Targeting DDX3X suppresses progression of KRAS-driven lung cancer by disrupting antioxidative homeostasis and inducing ferroptosis
Approximately 30% of human cancers carry various RAS mutations, including KRAS, NRAS, and HRAS. Among these mutations, KRAS is the most prevalent isoform detected in lung cancer. While several small molecular inhibitors targeting specifically KRASG12C have been developed and tested clinically, alternative approaches are still necessary due to expected drug resistance. In this study, we present evidence that the loss of DDX3X significantly delays tumor progression in various KRAS-driven lung cancer models. Inhibition of DDX3X disrupts cysteine and glutathione metabolism, thereby inducing ferroptosis in lung cancer cells. This effect is primarily mediated by the downregulation of Cystathionine-ß-synthase (CBS), the rate-limiting enzyme in cysteine generation. Mechanistically, DDX3X directly binds to the transcription factor JUND, which mediates the transcriptional regulation of METTL16, a key N6-methyladenosine methyltransferase, and subsequently regulates m6A modification and translation of CBS transcripts. This cascade induces hypermethylation and high expression of CBS, consequently triggering cysteine production and maintaining antioxidative homeostasis, which is essential for the survival of KRAS-driven lung cancer cells. Finally, we demonstrate that a newly developed DDX3X PROTAC degrader J10 efficiently delays lung cancer progression with multiple advantages compared to DDX3X small molecular inhibitor RK-33 and limited side effects. These findings unveil the potential of DDX3X as a valuable target for adjuvant therapies in managing KRAS-driven lung cancer. Overall design: To study the role of DDX3X in lung cancer progression, we undertook a label-free proteomic analysis using DDX3X knockdown (shDDX3X) A549 cells.