Gene Summary

Gene:ABCC4; ATP binding cassette subfamily C member 4
Aliases: MRP4, MOATB, MOAT-B
Summary:The 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 MRP subfamily which is involved in multi-drug resistance. This family member plays a role in cellular detoxification as a pump for its substrate, organic anions. It may also function in prostaglandin-mediated cAMP signaling in ciliogenesis. Alternative splicing of this gene results in multiple transcript variants. [provided by RefSeq, Sep 2014]
Databases:VEGA, OMIM, HGNC, Ensembl, GeneCard, Gene
Protein:multidrug resistance-associated protein 4
Source:NCBIAccessed: 11 March, 2017


What does this gene/protein do?
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Cancer Overview

Research Indicators

Publications Per Year (1992-2017)
Graph generated 11 March 2017 using data from PubMed using criteria.

Literature Analysis

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Tag cloud generated 11 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: ABCC4 (cancer-related)

Santos MD, Silva C, Rocha A, et al.
Prognostic and Therapeutic Potential Implications of Genetic Variability in Prostaglandin E2 Pathway Genes in Rectal Cancer.
Anticancer Res. 2017; 37(1):281-291 [PubMed] Related Publications
AIM: To evaluate the prognostic significance and potential therapeutic implication of genetic variability in prostaglandin E2 pathway genes in patients with locally advanced rectal cancer (LARC) treated with neoadjuvant chemoradiotherapy (nCRT) followed by surgery.
MATERIALS AND METHODS: This cohort study included 167 patients with LARC, treated with nCRT followed by surgery. A total of 61 single nucleotide polymorphisms (SNPs) were characterized using the Sequenom platform through multiplex amplification followed by mass-spectometric product separation. Surgical specimens were classified according to Mandard tumor regression grade (TRG). The patients were divided as 'good responders' (Mandard TGR1-2) and 'poor responders' (Mandard TRG3-5). We examined prognostic value of polymorphisms studied to determine if they are related to Mandard response.
RESULTS: Mandard tumor response and rs17268122 in ATP binding cassette subfamily C member (ABCC4) gene were the only two parameters with independent prognostic significance for disease-free survival.
CONCLUSION: tagSNP ABCC4 rs17268122 appears to be a prognostic factor in LARC treated with nCRT and surgery, independently of response to nCRT. The screening of ABCC4 rs17268122 tagSNP and the Mandard tumor response in clinical practice may help to identify patients with different rectal cancer prognosis and contribute to an individualized therapeutic decision tree.

Drenberg CD, Hu S, Li L, et al.
ABCC4 Is a Determinant of Cytarabine-Induced Cytotoxicity and Myelosuppression.
Clin Transl Sci. 2016; 9(1):51-9 [PubMed] Free Access to Full Article Related Publications
Resistance to cytarabine remains a major challenge in the treatment of acute myeloid leukemia (AML). Based on previous studies implicating ABCC4/MRP4 in the transport of nucleosides, we hypothesized that cytarabine is sensitive to ABCC4-mediated efflux, thereby decreasing its cytotoxic response against AML blasts. The uptake of cytarabine and its monophosphate metabolite was found to be facilitated in ABCC4-expressing vesicles and intracellular retention was significantly impaired by overexpression of human ABCC4 or mouse Abcc4 (P < 0.05). ABCC4 was expressed highly in AML primary blasts and cell lines, and cytotoxicity of cytarabine in cells was increased in the presence of the ABCC4 inhibitors MK571 or sorafenib, as well as after ABCC4 siRNA. In Abcc4-null mice, cytarabine-induced hematological toxicity was enhanced and ex vivo colony-forming assays showed that Abcc4-deficiency sensitized myeloid progenitors to cytarabine. Collectively, these studies demonstrate that ABCC4 plays a protective role against cytarabine-mediated insults in leukemic and host myeloid cells.

Tomonari T, Takeishi S, Taniguchi T, et al.
MRP3 as a novel resistance factor for sorafenib in hepatocellular carcinoma.
Oncotarget. 2016; 7(6):7207-15 [PubMed] Free Access to Full Article Related Publications
The mechanism of resistance of hepatocellular carcinoma (HCC) to sorafenib is unknown and no useful predictive biomarker for sorafenib treatment has been reported. Accordingly, we established sorafenib-resistant HCC cells and investigated the underlying mechanism of resistance to sorafenib. Sorafenib-resistant cell lines were established from the HCC cell line PLC/PRF5 by cultivation under continuous exposure to increasing concentration of sorafenib. The IC50 values of the 2 resistant clones PLC/PRF5-R1 and PLC-PRF5-R2 were 9.2±0.47 μM (1.8-fold) and 25±5.1 μM (4.6-fold) respectively, which were significantly higher than that of parental PLC/PRF5 cells (5.4±0.17 μM) (p < 0.01 respectively), as determined by MTT assay. Western blot analysis of signal transduction-related proteins showed no significant differences in expression of AKT/pAKT, mTOR/pmTOR, or ERK/pERK between the 2 resistant clones versus parent cells, suggesting no activation of an alternative signal transduction pathway. Likewise, when expression of membrane transporter proteins was determined, there were no significant differences in expression levels of BSEP, MDR1, MRP2, BCRP, MRP4 and OCT1 between resistant clones and parent cells. However, the expression levels of MRP3 in the 2 resistant clones were significantly higher than that of parent cells. When MRP3 gene was knocked down by siRNA in PLC-PRF5-R2 cells, the sensitivity of the cells to sorafenib was restored. In the analysis of gene mutation, there was no mutation in the activation segment of Raf1 kinase in the resistant clones. Our data clearly demonstrate that the efflux transporter MRP3 plays an important role in resistance to sorafenib in HCC cells.

Chen SF, Zhang ZY, Zhang JL
Meloxicam increases intracellular accumulation of doxorubicin via downregulation of multidrug resistance-associated protein 1 (MRP1) in A549 cells.
Genet Mol Res. 2015; 14(4):14548-60 [PubMed] Related Publications
It has been suggested that selected COX inhibitors can overcome multidrug resistance through the inhibition of ATP‑binding cassette-transporter proteins thereby enhancing the inhibitory effect of doxorubicin on human tumor growth and promoting the actions of cytostatics. However, their effect on lung cancer and the molecular mechanisms involved in the overcoming of multidrug resistance are unclear. In the present study, the ability of meloxicam, a COX-2-specific inhibitor to enhance doxorubicin‑mediated inhibition was investigated in human A549 lung cancer in vivo and in vitro. In order to unravel the molecular mechanisms involved in doxorubicin accumulation, we measured the levels of multidrug resistance-associated protein (MRP)-transporter protein activity and expression by western blotting, since this has been implicated in meloxicam action as well as in chemoresistance. We found that, in A549 cells, meloxicam could increase intracellular accumulation of doxorubicin, a substrate for MRP, through inhibition of cellular export. Western blot analysis indicated that meloxicam reduced the expression of MRP1 and MRP4. The results reported in the present study demonstrate for the first time that the specific COX-2 inhibitor meloxicam can increase the intracellular accumulation of doxorubicin and enhance doxorubicin-induced cytotoxicity in A549 cancer cells by reducing the expression of MRP1 and MRP4.

Zhang X, Zhao L, Li X, et al.
ATP-binding cassette sub-family C member 4 (ABCC4) is overexpressed in human NK/T-cell lymphoma and regulates chemotherapy sensitivity: Potential as a functional therapeutic target.
Leuk Res. 2015; 39(12):1448-54 [PubMed] Related Publications
Nasal-type natural killer/T-cell (NK/T-cell) lymphomas are subtypes of non-Hodgkin's lymphoma (NHL), which are typically more clinically aggressive. There is, however relatively little understanding of nasal-type NK/T-cell lymphoma molecular pathogenesis. Thus, in this study we applied RNA sequencing to systematically screen for altered gene expression in human NK/T-cell lymphoma cell lines YTS and SNK-6 versus normal NK cells. We found that ATP-binding cassette sub-family C Member 4 (ABCC4) levels were significantly upregulated both in human NK/T-cell lymphoma YTS and SNK-6 cells, as compared with normal NK cells. These expression levels were further confirmed by real-time PCR. Protein levels of ABCC4 were also significantly higher in YTS and SNK-6 cells as compared with normal NK cells. Clinically relevant, ABCC4 expression levels were significantly higher in human NK/T-cell lymphoma tissues as compared with control nasal mucosa tissues, confirmed by immunohistochemical staining. In addition, we explored the biological function of such ABCC4 upregulation. Overexpression of ABCC4 by lentivirus transfection induced chemotherapy resistance to epirubicin (EPI) and cisplatin (DDP) in YTS cells. In contrast, knockdown of ABCC4 expression by shRNA contributed to chemotherapy sensitivity by both EPI and DDP. Furthermore, overexpression of ABCC4 inhibited, while downregulation of ABCC4 increased, YTS cell apoptosis following treatment by EPI or DDP. Therefore, the present study identified ABCC4 to be overexpressed in human NK/T-cell lymphoma cells, to regulate chemotherapy sensitivity to EPI and DDP, and possibly to be a functional therapeutic target. These findings may provide a basic rationale for new approaches in the effort to develop anti-tumor therapeutics for NK/T-cell lymphoma.

Demidenko R, Razanauskas D, Daniunaite K, et al.
Frequent down-regulation of ABC transporter genes in prostate cancer.
BMC Cancer. 2015; 15:683 [PubMed] Free Access to Full Article Related Publications
BACKGROUND: ATP-binding cassette (ABC) transporters are transmembrane proteins responsible for the efflux of a wide variety of substrates, including steroid metabolites, through the cellular membranes. For better characterization of the role of ABC transporters in prostate cancer (PCa) development, the profile of ABC transporter gene expression was analyzed in PCa and noncancerous prostate tissues (NPT).
METHODS: TaqMan Low Density Array (TLDA) human ABC transporter plates were used for the gene expression profiling in 10 PCa and 6 NPT specimens. ABCB1 transcript level was evaluated in a larger set of PCa cases (N = 78) and NPT (N = 15) by real-time PCR, the same PCa cases were assessed for the gene promoter hypermethylation by methylation-specific PCR.
RESULTS: Expression of eight ABC transporter genes (ABCA8, ABCB1, ABCC6, ABCC9, ABCC10, ABCD2, ABCG2, and ABCG4) was significantly down-regulated in PCa as compared to NPT, and only two genes (ABCC4 and ABCG1) were up-regulated. Down-regulation of ABC transporter genes was prevalent in the TMPRSS2-ERG-negative cases. A detailed analysis of ABCB1 expression confirmed TLDA results: a reduced level of the transcript was identified in PCa in comparison to NPT (p = 0.048). Moreover, the TMPRSS2-ERG-negative PCa cases showed significantly lower expression of ABCB1 in comparison to NPT (p = 0.003) or the fusion-positive tumors (p = 0.002). Promoter methylation of ABCB1 predominantly occurred in PCa and was rarely detected in NPT (p < 0.001).
CONCLUSIONS: The study suggests frequent down-regulation of the ABC transporter genes in PCa, especially in the TMPRSS2-ERG-negative tumors.

Hareedy MS, El Desoky ES, Woillard JB, et al.
Genetic variants in 6-mercaptopurine pathway as potential factors of hematological toxicity in acute lymphoblastic leukemia patients.
Pharmacogenomics. 2015; 16(10):1119-34 [PubMed] Related Publications
AIM: We investigated the associations between variants in genes coding for enzymes and transporters related to the 6-mercaptopurine pathway and clinical outcomes in pediatric patients with acute lymphoblastic leukemia.
MATERIALS & METHODS: Statistical association between gender, age and genotypes of selected SNPs, and the risks of hematological toxicity and relapse were investigated using a Cox proportional hazard model in 70 acute lymphoblastic leukemia patients from upper Egypt.
RESULTS: We found significant associations between ITPA, IMPDH1, SLC29A1, SLC28A2, SLC28A3 and ABCC4 SNPs and one or more of the hematological toxicity manifestations (neutropenia, agranulocytosis and leukopenia); age was significantly related to relapse.
CONCLUSION: Genetic polymorphisms in enzymes and transporters involved in the 6-mercaptopurine pathway should be considered during its use to avoid hematological toxicity.

Suzuki R, Fukushima H, Noguchi E, et al.
Influence of SLCO1B1 polymorphism on maintenance therapy for childhood leukemia.
Pediatr Int. 2015; 57(4):572-7 [PubMed] Related Publications
BACKGROUND: Management of the adverse effects of chemotherapy is essential to improve outcome of children with leukemia. Some genetic polymorphisms can predict treatment-related toxicity, and be used individually in dose modification of 6-mercaptopurine (6-MP) and methotrexate (MTX) in maintenance therapy for childhood acute lymphoblastic leukemia (ALL). We investigated associations between clinical course and candidate gene polymorphisms less evaluated in Japanese patients.
METHODS: Fifty-three children who received maintenance chemotherapy were enrolled in this study. The scheduled dose of oral 6-MP was 40 mg/m(2) daily and that of oral MTX was 25 mg/m(2) weekly. The doses were adjusted according to white blood cell count (target range, 2.5-3.5 × 10(9) /L) and aspartate aminotransferase and alanine aminotransferase level (< 750 IU/L). Eight polymorphisms in six candidate genes, TPMT, ITPA, MRP4, MTHFR, RFC1, and SLCO1B1, were genotyped using the Taqman PCR method. Clinical course was reviewed retrospectively from medical records.
RESULTS: The average dose of 6-MP was lower in the patients with at least one variant allele at SLCO1B1 c.521 T > C than in the patients with wild homozygous genotype. The other analyzed polymorphisms were not associated with toxicity, 6-MP, or MTX dose.
CONCLUSIONS: Polymorphism of SLCO1B1 c.521 T > C could be a strong predictor of 6-MP dose reduction in maintenance chemotherapy in childhood ALL.

He Z, Hu B, Tang L, et al.
The overexpression of MRP4 is related to multidrug resistance in osteosarcoma cells.
J Cancer Res Ther. 2015 Jan-Mar; 11(1):18-23 [PubMed] Related Publications
Doxorubicin (Adriamycin, ADM) is an antimitotic drug used in the treatment of a wide range of malignant tumors, including acute leukemia, lymphoma, osteosarcoma, breast cancer, and lung cancer. Multidrug resistance-associated proteins (MRPs) are members of a superfamily of ATP-binding cassette (ABC) transporters, which can transport various molecules across extra- and intra-cellular membranes. The aim of this study was to investigate whether there was a correlation between MRP4 and primary ADM resistance in osteosarcoma cells. In this paper, we chose the human osteosarcoma cell line MG63, ADM resistant cell line MG63/DOX, and the patient's primary cell GSF-0686. We checked the ADM sensitivity and cytotoxicity of all the three cells by cell proliferation assay. The intracellular drug concentrations were measured by using LC-MS/MS. We also examined MRP4 gene expression by RT-PCR and Western Blot. We found that the intracellular ADM concentration of the parent osteosarcoma cell line MG63 was higher than the ADM resistant osteosarcoma MG63/DOX cell line or the GSF-0686 cell after ADM treatment (P < 0.05). In addition, MRP4 mRNA and protein levels in ADM resistant osteosarcoma cells were higher than in MG63 cell (P < 0.05). Taking together, this work suggests that overexpression of MRP4 may confer ADM resistance in osteosarcoma cells.

Carozzo A, Diez F, Gomez N, et al.
Dual role of cAMP in the transcriptional regulation of multidrug resistance-associated protein 4 (MRP4) in pancreatic adenocarcinoma cell lines.
PLoS One. 2015; 10(3):e0120651 [PubMed] Free Access to Full Article Related Publications
Cyclic AMP represents one of the most studied signaling molecules and its role in proliferation and differentiation processes has been well established. Intracellular cAMP levels are tightly regulated where the MRP4 transporter plays a major role. In the present study, we sought to establish whether cAMP modulated MRP4 expression in pancreatic adenocarcinoma cell lines. Quantitative PCR and western blot studies showed that cAMP-increasing agents enhanced MRP4 transcripts and protein levels in PANC-1 cells. Reporter luciferase experiments carried out in pancreatic AR42J cells showed that intracellular cAMP up-regulates MRP4 through an Epac2- and Rap1-mediated mechanism whereas extracellular cAMP reduced MRP4 promoter activity by a MEK/ERK-mediated pathway. Present results show that cAMP regulates MRP4 promoter activity, and further indicate that the balance between intracellular and extracellular cAMP levels determines MRP4 expression.

Islam MS, Islam MS, Parvin S, et al.
Effect of GSTP1 and ABCC4 gene polymorphisms on response and toxicity of cyclophosphamide-epirubicin-5-fluorouracil-based chemotherapy in Bangladeshi breast cancer patients.
Tumour Biol. 2015; 36(7):5451-7 [PubMed] Related Publications
The most important cytotoxic drug namely, cyclophosphamide used in breast cancer along with epirubicin and 5-fluorouracil, is transported by ABCC transporters and detoxified by glutathione S-transferases (GSTs). The activities of these enzymes and transporters may vary in different population due to the presence of genetic polymorphisms. This study was aimed to evaluate the effects of GSTP1rs1695 and ABCC4rs9561778 polymorphisms on the response and toxicities produced by chemotherapy used in the treatment of Bangladeshi breast cancer patients. A total of 200 and 56 patients with invasive breast cancers were recruited from different public and private hospitals of Bangladesh of which 117 patients received neoadjuvant chemotherapy to examine the response as well as the toxicity, and another 139 patients received adjuvant chemotherapy to evaluate only the toxicity. Genetic polymorphisms of the mentioned genes were detected by using Polymerase Chain Reaction Restriction Fragment Length Polymorphism (PCR RFLP). Patients carrying AG and AG plus GG genotype of GSTP1rs1695 were more likely to have a good response, whereas no association of ABCC4rs9561778 was found with the chemotherapy response. Patients carrying GT and GT plus TT genotypes of ABCC4rs9561778 were found to be associated with anemia, neutropenia, leukopenia, and gastrointestinal toxicities when compared with GG genotype whereas no association was found with thrombocytopenia. GSTP1rs1695 was not associated with any type of toxicities investigated. Our result indicates that GSTP1rs1695 polymorphism was strongly associated with the response of chemotherapy, whereas ABCC4rs9561778 polymorphism was significantly related with chemotherapy-induced toxicities.

Yu DM, Huynh T, Truong AM, et al.
ABC transporters and neuroblastoma.
Adv Cancer Res. 2015; 125:139-70 [PubMed] Related Publications
Neuroblastoma is the most common cancer of infancy and accounts for 15% of all pediatric oncology deaths. Survival rates of high-risk neuroblastoma remain less than 50%, with amplification of the MYCN oncogene the most important aberration associated with poor outcome. Direct transcriptional targets of MYCN include a number of ATP-binding cassette (ABC) transporters, of which ABCC1 (MRP1), ABCC3 (MRP3), and ABCC4 (MRP4) are the best characterized. These three transporter genes have been shown to be strongly prognostic of neuroblastoma outcome in primary untreated neuroblastoma. In addition to their ability to efflux a number of chemotherapeutic drugs, evidence suggests that these transporters also contribute to neuroblastoma outcome independent of any role in cytotoxic drug efflux. Endogenous substrates of ABCC1 and ABCC4 that may be potential candidates affecting neuroblastoma biology include molecules such as prostaglandins and leukotrienes. These bioactive lipid mediators have the ability to influence biological processes contributing to cancer initiation and progression, such as angiogenesis, cell signaling, inflammation, proliferation, and migration and invasion. ABCC1 and ABCC4 are thus potential targets for therapeutic suppression in high-risk neuroblastoma, and recently developed small-molecule inhibitors may be an effective strategy in treating aggressive forms of this cancer, as well as other cancers that express high levels of these transporters.

Johnson C, Pankratz VS, Velazquez AI, et al.
Candidate pathway-based genetic association study of platinum and platinum-taxane related toxicity in a cohort of primary lung cancer patients.
J Neurol Sci. 2015; 349(1-2):124-8 [PubMed] Free Access to Full Article Related Publications
BACKGROUND: Chemotherapy-induced peripheral neuropathy (CIPN) is a common toxicity secondary to chemotherapy. Genetic factors may be important in predisposing patients to this adverse effect.
PATIENTS AND METHODS: We studied 950 primary lung cancer patients, who received platinum or platinum-combination drug chemotherapy and who had DNA available for study. We analyzed epidemiological risk factors in 279 CIPN patients and 456 non-CIPN patients and genetic risk factors in 141 CIPN patients and 259 non-CIPN patients. The risk factors studied included demographic, diagnostic, and treatment data, as well as 174 tag SNPs (single nucleotide polymorphisms) across 43 candidate genes in the glutathione, cell cycle, DNA repair, cell signaling, and apoptosis pathways.
RESULTS: Patients who had diabetes mellitus were more likely to have CIPN (p=0.0002). Other epidemiologic risk factors associated with CIPN included number of cycles (p=0.0004) and type of concurrent chemotherapy (p<0.001). SNPs most associated with CIPN were in glutathione peroxidase 7 (GPX7) gene (p values 0.0015 and 0.0028, unadjusted and adjusted) and in ATP-binding cassette sub-family C member 4 (ABCC4) gene (p values 0.037 and 0.006, unadjusted and adjusted). We also found other suggestive associations in methyl-o-guanine-methyl-transferase (MGMT) and glutathione-S-transferase (GST) isoforms.
CONCLUSIONS: Epidemiological and genetic risk factors associated with CIPN in this cohort, included the type of chemotherapy drug, intensity of chemotherapy treatment, and genes known to be associated with chemotherapy resistance. These findings suggest that differentiating between cytotoxic and neurotoxic mechanisms of chemotherapy drugs is challenging but represents an important step toward individualized therapy and improving quality of life for patients.

Zhang G, Wang Z, Qian F, et al.
Silencing of the ABCC4 gene by RNA interference reverses multidrug resistance in human gastric cancer.
Oncol Rep. 2015; 33(3):1147-54 [PubMed] Related Publications
The identification of genes associated with recurrent drug resistance in gastric cancer and the elucidation of the underlying molecular mechanisms associated with recurrent drug resistance in gastric cancer are important for the effective treatment and prognosis of this cancer. Variations in the expression level of the ATP-binding cassette subfamily C member 4 (ABCC4) gene are correlated with the recurrence, development and chemotherapeutic susceptibility of various types of cancers. In the present study, we demonstrated that the ABCC4 gene was highly expressed in multiple types of gastric cancer cells, and ABCC4 expression was even more prominent in the drug-resistant gastric cancer cells. Conversely, in normal gastric mucosal cells, ABCC4 expression was very low or undetectable. We used RNA interference to decrease the expression of ABCC4 in drug-resistant gastric cancer cells, which resulted in an increase in apoptosis and cell cycle arrest in the G1 phase. In addition, we found that ABCC4 knockdown in 5-fluorouracil (5-FU)-resistant cancer cells restored 5-FU sensitivity, resulting in the inhibition of cell proliferation and tumour growth in nude mice. Our results showed that inhibition of ABCC4 gene expression can inhibit the proliferation of multidrug-resistant gastric cancer cells and can enhance gastric cancer cell sensitivity to chemotherapeutic drugs.

Wang Z, Xu Y, Meng X, et al.
Suppression of c-Myc is involved in multi-walled carbon nanotubes' down-regulation of ATP-binding cassette transporters in human colon adenocarcinoma cells.
Toxicol Appl Pharmacol. 2015; 282(1):42-51 [PubMed] Related Publications
Over-expression of ATP-binding cassette (ABC) transporters, a large family of integral membrane proteins that decrease cellular drug uptake and accumulation by active extrusion, is one of the major causes of cancer multi-drug resistance (MDR) that frequently leads to failure of chemotherapy. Carbon nanotubes (CNTs)-based drug delivery devices hold great promise in enhancing the efficacy of cancer chemotherapy. However, CNTs' effects on the ABC transporters remain under-investigated. In this study, we found that multiwalled carbon nanotubes (MWCNTs) reduced transport activity and expression of ABC transporters including ABCB1/Pgp and ABCC4/MRP4 in human colon adenocarcinoma Caco-2 cells. Proto-oncogene c-Myc, which directly regulates ABC gene expression, was concurrently decreased in MWCNT-treated cells and forced over-expression of c-Myc reversed MWCNTs' inhibitory effects on ABCB1 and ABCC4 expression. MWCNT-cell membrane interaction and cell membrane oxidative damage were observed. However, antioxidants such as vitamin C, β-mecaptoethanol and dimethylthiourea failed to antagonize MWCNTs' down-regulation of ABC transporters. These data suggest that MWCNTs may act on c-Myc, but not through oxidative stress, to down-regulate ABC transporter expression. Our findings thus shed light on CNTs' novel cellular effects that may be utilized to develop CNTs-based drug delivery devices to overcome ABC transporter-mediated cancer chemoresistance.

Matsuoka H, Kondo K, Takizawa H, et al.
Comprehensive evaluation of the response of genes to the administration of the antitumor drug S-1 using a low density array.
Int J Oncol. 2015; 46(2):569-77 [PubMed] Related Publications
S-1 is a newly developed dihydropyrimidine dehydrogenase inhibitory fluoropyrimidine that exhibits high clinical efficacy against non-small cell lung cancers. To identify genes that may be associated with chemosensitivity to the antitumor drug S-1, we used a low density array representing 93 genes to analyze expression profiles in 4 orthotopically implanted lung cancers derived from human lung cancer cell lines (Lu99, Lu130, LC6 and A549). The tumor growth inhibition (TGI) rates of S-1 in orthotopically implanted tumors of the Lu99, Lu130, LC6 and A549 cell lines were 34.6, 37.5, 32.1 and 3.6%, respectively. The expression of the PRSS3, ABCC4, TXN, SHMT1 and CMPK genes was significantly promoted in the orthotopically implanted SCID mouse model of the 4 lung cancer cell lines by the administration of S-1, while the expression of the LMO7 and FOLH1 genes was significantly suppressed. The expression of the ABCC1, 2 and TST genes was negatively correlated with TGI. The expression of the TK1 and ERCC2 genes was positively correlated with TGI. The results of the present study suggest that the expression of the ABCC1, 2, TST, TK1 and ERCC2 genes is related to resistance to the antitumor drug S-1.

Tanaka Y, Manabe A, Fukushima H, et al.
Multidrug resistance protein 4 (MRP4) polymorphisms impact the 6-mercaptopurine dose tolerance during maintenance therapy in Japanese childhood acute lymphoblastic leukemia.
Pharmacogenomics J. 2015; 15(4):380-4 [PubMed] Related Publications
Multidrug resistance protein 4 (MRP4) is involved in the efflux of nucleoside derivatives and has a role in the determination of drug sensitivity. We investigated the relationship between MRP4 genetic polymorphisms and doses of the 6-mercaptopurine (6-MP) and methotrexate. Further, we evaluated the frequency of therapeutic interruption during maintenance therapy in Japanese children with acute lymphoblastic leukemia (ALL). Ninety-four patients received an initial 6-MP dose in the range of 30-50 mg m(-2) in this analysis. Patients with homozygous variant allele in any of MRP4 G2269A, C912A and G559T required high frequency of 6-MP dose reduction compared with non-homozygous individuals. Average 6-MP dose for patients with homozygous variant allele on either MRP4 or inosine triphosphate pyrophosphatase was significantly lower than that for patients with non-homozygous variant allele during maintenance therapy (30.5 versus 40.0 mg m(-2), P=0.024). Therefore, MRP4 genotyping may be useful for personalizing the therapeutic dose of 6-MP during the ALL maintenance therapy in Japanese.

den Hoed MA, Lopez-Lopez E, te Winkel ML, et al.
Genetic and metabolic determinants of methotrexate-induced mucositis in pediatric acute lymphoblastic leukemia.
Pharmacogenomics J. 2015; 15(3):248-54 [PubMed] Related Publications
Methotrexate (MTX) is an effective and toxic chemotherapeutic drug in the treatment of pediatric acute lymphoblastic leukemia(ALL). In this prospective study, we aimed to identify metabolic and genetic determinants of MTX toxicity. One hundred and thirty-four Dutch pediatric ALL patients were treated with four high infusions MTX (HD-MTX: 5 g m(-2)) every other week according to the DCOG-ALL-10 protocol. Mucositis (National Cancer Institute grade ⩾ 3) was the most frequent occurring toxicity during the HD-MTX phase (20%) and occurred especially after the first MTX course. Mucositis was not associated with plasma MTX, plasma folate or plasma homocysteine levels. Patients with mucositis had higher erythrocyte folate levels at the start of protocol M than patients without mucositis (median 1.4 vs 1.2 μmol l(-1), P<0.008), this could reflect an increased MTX uptake in mucosal cells of patients with mucositis. From 17 single-nucleotide polymorphisms in the MTX pathway, only patients with the wild-type variant of rs7317112 SNP in the ABCC4 gene had more mucositis (AA (39%) vs AG/GG (15%), P=0.016). We found no evidence that erythrocyte folate levels mediate in the association between the rs7317112 and mucositis.

Warrier S, Bhuvanalakshmi G, Arfuso F, et al.
Cancer stem-like cells from head and neck cancers are chemosensitized by the Wnt antagonist, sFRP4, by inducing apoptosis, decreasing stemness, drug resistance and epithelial to mesenchymal transition.
Cancer Gene Ther. 2014; 21(9):381-8 [PubMed] Related Publications
Cancer stem cells (CSCs) of head and neck squamous cell carcinoma (HNSCC) are defined by high self-renewal and drug refractory potential. Involvement of Wnt/β-catenin signaling has been implicated in rapidly cycling cells such as CSCs, and inhibition of the Wnt/β-catenin pathway is a novel approach to target CSCs from HNSCC. In this study, we found that an antagonist of FrzB/Wnt, the secreted frizzled-related protein 4 (sFRP4), inhibited the growth of CSCs from two HNSCC cell lines, Hep2 and KB. We enriched the CD44(+) CSC population, and grew them in spheroid cultures. sFRP4 decreased the proliferation and increased the sensitivity of spheroids to a commonly used drug in HNSCC, namely cisplatin. Self-renewal in sphere formation assays decreased upon sFRP4 treatment, and the effect was reverted by the addition of Wnt3a. sFRP4 treatment of spheroids also decreased β-catenin, confirming its action through the Wnt/β-catenin signaling pathway. Quantitative PCR demonstrated a clear decrease of the stemness markers CD44 and ALDH, and an increase in CD24 and drug-resistance markers ABCG2 and ABCC4. Furthermore, we found that after sFRP4 treatment, there was a reversal in the expression of epithelial to mesenchymal (EMT) markers with the restoration of the epithelial marker E-cadherin, and depletion of EMT-specific markers twist, snail and N-cadherin. This is the first report demonstrating that the naturally occurring Wnt inhibitor, sFRP4, can be a potential drug to destroy CSC-enriched spheroids from HNSCCs. The repression of EMT and the decrease in stemness profile further strengthen the use of sFRP4 as a potent therapeutic against CSCs.

Rama AR, Alvarez PJ, Madeddu R, Aranega A
ABC transporters as differentiation markers in glioblastoma cells.
Mol Biol Rep. 2014; 41(8):4847-51 [PubMed] Related Publications
UNLABELLED: Glioblastoma multiforme (GBM) is the most common primary malignant brain tumour, characterized by a high aggressivity, a huge heterogeneity attending a hierarchical model and resistance to therapy. Drug resistance has been correlated with the presence of the ABC efflux transporters which are able to exclude drugs for the cellular cytoplasm. In the nucleus of the GBM, initiating cells (ICs) can self-renew and give rise to cancer stem cells, which differ to the side population cells and the different cellular subtypes that form the mass around them. The ICs do not express or express ATP binding cassette (ABC) at very low levels, but this expression may increase with the differentiation process. We suggest that the differentiation process may be responsible of chemoresistance of the GBM cells. We compared three ABC transporters expression: ABCA1, MRP4 and MRP5, in the ICs obtained from 9 patients with GBM and their respective differentiated GBM cells. We show an overexpression of the three ABC transporters in the differentiated GBM cells in comparison to ICs.
IMPLICATIONS OF THE HYPOTHESIS: The blockade of these ABC transporters could help to improve the drug effectivity and thus reduce the tumour growth and prevent the tumour recurrence.

Qian Z, Zhu G, Tang L, et al.
Whole genome gene copy number profiling of gastric cancer identifies PAK1 and KRAS gene amplification as therapy targets.
Genes Chromosomes Cancer. 2014; 53(11):883-94 [PubMed] Related Publications
Gastric cancer is the second leading cause of death from cancer worldwide, with an approximately 20% 5-year survival rate. To identify molecular subtypes associated with the clinical prognosis, in addition to genetic aberrations for potential targeted therapeutics, we conducted a comprehensive whole-genome analysis of 131 Chinese gastric cancer tissue specimens using whole-genome array comparative genomic hybridization. The analyses revealed gene focal amplifications, including CTSB, PRKCI, PAK1, STARD13, KRAS, and ABCC4, in addition to ERBB2, FGFR2, and MET. The growth of PAK1-amplified gastric cancer cells in vitro and in vivo was inhibited when the corresponding mRNA was knocked down. Furthermore, both KRAS amplification and KRAS mutation were identified in the gastric cancer specimens. KRAS amplification was associated with worse clinical outcomes, and the KRAS gene mutation predicted sensitivity to the MEK1/2 inhibitor AZD6244 in gastric cancer cell lines. In summary, amplified PAK1, as well as KRAS amplification/mutation, may represent unique opportunities for developing targeted therapeutics for the treatment of gastric cancer.

Pereira C, Queirós S, Galaghar A, et al.
Genetic variability in key genes in prostaglandin E2 pathway (COX-2, HPGD, ABCC4 and SLCO2A1) and their involvement in colorectal cancer development.
PLoS One. 2014; 9(4):e92000 [PubMed] Free Access to Full Article Related Publications
The pro-carcinogenic effects of prostaglandin E2 (PGE2) in colonic mucosa are not only regulated by the rates between Cyclooxygenase-2 (COX-2) biosynthesis and 15-Hydroxyprostaglandin Dehydrogenase (15-PGDH)-dependent degradation but also the steady-state levels of PGE2 in extracellular microenvironment, maintained by key specific prostaglandin transporters, the Multidrug Resistance Protein (MRP4) (efflux carrier) and Prostaglandin Transporter (PGT) (influx carrier). To understand the contribution of genetic variability in genes coding for COX-2/15-PGDH/MRP4/PGT proteins in CRC development, we conducted a hospital-based case-control study involving 246 CRC patients and 480 cancer-free controls. A total of 51 tagSNPs were characterized using the Sequenom platform through multiplexed amplification followed by mass-spectrometric product separation or allelic discrimination using real-time PCR. Seven tagSNPs were implicated in CRC development: the rs689466 in COX-2 gene, the rs1346271 and rs1426945 in 15-PGDH, the rs6439448 and rs7616492 in PGT and rs1751051 and rs1751031 in MRP4 coding genes. Upon a stratified analysis a measurable gene-environment interaction was noticed between rs689466 and smoking habits, with individuals ever-smokers carriers of rs689466 GG homozygous genotype having a nearly 6-fold increased susceptibility for CRC onset (95%CI: 1.49-22.42, P = 0.011). Furthermore, the multifactor dimensionality reduction (MDR) analysis identified an overall four-factor best gene-gene interactive model, including the rs1426945, rs6439448, rs1751051 and rs1751031 polymorphisms. This model had the highest cross-validation consistency (10/10, P<0.0001) and an accuracy of 0.6957 and was further associated with a 5-fold increased risk for CRC development (95%CI: 3.89-7.02, P<0.0001). In conclusion, specific low penetrance genes in the pro-carcinogenic PGE2 pathway appear to modulate the genetic susceptibility for CRC development. A clearer understanding on CRC etiology through the identification of biomarkers of colorectal carcinogenesis might allow a better definition of risk models that are more likely to benefit from targeted preventive strategies to reduce CRC burden.

Wang F, Wang XK, Shi CJ, et al.
Nilotinib enhances the efficacy of conventional chemotherapeutic drugs in CD34⁺CD38⁻ stem cells and ABC transporter overexpressing leukemia cells.
Molecules. 2014; 19(3):3356-75 [PubMed] Related Publications
Incomplete chemotherapeutic eradication of leukemic CD34⁺CD38⁻ stem cells is likely to result in disease relapse. The purpose of this study was to evaluate the effect of nilotinib on eradicating leukemia stem cells and enhancing the efficacy of chemotherapeutic agents. Our results showed that ABCB1 and ABCG2 were preferentially expressed in leukemic CD34⁺CD38⁻ cells. Nilotinib significantly enhanced the cytotoxicity of doxorubicin and mitoxantrone in CD34⁺CD38⁻ cells and led to increased apoptosis. Moreover, nilotinib strongly reversed multidrug resistance and increased the intracellular accumulation of rhodamine 123 in primary leukemic blasts overexpressing ABCB1 and/or ABCG2. Studies with ABC transporter-overexpressing carcinoma cell models confirmed that nilotinib effectively reversed ABCB1- and ABCG2-mediated drug resistance, while showed no significant reversal effect on ABCC1- and ABCC4-mediated drug resistance. Results from cytotoxicity assays showed that CD34⁺CD38⁻ cells exhibited moderate resistance (2.41-fold) to nilotinib, compared with parental K562 cells. Furthermore, nilotinib was less effective in blocking the phosphorylation of Bcr-Abl and CrkL (a substrate of Bcr-Abl kinase) in CD34⁺CD38⁻ cells. Taken together, these data suggest that nilotinib particularly targets CD34⁺CD38⁻ stem cells and MDR leukemia cells, and effectively enhances the efficacy of chemotherapeutic drugs by blocking the efflux function of ABC transporters.

Matimba A, Li F, Livshits A, et al.
Thiopurine pharmacogenomics: association of SNPs with clinical response and functional validation of candidate genes.
Pharmacogenomics. 2014; 15(4):433-47 [PubMed] Free Access to Full Article Related Publications
AIM: We investigated candidate genes associated with thiopurine metabolism and clinical response in childhood acute lymphoblastic leukemia.
MATERIALS & METHODS: We performed genome-wide SNP association studies of 6-thioguanine and 6-mercaptopurine cytotoxicity using lymphoblastoid cell lines. We then genotyped the top SNPs associated with lymphoblastoid cell line cytotoxicity, together with tagSNPs for genes in the 'thiopurine pathway' (686 total SNPs), in DNA from 589 Caucasian UK ALL97 patients. Functional validation studies were performed by siRNA knockdown in cancer cell lines.
RESULTS: SNPs in the thiopurine pathway genes ABCC4, ABCC5, IMPDH1, ITPA, SLC28A3 and XDH, and SNPs located within or near ATP6AP2, FRMD4B, GNG2, KCNMA1 and NME1, were associated with clinical response and measures of thiopurine metabolism. Functional validation showed shifts in cytotoxicity for these genes.
CONCLUSION: The clinical response to thiopurines may be regulated by variation in known thiopurine pathway genes and additional novel genes outside of the thiopurine pathway.

Chen L, Gu J, Xu L, et al.
RNAi-mediated silencing of ATP-binding cassette C4 protein inhibits cell growth in MGC80-3 gastric cancer cell lines.
Cell Mol Biol (Noisy-le-grand). 2014; 60(1):1-5 [PubMed] Related Publications
ATP-binding cassette C4/multidrug resistance associated protein 4 (ABCC4/MRP4) is a relatively well-studied member of the ATP-binding cassette drug transporter family. Recent studies suggested that ABCC4 is implicated in the development of several human cancers. In the present study, we report that knockdown of ABCC4 by lentivirus-delivered short hairpin RNA could inhibit gastric cancer cell growth in vitro. The proliferation of MGC80-3 cells was significantly reduced after infection with Lv-shABCC4, as determined by MTT and colony formation assays. In addition, knockdown of ABCC4 blocked the cell cycle progression in MGC80-3 cells. To our knowledge, it is the first report to investigate the role of ABCC4 in gastric tumorigenesis. Our data provides additional evidence that ABCC4/MRP4 could be a potential therapeutic target for gastric cancers.

Noori-Daloii MR, Saffari M, Raoofian R, et al.
The multidrug resistance pumps are inhibited by silibinin and apoptosis induced in K562 and KCL22 leukemia cell lines.
Leuk Res. 2014; 38(5):575-80 [PubMed] Related Publications
Silibinin have been introduced for several years as a potent antioxidant in the field of nutraceuticals. Based on wide persuasive effects of this drug, we have decided to investigate the effects of silibinin on chronic myelogenous leukemia (CML) in vitro models, K562 and KCL22 cell lines. Lactate dehydrogenase (LDH) release, microculture tetrazolium test (MTT assay) and real-time PCR were employed to evaluate the effects of silibinin on cell cytotoxicity, cell proliferation and expression of various multidrug resistance genes in these cell lines, respectively. Our results have shown that presence of silibinin has inhibitory effects on cell proliferation of K562 and KCL22 cell lines. Also, our data indicated that silibinin, in a dose-dependent manner with applying no cytotoxic effects, inhibited cell proliferation and reduced mRNA expression levels of some transporter genes e.g. MDR1, MRP3, MRP2, MRP1, MRP5, MRP4, ABCG2, ABCB11, MRP6 and MRP7. The multifarious in vitro inhibitory effects of silibinin are in agreement with growing body of evidence that silibinin would be an efficient anticancer agent in order to be used in multi-target therapy to prevail the therapeutic hold backs against CML.

Sun Y, Shi N, Lu H, et al.
ABCC4 copy number variation is associated with susceptibility to esophageal squamous cell carcinoma.
Carcinogenesis. 2014; 35(9):1941-50 [PubMed] Related Publications
Esophageal squamous cell carcinoma (ESCC) is the eighth most common cause of cancer-related death worldwide. However, previous genome-wide single nucleotide polymorphism association analyses have not explained the high heritability associated with ESCC. In this study, we performed genome-wide copy number variation (CNV) analysis on 128 discordant sibling pairs to identify novel genes that contribute to ESCC susceptibility. A total of 57 774 individual CNVs were identified, and an interactive network of common CNV-associated genes was constructed, which showed that several ABC transporter genes contain CNVs in ESCC patients. Independent validation of a CNV at 13q32.1 in 1048 northern Chinese Han subjects demonstrated that the amplification of ABCC4 significantly correlated with ESCC risk [odds ratio: 3.36 (1.65-7.93), P = 0.0013]. Immunohistochemistry staining suggested that high copy numbers correlated with increased protein levels. High expression of ABCC4 was an independent poor prognostic factor for ESCC [relative risk: 1.73 (1.10-2.73), P = 0.0181]. The CNV region showed strong enhancer activity. Furthermore, inhibition of ABCC4 protein in ESCC cells decreased cell proliferation and motility via the inhibition of COX-2, PGE2 receptors and c-Myc expression; AKT, extracellular signal-regulated kinase and cAMP response element-binding protein phosphorylation; and β-catenin nuclear translocation in ESCC cells. In conclusion, the CNV at 13q32.1 is associated with ESCC susceptibility, and a gene within this locus, ABCC4, activates the oncogenic pathways in ESCC and thus facilitates cancer cell development and progression. A direct genetic contribution of ESCC risk through CNV common variants was determined in this study, and ABCC4 might therefore have predictive and therapeutic potential for ESCC.

Harris M, Bhuvaneshwar K, Natarajan T, et al.
Pharmacogenomic characterization of gemcitabine response--a framework for data integration to enable personalized medicine.
Pharmacogenet Genomics. 2014; 24(2):81-93 [PubMed] Free Access to Full Article Related Publications
OBJECTIVES: Response to the oncology drug gemcitabine may be variable in part due to genetic differences in the enzymes and transporters responsible for its metabolism and disposition. The aim of our in-silico study was to identify gene variants significantly associated with gemcitabine response that may help to personalize treatment in the clinic.
METHODS: We analyzed two independent data sets: (a) genotype data from NCI-60 cell lines using the Affymetrix DMET 1.0 platform combined with gemcitabine cytotoxicity data in those cell lines, and (b) genome-wide association studies (GWAS) data from 351 pancreatic cancer patients treated on an NCI-sponsored phase III clinical trial. We also performed a subset analysis on the GWAS data set for 135 patients who were given gemcitabine+placebo. Statistical and systems biology analyses were performed on each individual data set to identify biomarkers significantly associated with gemcitabine response.
RESULTS: Genetic variants in the ABC transporters (ABCC1, ABCC4) and the CYP4 family members CYP4F8 and CYP4F12, CHST3, and PPARD were found to be significant in both the NCI-60 and GWAS data sets. We report significant association between drug response and variants within members of the chondroitin sulfotransferase family (CHST) whose role in gemcitabine response is yet to be delineated.
CONCLUSION: Biomarkers identified in this integrative analysis may contribute insights into gemcitabine response variability. As genotype data become more readily available, similar studies can be conducted to gain insights into drug response mechanisms and to facilitate clinical trial design and regulatory reviews.

Mayba O, Gnad F, Peyton M, et al.
Integrative analysis of two cell lines derived from a non-small-lung cancer patient--a panomics approach.
Pac Symp Biocomput. 2014; :75-86 [PubMed] Free Access to Full Article Related Publications
Cancer cells derived from different stages of tumor progression may exhibit distinct biological properties, as exemplified by the paired lung cancer cell lines H1993 and H2073. While H1993 was derived from chemo-naive metastasized tumor, H2073 originated from the chemo-resistant primary tumor from the same patient and exhibits strikingly different drug response profile. To understand the underlying genetic and epigenetic bases for their biological properties, we investigated these cells using a wide range of large-scale methods including whole genome sequencing, RNA sequencing, SNP array, DNA methylation array, and de novo genome assembly. We conducted an integrative analysis of both cell lines to distinguish between potential driver and passenger alterations. Although many genes are mutated in these cell lines, the combination of DNA- and RNA-based variant information strongly implicates a small number of genes including TP53 and STK11 as likely drivers. Likewise, we found a diverse set of genes differentially expressed between these cell lines, but only a fraction can be attributed to changes in DNA copy number or methylation. This set included the ABC transporter ABCC4, implicated in drug resistance, and the metastasis associated MET oncogene. While the rich data content allowed us to reduce the space of hypotheses that could explain most of the observed biological properties, we also caution there is a lack of statistical power and inherent limitations in such single patient case studies.

Bagnoli M, Beretta GL, Gatti L, et al.
Clinicopathological impact of ABCC1/MRP1 and ABCC4/MRP4 in epithelial ovarian carcinoma.
Biomed Res Int. 2013; 2013:143202 [PubMed] Free Access to Full Article Related Publications
Ovarian cancer is the main cause of death from gynaecological malignancies. In spite of the efficacy of platinum-paclitaxel treatment in patients with primary epithelial ovarian carcinoma, platinum-based chemotherapy is not curative and resistance remains one of the most important causes of treatment failure. Although ABC transporters have been implicated in cellular resistance to multiple drugs, the clinical relevance of these efflux pumps is still poorly understood. Thus, we examined the prognostic role of transporters of the MRP family (i.e., ABCC1/MRP1, ABCC4/MRP4) to gain insights into their clinical impacts. A case material of 127 patients with ovarian carcinoma at different stages and histotypes was used. The expression of MRP1 and MRP4 was examined by immunohistochemistry using tissue microarrays in tumor specimens collected at the time of initial surgery expression. We found an association between MRP1 expression and grading, and we observed that MRP4 displayed an unfavourable impact on disease relapse in multivariate analysis (HR = 2.05, 95% CI: 1.01-4.11; P = 0.045). These results suggest that in epithelial ovarian cancer, MRP1 may be a marker for aggressiveness because its expression was associated with tumor grade and support that MRP4 may play an unfavourable role in disease outcome.

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