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ABCB1-overexpressing MG63/DOX cell xenograft model: Maintain the MDR phenotype in vivo

Abstract Context: Multi-drug resistance (MDR) constitutes a major obstacle in the effectiveness of chemotherapy. P-Glycoprotein (P-gp), the product of ABCB1 gene, is a transmembrane transporter that actively pumps cytotoxic drugs out of tumor cells resulting in MDR. Objective: We sought to establish an MG63/DOX cell xenografts model that maintained the MDR phenotype and molecular properties in vivo in order to screen for new P-gp inhibitors. Materials and methods: The cytotoxicities of doxorubicin, paclitaxel and cytarabine were evaluated by MTT assays. P-gp activity was measured by rhodamine 123 accumulation using flow cytometry. P-gp expression in MG63/DOX cells and tumor tissues was detected by western blotting and immunohistochemistry. Results: Our results showed that MG63/DOX cells exhibited 70-fold resistance to doxorubicin and more than 150-fold resistance to paclitaxel compared with parent MG63 cells. Furthermore, the ABCB1 inhibitor verapamil (10 μM) effectively reversed doxorubicin and paclitaxel resistance by 90- and 200-fold, respectively. The intracellular accumulation of rhodamine 123 was significantly increased (8.35-fold) in MG63/DOX cell, as compared to MG63 cells, in the presence of 10 μM verapamil. MG63/DOX tumor chunk xenografts had a high formation rate (88%). Finally, we found that the ABCB1 gene was overexpressed in different generations of solid tumors. Discussion and conclusion: These data demonstrated that MG63/DOX tumor chunk subculture in vivo retained their molecular properties. This model could serve as a convenient system for the preclinical investigation of drug combinations and the screening of new agents to reverse ABCB1-mediated MDR.