RESUMO
OBJECTIVE: BCRP is overexpressed in many tumors and mediates multidrug resistance in breast cancer. In this study, we determined the involvement of miR-302S in the development of drug resistance in breast cancer. METHODS: The differential miRNA expression profiling in parental MCF-7 cells and its derivative mitoxantrone (MX)-resistant MCF-7 (MCF-7/MX) cells was determined by the microarray analysis. The levels of miR-302S family and BCRP mRNA expression were determined by using Quantitative Real-Time PCR. The targeting effect between the individuals of miR-302S and BCRP mRNA-3'UTR were detected by dual-luciferase reporter assay. Proteins of BCRP are represented by Western blot assay. Cell viability was assessed by MTS assay. Efflux capacity was evaluated using flow cytometry. RESULTS: The miR-302S family including miR-302a, miR-302b, miR-302c, and miR-302d was significantly down-regulated in BCRP-overexpressing MCF-7/MX cells. Luciferase activity assay showed that miR-302 inhibited BCRP expression by targeting the 3'-untranslated region (UTR) of the BCRP mRNA. Overexpression of miR-302 increased intracellular accumulation of MX and sensitized breast cancer cells to MX. Furthermore, intratumoral injection of miR-302 potentiated the inhibitory effect of MX on tumor growth in mice transplanted with MCF-7/MX cells. Most importantly, miR-302S produced stronger effects than each individual member alone. CONCLUSIONS: These findings suggest that miR-302 inhibits BCRP expression via targeting the 3'-UTR of BCRP mRNA. miR-302 members may cooperatively downregulate BCRP expression to increase chemosensitivity of breast cancer cells. miR-302 gene cluster may be a potential target for reversing BCRP-mediated chemoresistance in breast cancer.
Assuntos
Membro 2 da Subfamília G de Transportadores de Cassetes de Ligação de ATP/antagonistas & inibidores , Neoplasias da Mama/metabolismo , MicroRNAs/metabolismo , Proteínas de Neoplasias/antagonistas & inibidores , Membro 2 da Subfamília G de Transportadores de Cassetes de Ligação de ATP/biossíntese , Membro 2 da Subfamília G de Transportadores de Cassetes de Ligação de ATP/genética , Animais , Antineoplásicos/farmacologia , Sequência de Bases , Neoplasias da Mama/tratamento farmacológico , Neoplasias da Mama/genética , Regulação para Baixo , Resistencia a Medicamentos Antineoplásicos , Feminino , Xenoenxertos , Humanos , Células MCF-7 , Camundongos , Camundongos Endogâmicos BALB C , Camundongos Nus , MicroRNAs/genética , Mitoxantrona/farmacologia , Proteínas de Neoplasias/biossíntese , Proteínas de Neoplasias/genética , RNA Mensageiro/biossíntese , RNA Mensageiro/genética , TransfecçãoRESUMO
Breast cancer resistance protein (BCRP/ABCG2) specifically transports various chemotherapeutic agents and is involved in the development of multidrug resistance (MDR) in cancer cells. MicroRNAs (miRNAs) can play an important role in modulating the sensitivity of cancer cells to chemotherapeutic agents. Therefore, after confirming that BCRP was increased in the mitoxantrone (MX)-resistant MCF-7 breast cancer cell line MCF-7/MX compared with its parental sensitive MCF-7 cell line, we aimed to explore the miRNAs that regulate BCRP expression and sensitize breast cancer cells to chemotherapeutic agents. In the present study, bioinformatic analysis indicated that miR-487a was one of the miRNAs that could bind to the 3' untranslated region (3'UTR) of BCRP. Quantitative RT-PCR (qRT-PCR) analysis demonstrated that the expression of miR-487a was reduced in MCF-7/MX cells, and a luciferase reporter assay demonstrated that miR-487a directly bound to the 3'UTR of BCRP. Moreover, ectopic miR-487a down-regulated BCRP expression at the mRNA and protein levels, increasing the intracellular accumulation and cytotoxicity of MX in resistant MCF-7/MX breast cancer cells. Meanwhile, inhibition of miR-487a increased BCRP expression at the mRNA and protein levels and induced MX resistance in sensitive MCF-7 breast cancer cells. Furthermore, the reduced expression of BCRP and increased antitumor effects of MX were also detected in MCF-7/MX xenograft tumors treated with the miR-487a agmir. Thus, our results suggested that miR-487a can directly regulate BCRP expression and reverse chemotherapeutic drug resistance in a subset of breast cancers.
Assuntos
Transportadores de Cassetes de Ligação de ATP/genética , Antineoplásicos/farmacologia , Neoplasias da Mama/genética , Resistencia a Medicamentos Antineoplásicos/genética , MicroRNAs/genética , Mitoxantrona/farmacologia , Proteínas de Neoplasias/genética , Regiões 3' não Traduzidas , Membro 2 da Subfamília G de Transportadores de Cassetes de Ligação de ATP , Animais , Sobrevivência Celular/efeitos dos fármacos , Sobrevivência Celular/genética , Modelos Animais de Doenças , Feminino , Expressão Gênica , Regulação Neoplásica da Expressão Gênica , Humanos , Células MCF-7 , Camundongos , Interferência de RNA , Transplante HeterólogoRESUMO
Breast cancer resistance protein (BCRP)/ATP-binding cassette subfamily G member 2 (ABCG2) mediates multidrug resistance (MDR) in breast cancers. In this study, we aimed to investigate the role of microRNAs in regulation of BCRP expression and BCRP-mediated drug resistance in breast cancer cells. Microarray analysis was performed to determine the differential expression patterns of miRNAs that target BCRP between the MX-resistant breast cancer cell line MCF-7/MX and its parental MX-sensitive cell line MCF-7. MiR-181a was found to be the most significantly down-regulated miRNA in MCF-7/MX cells. Luciferase activity assay showed that miR-181a mimics inhibited BCRP expression by targeting the 3' untranslated region (UTR) of the BCRP mRNA. Overexpression of miR-181a down-regulated BCRP expression, and sensitized MX-resistant MCF-7/MX cells to MX. In a nude mouse xenograft model, intratumoral injection of miR-181a mimics inhibited BCRP expression, and enhanced the antitumor activity of MX. In addition, miR-181a inhibitors up-regulated BCRP expression, and rendered MX-sensitive MCF-7 cells resistant to MX. These findings suggest that miR-181a regulates BCRP expression via binding to the 3'-UTR of BCRP mRNA. MiR-181a is critical for regulation of BCRP-mediated resistance to MX. MiR-181a may be a potential target for preventing and reversing drug resistance in breast cancer.
Assuntos
Transportadores de Cassetes de Ligação de ATP/genética , Antineoplásicos/farmacologia , Neoplasias da Mama/tratamento farmacológico , Neoplasias da Mama/genética , Resistencia a Medicamentos Antineoplásicos/genética , MicroRNAs/genética , Mitoxantrona/farmacologia , Proteínas de Neoplasias/genética , Regiões 3' não Traduzidas , Membro 2 da Subfamília G de Transportadores de Cassetes de Ligação de ATP , Animais , Neoplasias da Mama/patologia , Linhagem Celular Tumoral/efeitos dos fármacos , Regulação para Baixo/efeitos dos fármacos , Resistencia a Medicamentos Antineoplásicos/efeitos dos fármacos , Feminino , Regulação Neoplásica da Expressão Gênica/efeitos dos fármacos , Humanos , Células MCF-7 , Camundongos Endogâmicos BALB C , MicroRNAs/metabolismo , RNA Mensageiro/metabolismo , Ensaios Antitumorais Modelo de XenoenxertoRESUMO
Breast cancer is the most common type of cancer among women worldwide, and the incidence of breast cancer is increasing in the developing world. Estrogen exposure is a major risk factor for breast cancer, and estrogen oxidative metabolites have been implicated in chemical carcinogenesis. Xeroderma pigmentosum complementary group C (XPC) plays an important and multifaceted role in cell protection from oxidative DNA damage. Thus, XPC inactivation may be involved in the early stage of breast cancer. The aim of this study was to investigate the expression of XPC protein in sporadic breast cancer tissues and determine whether XPC expression influences breast cancer malignancy and clinical outcome. Fifteen cases of adjacent non-tumor breast tissue, 28 cases of fibroadenomas and 235 cases of breast carcinomas were examined by immunohistochemistry using polyclonal antibody to XPC. Both cytoplasmic and nuclear expression level of XPC were downregulated in breast carcinoma when compared to non-tumor tissues (P < 0.05). The nuclear expression level of XPC was significantly associated with expression of BCL2 (r = 0.231, P = 0.033) and p53 (r = 0.205, P = 0.011), and nuclear expression of XPC was significantly associated with patients' age (P = 0.024). Neither cytoplasmic nor nuclear expression level of XPC had impact on patients' survival in the whole samples. However, XPC expression was correlated with adverse survival in HER2-positive, but not HER2-negative, tumors, as demonstrated by Kaplan-Meier analysis. Our results suggested that the XPC protein is involved in the occurrence and progression of breast cancer.