Breast Cancer Resistance Protein Gene Research Articles

Correlation between the mRNA levels of BCRP and LUNX genes and pathological types and stages of patients with non-small cell lung cancer

To analyze the correlation between the mRNA levels of breast cancer resistance protein (BCRP) and lung-specific X protein (LUNX) genes with pathological types and stages of patients with non-small cell lung cancer (NSCLC) and their significance for prognosis. Eighty nine patients with NSCLC admitted to Huaihe Hospital of Henan University between June 2015 and June 2018 were recruited, with 55 patients with benign lung lesions admitted during the same period of time selected as the control group. The mRNA levels of BCRP and LUNX genes were detected in the peripheral blood samples from the two groups, and their correlation with the clinicopathological characteristics and prognosis of the patients was analyzed. The expression rates of BCRP and LUNX mRNA in the NSCLC group were significantly higher compared with the control group (P < 0.05). The level of BCRP mRNA of the NSCLC patients has correlated with the degree of differentiation and TNM staging (P < 0.05), but not with gender, age, smoking, pathological types and lymph node metastasis (P > 0.05). The level of LUNX mRNA of them has correlated with the degree of differentiation, TNM staging and lymph node metastasis (P < 0.05), but not with gender, age, smoking, and pathological types (P > 0.05). Compared with those with no expression, the overall survival rate of patients with BCRP and LUNX expression was significantly lower (P < 0.05). The degree of differentiation, TNM staging, lymph node metastasis, and expression of the BCRP and LUNX mRNA may all affect the prognosis of the patients. The levels of BCRP and LUNX mRNA in the peripheral blood of patients with NSCLC are significantly increased. The expression of BCRP mRNA is correlated with the degree of differentiation and TNM staging, whilst the expression of LUNX mRNA is correlated with the differentiation degree, TNM staging and lymph node metastasis. Both may be used as independent predictors for the prognosis of patients with NSCLC.

Overexpression of Riboflavin Excretase Enhances Riboflavin Production in the Yeast Candida famata.

Many microorganisms are capable of riboflavin oversynthesis and accumulation in a medium, suggesting that they efficiently excrete riboflavin. The mechanisms of riboflavin efflux in microorganisms remain elusive. Candida famata are representatives of a group of so-called flavinogenic yeast species that overproduce riboflavin (vitamin B2) in response to iron limitation. The riboflavin overproducers of this yeast species have been obtained by classical mutagenesis and metabolic engineering. Overproduced riboflavin accumulates in the cultural medium rather than in the cells suggesting existence of the special mechanisms involved in riboflavin excretion. The appropriate protein and gene have not been identified in yeasts till recently. At the same time, the gene BCRP (breast cancer resistance protein) has been identified in mammal mammary glands. Several homologs of the mammal BCRP gene encoding putative riboflavin efflux protein (excretase) were identified in the flavinogenic yeasts Debaryomyces hansenii and C. famata. Here we evaluate the yeast homologs of BCRP with respect to improvement of a riboflavin production by C. famata. The closest homologs from D. hansenii or C. famata were expressed under the control of TEF1 promoter of these yeasts in the wild-type and riboflavin-overproducing strains of C. famata. Resulted transformants overexpressed the corresponding genes (designated as DhRFE and CfRFE) and produced 1.4- to 6-fold more riboflavin as compared to the corresponding parental strains. They also were characterized by overexpression of RIB1 and RIB6 genes which encode the first and the last structural enzymes of riboflavin synthesis and exhibited elevated specific activity of GTP cyclohydrolase II. Thus, overexpression of yeast homolog of mammal gene BCRP may be useful to increase the riboflavin yield in a riboflavin production process using a recombinant overproducing C. famata strain or other flavinogenic microorganisms.

Inhibition of Breast Cancer Resistance Protein (BCRP) by Ko143 Can Affect Pharmacokinetics of Enrofloxacin in Exopalaemon carinicauda

Adenosine triphosphate-binding cassette transporter breast cancer resistance protein (BCRP) exists highly in the apical membranes of epithelia, and is involved in drug availability. Ko143 is a typical inhibitor of BCRP in rodents. The synthetic antibacterial agent enrofloxacin (ENRO) is a fluoroquinolone employed as veterinary and aquatic medicine, and also a substrate for BCRP. BCRP gene highly expressed in the hepatopancreas and intestine of Exopalaemon carinicauda as was determined with real-time quantitative reverse transcription-polymerase chain reaction (RT-qPCR) method. The effects of Ko143 on the abundance of BCRP mRNA and ENRO pharmacokinetics in E. carinicauda were studied. The mRNA abundance of BCRP decreased significantly in hepatopancreas and intestine (P <0.05) after Ko143 treatment. Co-administration of Ko143 significantly changed the pharmacokinetics of orally administered enrofloxacin, which was supported by higher distribution half-life (t1/2α), elimination half-life (t1/2β), area under the curve up to the last measurable concentration (AUC0-t), peak concentration (Cmax) and lower clearance (CL/F). These findings revealed that Ko143 downregulates BCRP expression in hepatopancreas and intestine, thus affects the pharmacokinetics of orally administered enrofloxacin in E. carinicauda. The drug-drug interaction can be caused by the change in BCRP activity if ENRO is used in combination with other drugs in shrimp.

Talazoparib nanoparticles for overcoming multidrug resistance in triple-negative breast cancer.

Herein, we investigated efflux pumps-mediated talazoparib-resistance in the treatment of triple-negative breast cancer (TNBC). Furthermore, we produced a novel talazoparib-solid lipid nanoparticles (SLNs) and then explored in vitro therapeutic efficacy of talazoparib-SLNs to overcome talazoparib-resistance in TNBC cells. Talazoparib-SLNs formulation was produced and then characterized. Calcein and Rho-123 were used to analyze the functional activity of drug efflux pumps in these cells. Additionally, RT-PCR, western blot and immunofluorescence analysis were used to detect the messenger RNA, and protein expression level, and cellular localization of the multidrug resistance (MDR1), breast cancer resistance protein (BCRP), and MRP1. We found that talazoparib efflux was mediated by BCRP and MRP1 pumps in TNBC cells. Talazoparib-SLNs could significantly enhance therapeutic efficacy of talazoparib. Furthermore, talazoparib-SLNs were more effective in the suppression of MDR1, BCRP, and MRP1 gene and protein expression levels than talazoparib. Consequently, this study suggests that talazoparib-SLNs formulation represents a promising therapeutic carrier to reverse MDR-mediated resistance in TNBC.

Metabolome Analysis Reveals Dermal Histamine Accumulation in Murine Dermatitis Provoked by Genetic Deletion of P-Glycoprotein and Breast Cancer Resistance Protein.

P-glycoprotein (P-gp) and breast cancer resistance protein (BCRP) are xenobiotic transporters which pump out variety types of compounds, but information on their interaction with endogenous substrates in the skin is limited. The purpose of the present study was to clarify possible association of these transporters in dermal accumulation of inflammatory mediators. Dermatitis model was constructed by repeated topical application of oxazolone in wild-type, and P-gp and BCRP gene triple knockout (Mdr1a/1b/Bcrp-/-) mice to observe difference in phenotype. Target metabolome analysis of 583 metabolites was performed using skin and plasma. Dermatitis and scratching behavior in dermatitis model of Mdr1a/1b/Bcrp-/- mice were more severe than wild-type mice, suggesting protective roles of these transporters. This hypothesis was supported by the metabolome analysis which revealed that concentration of histamine and other dermatitis-associated metabolites like urate and serotonin in the dermatitis skin, but not normal skin, of Mdr1a/1b/Bcrp-/- mice was higher than that of wild-type mice. Gene expression of P-gp and BCRP was reduced in oxazolone-treated skin and the skin of patients with atopic dermatitis or psoriasis. These results suggest possible association of these efflux transporters with dermal inflammatory mediators, and such association could be observed in the dermatitis skin.

Antioxidant α‐mangostin downregulates ATP‐binding cassette transporters in HuT78 cells

Sézary syndrome (SS) is an aggressive form of cancer called cutaneous T‐cell lymphoma (CTCL). Patients with SS carry poor prognosis, with a median survival of approximately 40 months after diagnosis and a 5‐year survival rate below 40%. The offending neoplastic T cells for SS known as Sézary cells are aggressive and rapid growing. They are refractory to chemotherapy, and have been posting the biggest challenge for the treatment of SS. The principal mechanism by which the Sézary cells develop resistance to chemotherapeutic agents is through the overexpression of ATP‐binding cassette (ABC) transporter proteins such as P‐glycoprotein (P‐gp), multidrug‐resistance associated protein 1 (MRP1), and breast cancer resistance protein (BCRP). The expressions of P‐gp, MRP1 and BCRP genes appear to be regulated, in part, by nuclear factor E2‐related factor 2 (Nrf2), a transcriptional regulator of cellular resistance to oxidants. α‐Mangostin (α‐MGT) is a xanthone derivative that possesses antioxidant and cytotoxic activities in various types of cancers. This study is undertaken to support the hypothesis that through its antioxidant activity, α‐MGT mediates downregulation of ABC transporters expression in HuT78, the cell line isolated from a Sézary patient. The results revealed that HuT78 cells expressed P‐gp, MRP1 and BCRP at various frequencies, ranging from 31% to 78% where the expression level of MRP1 was the highest followed by that of BCRP and P‐gp. Upon exposure of HuT78 cells to 12 μM α‐MGT for 24 hours, the expression of MRP1 was decreased by 50%, BCRP was slightly downregulated, and the P‐gp was undetectable. Our preliminary data suggested that α‐MGT may be beneficial in reversing the resistant phenotype of Sézary cells for chemotherapy.This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Breast cancer resistance protein (BCRP) gene expression in a cohort of adult Egyptian patients with acute myeloid leukemia.

Acute myeloid leukemia (AML), an aggressive clonal disease, is genetically heterozygous. The prognostic role of expression of Breast Cancer Resistance Protein (BCRP) gene, which behaves as a multidrug transporter, in adult AML is ambiguous. The objective is to assess the level of mRNA expression of BCRP gene in newly diagnosed cytogenetically normal adult Egyptian AML patients; and to clarify its potential influence and association between therapeutic responsiveness and disease free survival. The BCRP gene expression was evaluated by quantifying its mRNA using real time RT-PCR in fifty newly diagnosed cytogenetically normal adult AML patients and 20 healthy normal controls. The expression was evaluated in relation to clinical and prognostic factors, response to treatment and the survival rate. BCRP mRNA was over expressed in adult AML patients compared to controls. This study showed a positive statistical correlation between BCRP gene expression and the percent of CD34 expression. Statistical analysis did not reveal any association between BCRP expression level and chemotherapeutic responsiveness or disease free survival rate. The significance of BCRP gene expression and its function in AML is very complicated, therefore more standardized clinical studies are needed.

The clinical significance of the expression of breast cancer resistance protein gene in hepatocellular carcinoma tissue and the effect of inhibiting its expression on the proliferation and apoptosis of hepatocellular carcinoma cells

Objective To investigate the relationship between the expression of breast cancer resistance protein (BCRP) and the clinicopathological features in hepatocellular carcinoma (HCC) and the influence of the BCRP expression on the proliferation and apoptosis of HCC cells. Methods To detect the expression of BCRP in hepatocellular carcinoma tissues by reverse transcriptase-polymerase chain reaction (RT-PCR), and analyze the relationship with clinicopathological parameters; BCRP-small interfering RNA (siRNA) was transfected into human hepatoma SMMC-7721 cells by Lipofectamine™ 2000 liposome mediated method; cell proliferation, apoptosis and BCRP, proliferation cell nuclear antigen (Ki-67), B cell lymphoma/leukemia-2 associated X protein (bax), Notch1 and Hes1 protein expression were detected by methyl thiazol tetrazolium (MTT) method, flow cytometry and Western blotting, respectively. Results The expression of BCRP in HCC was not related to the sex, age and tumor size of HCC patients, and it was related to pathological grade, clinical stage and metastasis of tumor; expression of BCRP in SMMC-7721 cells after BCRP-siRNA was transfected cells was inhibited in the level of transcription and translation; cell proliferation (0.287±0.022) and expression of Ki-67 (0.142±0.018), Notch1 (0.162±0.021) and Hes1 (0.111±0.015) protein in BCRP-siRNA group were significantly lower than Control group (0.411±0.026, 0.258±0.026, 0.462±0.032, 0.241±0.023; Pproliferation=0.001, PKi-67=0.001, PNotch1=0.000, PHes1=0.001), the apoptosis rate (14.63±0.88)% and the expression of bax protein (0.324±0.034) was significantly higher than Control group ([1.32±0.15)%, 0.106±0.012; Papoptosis=0.000, Pbax=0.000]. Conclusion The expression of BCRP is related to pathological grade, clinical stage and metastasis of HCC, inhibition of its expression can reduce the proliferation of hepatocellular carcinoma cells and induce cell apoptosis, the mechanism is related to the regulation of Ki-67, bax expression and Notch1 signaling pathway. Key words: Breast cancer resistance protein gene; Clinical significance; Liver cancer; Apoptosis; Signal pathway

Graphene Quantum Dots Downregulate Multiple Multidrug‐Resistant Genes via Interacting with Their C‐Rich Promoters

Multidrug resistance (MDR) is the major factor in the failure of many forms of chemotherapy, mostly due to the increased efflux of anticancer drugs that mediated by ATP-binding cassette (ABC) transporters. Therefore, inhibiting ABC transporters is one of effective methods of overcoming MDR. However, high enrichment of ABC transporters in cells and their broad substrate spectra made to circumvent MDR are almost insurmountable by a single specific ABC transporter inhibitor. Here, this study demonstrates that graphene quantum dots (GQDs) could downregulate the expressions of P-glycoprotein, multidrug resistance protein MRP1, and breast cancer resistance protein genes via interacting with C-rich regions of their promoters. This is the first example that a single reagent could suppress multiple MDR genes, suggesting that it will be possible to target multiple ABC transporters simultaneously with a single reagent. The inhibitory ability of the GQDs to these drug-resistant genes is validated further by reversing the doxorubicin resistance of MCF-7/ADR cells. Notably, GQDs have superb chemical and physical properties, unique structure, low toxicity, and high biocompatibility; hence, their capability of inhibiting multiple drug-resistant genes holds great potential in cancer therapy.

FBLN-4 and BCRP genes as two prognostic markers are downregulated in breast cancer tissue.

Fibulin-4 (FBLN-4) is an extracellular glycoprotein that is upregulated in some cancer and is khown as prognostic marker in ovarian and cervical cancer. Breast cancer resistance protein (BCRP) is an ATP-binding cassette transporter that facilitates the efflux of various anticancer drugs from the cell and cause MDR phenotype in breast tumors. Many studies are available that indicat overexpression of BCRP gene in breast cancer. In the present study we aimed to analyze the expression level of FBLN-4 and BCRP in Iranian breast cancer patients. We collected 40 samples of breast cancer and normal tissue from Tehran Khatam-al-Anbia hospital. To analyze the gene expression by using Real Time RT-PCR FBLN-4 and BCRP gene expression level were measured and then the association of gene expression with breast cancer were determined. Surprisingly the expression level of FBLN-4 and BCRP genes were downregulated in tumor tissues compared to adjacent normal tissues. Comparison of the gene expression and clinico-pathology reports indicate FBLN-4 gene expression was associated with breast cancer histological grade. We found no correlation between the expressions of BCRP gene with any clinico-pathological characters. Interestingly and in contrast with our expectation, we found that the expression level of FBLN-4 and BCRP were downregulated in tumor compared to adjacent normal tissues. FBLN-4 was associated with grade histology and therefore can be considered as a potential prognostic biomarker.

Preliminary study of the effects of β-elemene on MCF-7/ADM breast cancer stem cells.

We examined expression differences in breast cancer stem cells (BCSCs) of the doxorubicin-resistant breast cancer cell line MCF-7/ADM and doxorubicin-sensitive cell line MCF-7/S. The effects of Chinese medicine β-elemene on BCSCs and resistance protein expression were determined. The serum-free cell culture method was used for cell culture, and morphology was observed to determine the rate of cell sphere formation. Reverse transcription-polymerase chain reaction was used to detect breast cancer resistance protein (BCRP) and P-glycoprotein (P-gp) gene expression. Flow cytometry was used to determine BCRP- and P-gp-positive cell rates and CD44 + CD24-/low cell ratios. Morphological observation and gene amplification showed that compared with MCF-7/S cells, the serum-free cell sphere-forming rate and P-gp and BCRP gene expression levels were higher in MCF-7/ADM cells. Flow cytometry results showed that P-gp and BCRP protein expression in MCF-7/ADM cells was 77.78 ± 9.55% and 32.33 ± 5.12%, respectively, and the CD44 + CD24-/low cell rate was 64.79 ± 11.78%, which were all significantly higher than those in MCF-7/S cells (3.97 ± 1.51, 14.26 ± 2.51, 18.79 ± 3.28%; P < 0.05). β-elemene significantly decreased the serum-free cell sphere-forming rate in MCF-7/ADM cells and BCRP and P-gp gene/protein expression (P < 0.01). The proportion of CD44 + CD24-/low cells was reduced. MCF-7/ADM highly expressed the drug-resistant proteins BCRP and P-gp, which can be used for long-term in vitro culture and as a seed cell for studies of BCSCs. β-elemene can inhibit BCSC and the sphere-forming rate in MCF-7/ADM cells and reduce BCRP expression.

Establishment of human pancreatic cancer gemcitabine‑resistant cell line with ribonucleotide reductase overexpression.

A gemcitabine (GEM)-resistant human pancreatic cancer cell line (PANC-1RG7) was established in vitro by gradually increasing GEM concentrations and cloning cell cultures to develop a cellular model of acquired drug resistance studies. We found that PANC-1RG7 cells exhibited significantly different morphological characteristics from parental cells. PANC-1RG7 cells grew slowly (p<0.05), yet the cell cycle remained unchanged (p>0.05). PANC-1RG7, with a resistance index to GEM of 39.9, showed cross-resistance characteristics to methotrexate, gefitinib, cisplatin and 5-fluorouracil. The proliferation inhibition of GEM was significantly reduced in vivo (p<0.05). The known resistance-associated genes and proteins we detected remained unchanged, with the exception of cytidine deaminase, multidrug resistance-related protein and breast cancer resistance protein genes, which decreased; by contrast, 5'-nucleotidase, ribonucleotide reductase (RRM) 1 and RRM2 proteins increased (p<0.05). Therefore, a cell line with acquired GEM resistance was established successfully. Resistance was acquired by overexpressing RRM1 and RRM2 proteins.

Evaluation of multidrug resistance in acute leukemia using real-time polymerase chain reaction

Background Despite the advances in the cure rate for acute leukemia, ~25% of affected patients develop relapses. Expression of genes for the multidrug resistance ( MDR1 ) and breast cancer-resistance protein ( BCRP ) may confer the phenotype of resistance to the treatment of acute leukemia. Objective To analyze the expression of the MDR1 and BCRP genes in new cases of acute leukemia using real-time PCR (RT-PCR) and to determine the correlation between their expression and overall survival (OS). Patients and methods Patients diagnosed with acute myeloblastic leukemia (AML) ( n = 15) and acute lymphoblastic leukemia (ALL) ( n = 35), and 20 blood donors as a control group were included in this study. The expressions of mRNA for the MDR1 and BCRP genes were assessed by RT-PCR. Myeloid surface markers such as CD34, CD33, CD13, and CD14 and lymphoid surface markers such as CD3, CD5, CD2, CD4, CD8, and CD19 were analyzed using flow cytometry. Results The groups with the MDR gene and the BCRP gene showed a highly significant difference compared with the control group ( P MDR and BCRP in both AML and ALL groups showed no significant difference. There was a significant difference between BCRP expression in the AML and ALL groups ( P MDR+ cases and MDR- cases in the AML and ALL groups. In contrast, the OS in BCRP+ cases and BCRP- cases showed a significant difference between AML and ALL groups ( P MDR+, CD34+) and AML ( MDR+, CD34−). In contrast, OS between AML ( BCRP+, CD34+) and AML ( BCRP+, CD34−) showed a significant difference ( P MDR+, CD34+) and ALL ( MDR+, CD34−) was not significant. In contrast, a significant difference was detected between OS in ALL ( BCRP+, CD34+) and ALL ( BCRP+, CD34−) ( P BCRP+ (CD13+) showed a significant difference ( P BCRP+ and CD19+ did not affect the survival significantly. Conclusion We concluded that the evaluation of the expression of genes for resistance to antineoplastic drugs in acute leukemia upon diagnosis, and particularly the expression of the BCRP gene, may be of clinical relevance.

Clinical Significance of Breast Cancer Resistance Protein/ABCG2 in the Management of Malignancy

Breast cancer resistance protein (BCRP), also termed ABCG2, is a member of an ATP-binding cassette transporter G family, which was originally identified in relation to drug resistance in cancer cells. BCRP intrinsically interacts with a range of substances such as sterols, porphyrins and a variety of dietary compounds, but it mediates extrusion of toxic compounds out of cells and underlies multidrug resistance of cancer cells. Hence, BCRP expression levels in tumor and non-tumor cells may determine response to chemotherapy as well as adverse effects. In the former part of this paper, the latest findings are reviewed regarding clinical significance of BCRP expression in malignancy. In the latter part, reports on single nucleotide polymorphisms (SNPs) of the BCRP gene are reviewed focusing on impacts upon cancer chemotherapy. C421A and C376T, which result in very low and null expression of the protein, respectively, are particularly referred to regarding their phenotypes because of possible importance in cancer chemotherapy. Approximately one tenth of hyperuricemia/gout patients and a considerable part of population with Junior a (-) [jr(a-)] blood type are expected to bear these SNPs on the both alleles. Therefore, genotypic examination of the BCRP gene would be recommended in these populations before the start of chemotherapy including BCRP substrate drugs. Keywords: ABCG2, anticancer drug, BCRP, C376T, C421A, cancer, chemotherapy, clinical significance, drug resistance, gout, jr(a-), malignancy, SNPs.

Oleic acid decreases BCRP mediated efflux of mitoxantrone in Caco-2 cell monolayers

Breast cancer resistance protein (BCRP) efflux restricts intestinal absorption of substances like heterocyclic amines, mycotoxins and certain human and veterinary drugs. Fat rich meals seem to increase absorption of drugs which are BCRP substrates or inhibitors. We therefore hypothesize that absorption of toxicants normally effluxed by BCRP are increased by fatty acids in food. Transport across and accumulation of 3H-Mitoxantrone (MXR) in Caco-2 cell monolayers were measured after 60min exposure to emulsions of 3H-MXR (1μM) and oleic acid (0.5–5mM). In addition, BCRP gene expression (RT-PCR) and the amount of BCRP protein (Western blot) were measured in oleic acid exposed Caco-2 cells. Oleic acid increased transport of MXR in a concentration dependent manner and 2mM oleic acid or higher increased accumulation of MXR in cells, without any signs of cytotoxicity. Gene expression of BCRP was increased after exposure to oleic acid for 6h, but the amount of BCRP protein was not increased. In conclusion, oleic acid clearly induced BCRP gene expression and reduced BCRP mediated efflux, although the amount of BCRP in cells was not affected. Consequently, effects of fatty acids on BCRP mediated efflux are important to consider in risk assessment of toxicants in food.

Suppression of BCRP Expression and Restoration of Sensitivity to Chemotherapy in Multidrug-Resistant Hepatocellular Carcinoma Cell Line HEPG2/ADM by RNA Interference

Breast cancer resistance protein (BCRP) is an ATP-binding cassette multidrug transporter that confers resistance to various anticancer drugs like Adriamycin. Overexpression of BCRP confers multidrug resistance (MDR) in hepatocellular carcinoma cells and is a frequent impediment to successful chemotherapy. We evaluated a new approach using RNA interference for the specific knockdown of BCRP in hepatocellular carcinoma cells. To overcome the BCRP-mediated atypical multidrug drug resistance, one small interfering RNA construct (RNAi) targeting one special region of BCRP gene were designed to inhibit the atypical MDR expression by transfecting them into HepG2/ADM cell lines. We found that the overexpression of BCRP gene was suppressed efficiently by the introduction of small interfering RNA, which caused sequence specific gene silence. The level of BCRP mRNA reduced to 22.55% after transfected by pSUPER-BCRPs compared with those of the controls. Similarly, the level of BCRP decreased too. Furthermore, the sensitivity to Adriamycin of pSUPER-BCRPs-treated HEPG2/ADM cells is increased 3.55-fold compared to their control (p<0.05). The relative reverse rate of HepG2/ADM cell to Adriamycin is 72.2%. These data indicated that pSUPER-BCRPs could modulate MDR and may present a new approach to overcome BCRP-mediated drug resistance in HEPG2/ADM cells. It may reverse multidrug resistance phenotype and therefore provide promising therapeutic modalities in the treatment of hepatocellular carcinoma.

Breast cancer resistance protein (BCRP/ABCG2): its role in multidrug resistance and regulation of its gene expression

Breast cancer resistance protein (BCRP)/ATP-binding cassette subfamily G member 2 (ABCG2) is an ATP-binding cassette (ABC) transporter identified as a molecular cause of multidrug resistance (MDR) in diverse cancer cells. BCRP physiologically functions as a part of a self-defense mechanism for the organism; it enhances elimination of toxic xenobiotic substances and harmful agents in the gut and biliary tract, as well as through the blood-brain, placental, and possibly blood-testis barriers. BCRP recognizes and transports numerous anticancer drugs including conventional chemotherapeutic and targeted small therapeutic molecules relatively new in clinical use. Thus, BCRP expression in cancer cells directly causes MDR by active efflux of anticancer drugs. Because BCRP is also known to be a stem cell marker, its expression in cancer cells could be a manifestation of metabolic and signaling pathways that confer multiple mechanisms of drug resistance, self-renewal (sternness), and invasiveness (aggressiveness), and thereby impart a poor prognosis. Therefore, blocking BCRP-mediated active efflux may provide a therapeutic benefit for cancers. Delineating the precise molecular mechanisms for BCRP gene expression may lead to identification of a novel molecular target to modulate BCRP-mediated MDR. Current evidence suggests that BCRP gene transcription is regulated by a number of trans-acting elements including hypoxia inducible factor 1α, estrogen receptor, and peroxisome proliferator-activated receptor. Furthermore, alternative promoter usage, demethylation of the BCRP promoter, and histone modification are likely associated with drug-induced BCRP overexpression in cancer cells. Finally, PI3K/AKT signaling may play a critical role in modulating BCRP function under a variety of conditions. These biological events seem involved in a complicated manner. Untangling the events would be an essential first step to developing a method to modulate BCRP function to aid patients with cancer. This review will present a synopsis of the impact of BCRP-mediated MDR in cancer cells, and the molecular mechanisms of acquired MDR currently postulated in a variety of human cancers.

The Impact of FLT3-ITD Mutation on the Expression of Multidrug Resistance Genes MDR-1, MRP-1, BCRP and LRP In Adult Acute Myeloid Leukemia

AbstractAbstract 1808 BackgroundMultidrug resistance (MDR) is a clinically relevant problem in the treatment of acute myeloid leukaemia (AML). From 20–50% of patients with AML are primarily resistant to induction chemotherapy and in the great majority of those who respond well to initial therapy the disease relapses. While some mechanisms of MDR have been well characterized, this phenomenon still remains incompletely understood. Three ATP-dependent drug transporting proteins: p-glycoprotein (Pgp; MDR-1), multidrug resistant protein-1 (MRP-1), breast cancer resistance protein (BCRP) and one major vault protein-lung resistance-related protein (LRP) and the internal tandem duplication (ITD) in the receptor tyrosine kinase FLT3 have been found to have a strong correlation with MDR and poor outcome in AML. About 30% of AML cases harbor FLT3-ITD mutation. Mainly MDR-1 protein and FLT3-ITD mutation are targets for inhibition by numerous agents in clinical practice. ObjectivesIn this retrospective study we estimated expression of MDR genes encoding MDR-1, MRP-1, BCRP, LRP proteins and detected FLT3-ITD mutation in patients with AML. We divided all patients into two groups according to FLT3-ITD mutation and we compared expression of MDR genes and other prognostic factors in AML: age (<60 vs ≥60 years), cytogenetic/molecular aberrations (good, intermediate, poor), de novo/secondary AML, white blood cell count (WBC), extramedullary involvement, type of AML according to the FAB classification, CD34 expression on blast cells and myeloperoxidase activity (<50% of blast cells, ≥50%) between groups Moreover the rate of complete remissions (CR) and relapses and disease free survival (DFS) and overall survival (OS) in both groups were estimated. Materials and MethodsA total of 126 adult patients at median age of 53 years (range 21–87) with newly diagnosed between June 2005 and March 2010, previously untreated AML and 40 healthy donors were included in this study. Diagnosis of AML was based on standard morphological and immunophenotypical criteria according to the WHO classification. Most of the patients were treated with anthracycline and cytarabine during the induction regime. There were 39 FLT3-ITD positive (30,4%) and 87 FLT3-ITD negative (69,6%) patients. DNA was extracted from bone marrow (90 patients) or peripheral blood (36 patients) samples and used to detect FLT3-ITD with PCR method. RNA was extracted from the same samples and following reverse transcription RQ-PCR method was performed for assessment of expression of MDR-1, MRP-1, BCRP and LRP genes. Parameters of RQ-PCR reaction were established based on the Europe Against Cancer protocol. Every tested sample was amplified simultaneously for the presence of control ABL gene for standardization of mRNA level for tested genes. Results of the expression of tested genes were presented as coefficients calculated with an intermediate method according to Pfaffl's rule. ResultsTo our surprise, significant higher expression of MDR-1 gene was found either in bone marrow or peripheral blood samples of the patients who do not harbor FLT3-ITD in contrast to the patients harboring this mutation (median 0,3025 vs 0,0756, p=0,003 total; median 0,2690 vs 0,0583, p= 0,002 bone marrow samples; median 0,5775 vs 0,0920, p=0,001 peripheral blood samples). For MRP-1, BCRP and LRP genes we did not find significant differences in their expression between two groups. When adjusted for other prognostic factors, only WBC was significantly higher in FLT3-ITD positive group of patients: 1–294×109/l, median 74 vs 0–286×109/l, median 6,5 in FLT3-ITD negative group of patients (p=0,0001). We did not observe significant differences in CR and relapses rates, DFS and OS between groups. ConclusionsIt seems that FLT3-ITD mutation may in some mechanisms influence MDR-1 gene expression We observed significant inhibition of MDR-1 expression in FLT3-ITD positive patients. Because risk factors for AML and outcome of AML therapy did not differ between groups it seems that FLT3-ITD mutation and high expression of MDR-1 gene are independent high risk factors which negatively influence results of AML therapy. These results might provide a powerful risk classification and useful information for treatment strategies including inhibitors of tyrosine kinase or MDR-1 protein.This project was supported by grant of The Ministry of Science (N N402 208935). Disclosures:No relevant conflicts of interest to declare.

Transcriptional suppression of breast cancer resistance protein (BCRP) by wild-type p53 through the NF-κB pathway in MCF-7 cells

Breast cancer resistance protein (BCRP) has been shown to confer multidrug resistance, but the mechanisms of its regulation are poorly understood. Here, we investigate the effects of wild-type and mutant p53, and nuclear factor kappa-B (NF-κB) (p50) on BCRP promoter activity in MCF-7 cells. Our results demonstrated that wild-type p53 markedly suppressed BCRP activity and enhanced the chemosensitivity of cells to mitoxantrone, whereas mutant p53 had little inhibitory effect. After inhibition of NF-κB, similar results were obtained. Following knockdown of endogenous p53, BCRP and p50 expressions were increased, and the chemosensitivity of the cells to mitoxantrone was decreased. We conclude that wild-type p53 acts as a negative regulator of BCRP gene transcription.

All- trans retinoic acid enhances the transport of phase II metabolites of benzo[ a]pyrene by inducing the Breast Cancer Resistance Protein expression in Caco-2 cells

All- trans retinoic acid (atRA) is the most active metabolite of vitamin A. It is a ligand of retinoic acid receptors (RAR) as well as of retinoid X receptors (RXR) and effectively stimulates the RAR/RXR signalling pathway. In this study effects of atRA on the detoxification of the food contaminant benzo[ a]pyrene (B[ a]P) was elucidated by using the Caco-2 cell line as model system for the human small intestine. Caco-2 cells express a number of phase I and II xenobiotic-metabolising enzymes as well as several transport proteins of the ATP-binding cassette (ABC) superfamily. Pre-treatment of the cells with atRA resulted in enhanced apical excretion of B[ a]P-3-sulfate, a phase II metabolite of B[ a]P. Gene expression analysis revealed that the Breast Cancer Resistance Protein (BCRP), an ABC-transporter known to be involved in B[ a]P-3-sulfate excretion, was strongly stimulated already at low concentrations of atRA. Furthermore co-incubation of the intestinal cell with RAR agonist and RXR agonist resulted in a strong additive induction of mRNA expression of BCRP. Thus, atRA was shown to induce BCRP gene expression probably via the RAR/RXR signalling pathway, resulting in effective removal of B[ a]P metabolites from intestinal cells.