Synthesis and biological evaluation of cyanoenone- and enone-fused 4-androstene-3,17-dione derivatives against triple-negative breast cancer.

A series of cyanoenone- and enone-modified 4-androstene-3,17-dione (4-AD) analogs were synthesized and evaluated for their antiproliferative activity against triple-negative breast cancer (TNBC) cells. Among them, compound 48 (SH458) exhibited the most potent antiproliferative activity against various TNBC cell lines, with IC50 values ranging from 0.14 to 0.28 μM. Mechanistic studies demonstrated that SH458 inhibited TNBC cell proliferation by inducing apoptosis and cell cycle arrest. Moreover, SH458 markedly upregulated the expression of unfolded protein response (UPR)-related genes, including ATF4, ATF6, PERK, CHOP, IRE1, XBP1, GRP78, GADD34, PBGD, and ERdj4/DNAJB9, as well as UPR-related proteins, including eIF2α, p-eIF2α, IRE1α, and p-IRE1α, in a time- and dose-dependent manner. These results suggest that SH458 induces persistent ER stress and sustained activation of the UPR pathway, ultimately triggering apoptotic signaling and TNBC cell death. In vivo, SH458 significantly inhibited TNBC tumor growth, exhibiting superior efficacy compared with doxorubicin, without causing significant toxicity. Thus, SH458 may serve as a promising lead compound for the development of novel agents against TNBC.