Purpose: 17-(demethoxy), 17-allylamino geldanamycin (17-AAG) suppresses growth in some cancers by inhibiting Heat shock protein 90 (Hsp90). We examined the effects of 17-AAG-mediated Hsp90 inhibition on human hepatocellular carcinoma (HCC) growth in vitro and in vivo. Methods: Human HCC cell lines, Hep3B and HuH7, were exposed to 17-AAG and cell viabilities and apoptosis were determined. Cell cycle profiles were analyzed and the G2/M cell cycle checkpoint proteins cdc2 and cyclin B1 were examined. Studies were performed to determine whether 17-AAG-mediated cdc2 decrease was due to altered gene expression, transcription, or protein degradation. The effects of 17-AAG on Hep3B and HuH7 xenograft growth in athymic nude mice were also examined. Results: Hep3B and HuH7 treated with 17-AAG versus untreated controls showed decreased cell viability and increased apoptosis. Cells treated with 17-AAG also showed an increased fraction in G2/M phase and an associated decrease in cdc2 through protein degradation rather than through other mechanisms. Hsp90 inhibition by 17-AAG also decreased HCC xenograft growth in association with decreased cdc2 expression. Conclusions: 17-AAG-mediated inhibition of Hsp90 abrogates human HCC cell growth in vitro and in vivo through cdc2 decrease, which in turn induces G2/M cell cycle arrest and apoptosis. Hsp90 is a mediator of HCC growth and survival and its inhibition may serve as a potential treatment.
- Hepatocellular cancer