Ferroptosis is an iron-dependent form of necrotic cell death marked by oxidative damage to phospholipids. Selenoenzyme GPX4 could control Ferroptosis. Flavoprotein apoptosis-inducing factor mitochondria-associated 2 (AIFM2) is an anti-ferroptosis gene. AIFM2 (ferroptosis suppressor protein 1, FSP1) confers protection against ferroptosis elicited by GPX4 deletion. The anti-ferroptosis function of FSP1 is independent of cellular glutathione levels, GPX4 activity, ACSL4 expression, and oxidizable fatty acid content. Thus, FSP1 does not interfere with canonical ferroptosis mechanisms. Moreover, the protection against cell death conferred by FSP1 is specific to ferroptosis-inducing agents. Moreover, p53 status did not affect FSP1 expression. In contrast to FSP1, overexpression of AIFM1 failed to suppress ferroptosis. In this study, iFSP1 is a potent and selective inhibitor of FSP1 with an EC50 of 103 nM. It selectively induces ferroptosis in GPX4-knockout cells which overexpressed FSP1.
iFSP1 also inhibits the Gpx4-knockout cell growth as a dose-dependent manner but does not inhibit the wild type cell growth. Treatment with the ferroptosis inhibitor Lip-1 protects GPX4-knockout cells from iFSP1-induced ferroptosis. iFSP1 is less efficient than the genetic deletion of FSP1, whereas iFSP1 treatment in the FSP1-knockout background has no additive effect on RSL3-induced ferroptosis. iFSP1 treatment results in the obvious toxicity of RSL3 in a panel of genetically engineered (FSP1-knockout) human cancer cell lines. iFSP1 selectively induces ferroptosis in GPX4-knockout Pfa1 and HT1080 cells. It is able to sensitize a variety of human cancer cell lines to the ferroptosis inducer, such as (1S,3R)-RSL3.
In summary, iFSP1 is a potent, selective FSP1inhibitor. iFSP1 selectively induces ferroptosis in GPX4-knockout cells which overexpressed FSP1.