The RSL3 Induction of KLK Lung Adenocarcinoma Cell Ferroptosis by Inhibition of USP11 Activity and the NRF2-GSH Axis

SIMPLE SUMMARY: High NRF2 level confers KLK LUAD cell resistance to ferroptosis. Here, we showed that the inhibition of NRF2-GSH axis sensitized a small molecule RSL3 to induce KLK LUAD cell ferroptosis in vitro. RSL3 treatment inhibited activity of the NRF2-GSH signaling during KLK LUAD cell ferroptosis in vitro and in vivo. The mechanism is that RSL3 was able to directly bind to USP11, a recently identified de-ubiquitinase of NRF2, and inactivate USP11 protein to induce NRF2 protein ubiquitination and degradation in KLK LUAD cells. It was discovered for the first time that RSL3 induction in KLK LUAD cell ferroptosis by the suppression of USP11-NRF2-GSH signaling, in parallel to GPX4 inhibition. ABSTRACT: Antioxidant transcription factor NRF2 plays a pivotal role in cell ferroptosis. KLK lung adenocarcinoma (LUAD) is a specific molecular subtype of Kras-mutant LUAD. The activation of mutant Kras in combination with the inactivation of Lkb1 and Keap1 abnormally increases NRF2 expression, while high NRF2 confers KLK LUAD cell resistance to ferroptosis. This study assessed the inhibition of NRF2-GSH axis to sensitize a small molecule RSL3 to induce KLK LUAD cell ferroptosis and then explored the underlying molecular mechanisms. The data showed that the NRF2-GSH inhibition sensitized RSL3 induction of KLK LUAD cell ferroptosis in vitro, while RSL3 treatment reduced level of NRF2 protein in KLK LUAD during ferroptosis. Moreover, RSL3 treatment inhibited activity of the NRF2-GSH signaling during in KLK LUAD cell ferroptosis in vitro and in vivo. Mechanistically, the RSL3 reduction of NRF2 expression was through the promotion of NRF2 ubiquitination in KLK LUAD cells. In addition, RSL3 was able to directly bind to USP11, a recently identified de-ubiquitinase of NRF2, and inactivate USP11 protein to induce NRF2 protein ubiquitination and degradation in KLK LUAD cells. These data revealed a novel mechanism of RSL3 induction in KLK LUAD cell ferroptosis by suppression of the USP11-NRF2-GSH signaling. Future study will confirm RSL3 as a novel therapeutic approach in control of KLK lung adenocarcinoma.