In vitro antitumor activity of progesterone in human adrenocortical carcinoma.

PURPOSE: The management of patients with adrenocortical carcinoma (ACC) is challenging. As mitotane and chemotherapy show limited efficacy, there is an urgent need to develop therapeutic approaches. The aim of this study was to investigate the antitumor activity of progesterone and explore the molecular mechanisms underlying its cytotoxic effects in the NCI-H295R cell line and primary cell cultures derived from ACC patients. METHODS: Cell viability, cell cycle, and apoptosis were analyzed in untreated and progesterone-treated ACC cells. The ability of progesterone to affect the Wnt/β-catenin pathway in NCI-H295R cells was investigated by immunofluorescence. Progesterone and mitotane combination experiments were also performed to evaluate their interaction on NCI-H295R cell viability. RESULTS: We demonstrated that progesterone exerted a concentration-dependent inhibition of ACC cell viability. Apoptosis was the main mechanism, as demonstrated by a significant increase of apoptosis and cleaved-Caspase-3 levels. Reduction of β-catenin nuclear translocation may contribute to the progesterone cytotoxic effect. The progesterone antineoplastic activity was synergically increased when mitotane was added to the cell culture medium. CONCLUSIONS: Our results show that progesterone has antineoplastic activity in ACC cells. The synergistic cytotoxic activity of progesterone with mitotane provides the rationale for testing this combination in a clinical study.