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


METHODS
The BGC-823 gastric cancer cell line was incubated for 48 h with 0.1 micromol/L rofecoxib, 5-FU, DDP and VP-16 (1 microg/mL, 10 microg/mL and 100 microg/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-pi (GST-pi) 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-pi mRNA, but MDR1 mRNA was undetectable. After administration with different concentrations of rofecoxib (0.1, 1.0, 10 micromol/L), significant downregulation of MRP1 and GST-pi mRNA was observed (MRP1: from 0.984 +/- 0.093-0.513 +/- 0.098; GST-pi: from 1.078 +/- 0.201-0.472 +/- 0.084, P < 0.01 or 0.05). In addition, MRP1 and GST-pi protein expression induced by rofecoxib were also reduced (P < 0.01 or 0.05).


CONCLUSIONS
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-piin vitro.
Department of Gastroenterology, Tongji Hospital, Digestive Disease Institute of Tongji University, Shanghai, China.
Feng Shang
FS
Zhu
Xi Mei
XM
Chen
Zhi Gang
ZG
Huang
Zhi Rong
ZR
Wang
Dong Wei
DW
Zhang
Xia
X
Zhang
D000230:Adenocarcinoma / Q000188:drug therapy*; D000971:Antineoplastic Combined Chemotherapy Protocols / Q000627:therapeutic use*; D017209:Apoptosis / Q000187:drug effects; D045744:Cell Line, Tumor; D002945:Cisplatin / Q000494:pharmacology; D052246:Cyclooxygenase 2 Inhibitors / Q000627:therapeutic use*; D004305:Dose-Response Relationship, Drug; D015536:Down-Regulation / Q000187:drug effects; D019008:Drug Resistance, Neoplasm / Q000235:genetics; D004357:Drug Synergism; D005047:Etoposide / Q000494:pharmacology; D005472:Fluorouracil / Q000494:pharmacology; D005786:Gene Expression Regulation / Q000187:drug effects*; D051549:Glutathione S-Transferase pi / Q000187:drug effects / Q000235:genetics / Q000378:metabolism; D006801:Humans; D015151:Immunoblotting; D007783:Lactones / Q000627:therapeutic use*; D027425:ATP-Binding Cassette, Sub-Family C Proteins / Q000187:drug effects / Q000235:genetics / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013274:Stomach Neoplasms / Q000188:drug therapy*; D013450:Sulfones / Q000627:therapeutic use*
D002945:Cisplatin; D052246:Cyclooxygenase 2 Inhibitors; D005047:Etoposide; D005472:Fluorouracil; D051549:Glutathione S-Transferase pi; D007783:Lactones; D027425:ATP-Binding Cassette, Sub-Family C Proteins; D013450:Sulfones; C116926:rofecoxib; C421109:multidrug resistance-associated protein 1