide insight into the mechanisms underlying expression of transporters related to colon carcinogenesis. The expression of ABCB1, ABCC1, ABCC2, ABCC3, and ABCG2 was altered in association with colon carcinogenesis. Among these transporters, the expression of ABCC3 was repressed by Wnt signaling pathway in colon cancer cell lines. Knockdown of the pathway components transcription factor 7-like 2 (TCF7L2) or β-catenin thus increased ABCC3 expression, whereas activation of Wnt signaling with inhibitors of glycogen synthase kinase-3β (GSK-3β) reduced it. ChIP and luciferase reporter assays also showed that TCF7L2 binds to the ABCC3 locus and regulates its expression. Finally, overexpression of ABCC3 in colon cancer cells conferred resistance to anticancer drug-induced cytotoxicity. Our data thus suggest that Wnt signaling represses ABCC3 expression during colon carcinogenesis, and that subsequent upregulation of ABCC3 expression during drug treatment might contribute to acquired drug resistance.

Feng R, Zhang HX, Zhang HG, Zhang CF
Role of ABCB1 C1236T, G2677T, and C3435T genetic polymorphisms in the development of acute leukemia in a Chinese population.
Genet Mol Res. 2016; 15(3) [PubMed] Related Publications
We carried out a case-control study to examine the relationship between the ATP-binding cassette subfamily B member 1 (ABCB1) gene polymorphisms C1236T, G2677T, and C3435T and risk of acute leukemia in a Chinese population. Between May 2013 and April 2015, we recruited 164 acute leukemia patients and 285 healthy controls, and determined polymorphism genotypes by polymerase chain reaction-restriction fragment length polymorphism. Using unconditional logistic regression analysis, we observed that in comparison to the wild-type sequence, the TT genotype [odds ratio (OR) = 2.15, 95% confidence interval (CI) = 1.12-4.10; P = 0.01] and the T allele (OR = 1.39, 95%CI = 1.05-1.86; P = 0.02) of ABCB1 G2677T were associated with acute leukemia susceptibility. The TT genotype (OR = 2.03, 95%CI = 1.11- 3.69; P = 0.01) and the T allele (OR = 1.39, 95%CI = 1.05-1.85; P = 0.02) of the C3435T polymorphism also increased acute leukemia risk compared to the wild-type form. However, no significant relationship was established between the ABCB1 C1236T variant and this disease. Our results suggest that the ABCB1 G2677T and C3435T sequence variations may affect susceptibility to acute leukemia.

Jiang YQ, Xu XP, Guo QM, et al.
Reversal of cisplatin resistance in non-small cell lung cancer stem cells by Taxus chinensis var.
Genet Mol Res. 2016; 15(3) [PubMed] Related Publications
Drug resistance in cells is a major impedance to successful treatment of lung cancer. Taxus chinensis var. inhibits the growth of tumor cells and promotes the synthesis of interleukins 1 and 2 and tumor necrosis factor, enhancing immune function. In this study, T. chinensis var.-induced cell death was analyzed in lung cancer cells (H460) enriched for stem cell growth in a defined serum-free medium. Taxus-treated stem cells were also analyzed for Rhodamine 123 (Rh-123) expression by flow cytometry, and used as a standard functional indicator of MDR. The molecular basis of T. chinensis var.-mediated drug resistance was established by real-time PCR analysis of ABCC1, ABCB1, and lung resistance-related protein (LRP) mRNA, and western blot analysis of MRP1, MDR1, and LRP. Our results revealed that stem cells treated with higher doses of T. chinensis var. showed significantly lower growth inhibition rates than did H460 cells (P < 0.05). The growth of stem and H460 cells treated with a combination of T. chinensis var. and cisplatin was also significantly inhibited (P < 0.05). Rh-123 was significantly accumulated in the intracellular region and showed delayed efflux in stem cells treated with T. chinensis var. (P < 0.05), compared to those treated with verapamil. T. chinensis var.-treated stem cells showed significant downregulation of the ABCC1, ABCB1, and LRP mRNA and MRP1, MDR1, and LRP (P < 0.05) compared to H460 cells. Thus, T. chinensis var.-mediated downregulation of MRP1, MDR1, and LRP might contribute to the reversal of drug resistance in non-small cell lung cancer stem cells.

Paszel-Jaworska A, Totoń E, Dettlaff K, et al.
Increased proapoptotic activity of electron beam irradiated doxorubicin and epirubicin in multidrug-resistant human leukemic cells.
Chem Biol Interact. 2016; 258:69-78 [PubMed] Related Publications
This study evaluated the effect of electron beam irradiation on the cytotoxic activity of anthracycline antibiotics such as doxorubicin (DOX), epirubicin (EPI), and dunorubicin (DAU) in human acute lymphoblastic leukemia cell line CCRF-CEM and its multidrug-resistant variant CCRF-VCR1000 cell line characterized by the overexpression of ABCB1 gene. Drugs were irradiated at doses of 10 and 25 kGy. Data from EPR studies proved that the highest concentration of free radicals was found in DOX and that the number of stable free radicals is always greater after irradiation. In in vitro studies, a higher cytotoxic activity of irradiated DOX and EPI in multidrug-resistant CCRF-VCR1000 cells was observed. This tendency was maintained during the storage at 4 °C for 90 days. Changes in CCRF-CEM cells' viability were not dependent on the irradiation status and its dose and were only drug-concentration dependent in all measurement time points. It was proved that increased potency of 25 kGy e-beam irradiated drugs results from their enhanced proapoptotic activity. Apoptotic cell death observed in CCRF-VCR1000 cells treated with irradiated drugs was caspase-8, -9, and -3 dependent and related to the increased Bax/Bcl-2 ratio. No significant differences in the effects of irradiated and non-irradiated drugs on p53 and NFκB transcription factor level and their translocation to the nucleus were noted. Increased activity of the irradiated drugs was not dependent on ABCB1 level.

Xue X, Chen F, Liu A, et al.
Reversal of the multidrug resistance of human ileocecal adenocarcinoma cells by acetyl-11-keto-β-boswellic acid via downregulation of P-glycoprotein signals.
Biosci Trends. 2016; 10(5):392-399 [PubMed] Related Publications
Multidrug resistance (MDR) represents a clinical obstacle to cancer chemotherapy since it causes cancer recurrence and metastasis. Acetyl-11-keto-β-boswellic acid (AKBA), an active ingredient derived from the plant Boswellia serrata, has been found to inhibit the growth of a wide variety of tumor cells, including glioma, colorectal cancer, leukemia, human melanoma, hepatocellular carcinoma, and prostate cancer cells. However, the actions of AKBA in multidrug-resistant cancer cells have not been fully elucidated. The current study examined the reversal of MDR by AKBA in a human ileocecal adenocarcinoma cell line with vincristine-induced resistance, HCT-8/VCR. A 3-[4, 5-dimethylthiazol-2-yl]-2,5-diphenyl-tetrazolium bromide (MTT) assay indicated that cytotoxicity increased drastically and the IC50 of VCR in HCT-8/VCR cells decreased in the presence of AKBA. AKBA had a maximum "fold reversal" of MDR (FR) of 9.19-fold. In addition, HCT-8/VCR cells treated with AKBA and VCR exhibited a higher percentage of apoptotic tumor cells according to flow cytometry. The reversal of MDR by AKBA was evident in an intracellular increase in Rhodamine (Rh123), indicating that the activity of P-glycoprotein (P-gp) was blocked. Furthermore, AKBA inhibited the expression of P-gp and decreased levels of expression of multidrug resistance gene 1 in HCT-8/VCR cells. The current results indicated that AKBA might be a potential agent to reverse MDR in human ileocecal adenocarcinoma.

Zhang J, Liu D, Zhang M, et al.
The cellular uptake mechanism, intracellular transportation, and exocytosis of polyamidoamine dendrimers in multidrug-resistant breast cancer cells.
Int J Nanomedicine. 2016; 11:3677-90 [PubMed] Free Access to Full Article Related Publications
Polyamidoamine dendrimers, which can deliver drugs and genetic materials to resistant cells, are attracting increased research attention, but their transportation behavior in resistant cells remains unclear. In this paper, we performed a systematic analysis of the cellular uptake, intracellular transportation, and efflux of PAMAM-NH2 dendrimers in multidrug-resistant breast cancer cells (MCF-7/ADR cells) using sensitive breast cancer cells (MCF-7 cells) as the control. We found that the uptake rate of PAMAM-NH2 was much lower and exocytosis of PAMAM-NH2 was much greater in MCF-7/ADR cells than in MCF-7 cells due to the elimination of PAMAM-NH2 from P-glycoprotein and the multidrug resistance-associated protein in MCF-7/ADR cells. Macropinocytosis played a more important role in its uptake in MCF-7/ADR cells than in MCF-7 cells. PAMAM-NH2 aggregated and became more degraded in the lysosomal vesicles of the MCF-7/ADR cells than in those of the MCF-7 cells. The endoplasmic reticulum and Golgi complex were found to participate in the exocytosis rather than endocytosis process of PAMAM-NH2 in both types of cells. Our findings clearly showed the intracellular transportation process of PAMAM-NH2 in MCF-7/ADR cells and provided a guide of using PAMAM-NH2 as a drug and gene vector in resistant cells.

Li L, Liu HC, Wang C, et al.
Overexpression of β-Catenin Induces Cisplatin Resistance in Oral Squamous Cell Carcinoma.
Biomed Res Int. 2016; 2016:5378567 [PubMed] Free Access to Full Article Related Publications
Abnormal expression of β-catenin contributes to tumor development, progression, and metastasis in various cancers. However, little is known about the relationship between abnormal expression of β-catenin and cisplatin chemotherapy in oral squamous cell carcinoma (OSCC). The present study aimed to investigate the effect of β-catenin on OSCC cisplatin resistance and evaluated the drug susceptibility of stable cell lines with β-catenin knockin and knockdown. In this study, we found that higher expression level of β-catenin can be observed in CDDP-treated cell lines as compared with the control group. Furthermore, the expression levels of β-catenin increased in both a concentration- and time-dependent manner with the cisplatin treatment. More importantly, the nuclear translocation of β-catenin could also be observed by confocal microscope analysis. Stable cell lines with CTNNB1 knockin and knockdown were established to further investigate the potential role and mechanism of β-catenin in the chemoresistance of OSCC in vitro and in vivo. Our findings indicated that overexpression of β-catenin promoted cisplatin resistance in OSCC in vitro and in vivo. We confirmed that GSK-3β, C-myc, Bcl-2, P-gp, and MRP-1 were involved in β-catenin-mediated drug resistance. Our findings indicate that the Wnt/β-catenin signaling pathway may play important roles in cisplatin resistance in OSCC.

Li K, Li X, Tian J, et al.
Downregulation of DNA-PKcs suppresses P-gp expression via inhibition of the Akt/NF-κB pathway in CD133-positive osteosarcoma MG-63 cells.
Oncol Rep. 2016; 36(4):1973-80 [PubMed] Related Publications
The development of chemoresistance is closely linked to the plateau of the survival rate in osteosarcoma (OS) patients. CD133-positive (CD133+) OS cells are known as cancer stem cells (CSCs) in OS and exhibit the characteristic of chemoresistance. In this study, CD133+ and CD133‑negative (CD133‑) MG‑63 cells were isolated by magnetic activated cell sorting (MACS). We verified that CD133+ MG‑63 cells were more resistant to cisplatin (CDDP) than CD133‑ MG‑63 cells. DNA‑dependent protein kinase catalytic subunit (DNA‑PKcs) and P‑glycoprotein (P‑gp) were expressed at higher levels in the CD133+ MG‑63 cells compared with those levels in the CD133‑ MG‑63 cells, whereas downregulation of DNA‑PKcs by small interfering RNA (siRNA) decreased chemoresistance to CDDP and P‑gp expression at the mRNA and protein levels in these cells. This indicated that DNA‑PKcs was correlated with P‑gp expression in the CD133+ MG‑63 cells. The Akt/NF‑κB pathway was hyperactivated in the CD133+ MG‑63 cells, whereas inhibition of the Akt/NF‑κB pathway downregulated P‑gp expression. In addition, downregulation of DNA‑PKcs suppressed the activity of the Akt/NF‑κB pathway. These results revealed that downregulation of DNA‑PKcs could decrease P‑gp expression via suppression of the Akt/NF‑κB pathway in CD133+ MG‑63 cells. Therefore, inhibition of DNA‑PKcs decreases P‑gp expression and sensitizes OS CSCs to chemotherapeutic agents in vitro, which needs to be further validated in vivo.

Kang G, Kim KR, Shim HJ, et al.
Effect of the allelic variants of ABCB1, CYP2D6 and HTR3B on response of ramosetron to prevent chemotherapy-induced nausea and vomiting in Korean cancer patients.
Asia Pac J Clin Oncol. 2017; 13(1):53-60 [PubMed] Related Publications
AIM: Despite appropriate use of antiemetics including 5-hydroxytryptamine type 3 (5-HT3 ) receptor antagonists, chemotherapy-induced nausea and vomiting (CINV) is still an unsolved problem in patients with anticancer drugs. We examined whether the variants of ABCB1, CYP2D6 and HTR3B affect efficacy of ramosetron, a selective 5-HT3 receptor antagonist in a dose escalation clinical trial.
METHODS: We conducted a clinical trial on patients who underwent FOLFOX combination chemotherapy. The participants were randomized into three groups of ramosetron: 0.3 mg (standard dose), 0.45 mg and 0.6 mg. Rhodes index of nausea, vomiting and retching were measured at 1, 6 h, day 1, day 2 and day 7 after the administration of ramosetron as a clinical parameter of CINV and polymorphism was analyzed from genomic DNA.
RESULTS: There was a dose-dependent decrease in the nausea and vomiting scores at day 1 and day 2, not statistically significant. The Rhodes index of nausea, vomiting and retching score at day 1 in participants with HTR3B-100_-102delAAG deletion variants was significantly higher than wild type participants, regardless of dosages. However, the polymorphisms including ABCB1, CYP2D6 and other HTR3B genes did not affect response to ramosetron after chemotherapy.
CONCLUSION: These results suggest that the -AAG deletion variant of the 5-HT3B receptor gene may contribute to variability in response to antiemetic therapy for CINV regardless of dose escalation. These results suggest that carrying a -100_-102delAAG variant of 5-HT3 gene should be supported by alternate or additive antiemetics in addition to 5-HT3 antagonists to control acute emesis.

Disulphide cross linked pullulan based cationic polymer for improved gene delivery and efflux pump inhibition.
Colloids Surf B Biointerfaces. 2016; 146:879-87 [PubMed] Related Publications
Multidrug resistance is a hurdle to successful cancer chemotherapy. Over expression of P-glycoprotein (P-gp) is a prime contributing factor for drug resistance. In this study, a disulphide cross-linked pullulan-based cationic polymer (PPSS) was synthesized to act simultaneously as gene delivery vehicle and efflux pump inhibitor. The PPSS nanoplexes were of size <200nm with the zeta potential of +15 to +20mV. The cytotoxicity studies using C6 and L929 cells showed that PPSS polymers are non-toxic even at high polymer concentrations. The PPSS/pDNA nanoplex showed superior uptake in confocal microscopy with 97% uptake by flow cytometry. The efficacy of efflux pump inhibition by the PPSS nanoplex was established by the enhanced intracellular retention of DOX. The enhanced cell death by p53/PPSS/DOX nanoplexes was attributed to the synergistic effect of P-gp inhibition and p53 transfection efficiency. Therefore, this multifunctional polymeric system may have significant promise for therapeutic application against cancer drug resistance.

Arrigoni E, Galimberti S, Petrini M, et al.
ATP-binding cassette transmembrane transporters and their epigenetic control in cancer: an overview.
Expert Opin Drug Metab Toxicol. 2016; 12(12):1419-1432 [PubMed] Related Publications
INTRODUCTION: Members of the ATP-binding cassette (ABC) transmembrane transporters control the passage of several substrates across cell membranes, including drugs. This means that ABC transporters may exert a significant influence on the kinetics and dynamics of pharmacological agents, being responsible for the occurrence of multidrug-resistant (MDR) phenotype. Pharmacogenetic analyses have shed light on gene expression and polymorphisms as possible markers predictive of transporter activity. However, a non-negligible part of the variability in drug pharmacokinetics and pharmacodynamics still remains. Further research has demonstrated that different epigenetic mechanisms exert a coordinated control over ABC genes, and on the corresponding MDR phenotype. Areas covered: DNA methylation and histone modifications (namely acetylation, methylation, phosphorylation, etc.) significantly impact gene expression, as well as noncoding RNA molecules that are involved in the post-transcriptional control of the ABC transporters ABCB1, ABCC1 and ABCG2. We describe the epigenetic mechanisms of gene expression control for ABC transporters and their relevant association with the MDR phenotype in human cancer. Expert opinion: The clinical meaning of those observations is discussed in the review, highlighting the importance of the epigenetic control of the ABC transporters for the clinical therapeutic outcomes that despite their effects and applications, requires further investigation.

Moiseeva NI, Susova OY, Mitrofanov AA, et al.
Connection between Proliferation Rate and Temozolomide Sensitivity of Primary Glioblastoma Cell Culture and Expression of YB-1 and LRP/MVP.
Biochemistry (Mosc). 2016; 81(6):628-35 [PubMed] Related Publications
Glioblastomas (GBL) are the most common and aggressive brain tumors. They are distinguished by high resistance to radiation and chemotherapy. To find novel approaches for GBL classification, we obtained 16 primary GBL cell cultures and tested them with real-time PCR for mRNA expression of several genes (YB-1, MGMT, MELK, MVP, MDR1, BCRP) involved in controlling cell proliferation and drug resistance. The primary GBL cultures differed in terms of proliferation rate, wherein a group of GBL cell cultures with low proliferation rate demonstrated higher resistance to temozolomide. We found that GBL primary cell cultures characterized by high proliferation rate and lower resistance to temozolomide expressed higher mRNA level of the YB-1 and MDR1 genes, whereas upregulated expression of MVP/LRP mRNA was a marker in the group of GBL with low proliferation rate and high resistance. A moderate correlation between expression of YB-1 and MELK as well as YB-1 and MDR1 was found. In the case of YB-1 and MGMT expression, no correlation was found. A significant negative correlation was revealed between mRNA expression of MVP/LRP and MELK, MDR1, and BCRP. No correlation in expression of YB-1 and MVP/LRP genes was observed. It seems that mRNA expression of YB-1 and MVP/LRP may serve as a marker for GBL cell cultures belonging to distinct groups, each of which is characterized by a unique pattern of gene activity.

Chhikara S, Sazawal S, Mishra P, et al.
C1236T polymorphism in MDR1 gene correlates with therapeutic response to imatinib mesylate in Indian patients with chronic myeloid leukaemia.
Natl Med J India. 2015 Nov-Dec; 28(6):272-5 [PubMed] Related Publications
Patients with chronic myeloid leukaemia show an excellent response to treatment with imatinib. However, in some patients, the disease is resistant to imatinib. This resistance may be related to the presence of genetic variations on the drug's pharmacokinetics and metabolism. We therefore studied three polymorphisms (C1236T, G2677T and C3435T) in the human multidrug-resistance gene (MDR1) in 86 patients with chronic myeloid leukaemia treated with imatinib. Imatinib resistance was more frequent in patients with TT genotype at locus 1236 than in those with CT/CC genotypes (p=0.003). For the other two loci (G2677T and C3435T), resistance was seen to be higher for TT genotype when compared to GG/GT and CT/CC but it was not statistically significant (p=0.13 and p=0.099). In conclusion, determination of C1236T MDR1 genotype may help to predict response to imatinib therapy in patients with chronic myeloid leukaemia.

Yang H, Ding R, Tong Z, et al.
siRNA Targeting of MDR1 Reverses Multidrug Resistance in a Nude Mouse Model of Doxorubicin-resistant Human Hepatocellular Carcinoma.
Anticancer Res. 2016; 36(6):2675-82 [PubMed] Related Publications
AIM: To investigate the effects of vector-based small interfering RNA (siRNA) targeting MDR1 on the reversal of multidrug resistance in a mouse model of doxorubicin (DOX)-resistant human hepatocellular carcinoma.
MATERIALS AND METHODS: Three siRNAs plasmid vectors (MDR1 siRNA1, MDR1 siRNA2 and MDR1 siRNA3) targeting MDR1 were constructed and transfected into DOX-resistant human hepatocellular carcinoma Bel-7402/ADM cells. The expression of MDR1 mRNA and P-glycoprotein (P-gp) was detected with RT-PCR and western blotting, respectively. A nude mouse model of DOX-resistance was established with untransfected Bel-7402/ADM or Bel-7402/ADM transfected with MDR1 siRNA (Bel-7402/ADMsi). The nude mice with tumors from untransfected Bel-7402/ADM cells were treated with either saline (Group 1); intravenous DOX (Group 2); or the combination of intra-tumoral MDR1 siRNA and intravenous DOX (Group 3). The nude mice with tumors from Bel-7402/ADMsi cells were treated with intravenous DOX (Group 4). DOX and MDR1 siRNA were administered twice a week at 20 mg/kg/dose and 9.8 mg/kg/dose, respectively. Tumor growth was measured to assess reversal of multidrug resistance by MDR1 siRNA.
RESULTS: MDRl mRNA and P-gp expression of Bel-7402/ADM cells was reduced by transfection of three siRNAs with different silencing efficiency (p<0.05). DOX treatment (Group 4) resulted in significant reduction in tumor size in the Bel-7402/ADMsi tumor model (p<0.05), indicating reversal of multidrug resistance in tumor by MDR1 siRNA. However, the combination treatment of intratumoral MDR1 siRNA and DOX (Group 3) showed no significant anti-tumor efficacy in the untransfected Bel-7402/ADM (p>0.05) tumor model, suggesting poor in vivo transfection efficiency of MDR1 siRNA. Analysis of the tumor samples showed the reduced expression level of MDR1 mRNA and P-gp was due to efficacy of MDR1 siRNA.
CONCLUSION: In vitro transfection of siRNAs' vectors targeting the MDR1 gene can effectively silence MDR1 mRNA and P-gp expression in DOX-resistant human hepatocellular carcinoma Bel-7402/ADM cells that resulted in reversal of multidrug resistance to DOX in the xenograft tumor model.

Niazi M, Zakeri-Milani P, Najafi Hajivar S, et al.
Nano-based strategies to overcome p-glycoprotein-mediated drug resistance.
Expert Opin Drug Metab Toxicol. 2016; 12(9):1021-33 [PubMed] Related Publications
INTRODUCTION: The discussion about cancer treatment has a long history. Chemotherapy, one of the promising approaches in cancer therapy, is limited in the clinic as plenty of factors evolve and prevent appropriate therapeutic response to drugs. Multi-drug resistance (MDR), which is mostly P-glycoprotein-mediated, is described as the most well-known impediment in this contribution. It extrudes several agents out of cells, arising MDR and decreasing the bioavailability of drugs. Hence, cancer cells become insensitive to chemotherapy.
AREAS COVERED: Many agents have been developed to reverse MDR, but it is difficult to deliver them into cancer sites and cancer cells. The emerging nano-based drug delivery systems have been more effective to overcome P-glycoprotein-mediated MDR by increasing the intracellular delivery of these agents. Here, we represent systems including siRNA-targeted inhibition of P-gp, monoclonal antibodies, natural extracts, conventional inhibitors, hard nanoparticles and soft nanoparticles as delivery systems in addition to a novel approach applying cell penetrating peptides.
EXPERT OPINION: Overcoming cancer drug resistance using innovative nanotechnology is being increasingly used and developed. Among resistance mechanisms, drug efflux transporter inhibitors and MDR gene expression silencing are among the those being investigated. In the near future, it seems some of these nanomedical approaches might become the mainstay of effective treatment of important human conditions like cancer.

Li GY, Zhang L, Liu JZ, et al.
Marine drug Haishengsu increases chemosensitivity to conventional chemotherapy and improves quality of life in patients with acute leukemia.
Biomed Pharmacother. 2016; 81:160-5 [PubMed] Related Publications
BACKGROUND: Pharmacological management of acute leukemia remains a challenge. A seashell protein Haishengsu (HSS) has been found to exert anticancer activities in recent in vitro studies. The aim of this study was to determine whether the addition of HSS to the conventional chemotherapies would increase chemosensitivity and improves quality of life in patients with acute leukemia.
METHODS: Two hundred and forty-eight patients with acute leukemia were enrolled in a double-blind, and placebo-controlled study. In addition to conventional chemotherapy, 142 patients received HSS and 106 received placebo. In an in vitro study, the expression of P-gp was evaluated by flow cytometry in a drug-resistant leukemia cell line (K562/ADM cells). Sorcin was examined by Western blot.
RESULTS: The complete remission rates in the HSS treatment group were all higher than in the placebo group with non-relapsing leukemia and relapsed leukemia (p<0.05). Less patients in the HSS group experienced gastrointestinal side effects from chemotherapy, whereas more patients had increased food take and an increase in Karnofsky performance status (KPS) score (p<0.01). In vitro, the expression of P-gp and sorcin in the HSS treated cells were lower than in the control group cells (p<0.01).
CONCLUSION: When added to conventional chemotherapy, HSS improves the complete remission rates and quality of life in patients with acute leukemia. The in vitro findings indicate that suppression of P-gp and sorcin genes in leukemia cells may be involved in the beneficial effects of HSS.

Šemeláková M, Jendželovský R, Fedoročko P
Drug membrane transporters and CYP3A4 are affected by hypericin, hyperforin or aristoforin in colon adenocarcinoma cells.
Biomed Pharmacother. 2016; 81:38-47 [PubMed] Related Publications
Our previous results have shown that the combination of hypericin-mediated photodynamic therapy (HY-PDT) at sub-optimal dose with hyperforin (HP) (compounds of Hypericum sp.), or its stable derivative aristoforin (AR) stimulates generation of reactive oxygen species (ROS) leading to antitumour activity. This enhanced oxidative stress evoked the need for an explanation for HY accumulation in colon cancer cells pretreated with HP or AR. Generally, the therapeutic efficacy of chemotherapeutics is limited by drug resistance related to the overexpression of drug efflux transporters in tumour cells. Therefore, the impact of non-activated hypericin (HY), HY-PDT, HP and AR on cell membrane transporter systems (Multidrug resistance-associated protein 1-MRP1/ABCC1, Multidrug resistance-associated protein 2-MRP2/ABCC2, Breast cancer resistance protein - BCRP/ABCG2, P-glycoprotein-P-gp/ABCC1) and cytochrome P450 3A4 (CYP3A4) was evaluated. The different effects of the three compounds on their expression, protein level and activity was determined under specific PDT light (T0+, T6+) or dark conditions (T0- T6-). We found that HP or AR treatment affected the protein levels of MRP2 and P-gp, whereas HP decreased MRP2 and P-gp expression mostly in the T0+ and T6+ conditions, while AR decreased MRP2 in T0- and T6+. Moreover, HY-PDT treatment induced the expression of MRP1. Our data demonstrate that HP or AR treatment in light or dark PDT conditions had an inhibitory effect on the activity of individual membrane transport proteins and significantly decreased CYP3A4 activity in HT-29 cells. We found that HP or AR significantly affected intracellular accumulation of HY in HT-29 colon adenocarcinoma cells. These results suggest that HY, HP and AR might affect the efficiency of anti-cancer drugs, through interaction with membrane transporters and CYP3A4.

Stavrovskaya AA, Shushanov SS, Rybalkina EY
Problems of Glioblastoma Multiforme Drug Resistance.
Biochemistry (Mosc). 2016; 81(2):91-100 [PubMed] Related Publications
Glioblastoma multiforme (GBL) is the most common and aggressive brain neoplasm. A standard therapeutic approach for GBL involves combination therapy consisting of surgery, radiotherapy, and chemotherapy. The latter is based on temozolomide (TMZ). However, even by applying such a radical treatment strategy, the mean patient survival time is only 14.6 months. Here we review the molecular mechanisms underlying the resistance of GBL cells to TMZ including genetic and epigenetic mechanisms. Present data regarding a role for genes and proteins MGMT, IDH1/2, YB-1, MELK, MVP/LRP, MDR1 (ABCB1), and genes encoding other ABC transporters as well as Akt3 kinase in developing resistance of GBL to TMZ are discussed. Some epigenetic regulators of resistance to TMZ such as microRNA and EZH2 are reviewed.

Sribenja S, Natthasirikul N, Vaeteewoottacharn K, et al.
 Thymosin β10 as a predictive biomarker of response to 5-fluorouracil chemotherapy in cholangiocarcinoma.
Ann Hepatol. 2016 Jul-Aug; 15(4):577-85 [PubMed] Related Publications
UNLABELLED:  Introduction and aim. 5-Fluorouracil (5-FU) is the most commonly used chemotherapeutic drug in the treatment of cholangiocarcinoma (CCA). Since development of drug resistance to 5-FU in CCA patients is the primary cause of treatment failure, a better understanding of the mechanism of drug resistance of this cancer is essential to improve the efficacy of 5-FU in CCA therapy.
MATERIAL AND METHODS: A 5-FU resistant CCA cell line (M214-5FUR) for a comparative chemo-resistance study was established. Real time RT-PCR was used to determine gene expression levels. Cell cytotoxicity was measured by the MTT assay. Protein expression levels were detected by the immunofluorescene method.
RESULTS: It was found that 5-FU resistance was associated with the overexpression of T?10 in CCA cell lines. 5-FU treatment at various concentrations induced the expressions of T?10 and ABC transporters (ABCB1, ABCG2 ABCA3) in two CCA cell lines, KKU-M055 and KKU-M214. M214-5FUR, a 5-FU-resistant cell line, exhibited a 5-FU resistant phenotype with a 16-fold extremely high expression of T?10 and ABC transporters, as compared to the parental cells, KKU-M214. siRNA targeted to T?10 significantly reduced expression of ABC transporters tested in the M214-5FUR cells (P < 0.05).
CONCLUSIONS: The present novel findingsof T?10 connected with drug resistance as shown in this study provides a new insight for the therapeutic value of T?10 as a predictive biomarker of 5-FU chemoresistance. Inhibiting T?10 may be a valuable adjunct for suppression of ABC transporters and sensitizing chemotherapy treatment, especially 5-FU in CCA patients.

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