Synergistic antitumor effect of ginsenoside Rg3 and cisplatin in cisplatin resistant bladder tumor cell line

Abstract

Introduction: Cisplatin-based chemotherapy remains the first-line treatment for metastatic urothelial cell carcinoma. For cisplatin resistant patients, no chemotherapeutic agent has been established as a standard of care. We investigated the synergistic antitumor effect of ginsenoside Rg3 on cisplatin in cisplatin resistant bladder cancer cells (T24R2). Methods: T24R2 cells, cisplatin resistant human bladder cancer cell line, were treated with cisplatin and/or ginsenoside Rg3. Cell viability was assessed by cell counting kit-8 assay and clonogenic assay. Synergism between ginsenoside Rg3 and cisplatin was determined if the combination index was less than 1.0. Flow cytometry was used to evaluate the cell cycle distribution. To estimate the changes of proteins related with the cell cycle and apoptosis after the treatment of ginsenoside Rg3, western blot and densitometric assay were performed for caspase-3, -8, -9, cyclin B1, Bcl-2, Bad, p21 and cytochrome C. Results: Cell counting kit-8 assay and clonogenic assay revealed the synergistic antitumor effect of ginsenoside Rg3 on cisplatin, and the combination index was less than 1.0, confirming the synergism. Cell cycle alterations at G2/M phase caused by cisplatin were greater after the combined treatment of cisplatin and ginsenoside Rg3. Western blot and densitometric assay showed that the expression of Bcl-2 was decreased after the combined treatment of ginsenoside Rg3 and cisplatin whereas the expression of cytochrome C and caspase-3 were increased, which implies the activation of the intrinsic apoptotic pathway. Conclusions: Ginsenoside Rg3 inhibited the proliferation of cisplatin resistant bladder cancer cells in a synergistic way with cisplatin. The activation of the intrinsic apoptotic pathway and the enhancement of cell cycle alterations may be a possible explanation.