High expression of ABCG2 is associated with doxorubicin resistance of osteosarcoma

Abstract

Objectives Previous studies showed overexpression of ABCG2 in a variety of tumor tissues, which could potentially indicate the probability of chemotherapy resistance. This study aimed to reveal the role of ABCG2 in the development of doxorubicin (DOX) resistance and the prognosis of OS. Methods 68 OS patients were included in this study. Tumor tissues were collected for each patient during surgery. DOX-resistant OS cell lines were induced by consecutive exposure of gradually increasing concentration of DOX to the parental cell lines. Lentivirus was used for the knockdown of ABCG2 in OS cells. Cells were treated with the gradient concentration of DOX and the viability was assessed by CCK8 assay. Total RNA was isolated from the tumor tissues or tumor cells, and the expression of ABCG2 was analyzed by qPCR. The relationship between ABCG2 expression and clinicopathological characteristics of the patients was analyzed using the Student’s t-test or the Chi-square test. Cumulative survival time was calculated by the Kaplan-Meier method and analyzed by the log-rank test. P < 0.05 was considered statistically significant. Results DOX-resistant OS cells were successfully established through continuous exposure to DOX. 48 h after DOX exposure, the IC 50 value of DOX-resistant HOS cells and DOX-resistant U2OS were 3.5 µM and 3.25 µM, respectively. By contrast, those of the untreated HOS and U2OS cells were 1.15 µM and 0.93 µM, respectively (p < 0.01). The mRNA expression level of ABCG2 was significantly increased in DOX-resistant cell lines. The CCK-8 assay showed that the DOX-resistant HOS cells and DOX-resistant U2OS cells transfected with ShABCG2 were more sensitive to the DOX treatment than those transfected with ShCtrl. Analysis of gene expression in OS tissues showed remarkably higher expression of ABCG2 as compared with adjacent normal tissues (p < 0.01). The disease-free survival time of patients with high expression level of ABCG2 had obviously decreased survival time than the patients with low expression (p < 0.01). Conclusions ABCG2 expression level was significantly associated with the resistance to DOX and the overall survival of OS patients. ABCG2 may become a promising therapeutic target for OS patients.