Oxidative stress and Kras mutation in Mist1+ cells act in a double-hit manner to drive gastric tumorigenesis.

Oxidative stress is a "double-edged sword" in mediating cellular activities. Here, we report that Mist1+ cells are resistant to oxidative-stress-induced cell death and that persistent oxidative stress and Kras mutation act in Knudson's "two-hit" paradigm to promote gastric cancer initiation. Reactive oxygen species (ROS) accumulation causes metaplastic lineage expansion of Mist1+ cells, licensing them as a cellular origin of gastric cancer. Mechanistically, the transcription factor Mist1 upregulates its downstream target genes Bnip3 and Tmed6, enhancing ROS resistance. Persistent ROS induce R-loop accumulation and activate YAP signaling in Mist1+ cells for proliferation and tumorigenesis. Importantly, ROS and Kras mutation synergistically drive the malignant transformation of Mist1+ cells, while ROS or Kras mutation alone could not do so. Collectively, our study offers insights into the two-hit theory by demonstrating that oxidative stress and oncogenic mutation cooperatively drive Mist1+ cell expansion and transcriptional reprogramming-critical events during early tumor initiation.