Synthesis and cytotoxicity evaluation of steroidal 17β-hydroxy-17α-methylisoxazoles

The aim of this study was to develop an approach to the synthesis of 17β-hydroxy-17α-methylisoxazoles and to evaluate their cytotoxic effects against prostate cancer cell lines. The key reaction in their synthesis was the addition of a dianion generated from ethyl acetoacetate and butyllithium to androstenolone. Subsequent stages included the reaction of the intermediate β-hydroxyketone with hydroxylamine to form an isoxazole heterocycle, as well as manipulations with protecting groups. The cytotoxicity of the obtained compounds was studied using hormone-sensitive and hormone-independent prostate and breast carcinoma cell lines. It was found that 17β-hydroxy-17α-methylisoxazoles exerted a more pronounced inhibitory effect on LNCaP cells in comparison with abiraterone, while only minor cytotoxicity was observed toward PC3, MCF-7, and MDA-MB-231 cells. Analysis of the effects of the compounds on cell cycle progression in LNCaP cells demonstrated that they induced cell cycle arrest in the G0/G1 phase. Compound 4 (17α-(Isoxazol-3-ylmethyl)-androst-5-en-3β,17β-diol) suppressed the activity of key signaling pathways (AKT, S6K, ERKs) in LNCaP cells. Binding analysis of the studied compounds to human CYP17A1 revealed a weak spectral response, suggesting that effective binding does not occur in the active site and their mechanism of action is likely unrelated to CYP17A1 inhibition. The steroidal 17β-hydroxy-17α-methylisoxazoles are the basis for the development of new drugs that regulate the activity of kinase signaling pathways in tumor cells.