NS-398, a selective cyclooxygenase 2 inhibitor, inhibited cell growth and induced cell cycle arrest in human hepatocellular carcinoma cell lines.

Cyclooxygenase 2 (COX-2) has been suggested to be associated with liver carcinogenesis. Several reports have shown that NSAIDs inhibit the growth of hepatocellular carcinoma cell lines. There is little evidence of how COX-2 inhibitors regulate the proliferation of hepatocellular carcinoma cells or the mechanism involved. In our study, we investigated the growth-inhibitory mechanism of a selective COX-2 inhibitor, NS-398, in 4 hepatocellular carcinoma cell lines by studying cell growth, COX-2 and proliferating cell nuclear antigen (PCNA) expression, cell cycle distribution and the evidence of apoptosis. NS-398 inhibited the growth of all 4 cell lines in a time- and dose-dependent manner and the inhibitory effects were independent of the level of COX-2 protein expression. PCNA expression was downregulated by NS-398 in a dose-independent manner. NS-398 caused cell cycle arrest in the S phase with a reduction in cell numbers and cell accumulation in the G0/G1 phase, for all 4 cell lines. No evidence of apoptosis was observed in our present study. Our findings suggest that a selective COX-2 inhibitor might serve as an effective tool for the chemoprevention and treatment of hepatocellular carcinomas. A reduction in cell number in the S phase may be an important event in cell cycle arrest caused by NS-398 in hepatocellular carcinoma cell lines. Copyright 2002 Wiley-Liss, Inc.