Rofecoxib augments anticancer effects by reversing intrinsic multidrug resistance gene expression in BGC-823 gastric cancer cells

Abstract

Objective: To investigate combined chemotherapeutic effects of rofecoxib in combination with 5-fluorouracil (5-FU), cisplatin (DDP) and etoposide (VP-16) in vitro, and to explore the potential mechanisms in modulating multidrug resistance (MDR) expression. MEHTODS: The BGC-823 gastric cancer cell line was incubated for 48 h with 0.1 μmol/L rofecoxib, 5-FU, DDP and VP-16 (1 μg/mL, 10 μg/mL and 100 μg/mL) alone, and combined with rofecoxib, respectively. Methyl-thiazolyl-tetrazolium and the terminal deoxynucleotidyl transferase-mediated 2′-deoxyuridine 5′-yriphosphate nick-end labeling assays were performed to calculate inhibitory rates and apoptotic index. Middle effects principles (CI values) were used to determine the interaction between rofecoxib and chemotherapeutic agents. Reverse transcription-polymerase chain reaction (RT-PCR) and Western blot analysis were employed to determine expression of MDR1, multidrug resistance-associated protein 1 (MRP1), glutathione S-tranferase-Π (GST-Π) mRNA and protein in gastric cancer cells administered by rofecoxib, respectively. RESULTS: Both anticancer drugs such as 5-FU, DDP and VP-16 and rofecoxib inhibited the cells' proliferation and induced apoptosis in a dose-dependent manner, and a more significant inhibition was achieved when the cells were co-treated with anticancer drugs and rofecoxib. There was a synergetic role when different concentrations of chemotherapeutic agents were combined with rofecoxib (all CI < 1, P < 0.01 or 0.05). RT-PCR analyses of MDR gene families in BGC-823 gastric cancer cells revealed a strong expression in MRP1 and GST-Π mRNA, but MDR1 mRNA was undetectable. After administration with different concentrations of rofecoxib (0.1, 1.0, 10 μmol/L), significant downregulation of MRP1 and GST-Π mRNA was observed (MRP1: from 0.984 ± 0.093-0.513 ± 0.098; GST-Π: from 1.078 ± 0.201-0.472 ± 0.084, P < 0.01 or 0.05). In addition, MRP1 and GST-Π protein expression induced by rofecoxib were also reduced (P < 0.01 or 0.05). CONCLUSION: Rofecoxib, a specific cyclooxygenase-2 inhibitor, plays a chemotherapeutic sensitizer role in various anticancer agents on the BGC-823 gastric cancer cell line, which could be partly explained by its ability to reverse the intrinsic MRP1 and GST-Π.in vitro. © 2010 The Authors. Journal compilation © 2010 Chinese Medical Association Shanghai Branch, Chinese Society of Gastroenterology and Blackwell Publishing Asia Pty Ltd.