Xanthocillin X Dimethyl Ether Exhibits Anti-Proliferative Effect on Triple-Negative Breast Cancer by Depletion of Mitochondrial Heme.

Triple-negative breast cancer (TNBC) presents a significant therapeutic challenge due to the absence of specific targeted treatments. In this study, we explored the therapeutic potential of xanthocillin X dimethyl ether (XanDME), a naturally occurring isocyanide isolated from the marine fungus Scedosporium apiospermum, on TNBC. To elucidate the underlying mechanism, we initially demonstrated that XanDME directly binds to hemin, the oxidized form of heme, in vitro, corroborating previous reports. This interaction led to the depletion of intracellular regulatory heme. We further established that XanDME translocates into the mitochondria, where it interacts with crucial hemoproteins, namely cytochromes. The binding of XanDME with mitochondrial cytochromes disrupts the electron transport chain (ETC), inhibits the activity of mitochondrial complexes, and inactivates mitochondrial respiration. The inhibitory activity of XanDME on mitochondrial function significantly contributes to its anti-TNBC effects, as observed both in vitro and in vivo. Our study underscores the potential of XanDME against TNBC, warranting further investigations.