Inhibition of human hepatocarcinoma cell proliferation by mammalian and fish gonadotropin-releasing hormones.

This study provides the first demonstration that human hepatocarcinoma-derived cell line HepG2 contains GnRH receptors and responds to various molecular forms of GnRH in terms of inhibition of proliferation in a time- and dose-related manner. In addition, GnRH peptides also significantly inhibited the uptake of [3H]thymidine by these cells. The effect of GnRH was specific because GnRH antagonists reversed the GnRH-mediated inhibition, and non-GnRH peptides had no effect on HepG2 cell proliferation. An important finding is that certain fish GnRH molecules such as lamprey GnRH, which has little gonadotropin (LH) release activity in mammals, suppress hepatocarcinoma cell proliferation with similar potency to a superactive mammalian GnRH analog, [D-Lys6]GnRH. These findings may have profound implications in the development of an effective chemotherapy for treatment of human liver cancer. An added advantage is that fish GnRH forms will likely exert little side effect in terms of human pituitary gonadotropin release, gonadal steroidogenesis, and reproductive functions in general.