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Objective: A novel retinoid, TAC-101 (4-[3,5-bis (trimethylsilyl) benzamido] benzoic acid), induces apoptosis of ovarian clear cell adenocarcinoma. The antitumor effect of TAC-101 alone or combined with cisplatin was tested using human ovarian carcinoma., Methods: Induction of genes related to apoptosis by TAC-101 or cisplatin was assessed by DNA microarray analysis. TAC-101 (8 mg/kg/day orally for 21 days), cisplatin (7 mg/kg intravenously on day 1), or a combination of both drugs at the same dosages was administered to nude mice implanted subcutaneously with RMG-I or RMG-II clear cell adenocarcinoma cells. The antitumor effect was evaluated by calculating the treated/control tumor volume ratio at 21 days after implantation. The histoculture drug response assay was also performed using fresh surgical specimens of human ovarian cancer to determine the 50% inhibitory concentration (IC50)., Results: Different apoptosis-related genes were induced by TAC-101 and cisplatin. Compared with control mice, the volume of both RMG-I and RMG-II tumors was significantly reduced (p<0.05) by either drug. The IC50 values of cisplatin and TAC-101 showed a significant correlation (p<0.01)., Conclusion: These in vitro findings suggest that a combination of TAC-101 and cisplatin may be a potential new treatment for ovarian clear cell adenocarcinoma.

Objectives: A novel retinobenzoic acid derivative, 4-[3,5-bis (trimethylsilyl) benzamido] benzoic acid (TAC-101), was reported to suppress the growth and invasion of human gastric cancer or hepatocellular carcinoma by induction of apoptosis. We examined the antitumor activity of TAC-101 against human ovarian carcinoma cell lines., Methods: Apoptosis of human epithelial ovarian carcinoma-derived cell lines (RMG-I, RMG-II, RTSG, RMUG-S, RMUG-L, and KF) was investigated by detecting DNA laddering and was quantified by an enzyme-linked immunosorbent assay. Inhibition of apoptosis was also examined using a caspase inhibitor. Furthermore, TAC-101 (8 mg kg(-1) day(-1) orally for 30 days) was investigated in nude mice with subcutaneous RMG-II tumors. A prominent apoptotic response to TAC-101 was observed. The antitumor effects of cisplatin (7 mg/kg intravenously on day 1) and paclitaxel (36 mg/kg intravenously on days 1 and 5) were also assessed for comparison., Results: Apoptosis occurred in all of the cell lines (except KF) in a concentration-dependent manner after exposure to TAC-101 and was markedly induced in RMG-I and RMG-II cells (derived from ovarian clear cell adenocarcinomas). A caspase inhibitor blocked the induction of apoptosis by TAC-101. The maximum inhibition of RMG-II tumor growth in nude mice by TAC-101, cisplatin, and paclitaxel was 45%, 34%, and 47%, respectively., Conclusion: Oral TAC-101 shows potential as a novel antitumor agent for ovarian carcinoma, especially ovarian clear cell adenocarcinoma.