To investigate the function and regulation mechanism of ATP-binding cassette, subfamily G, member 2 (ABCG2) in retinoblastoma cancer stem cells (RCSCs), a long-term culture of RCSCs from WERI-Rb1 cell line was successfully established based on the high expression level of ABCG2 on the surface of RCSCs. To further explore the molecular mechanism of ABCG2 on RCSCs, a microRNA that specifically targets ABCG2 was predicted. Subsequently, miR-3163 was selected and confirmed as the ABCG2-regulating microRNA. Overexpression of miR-3163 led to a significant decrease in ABCG2 expression. Additionally, ABCG2 loss-of-function induced anti-proliferation and apoptosis-promoting functions in RCSCs, and multidrug resistance to cisplatin, carboplatin, vincristine, doxorubicin, and etoposide was greatly improved in these cells. Our data suggest that miR-3163 has a significant impact on ABCG2 expression and can influence proliferation, apoptosis, and drug resistance in RCSCs. This work may provide new therapeutic targets for retinoblastoma.
3' Untranslated Regions ; ATP Binding Cassette Transporter, Sub-Family G, Member 2/antagonists & inhibitors/genetics/*metabolism ; Antagomirs/metabolism ; Antineoplastic Agents/toxicity ; Apoptosis/drug effects ; Base Sequence ; Cell Line, Tumor ; Cell Proliferation/drug effects ; Drug Resistance, Neoplasm/drug effects ; Gene Silencing ; Humans ; MicroRNAs/antagonists & inhibitors/genetics/*metabolism ; Neoplasm Proteins/antagonists & inhibitors/genetics/*metabolism ; Neoplastic Stem Cells/*metabolism ; Retinoblastoma/metabolism/pathology ; Sequence Alignment ; Transfection

OBJECTIVETo evaluate whether ursolic acid can inhibit breast cancer resistance protein (BCRP)-mediated transport of rosuvastatin in vivo and in vitro.

METHODSFirstly, we explored the pharmacokinetics of 5-fluorouracil (5-FU, a substrate of BCRP) in rats in the presence or absence of ursolic acid. Secondly, we studied the pharmacokinetics of rosuvastatin in rats in the presence or absence of ursolic acid or Ko143 (inhibitor of BCRP). Finially, the concentration-dependent transport of rosuvastatin and the inhibitory effects of ursolic acid and Ko143 were examined in Madin-Darby Canine Kidney (MDCK) 2-BCRP421CC (wild type) cells and MDCK2-BCRP421AA (mutant type) cells.

RESULTSAs a result, significant changes in pharmacokinetics parameters of 5-FU were observed in rats following pretreatment with ursolic acid. Both ursolic acid and Ko143 could significantly affect the pharmacokinetics of rosuvastatin. The rosuvastatin transport in the BCRP overexpressing system was increased in a concentration-dependent manner. However, there was no statistical difference in BCRP-mediated transport of rosuvastatin betweent the wild type cells and mutant cells. The same as Ko143, ursolic acid inhibited BCRP-mediated transport of rosuvastatin in vitro.

CONCLUSIONUrsolic acid appears to be a potent modulator of BCRP that affects the pharmacokinetic of rosuvastatin in vivo and inhibits the transport of rosuvastatin in vitro.

ATP Binding Cassette Transporter, Sub-Family G, Member 2 ; ATP-Binding Cassette Transporters ; physiology ; Adenosine ; analogs & derivatives ; pharmacology ; Animals ; Biological Transport ; drug effects ; Diketopiperazines ; Heterocyclic Compounds, 4 or More Rings ; Hydroxymethylglutaryl-CoA Reductase Inhibitors ; pharmacokinetics ; Rats ; Rats, Sprague-Dawley ; Rosuvastatin Calcium ; pharmacokinetics ; Triterpenes ; pharmacology

Multidrug regimens and corresponding drug interactions cause many adverse reactions and treatment failures. Drug efflux transporters: P-glycoprotein (P-gp), multidrug resistance associated protein (MRP) and breast cancer resistance protein (BCRP) in conjunction with metabolizing enzymes (cytochrome P450, CYP450) are major factors in such interaction. In recent years, a large number of studies have shown that P-gp plays a role in the oxidative metabolism of its substrates that are also substrates of CYP3A4. Combined actions of P-gp and CYP3A could account in some part for the low oral bioavailability determined for many of these dual substrates. P-gp along with efflux transporters (MRP and BCRP) having overlapping substrate specificity plays critical role in drug disposition. The relationship between MRP or BCRP and CYP3A is similar to that between P-gp and CYP3A. In this paper, we summarize the classification of efflux transporters, the main metabolizing enzymes CYP3A, clinical significance interactions mediated by efflux transporters and CYP450 enzymes and in vitro studies.
ATP Binding Cassette Transporter, Sub-Family G, Member 2 ; ATP-Binding Cassette Transporters ; metabolism ; ATP-Binding Cassette, Sub-Family B, Member 1 ; metabolism ; Biological Availability ; Cytochrome P-450 CYP3A ; metabolism ; Cytochrome P-450 Enzyme System ; metabolism ; Drug Interactions ; Humans ; Multidrug Resistance-Associated Proteins ; metabolism ; Neoplasm Proteins ; metabolism ; Substrate Specificity

OBJECTIVETo explore the expression of breast cancer resistance protein (ABCG2), p-glycoprotein (P-gp) in residual breast cancer tissue after chemotherapy and their correlation with epithelial mesenchymal transition (EMT).

METHODSSeventy-six cases of breast cancer were collected. The expression of ABCG2, P-gp and EMT markers E-cadherin and vimentin in residual breast cancer tissue after chemotherapy was detected by immunohistochemistry (EnVision method). MCF7 cells were divided into three group:untreated control group, positive control (TGF-β1 induced) group and drug surviving cells (DSC) group (selected viable MCF7 cells after docetaxel and epirubicin treatment). The expression of EMT markers E-cadherin and vimentin was detected by immunofluorescence. The mRNA and protein expression of ABCG2, P-gp and EMT markers were detected by reverse transcription-polymerase chain reaction (RT-PCR) and Western blot, respectively.

RESULTSCompared with breast cancer tissue before chemotherapy, ABCG2, P-gp and vimentin protein were highly expressed in residual breast cancer tissue after chemotherapy. The expression of ABCG2 and P-gp correlated positively with vimentin protein (r1=0.97, P1=0.000; r2=0.83, P2=0.001) and negatively with E-cadherin protein (r3=-0.55, P3=0.010; r4=-0.43, P4=0.020) expression. RT-PCR results showed that ABCG2, P-gp and vimentin mRNA were highly expressed in residual breast cancer tissue after chemotherapy. The expression of ABCG2 and P-gp mRNA correlated positively with vimentin mRNA (r1=0.99, r2=0.96, P<0.05) but negatively with E-cadherin protein (r3=-0.99, r4=-0.98, P<0.05); Western blot showed that ABCG2, P-gp and vimentin protein were highly expressed in residual breast cancer tissue after chemotherapy. The expression of ABCG2 and P-gp protein correlated positively with vimentin protein (r1=0.98, r2=0.89, P<0.05) and negatively with E-cadherin protein (r3=-0.47, r4=-0.33, P<0.05).

CONCLUSIONSThe expression of resistance-associated proteins in the residual breast cancer tissue after chemotherapy is significantly correlated with EMT. The expression of EMT profile may be one of important mechanisms for multidrug resistance in breast cancer.

ATP Binding Cassette Transporter, Sub-Family B ; genetics ; metabolism ; ATP Binding Cassette Transporter, Sub-Family G, Member 2 ; ATP-Binding Cassette Transporters ; genetics ; metabolism ; Adult ; Aged ; Antibiotics, Antineoplastic ; pharmacology ; Antineoplastic Agents ; pharmacology ; Antineoplastic Combined Chemotherapy Protocols ; therapeutic use ; Breast Neoplasms ; metabolism ; pathology ; therapy ; Cadherins ; genetics ; metabolism ; Cyclophosphamide ; therapeutic use ; Doxorubicin ; therapeutic use ; Epirubicin ; pharmacology ; Epithelial-Mesenchymal Transition ; Female ; Humans ; MCF-7 Cells ; Middle Aged ; Neoplasm Proteins ; genetics ; metabolism ; Neoplasm, Residual ; metabolism ; RNA, Messenger ; metabolism ; Taxoids ; pharmacology ; therapeutic use ; Vimentin ; genetics ; metabolism

OBJECTIVEto investigate the effects of antidiabetic drug metformin on proliferation and apoptosis in human hepatocellular carcinoma cell line Huh-7 cells.

METHODSHuh-7 cells were treated with metformin at different concentrations. Cell viability was determined by MTT assay. Cell apoptosis and CD133(+) expression rate were detected by flow cytometery (FCM). Expressions of PTEN, Akt, p-Akt, Bcl-2, Bax proteins in the cells were measured by Western blot. The effect of metformin on the hepatosphere formation was observed in the serum-free suspension culture. Reverse transcription-polymerase chain reaction (RT-PCR) was used to validate the expression levels of stemness marker genes CD133, β-catenin, and ABCG2 mRNA in the hepatospheres.

RESULTSThe proliferation of Huh-7 cells was inhibited by metformin in a dose- and time-dependent manner. The early and late cell apoptosis rates induced by metformin at dose of 10 mmol/L for 48 hrs were (22.29 ± 0.8)% and (13.87 ± 1.2)%, respectively, and 25 mmol/L for 48 hrs (15.28 ± 2.1)% and (25.89 ± 2.3)%, respectively. Western blotting results revealed that the expression of CD133, phosphorylated Akt and the Bcl-2/Bax ratio were downregulated, and PTEN was upregulated in the Huh-7 cells after treated with 25 mmol/L metformin for 48 hrs. Metformin inhibited the formation of hepatospheres. Metformin also downregulated the expression of several cancer stem cells (CSCs)-related genes which are involved in the signaling pathways governing the self-renewal, proliferation and differentiation of CSCs in the hepatospheres.

CONCLUSIONSMetformin inhibits the proliferation of human hepatocellular carcinoma Huh-7 cells and enhances their apoptosis in vitro. It may be related to the downregulation of PI3K/Akt signal pathway and selectively targeting CD133(+) cells.

AC133 Antigen ; ATP Binding Cassette Transporter, Sub-Family G, Member 2 ; ATP-Binding Cassette Transporters ; genetics ; metabolism ; Antigens, CD ; genetics ; metabolism ; Antineoplastic Agents ; administration & dosage ; pharmacology ; Apoptosis ; drug effects ; Carcinoma, Hepatocellular ; metabolism ; pathology ; Cell Line, Tumor ; Cell Proliferation ; drug effects ; Cell Survival ; drug effects ; Dose-Response Relationship, Drug ; Glycoproteins ; genetics ; metabolism ; Humans ; Liver Neoplasms ; metabolism ; pathology ; Metformin ; administration & dosage ; pharmacology ; Neoplasm Proteins ; genetics ; metabolism ; PTEN Phosphohydrolase ; metabolism ; Peptides ; genetics ; metabolism ; Phosphatidylinositol 3-Kinases ; metabolism ; Phosphorylation ; Proto-Oncogene Proteins c-akt ; metabolism ; Proto-Oncogene Proteins c-bcl-2 ; metabolism ; RNA, Messenger ; metabolism ; Signal Transduction ; drug effects ; Time Factors ; bcl-2-Associated X Protein ; metabolism ; beta Catenin ; metabolism

OBJECTIVETo investigate the correlation of MDR1 and ABCG2 genetic polymorphisms with the efficacy and adverse events of irinotecan chemotherapy in patients with colorectal cancer (CRC).

METHODSClinical data of CRC patients treated with irinotecan-based chemotherapy in the Peking University Cancer Hospital between January 1996 and December 2011 were collected, and their blood samples were collected accordingly. Genomic DNA was extracted from blood samples. The following SNP detection of MDR1 and ABCG2 genes was conducted by direct sequencing method. The correlation of genetic SNPs with efficacy and toxicity of irinotecan treatment was further analyzed.

RESULTSAllele frequencies of MDR1 2677 G>T/A, ABCG2 421 C>A, 34 G>A, 376 C>T were comparable with previous studies. Genetic SNPs results from peripheral blood samples and tumor tissues were highly consistent. Patients carrying MDR1 2677 wild type had higher clinical benefit than those carrying mutant genotype, while the differences were not significant. The progression-free survival (PFS) was longer in wild-type patients as compared to mutant-type patients in second-line chemotherapy (P=0.012). There were no significant correlations between ABCG2 421 C>A, 34 G>A, 376 C>T and chemotherapy efficacy. No significant correlations were observed between MDR1 2677 G>T/A, ABCG2 421 C>A, ABCG2 34 G>A, ABCG2 376 C>T and irinotecan-related grade 3 and 4 neutropenia or diarrhea.

CONCLUSIONMDR1 2677 G>T/A may be served as a biomarker in predicting the efficacy of irinotecan chemotherapy in patients with colorectal cancer.

ATP Binding Cassette Transporter, Sub-Family B ; ATP Binding Cassette Transporter, Sub-Family G, Member 2 ; ATP-Binding Cassette Transporters ; genetics ; ATP-Binding Cassette, Sub-Family B, Member 1 ; genetics ; Adult ; Aged ; Camptothecin ; analogs & derivatives ; therapeutic use ; Colorectal Neoplasms ; drug therapy ; genetics ; Female ; Humans ; Male ; Middle Aged ; Neoplasm Proteins ; genetics ; Polymorphism, Single Nucleotide ; Retrospective Studies ; Treatment Outcome ; Young Adult

OBJECTIVETo investigate the effect of 5-fluorouracil (5-FU) on the expression of ATP-binding cassette superfamily G member 2 (ABCG2) in human colon cancer cell SW480.

METHODSSW480 cells were treated with various concentrations of 5-FU. CCK8 assay was utilized to detect the 5-FU IC50 to SW480 cells. Positive expression of ABCG2 was detected by flow cytometry, and mRNA expression of ABCG2 was detected by real time polymerase chain reaction (RT-PCR).

RESULTSThe 5-FU IC50 to SW480 cells increased as the drug concentration increased (P<0.05). Flow cytometry revealed that positive expression rate of ABCG2 in normal SW480 cells (group A) was (6.26±0.86)%. Immediately after treatment with 5-FU for 48 hours, the positive expression rate of ABCG2 (group B) was (3.43±1.18)% (P<0.05). In the second passage of cells after treatment with 5-FU for 48 hours, the positive expression rate of ABCG2 (group C) was (12.91±3.42)% (P<0.05). The mRNA expression of ABCG2 detected by RT-PCR was in accordance with the results from flow cytometry.

CONCLUSIONExpression of ABCG2 in SW480 cells can be affected by various concentrations of 5-FU.

ATP Binding Cassette Transporter, Sub-Family G, Member 2 ; ATP-Binding Cassette Transporters ; metabolism ; Cell Line, Tumor ; Colonic Neoplasms ; metabolism ; Fluorouracil ; pharmacology ; Humans ; Neoplasm Proteins ; metabolism

OBJECTIVETo compare the expression differences of breast cancer resistance protein(BCRP/ABCG2) and P-glycoprotein(P-gp) in breast cancer tissue before chemotherapy and in residual breast cancer tissue, and to explore its correlation with breast cancer stem cells.

METHODSImmunohistochemistry was used to detect the expression of ABCG2, P-gp, and breast cancer stem cells(BCSCs) markers(CD44 and CD24) in breast cancer tissue before chemotherapy and residual breast cancer tissue after chemotherapy. Immunofluorescence was applied for determination of the CD44 and CD24 protein expressions of BCSCs microspheres cells. The monoclone-forming ability of BCSCs microspheres cells was detected by limited dilution assay. The expressions of ABCG2, P-gp, CD44, and CD24 proteins were detected by Western blot.

RESULTSCompared with those in breast cancer tissue before chemotherapy, the expression levels of ABCG2 and P-gp were positively correlated with the expression level of CD44 protein(Χ(2)=41.34, r=0.83;Χ(2)=22.81, r=0.61) in residual breast cancer tissue after chemotherapy;meanwhile, they were negatively correlated with the expression of CD24 protein(Χ(2)=-21.25, r=0.72;Χ(2)=-17.26, r=0.65) (all P<0.05) .The diameter of BCSCs microspheres were increased significantly after chemotherapy.The content of BCSCs increased by about 2.5 times after chemotherapy.The expressions of ABCG2, P-gp and CD44 proteins significantly increased and that of CD24 protein significantly declined(P<0.05) .

CONCLUSIONChemotherapy endows residual breast cancer tissue with cancer stem cells-like features, leading to multidrug resistance of breast cancer.

ATP Binding Cassette Transporter, Sub-Family B ; ATP Binding Cassette Transporter, Sub-Family G, Member 2 ; ATP-Binding Cassette Transporters ; metabolism ; ATP-Binding Cassette, Sub-Family B, Member 1 ; metabolism ; Adult ; Aged ; Breast Neoplasms ; drug therapy ; metabolism ; CD24 Antigen ; metabolism ; Cell Culture Techniques ; Drug Resistance, Neoplasm ; Female ; Humans ; Hyaluronan Receptors ; metabolism ; Middle Aged ; Neoplasm Proteins ; metabolism ; Neoplasm, Residual ; Neoplastic Stem Cells ; cytology ; metabolism

S1-M1-80 cells, derived from human colon carcinoma S1 cells, are mitoxantrone-selected ABCG2-overexpressing cells and are widely used in in vitro studies of multidrug resistance(MDR). In this study, S1-M1-80 cell xenografts were established to investigate whether the MDR phenotype and cell biological properties were maintained in vivo. Our results showed that the proliferation, cell cycle, and ABCG2 expression level in S1-M1-80 cells were similar to those in cells isolated from S1-M1-80 cell xenografts (named xS1-M1-80 cells). Consistently, xS1-M1-80 cells exhibited high levels of resistance to ABCG2 substrates such as mitoxantrone and topotecan, but remained sensitive to the non-ABCG2 substrate cisplatin. Furthermore, the specific ABCG2 inhibitor Ko143 potently sensitized xS1-M1-80 cells to mitoxantrone and topotecan. These results suggest that S1-M1-80 cell xenografts in nude mice retain their original cytological characteristics at 9 weeks. Thus, this model could serve as a good system for further investigation of ABCG2-mediated MDR.
ATP Binding Cassette Transporter, Sub-Family G, Member 2 ; ATP-Binding Cassette Transporters ; antagonists & inhibitors ; metabolism ; Adenosine ; analogs & derivatives ; pharmacology ; Animals ; Antineoplastic Agents ; pharmacology ; Cell Cycle ; Cell Line, Tumor ; Cell Proliferation ; Cell Survival ; drug effects ; Cisplatin ; pharmacology ; Colonic Neoplasms ; metabolism ; pathology ; Diketopiperazines ; Doxorubicin ; metabolism ; Drug Resistance, Multiple ; Drug Resistance, Neoplasm ; Female ; Heterocyclic Compounds, 4 or More Rings ; Humans ; Inhibitory Concentration 50 ; KB Cells ; Male ; Mice ; Mice, Inbred BALB C ; Mice, Nude ; Mitoxantrone ; pharmacology ; Neoplasm Proteins ; antagonists & inhibitors ; metabolism ; Neoplasm Transplantation ; Rhodamine 123 ; metabolism ; Topotecan ; pharmacology

Multidrug resistance (MDR) in cancer cells can significantly attenuate the response to chemotherapy and increase the likelihood of mortality. The major mechanism involved in conferring MDR is the overexpression of ATP-binding cassette (ABC) transporters, which can increase efflux of drugs from cancer cells, thereby decreasing intracellular drug concentration. Modulators of ABC transporters have the potential to augment the efficacy of anticancer drugs. This editorial highlights some major findings related to ABC transporters and current strategies to overcome MDR.
ATP Binding Cassette Transporter, Sub-Family G, Member 2 ; ATP-Binding Cassette Transporters ; antagonists & inhibitors ; metabolism ; ATP-Binding Cassette, Sub-Family B, Member 1 ; antagonists & inhibitors ; metabolism ; Antineoplastic Agents ; therapeutic use ; Drug Resistance, Multiple ; Drug Resistance, Neoplasm ; Humans ; Molecular Targeted Therapy ; Multidrug Resistance-Associated Proteins ; antagonists & inhibitors ; metabolism ; Nanomedicine ; Neoplasm Proteins ; antagonists & inhibitors ; metabolism ; Neoplasms ; drug therapy ; metabolism ; Protein-Tyrosine Kinases ; antagonists & inhibitors