Gene Summary

Gene:ABCB4; ATP-binding cassette, sub-family B (MDR/TAP), member 4
Aliases: GBD1, ICP3, MDR2, MDR3, PGY3, ABC21, MDR2/3, PFIC-3
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 as well as antigen presentation. This gene encodes a full transporter and member of the p-glycoprotein family of membrane proteins with phosphatidylcholine as its substrate. The function of this protein has not yet been determined; however, it may involve transport of phospholipids from liver hepatocytes into bile. Alternative splicing of this gene results in several products of undetermined function. [provided by RefSeq, Jul 2008]
Databases:OMIM, VEGA, HGNC, Ensembl, GeneCard, Gene
Protein:multidrug resistance protein 3
Source:NCBIAccessed: 27 February, 2015


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 (1990-2015)
Graph generated 28 February 2015 using data from PubMed using criteria.

Literature Analysis

Mouse over the terms for more detail; many indicate links which you can click for dedicated pages about the topic.

  • Chromosome 7
  • Melanocytes
  • Single Nucleotide Polymorphism
  • Antineoplastic Agents
  • P-Glycoprotein
  • Breast Cancer
  • Messenger RNA
  • Multiple Drug Resistance
  • Survival Rate
  • Vinblastine
  • Protein Array Analysis
  • Gene Expression
  • Cholangiocarcinoma
  • Membrane Transport Proteins
  • ATP-Binding Cassette Transporters
  • Cancer RNA
  • Melanoma
  • Cancer Gene Expression Regulation
  • Tumor Markers
  • Gene Amplification
  • Transcription
  • Chromosome Aberrations
  • Mutation
  • RT-PCR
  • P-Glycoproteins
  • Phytogenic Anticancer Agents
  • Ovarian Cancer
  • Gene Expression Profiling
  • Vincristine
  • Neoplasm Proteins
  • Liver Cancer
  • Nucleic Acid Hybridization
  • Drug Resistance
  • Protein-Serine-Threonine Kinases
  • Estrogen Receptors
  • Up-Regulation
  • Oligonucleotide Array Sequence Analysis
  • ras Proteins
Tag cloud generated 27 February, 2015 using data from PubMed, MeSH and CancerIndex

Latest Publications: ABCB4 (cancer-related)

Vaz AP, Ponnusamy MP, Rachagani S, et al.
Novel role of pancreatic differentiation 2 in facilitating self-renewal and drug resistance of pancreatic cancer stem cells.
Br J Cancer. 2014; 111(3):486-96 [PubMed] Article available free on PMC after 29/07/2015 Related Publications
BACKGROUND: Cancer stem cells (CSCs) contribute towards disease aggressiveness and drug resistance. Specific identification of CSC maintenance genes and targeting can improve the efficiency of currently available treatment modalities. Pancreatic differentiation 2 (PD2) has a major role in the self-renewal of mouse embryonic stem cells. In the present study, we investigated the role of PD2 in pancreatic CSCs.
METHODS: Characterisation of CSCs and non-CSCs from mouse models, pancreatic cancer cells and human tissues by CSC and self-renewal marker analysis using confocal assay. Effect of PD2 knockdown in CSCs (after gemcitabine treatment) was studied by immunoblot and apoptosis assays.
RESULTS: A subpopulation of cells displayed PD2 overexpression in mouse (Kras(G12D); Pdx1-Cre and Kras(G12D); Trp53(R172H/+); Pdx1-Cre) and human pancreatic tumours, which co-express CSC markers. Cancer stem cells exhibited elevated expression of PD2 and self-renewal markers, such as Oct3/4, Shh and β-catenin. Gemcitabine treatment maintained the CSC population with simultaneous maintenance of PD2 and CSC marker expression. Knockdown of PD2 in CSCs resulted in reduced viability of cells and enhanced apoptosis along with abrogated expression of CD133 and MDR2.
CONCLUSIONS: Our results suggest that PD2 is a novel CSC maintenance protein, loss of which renders the CSCs more susceptible to drug-induced cell death.

Januchowski R, Zawierucha P, Ruciński M, et al.
Drug transporter expression profiling in chemoresistant variants of the A2780 ovarian cancer cell line.
Biomed Pharmacother. 2014; 68(4):447-53 [PubMed] Related Publications
Ovarian cancer is characterized by the higher mortality among gynecological cancers. In results of MDR development during chemotherapy cancer cells become resistant to further treatment. Microarray techniques can provide information about MDR development at gene expression level. ABC and SLC transporters are most important proteins responsible for this phenomenon. In this study changes of ABC and SLC genes expression pattern in drugs resistant sublines of the A2780 ovarian cancer cell line were demonstrated. The cytostatic resistant sublines were generated by culture of A2780 cell line with an increasing concentration of the indicated drugs. As screening methods, we used Affymetrix U219 Human Genome microarrays. Independent t-tests were used to determinate statistical significances of results. Genes that expression levels were higher than assumed threshold (upregulated above threefold and downregulated under -3 fold) were visualized using scatter plot method, selected and listed in table. Between the ABC genes increased expression of seven genes and decreased expression of three genes were observed. Expression of two genes was increased or decreased depending on the cell line. We observed significant (more than tenfold) increase in expression of four ABC genes: ABCA8, ABCB1, ABCB4 and ABCG2 and decreased expression of ABCA3 gene. We also observed changes in expression of 32 SLC genes. Between them we observe increased expression of 17 genes and decreased expression of 15 genes. Expression of four genes was increased or decreased dependent on cell line. The expression of nine SLC genes increased or decreased very significantly (more than tenfold). Five genes were significantly upregulated: SLC2A9, SLC16A3, SLC16A14, SLC38A4 and SLC39A8. Four additional genes were significantly downregulated: SLC2A14, SLC6A15, SLC8A1 and SLC27A2. Expression profiles of these genes give strong arguments for assumption of correlation between expression of ABC and SLC genes and drug resistance phenomenon. Identifying correlations between specific drug transporters and cytostatic drug resistance will require further investigation.

Januchowski R, Wojtowicz K, Andrzejewska M, Zabel M
Expression of MDR1 and MDR3 gene products in paclitaxel-, doxorubicin- and vincristine-resistant cell lines.
Biomed Pharmacother. 2014; 68(1):111-7 [PubMed] Related Publications
Multiple drug resistance is one of the main reasons for low chemotherapeutic efficiency in cancer patients. The proteins that are most frequently implicated to play a role in this mechanism are transmembrane proteins that are members of the ABC family. The most important ABC protein is MDR1 (ABCB1), which is expressed in over fifty percent of drug-resistant cancers. The phosphatidylcholine transporter, MDR3 (ABCB4), exhibits high homology with MDR1. An increasing body of evidence suggests that MDR3 plays a role in drug resistance. In the present study, we used doxorubicin-, paclitaxel- and vincristine-resistant cancer cell lines. A chemosensitivity assay MTT test was performed to assess drug resistance. Quantitative real-time polymerase chain reaction analyses were performed to determine the mRNA expression levels of the MDR1 and MDR3 genes. We observed dose-dependent responses to doxorubicin, paclitaxel and vincristine in the investigated cell lines. In all of the drug-resistant cell lines that we studied, we observed increased MDR1 and MDR3 transcript levels. In a doxorubicin-resistant variant of the LoVo cell line (LoVoDx), MDR3 was expressed at higher levels than MDR1. We also observed high correlations between MDR3 expression and resistance to doxorubicin and paclitaxel. Our results suggest that MDR3 plays an active and important role in drug resistance in the investigated cell lines.

Vaquero J, Briz O, Herraez E, et al.
Activation of the nuclear receptor FXR enhances hepatocyte chemoprotection and liver tumor chemoresistance against genotoxic compounds.
Biochim Biophys Acta. 2013; 1833(10):2212-9 [PubMed] Related Publications
The success of pharmacological treatments in primary liver cancers is limited by the marked efficacy of mechanisms of chemoresistance already present in hepatocytes. The role of the nuclear receptor FXR is unclear. Although, in non-treated liver tumors, its expression is reduced, the refractoriness to anticancer drugs is high. Moreover, the treatment with cisplatin up-regulates FXR. The aim of this study was to investigate whether FXR is involved in stimulating chemoprotection/chemoresistance in healthy and tumor liver cells. In human hepatocytes, the activation of FXR with the agonist GW4064 resulted in a significant protection against cisplatin-induced toxicity. In human hepatoma Alexander cells, with negligible endogenous expression of FXR, GW4064 also protected against cisplatin-induced toxicity, but only if they were previously transfected with FXR/RXR. Investigation of 109 genes potentially involved in chemoresistance revealed that only ABCB4, TCEA2, CCL14, CCL15 and KRT13 were up-regulated by FXR activation both in human hepatocytes and FXR/RXR-expressing hepatoma cells. In both models, cisplatin, even in the absence of FXR agonists, such as bile acids and GW4064, was able to up-regulate FXR targets genes, which was due to FXR-mediated trans-activation of response elements in the promoter region. FXR-dependent chemoprotection was also efficient against other DNA-damaging compounds, such as doxorubicin, mitomycin C and potassium dichromate, but not against non-genotoxic drugs, such as colchicine, paclitaxel, acetaminophen, artesunate and sorafenib. In conclusion, ligand-dependent and independent activation of FXR stimulates mechanisms able to enhance the chemoprotection of hepatocytes against genotoxic compounds and to reduce the response of liver tumor cells to certain pharmacological treatments.

Shukla R, Upton KR, Muñoz-Lopez M, et al.
Endogenous retrotransposition activates oncogenic pathways in hepatocellular carcinoma.
Cell. 2013; 153(1):101-11 [PubMed] Article available free on PMC after 29/07/2015 Related Publications
LINE-1 (L1) retrotransposons are mobile genetic elements comprising ~17% of the human genome. New L1 insertions can profoundly alter gene function and cause disease, though their significance in cancer remains unclear. Here, we applied enhanced retrotransposon capture sequencing (RC-seq) to 19 hepatocellular carcinoma (HCC) genomes and elucidated two archetypal L1-mediated mechanisms enabling tumorigenesis. In the first example, 4/19 (21.1%) donors presented germline retrotransposition events in the tumor suppressor mutated in colorectal cancers (MCC). MCC expression was ablated in each case, enabling oncogenic β-catenin/Wnt signaling. In the second example, suppression of tumorigenicity 18 (ST18) was activated by a tumor-specific L1 insertion. Experimental assays confirmed that the L1 interrupted a negative feedback loop by blocking ST18 repression of its enhancer. ST18 was also frequently amplified in HCC nodules from Mdr2(-/-) mice, supporting its assignment as a candidate liver oncogene. These proof-of-principle results substantiate L1-mediated retrotransposition as an important etiological factor in HCC.

Mohelnikova-Duchonova B, Brynychova V, Oliverius M, et al.
Differences in transcript levels of ABC transporters between pancreatic adenocarcinoma and nonneoplastic tissues.
Pancreas. 2013; 42(4):707-16 [PubMed] Related Publications
OBJECTIVES: The aim of this study was to evaluate transcript levels of all 49 human ATP-binding cassette transporters (ABCs) in one of the most drug-resistant cancers, namely, the pancreatic ductal adenocarcinoma (PDAC). Association of ABCs levels with clinical-pathologic characteristics and KRAS mutation status was followed as well.
METHODS: Tumors and adjacent nonneoplastic tissues were obtained from 32 histologically verified PDAC patients. The transcript profile of ABCs was assessed using quantitative real-time polymerase chain reaction with a relative standard curve. KRAS mutations in exon 2 were assessed by high-resolution melting analysis and sequencing.
RESULTS: Most ABCs were deregulated in PDAC and 10 ABCs were associated with clinical-pathologic characteristics. KRAS mutations did not change the global expression profile of ABCs.
CONCLUSIONS: The expression of ABC transporters was significantly deregulated in PDAC tumors when compared to nonmalignant tissues. The observed up-regulation of ABCB4, ABCB11, ABCC1, ABCC3, ABCC5, ABCC10, and ABCG2 in tumors may contribute to the generally poor treatment response of PDAC. The up-regulation of ABCA1, ABCA7, and ABCG1 implicates a serious impairment of cellular cholesterol homeostasis in PDAC. On the other hand, the observed down-regulation of ABCA3, ABCC6, ABCC7, and ABCC8 suggests a possible role of stem cells in the development and progression of PDAC.

Januchowski R, Zawierucha P, Andrzejewska M, et al.
Microarray-based detection and expression analysis of ABC and SLC transporters in drug-resistant ovarian cancer cell lines.
Biomed Pharmacother. 2013; 67(3):240-5 [PubMed] Related Publications
Multiple drug resistance of cancer cells is multifactorial. A microarray technique may provide information about new candidate genes playing a role in drug resistance. Drug membrane transporters from ABC and SLC families play a main role in this phenomenon. This study demonstrates alterations in ABC and SLC gene expression levels in methotrexate, cisplatin, doxorubicin, vincristine, topotecan and paclitaxel-resistant variant of W1 ovarian cancer cell line. Resistant W1 cell lines were derived by stepwise selection of cells in increasing concentration of drugs. Affymetrix GeneChip(®) Human Genome U219 Array Strip was used for hybridizations. Statistical significance was determined by independent sample t-test. The genes having altered expression levels in drug-resistant sublines were selected and filtered by scater plot. Genes up/downregulated more than threefolds were selected and listed. Among ABC genes, seven were upregulated and three were downregulated. Three genes: ABCB1, ABCB4 and ABCG2 were upregulated very significantly (over tenfold). One ABCA8 was significantly downregulated. Among 38 SLC genes, 18 were upregulated, 16 were downregulated and four were up- or downregulated dependent on the cell line. Expression of 10 SLC genes was changed very significantly (over tenfold). Four genes were significantly increased: SLC6A1, SLC9A2, SLC12A1, SLC16A6 and six genes were significantly decreased: SLC2A14, SLC7A3, SLC7A8, SLC7A11, SLC16A14, SLC38A9. Based on the expression profiles, our results provide a preliminary insight into the relationship between drug resistance and expression of membrane transporters involved in drug resistance. Correlation of specific drug transporter with drug resistance requires further analysis.

Honda A, Ikegami T, Nakamuta M, et al.
Anticholestatic effects of bezafibrate in patients with primary biliary cirrhosis treated with ursodeoxycholic acid.
Hepatology. 2013; 57(5):1931-41 [PubMed] Related Publications
UNLABELLED: Bezafibrate is a widely used hypolipidemic agent and is known as a ligand of the peroxisome proliferator-activated receptors (PPARs). Recently this agent has come to be recognized as a potential anticholestatic medicine for the treatment of primary biliary cirrhosis (PBC) that does not respond sufficiently to ursodeoxycholic acid (UDCA) monotherapy. The aim of this study was to explore the anticholestatic mechanisms of bezafibrate by analyzing serum lipid biomarkers in PBC patients and by cell-based enzymatic and gene expression assays. Nineteen patients with early-stage PBC and an incomplete biochemical response to UDCA (600 mg/day) monotherapy were treated with the same dose of UDCA plus bezafibrate (400 mg/day) for 3 months. In addition to the significant improvement of serum biliary enzymes, immunoglobulin M (IgM), cholesterol, and triglyceride concentrations in patients treated with bezafibrate, reduction of 7α-hydroxy-4-cholesten-3-one (C4), a marker of bile acid synthesis, and increase of 4β-hydroxycholesterol, a marker of CYP3A4/5 activity, were observed. In vitro experiments using human hepatoma cell lines demonstrated that bezafibrate controlled the target genes of PPARα, as well as those of the pregnane X receptor (PXR); down-regulating CYP7A1, CYP27A1, and sinusoidal Na(+) /taurocholate cotransporting polypeptide (NTCP), and up-regulating CYP3A4, canalicular multidrug resistance protein 3 (MDR3), MDR1, and multidrug resistance-associated protein 2 (MRP2).
CONCLUSION: Bezafibrate is a dual PPARs/PXR agonist with potent anticholestatic efficacy in early-stage PBC patients with an incomplete biochemical response to UDCA monotherapy.

Citti A, Boldrini R, Inserra A, et al.
Expression of multidrug resistance-associated proteins in paediatric soft tissue sarcomas before and after chemotherapy.
Int J Oncol. 2012; 41(1):117-24 [PubMed] Related Publications
Expression of multidrug resistance (MDR) proteins is thought to significantly contribute to the different biological/clinical behaviour of soft tissue sarcomas (STS) of various histological types and clinicopathological stages, as they are responsible for active efflux of cytotoxic drugs from tumour cells. We investigated the expression of 3 MDR proteins, i.e., permeability glycoprotein 1 (P-gp), multidrug resistance-associated protein 1 (MRP1) and multidrug resistance 3 (MDR3), in 43 STS specimens from newly-diagnosed paediatric patients, 31 with rhabdomyosarcoma (RMS) and 12 with non-RMS STS. To assess the influence of chemotherapy on STS drug resistance, the number of MDR-associated protein-positive cells was determined in 15 patients on both primary lesions before chemotherapy and on residual tumour after chemotherapy. At least one of the MDR-associated proteins tested was detected in 84% of primary untreated STS specimens. In these specimens, MRP1 was detected in a high percentage (70%) of the cases, followed by MDR3 in 58% and P-gp in 44%. Many specimens showed co-expression of two different MDR proteins. Interestingly, MDR3 was significantly associated with the presence of PAX3/PAX7-FKHR transcripts in RMS (p<0.05). Moreover, expression of MRP1 and MDR3 was significantly more frequent in group III and IV tumours as compared with those of groups I and II (p<0.01). After chemotherapy MRP1, MDR3 and, to a lesser extent, P-gp expression was found to be increased in most of the samples. The frequent expression of these MDR-associated proteins in primary tumour cells before chemotherapy and the increase of their levels after chemotherapy, suggest that these proteins play a pivotal role in conferring drug resistance and in producing therapy-induced differentiation on STS.

Yu Z, Peng S, Hong-Ming P, Kai-Feng W
Expression of multi-drug resistance-related genes MDR3 and MRP as prognostic factors in clinical liver cancer patients.
Hepatogastroenterology. 2012 Jul-Aug; 59(117):1556-9 [PubMed] Related Publications
BACKGROUND/AIMS: To investigate the expression of multi-drug resistance-related genes, MDR3 and MRP, in clinical specimens of primary liver cancer and their potential as prognostic factors in liver cancer patients.
METHODOLOGY: A total of 26 patients with primary liver cancer were enrolled. The expression of MDR3 and MRP genes was measured by real-time PCR and the association between gene expression and the prognosis of patients was analyzed by the Kaplan-Meier method and COX regression model.
RESULTS: This study showed that increases in MDR3 gene expression were identified in cholangiocellular carcinoma, cirrhosis and HBsAg-positive patients, while MRP expression increased in hepatocellular carcinoma, non-cirrhosis and HBsAg-negative patients. Moreover, conjugated bilirubin and total bile acid in the serum were significantly reduced in patients with high MRP expression compared to patients with low expression. The overall survival tended to be longer in patients with high MDR3 and MRP expression compared to the control group. MRP might be an independent prognostic factor in patients with liver cancer by COX regression analysis.
CONCLUSIONS: MDR3 and MRP may play important roles in liver cancer patients as prognostic factors and their underlying mechanisms in liver cancer are worthy of further investigation.

Hlavata I, Mohelnikova-Duchonova B, Vaclavikova R, et al.
The role of ABC transporters in progression and clinical outcome of colorectal cancer.
Mutagenesis. 2012; 27(2):187-96 [PubMed] Related Publications
Worldwide, colorectal cancer (CRC) is the third most common cancer, with the highest mortality rates occurring in Central Europe. The use of chemotherapy to treat CRC is limited by the inter-individual variability in drug response and the development of cancer cell resistance. ATP-binding cassette (ABC) transporters play a crucial role in the development of resistance by the efflux of anticancer agents outside of cancer cells. The aim of this study was to explore transcript levels of all human ABCs in tumours and non-neoplastic control tissues from CRC patients collected before the first line of treatment by 5-fluorouracil (5-FU)-containing regimen. The prognostic potential of ABCs was evaluated by the correlation of transcript levels with clinical factors. Relations between transcript levels of ABCs in tumours and chemotherapy efficacy were also addressed. The transcript profile of all known human ABCs was assessed using real-time polymerase chain reaction with a relative standard curve. The majority of the studied ABCs were down-regulated or unchanged between tumours and control tissues. ABCA12, ABCA13, ABCB6, ABCC1, ABCC2 and ABCE1 were up-regulated in tumours versus control tissues. Transcript levels of ABCA12, ABCC7 and ABCC8 increased in direction from colon to rectum. Additionally, transcript levels of ABCB9, ABCB11, ABCG5 and ABCG8 followed the reverse significant trend, i.e. a decrease in direction from colon to rectum. The transcript level of ABCC10 in tumours correlated with the grade (P = 0.01). Transcript levels of ABCC6, ABCC11, ABCF1 and ABCF2 were significantly lower in non-responders to palliative chemotherapy in comparison with responders. The disease-free interval of patients treated by adjuvant chemotherapy was significantly shorter in patients with low transcript levels of ABCA7, ABCA13, ABCB4, ABCC11 and ABCD4. In conclusion, ABCC11 may be a promising candidate marker for a validation study on 5-FU therapy outcome.

Bernhardt GA, Zollner G, Cerwenka H, et al.
Hepatobiliary transporter expression and post-operative jaundice in patients undergoing partial hepatectomy.
Liver Int. 2012; 32(1):119-27 [PubMed] Related Publications
BACKGROUND AND AIMS: Post-operative hyperbilirubinaemia in patients undergoing liver resections is associated with high morbidity and mortality. Apart from different known factors responsible for the development of post-operative jaundice, little is known about the role of hepatobiliary transport systems in the pathogenesis of post-operative jaundice in humans after liver resection.
METHODS: Two liver tissue samples were taken from 14 patients undergoing liver resection before and after Pringle manoeuvre. Patients were retrospectively divided into two groups according to post-operative bilirubin serum levels. The two groups were analysed comparing the results of hepatobiliary transporter [Na-taurocholate cotransporter (NTCP); multidrug resistance gene/phospholipid export pump(MDR3); bile salt export pump (BSEP); canalicular bile salt export pump (MRP2)], heat shock protein 70 (HSP70) expression as well as the results of routinely taken post-operative liver chemistry tests.
RESULTS: Patients with low post-operative bilirubin had lower levels of NTCP, MDR3 and BSEP mRNA compared to those with high bilirubin after Pringle manoeuvre. HSP70 levels were significantly higher after ischaemia-reperfusion (IR) injury in both groups resulting in 4.5-fold median increase. Baseline median mRNA expression of all four transporters prior to Pringle manoeuvre tended to be lower in the low bilirubin group whereas expression of HSP70 was higher in the low bilirubin group compared to the high bilirubin group.
DISCUSSION: Higher mRNA levels of HSP70 in the low bilirubin group could indicate a possible protective effect of high HSP70 levels against IR injury. Although the exact role of hepatobiliary transport systems in the development of post-operative hyper bilirubinemia is not yet completely understood, this study provides new insights into the molecular aspects of post-operative jaundice after liver surgery.

Krones E, Graziadei I, Trauner M, Fickert P
Evolving concepts in primary sclerosing cholangitis.
Liver Int. 2012; 32(3):352-69 [PubMed] Related Publications
Patients suffering from primary sclerosing cholangitis (PSC) show considerable differences regarding clinical manifestations (i.e. large duct versus small-duct PSC, presence or absence of concomitant inflammatory bowel disease), disease progression, risk for malignancy and response to therapy, raising the question whether PSC may represent a mixed bag of diseases of different aetiologies. The growing list of secondary causes and diseases 'mimicking' or even overlapping with PSC (e.g. IgG4-associated sclerosing cholangitis), which frequently causes problems in clear-cut discrimination from classic PSC and the emerging knowledge about potential disease modifier genes (e.g. variants of CFTR, TGR5 and MDR3) support such a conceptual view. In addition, PSC in children differs significantly from PSC in adults in several aspects resulting in distinct therapeutic concepts. From a clinical perspective, appropriate categorization and careful differential diagnosis are essential for the management of concerned patients. Therefore, the aim of the current review is to summarize current and evolving pathophysiological concepts and to provide up-to-date perspectives including future treatment strategies for PSC.

Visscher H, Ross CJ, Rassekh SR, et al.
Pharmacogenomic prediction of anthracycline-induced cardiotoxicity in children.
J Clin Oncol. 2012; 30(13):1422-8 [PubMed] Related Publications
PURPOSE: Anthracycline-induced cardiotoxicity (ACT) is a serious adverse drug reaction limiting anthracycline use and causing substantial morbidity and mortality. Our aim was to identify genetic variants associated with ACT in patients treated for childhood cancer.
PATIENTS AND METHODS: We carried out a study of 2,977 single-nucleotide polymorphisms (SNPs) in 220 key drug biotransformation genes in a discovery cohort of 156 anthracycline-treated children from British Columbia, with replication in a second cohort of 188 children from across Canada and further replication of the top SNP in a third cohort of 96 patients from Amsterdam, the Netherlands.
RESULTS: We identified a highly significant association of a synonymous coding variant rs7853758 (L461L) within the SLC28A3 gene with ACT (odds ratio, 0.35; P = 1.8 × 10(-5) for all cohorts combined). Additional associations (P < .01) with risk and protective variants in other genes including SLC28A1 and several adenosine triphosphate-binding cassette transporters (ABCB1, ABCB4, and ABCC1) were present. We further explored combining multiple variants into a single-prediction model together with clinical risk factors and classification of patients into three risk groups. In the high-risk group, 75% of patients were accurately predicted to develop ACT, with 36% developing this within the first year alone, whereas in the low-risk group, 96% of patients were accurately predicted not to develop ACT.
CONCLUSION: We have identified multiple genetic variants in SLC28A3 and other genes associated with ACT. Combined with clinical risk factors, genetic risk profiling might be used to identify high-risk patients who can then be provided with safer treatment options.

Drain S, Flannely L, Drake MB, et al.
Multidrug resistance gene expression and ABCB1 SNPs in plasma cell myeloma.
Leuk Res. 2011; 35(11):1457-63 [PubMed] Related Publications
Multi-drug resistance (MDR) leads to impaired treatment efficacy in all forms of malignancy. The main forms of MDR are thought to be mediated by the substrate transporting actions of certain adenosine triphosphate binding cassette (ABC) transport proteins. The genes ABCB1, ABCB4, ABCC1, ABCG2 and LRP1 have been identified as the most prominent contributors to clinically significant MDR. To date, no study has investigated the expression of these genes in plasma cell myeloma (PCM), or attempted to relate their expression to the incidence of relapse and/or stage at presentation. Here, we show that ABCB4 may be a prominent mediator of tumour cell MDR within PCM. Additionally, there are three SNPs (rs1045642, rs2032582 and rs1128503) within the most widely studied of these genes, ABCB1, which have been suggested to have a potential impact on OS in PCM and which may form a haplotype in ABCB1. rs1045642 in ABCB1 appears to be the only SNP affecting OS within the PCM patients studied, with minimal linkage disequilibrium demonstrated between it and rs2032582 and rs1128503.

Wadsworth CA, Dixon PH, Wong JH, et al.
Genetic factors in the pathogenesis of cholangiocarcinoma.
Dig Dis. 2011; 29(1):93-7 [PubMed] Article available free on PMC after 29/07/2015 Related Publications
BACKGROUND: Cholangiocarcinoma (CC) is increasing in incidence, but its pathogenesis remains poorly understood. Chronic inflammation of the bile duct and cholestasis are major risk factors, but most cases in the West are sporadic. Genetic polymorphisms in biliary transporter proteins have been implicated in benign biliary disease and, in the case of progressive familial cholestasis, have been associated with childhood onset of CC. In the current study, five biologically plausible candidate genes were investigated: ABCB11 (BSEP), ABCB4 (MDR3), ABCC2 (MRP2), ATP8B1 (FIC1) and NR1H4 (FXR).
METHODS: DNA was collected from 172 Caucasian individuals with confirmed CC. A control cohort of healthy Caucasians was formed. Seventy-three SNPs were selected using the HapMap database to capture genetic variation around the five candidate loci. Genotyping was undertaken with a competitive PCR-based system. Confirmation of Hardy-Weinberg equilibrium and Cochran-Armitage trend testing were performed using PLINK. Haplotype frequencies were compared using haplo.stats.
RESULTS: All 73 SNPs were in Hardy-Weinberg equilibrium. Four SNPs in ABCB11 were associated with altered susceptibility to CC, including the V444A polymorphism, but these associations did not retain statistical significance after Bonferroni correction for multiple testing. Haplotype analysis of the genotyped SNPs in ATP8B1 identified significant differences in frequencies between cases and controls (global p value of 0.005).
CONCLUSION: Haplotypes in ATP8B1 demonstrated a significant difference between CC and control groups. There was a trend towards significant association of V444A with CC. Given the biological plausibility of polymorphisms in ABCB11 and ATP8B1 as risk modifiers for CC, further study in a validation cohort is required.

Bartuma H, Nord KH, Macchia G, et al.
Gene expression and single nucleotide polymorphism array analyses of spindle cell lipomas and conventional lipomas with 13q14 deletion.
Genes Chromosomes Cancer. 2011; 50(8):619-32 [PubMed] Related Publications
Spindle cell lipomas (SCL) are circumscribed, usually s.c. tumors that typically occur on the posterior neck, shoulder, and back of middle aged men. Cytogenetically, almost all SCL are characterized by deletions of chromosome arm 13q, often in combination with loss of 16q. Deletions of 13q are seen also in approximately 15% of conventional lipomas. Through single nucleotide polymorphism (SNP) array analyses, we identified two minimal deleted regions (MDR) in 13q14 in SCL. In MDR1, four genes were located, including the tumor suppressor gene RB1. MDR1 in SCL overlapped with the MDR detected in conventional lipomas with 13q14 deletion. In MDR2 in SCL there were 34 genes and the two microRNA (miRNA) genes miR-15a and miR-16-1. Global gene expression analysis was used to study the impact of the deletions on genes mapping to the two SCL-associated MDR. Five genes (C13orf1, DHRS12, ATP7B, ALG11, and VPS36) in SCL and one gene (C13orf1) in conventional lipomas with 13q-deletions were found to be significantly underexpressed compared with control tissues. Quantitative real-time PCR showed that miR-16-1 was expressed at lower levels in SCL than in the control samples. No mutations were found at sequencing of RB1, miR-15a, and miR-16-1. Our findings further delineate the target region for the 13q deletion in SCL and conventional lipomas and show that the deletions are associated with down-regulated expression of several genes, notably C13orf1, which was the only gene to be significantly down-regulated in both tumor types.

Edrei Y, Gross E, Corchia N, et al.
Vascular profile characterization of liver tumors by magnetic resonance imaging using hemodynamic response imaging in mice.
Neoplasia. 2011; 13(3):244-53 [PubMed] Article available free on PMC after 29/07/2015 Related Publications
Recently, we have demonstrated the feasibility of using hemodynamic response imaging (HRI), a functional magnetic resonance imaging (MRI) method combined with hypercapnia and hyperoxia, for monitoring vascular changes during liver pathologies without the need of contrast material. In this study, we evaluated HRI ability to assess changes in liver tumor vasculature during tumor establishment, progression, and antiangiogenic therapy. Colorectal adenocarcinoma cells were injected intrasplenically to model colorectal liver metastasis (CRLM) and the Mdr2 knockout mice were used to model primary hepatic tumors. Hepatic perfusion parameters were evaluated using the HRI protocol and were compared with contrast-enhanced (CE) MRI. The hypovascularity and the increased arterial blood supply in well-defined CRLM were demonstrated by HRI. In CRLM-bearing mice, the entire liver perfusion was attenuated as the HRI maps were significantly reduced by 35%. This study demonstrates that the HRI method showed enhanced sensitivity for small CRLM (1-2 mm) detection compared with CE-MRI (82% versus 38%, respectively). In addition, HRI could demonstrate the vasculature alteration during CRLM progression (arborized vessels), which was further confirmed by histology. Moreover, HRI revealed the vascular changes induced by rapamycin treatment. Finally, HRI facilitates primary hepatic tumor characterization with good correlation to the pathologic differentiation. The HRI method is highly sensitive to subtle hemodynamic changes induced by CRLM and, hence, can function as an imaging tool for understanding the hemodynamic changes occurring during CRLM establishment, progression, and antiangiogenic treatment. In addition, this method facilitated the differentiation between different types of hepatic lesions based on their vascular profile noninvasively.

Moitra K, Scally M, McGee K, et al.
Molecular evolutionary analysis of ABCB5: the ancestral gene is a full transporter with potentially deleterious single nucleotide polymorphisms.
PLoS One. 2011; 6(1):e16318 [PubMed] Article available free on PMC after 29/07/2015 Related Publications
BACKGROUND: ABCB5 is a member of the ABC protein superfamily, which includes the transporters ABCB1, ABCC1 and ABCG2 responsible for causing drug resistance in cancer patients and also several other transporters that have been linked to human disease. The ABCB5 full transporter (ABCB5.ts) is expressed in human testis and its functional significance is presently unknown. Another variant of this transporter, ABCB5 beta possess a "half-transporter-like" structure and is expressed in melanoma stem cells, normal melanocytes, and other types of pigment cells. ABCB5 beta has important clinical implications, as it may be involved with multidrug resistance in melanoma stem cells, allowing these stem cells to survive chemotherapeutic regimes.
METHODOLOGY/PRINCIPAL FINDINGS: We constructed and examined in detail topological structures of the human ABCB5 protein and determined in-silico the cSNPs (coding single nucleotide polymorphisms) that may affect its function. Evolutionary analysis of ABCB5 indicated that ABCB5, ABCB1, ABCB4, and ABCB11 share a common ancestor, which began duplicating early in the evolutionary history of chordates. This suggests that ABCB5 has evolved as a full transporter throughout its evolutionary history.
CONCLUSIONS/SIGNIFICANCE: From our in-silco analysis of cSNPs we found that a large number of non-synonymous cSNPs map to important functional regions of the protein suggesting that these SNPs if present in human populations may play a role in diseases associated with ABCB5. From phylogenetic analyses, we have shown that ABCB5 evolved as a full transporter throughout its evolutionary history with an absence of any major shifts in selection between the various lineages suggesting that the function of ABCB5 has been maintained during mammalian evolution. This finding would suggest that ABCB5 beta may have evolved to play a specific role in human pigment cells and/or melanoma cells where it is predominantly expressed.

Barash H, R Gross E, Edrei Y, et al.
Accelerated carcinogenesis following liver regeneration is associated with chronic inflammation-induced double-strand DNA breaks.
Proc Natl Acad Sci U S A. 2010; 107(5):2207-12 [PubMed] Article available free on PMC after 29/07/2015 Related Publications
Hepatocellular carcinoma (HCC) is the third leading cause of cancer mortality worldwide and is considered to be the outcome of chronic liver inflammation. Currently, the main treatment for HCC is surgical resection. However, survival rates are suboptimal partially because of tumor recurrence in the remaining liver. Our aim was to understand the molecular mechanisms linking liver regeneration under chronic inflammation to hepatic tumorigenesis. Mdr2-KO mice, a model of inflammation-associated cancer, underwent partial hepatectomy (PHx), which led to enhanced hepatocarcinogenesis. Moreover, liver regeneration in these mice was severely attenuated. We demonstrate the activation of the DNA damage-response machinery and increased genomic instability during early liver inflammatory stages resulting in hepatocyte apoptosis, cell-cycle arrest, and senescence and suggest their involvement in tumor growth acceleration subsequent to PHx. We propose that under the regenerative proliferative stress induced by liver resection, the genomic unstable hepatocytes generated during chronic inflammation escape senescence and apoptosis and reenter the cell cycle, triggering the enhanced tumorigenesis. Thus, we clarify the immediate and long-term contributions of the DNA damage response to HCC development and recurrence.

Hoellein A, Decker T, Bogner C, et al.
Expression of multidrug resistance-associated ABC transporters in B-CLL is independent of ZAP70 status.
J Cancer Res Clin Oncol. 2010; 136(3):403-10 [PubMed] Related Publications
PURPOSE: To assess whether the poor prognosis of ZAP70-positive B-cell chronic lymphocytic leukemia (CLL) is associated with the overexpression of ABC transporter genes that are responsible for pleiotropic drug resistance.
MATERIALS AND METHODS: The transcript level of ten drug transporters was analyzed using semiquantitative and quantitative RT-PCR in control hematopoietic cells, in 41 CLL patient samples and in 5 lymphoma cell lines. ZAP70 status was determined by immunoblotting.
RESULTS: Of all analyzed transporters, MDR1, MDR2, MRP1, MRP4, MRP5, and MRP7 were expressed at a significantly higher level in B lymphocytes when compared with other hematopoietic cells in peripheral blood. A subgroup of 41 CLL patient samples showed similar or higher expression of these genes than control B cells, and CLL cells exhibited high expression when compared with multiple lymphoma cell lines. No significant correlation between ZAP70 expression and ABC transporter expression was observed.
CONCLUSION: The ZAP70 status is independent of the multidrug resistance phenotype in CLL.

Németh J, Stein I, Haag D, et al.
S100A8 and S100A9 are novel nuclear factor kappa B target genes during malignant progression of murine and human liver carcinogenesis.
Hepatology. 2009; 50(4):1251-62 [PubMed] Related Publications
UNLABELLED: The nuclear factor-kappaB (NF-kappaB) signaling pathway has been recently shown to participate in inflammation-induced cancer progression. Here, we describe a detailed analysis of the NF-kappaB-dependent gene regulatory network in the well-established Mdr2 knockout mouse model of inflammation-associated liver carcinogenesis. Expression profiling of NF-kappaB-deficient and NF-kappaB-proficient hepatocellular carcinoma (HCC) revealed a comprehensive list of known and novel putative NF-kappaB target genes, including S100a8 and S100a9. We detected increased co-expression of S100A8 and S100A9 proteins in mouse HCC cells, in human HCC tissue, and in the HCC cell line Hep3B on ectopic RelA expression. Finally, we found a synergistic function for S100A8 and S100A9 in Hep3B cells resulting in a significant induction of reactive oxygen species (ROS), accompanied by enhanced cell survival.
CONCLUSION: We identified S100A8 and S100A9 as novel NF-kappaB target genes in HCC cells during inflammation-associated liver carcinogenesis and provide experimental evidence that increased co-expression of both proteins supports malignant progression by activation of ROS-dependent signaling pathways and protection from cell death.

Lehne G, Grasmo-Wendler UH, Berner JM, et al.
Upregulation of stem cell genes in multidrug resistant K562 leukemia cells.
Leuk Res. 2009; 33(10):1379-85 [PubMed] Related Publications
The transmembrane transporter P-glycoprotein (P-gp) encoded by ABCB1, is one major cause for multidrug resistance (MDR). We compared the genomic profile and gene expression pattern of the P-gp positive K562VCR cells with parental P-gp negative K562wt cells. In K562VCR array CGH revealed amplification of ABCB1, ABCB4, ABCB5 and SEMA3D, whereas expression microarrays demonstrated upregulation of stem cell genes (e.g. KIT and HOXB4), anti-apoptotic genes (e.g. IGF1R and CCNG1), and downregulation of pro-apoptotic genes (e.g. CASP4, 6 and 7). Thus, K562VCR cells disclose stem cell characteristics including a range of drug resistance mechanisms possibly attained as a stem cell program switched on en bloc.

Reed K, Hembruff SL, Laberge ML, et al.
Hypermethylation of the ABCB1 downstream gene promoter accompanies ABCB1 gene amplification and increased expression in docetaxel-resistant MCF-7 breast tumor cells.
Epigenetics. 2008; 3(5):270-80 [PubMed] Related Publications
Drug transporters have been implicated in resistance of solid and non-solid tumors to a variety of chemotherapeutic agents. Higher expression of the ABCB1 drug transporter is often observed in drug-resistant tumor cells, although the precise mechanism remains unclear. During selection of MCF-7 cells for survival in increasing concentrations of docetaxel (MCF-7TXT cells), we observed in this study a temporal correlation between the acquisition of docetaxel resistance at selection dose 9 and the increased expression of ABCB1. Both the magnitude of docetaxel resistance and the level of ABCB1 expression then rose as the selection dose was further elevated. We also observed through bisulfite sequencing experiments that the ABCB1 downstream promoter became increasingly methylated following the acquisition of drug resistance (selection doses 10-12). Transcription was solely attributed to the upstream ABCB1 promoter within MCF-7TXT cells at the highest selection dose suggesting that hypermethylation caused a shift in promoter usage. The hypermethylation was also accompanied by regional amplification of chromosome 7 containing the ABCB1 gene and its neighbor ABCB4 but not DBF-4. The amplification of the ABCB1 gene correlated positively both with the hypermethylation of the ABCB1 downstream promoter (r=0.90) and the increased expression of ABCB1 (r=0.78). Moreover demethylation of the ABCB1 downstream promoter induced by 5-aza-2A'deoxycytidine treatment decreased the expression of ABCB1 mRNA in MCF-7TXT cells. Taken together, our findings suggest that the increased expression of ABCB1 upon acquisition of docetaxel resistance in breast tumor cells can be multifactorial, involving both epigenetic changes in promoter usage and regional chromosome amplification.

Wang J, Tai LS, Tzang CH, et al.
1p31, 7q21 and 18q21 chromosomal aberrations and candidate genes in acquired vinblastine resistance of human cervical carcinoma KB cells.
Oncol Rep. 2008; 19(5):1155-64 [PubMed] Related Publications
Vinblastine (VBL) is used to treat certain kinds of cancer including Hodgkin's lymphoma, lung cancer, breast cancer, testicular cancer and cervical carcinoma. However, the rapid development of resistance during therapy remains a major clinical challenge. In order to reverse cancer cell resistance, the goal of this study was to find differentially expressed genes and chromosomal alterations in multidrug resistant (MDR) KB-v1 cells, further to probe the relationship between drug resistance and differential genes, and chromosomal changes in MDR cancer cells. Comparative genomic hybridization (CGH) analysis of MDR KB-v1 and their parental KB-3-1 cells revealed chromosomal changes; microarray-based expression profiling was carried out by comparing the gene expressions of MDR KB-v1 cells and KB-3-1 cells. We have identified 3 chromosomal gains in regions of 1p31, 7q21 and 18q21 in MDR cells and 10 genes (CYR61, UGTREL7, MBD1, NARS, ATP5A1, ABCB1, ABCB4, PEG10, MCM7, SERPINE1) contained in these regions were also up-regulated in MDR KB-v1 cells. Forty-nine genes were down-regulated when KB-v1 cells were subjected to lower dose or depletion of the drug. We have confirmed some gene expression changes by reverse transcription-polymerase chain reaction and Northern blots. These are the first data describing the relationship of 1p31 and 18q21 chromosomal aberrations and candidate genes in acquired vinblastine-resistance. This study also demonstrates that the combination of CGH and cDNA microarray is a very useful tool to detect drug resistant targets in cancer treatment.

Kotaka M, Onishi Y, Ohno T, et al.
Identification of negative transcriptional factor E4BP4-binding site in the mouse circadian-regulated gene Mdr2.
Neurosci Res. 2008; 60(3):307-13 [PubMed] Related Publications
The hepatic transporter Mdr2 is an ATP-binding cassette transporter which excretes phosphatidylcholine into the bile. We showed that the level of Mdr2 mRNA oscillated in circadian fashion in mouse liver whereas such oscillation was dampened in the liver of Clock mutants. To examine transcriptional regulation of the Mdr2 gene we performed luciferase reporter assays using plasmid constructs containing the 5'-flanking region of the Mdr2 gene. Reporter assays using deletion constructs demonstrated that E4BP4 represses the transcriptional activity of the promoter including the D1 and D2 sites within four putative E4BP4-binding sites. Chromatin immunoprecipitation and gel shift assays showed that E4BP4 binds to the D2 site, but not to the D1 site. These data suggested that E4BP4 is a negative transcription factor for circadian Mdr2 mRNA expression.

Ren L, Xiao L, Hu J
MDR1 and MDR3 genes and drug resistance to cisplatin of ovarian cancer cells.
J Huazhong Univ Sci Technolog Med Sci. 2007; 27(6):721-4 [PubMed] Related Publications
To investigate the relationship between MDR1 and MDR3 gene and drug resistance to cisplatin of ovarian cancer cells. Two siRNAs (MDR1, MDR3) which specifically targeted MDR1 and MDR3 genes were transferred into A2780/DDP cells. Then double staining with Annexin-V-FITC/PI was used to detect cell apoptosis by the flow cytometry (FCM). A2780/DDP cell viability was determined by MTT. MDR1 and MDR3 mRNA were assessed by RT-PCR. Caspase-3 protein was detected by Western blotting. Transfection of MDR1 and MDR3 siRNA into A2780/DDP cells failed to reverse the drug-resistance of A2780/DDP cells to cisplatin (P>0.05). No significant difference in the apoptosis efficiency was observed between the MDR1 and MDR3 siRNA, pSuppressorNeo vector transfection cells and untreated cells (P>0.05). In the presence of cisplatin of different concentrations, the viability of A2780/DDP cells was not significantly decreased after the transfection. No changes in MDR1 and MDR3 mRNA were found in MDR1 and MDR3 siRNA-transfected A2780/DDP cells. As compared with pSuppressorNeo and untreated groups, no significant difference existed in the expression of MDR1 and MDR3 mRNA (P>0.05). The expression of caspase-3 protein in MDR1 and MDR3 siRNA transfected A2780/DDP cells was not significantly increased. It is concluded that multidrug resistance induced by cisplatin in ovarian carcinoma cell lines is not due to overexpression of MDR1 and MDR3 gene. The drug resistance of ovarian carcinoma cells to cisplatin is not mediated by P-glycoprotein.

Heimerl S, Bosserhoff AK, Langmann T, et al.
Mapping ATP-binding cassette transporter gene expression profiles in melanocytes and melanoma cells.
Melanoma Res. 2007; 17(5):265-73 [PubMed] Related Publications
ATP-binding cassette (ABC) transporters regulate the transport of a variety of physiologic substrates. Moreover, several human ABC proteins are responsible for drug exclusion in compound-treated tumor cells, providing cellular mechanisms for the development of multidrug resistance and, therefore, playing an important role in malignant transformation. As only limited information exists on the role of ABC transporters in melanoma, the aim of the study was to generate a complete expression profile of ABC transporters in this tumor entity. Using a TaqMan low-density array for 47 human ABC transporters, mRNA expression analysis was performed from normal human epidermal melanocytes (NHEM P2 and NHEM P3), nine different cell lines originating from primary melanoma (Mel Ei, Mel Juso, Mel Ho and Mel Wei), and metastases of malignant melanoma (Mel Im, Mel Ju, SK Mel 28, HTZ 19 and HMB2). Cell line-specific expression levels were compared with gene expression in pooled RNA from a variety of other human tissues. High expression levels were detected in pooled tissue RNA as well as in cells of melanocytic origin for ABCA5, ABCB2, ABCB6, ABCD3, ABCD4, ABCF1, ABCF2 and ABCF3, whereas ABCB5 revealed a melanocyte-specific high transcript level. In relation to normal melanocytes, ABCB3, ABCB6, ABCC2, ABCC4, ABCE1 and ABCF2 were significantly increased in melanoma cell lines, whereas ABCA7, ABCA12, ABCB2, ABCB4, ABCB5 and ABCD1 showed lower expression levels. In summary, we present here for the first time an ABC-transporter mRNA expression profile in melanoma in comparison to normal melanocytes. The differentially regulated ABC transporters detected by our approach may be candidate genes involved in melanoma tumorigenesis, progression and therapy resistance and could therefore be of great importance to identify novel options for melanoma therapy.

Xiao L, Gao R, Lu S, et al.
Reversal of adriamycin resistance in human mammary cancer cells by small interfering RNA of MDR1 and MDR3 genes.
J Huazhong Univ Sci Technolog Med Sci. 2006; 26(6):735-7 [PubMed] Related Publications
The purpose of this paper is to investigate the reversal effect of small interfering RNA (siRNA) targeting MDR1 and MDR3 genes on the resistance of MCF-7/ADR cells to adriamycin. siRNA plasmid vector targeting MDR1 and MDR3 genes was transfected into MCF-7/ADR cells, and then was stained with Annexin-V FITC (fluorescein isothiocyanate conjugated) to detect the early stage cell apoptosis by flow cytometry (FCM). 50% inhibition concentration (IC50) of adriamycin for MCF-7/ADR cells was determined by MTT method. MDR1 and MDR3 mRNA was assessed by RT-PCR. Treatment of MCF-7/ADR cells with the two kinds of siRNAs resulted in a reversal of adriamycin resistance of MDR to different extents. 1) The apoptosis efficiency of MDR1 and MDR3 siRNA vector after transfection was (18.21+/-1.65) % and (9.07+/-2.16) % respectively (P<0.05), and there was significant differences in the apoptosis efficiency between p Suppressor Neo vector and the MDR1 siRNA or MDR3 siRNA vector (P<0.01); 2) The reversal effect of MDR1 siRNA is higher than that of MDR3 siRNA (P<0.05); 3) The expression of MDRI and MDR3 mRNA can be restrained by p Suppressor Neo MDR1 and MDR3 siRNA respectively, and the reduction in the mRNA level was in a time-dependent manner (P<0.01). MDR1 and MDR3 gene silencing can enhance intracellular adriamycin accumulation in MCF-7/ADR cells, improve sensitivity of MCF-7/ADR cells to adriamycin, and induce cell apoptosis. The reversal effect of adriamycin resistance by siRNA of MDR1 was more effective than that of MDR3.

Matthews C, Catherwood MA, Larkin AM, et al.
MDR-1, but not MDR-3 gene expression, is associated with unmutated IgVH genes and poor prognosis chromosomal aberrations in chronic lymphocytic leukemia.
Leuk Lymphoma. 2006; 47(11):2308-13 [PubMed] Related Publications
Two P-glycoprotein (P-gp) genes, MDR-1 (ABCB1) and MDR-3 (ABCB4), have been identified in humans. This study was designed to investigate whether associations exist between expression of MDR-1 and MDR-3 P-gp and other markers of poor prognosis and/or prior exposure to therapeutic agents in chronic lymphocytic leukemia (CLL). IgVH mutational status, gene usage, CD38 positivity, FISH analysis and clinical information were available on all patients. Twenty-one of 101 patients tested showed MDR-3 P-gp positivity. Associations with markers of poor prognosis or prior chemotherapy did not reach statistical significance, but MDR-3 P-gp positive patients had significantly shorter survivals than MDR-3 P-gp negative patients. MDR-1 P-gp expression (18/25) showed a strong association with unmutated IgVH genes and adverse prognosis cytogenetics (p = 0.015, p = 0.014, respectively), but was independent of prior exposure to chemotherapeutic agents. These results suggest a role for MDR-1 and MDR-3 in chemoresistant disease. This study highlights the value of determining MDR phenotype in CLL patients prior to treatment, to allow the design of novel drug regimens containing agents that reverse MDR function.

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