Arsenic exposure increases susceptibility to Ptpn11-induced malignancy in mouse embryonic fibroblasts through mitochondrial hypermetabolism

Objective: To explore the synergistic effect and metabolic mechanism of chronic arsenic exposure and PTPN11 gain-of-function mutation on tumorigenesis. Methods: Arsenic-transformed Ptpn11(+/+) (WT-As) and Ptpn11(D61G/+)-mutant (D61G-As) mouse embryonic fibroblasts (MEFs) were established by chronic treatment of low-dose arsenic. We used cell counting, plate colony and soft agar colony formation, and a nude mouse xenograft mod-el to detect malignant transformation and tumorigenesis in vitro and in vivo. To detect mitochondrial oxidative phosphorylation (OXPHOS), we used Seahorse real-time cell metabolic analysis as well as adenosine triphosphate (ATP) and ROS production assays. Lastly, we examined mTOR signaling pathway changes by western blotting. Results: Low-dose arsenic exposure promoted WT MEFs proliferation and exacerbated malignancy driven by Ptpn11(D61G/+ )mutation. Additionally, Ptpn11D61G/+-mutant MEFs exhibited increased mitochondrial metabolism and low-dose arsenic amplified this malignant metabolic activity. Mechanistically, the mTOR signaling pathway was activated in Ptpn11(D61G/+)-mutant MEFs and was further phosphorylated in arsenic-treated MEFs expressing Ptpn11(D61G/+). Critically, tumorigenesis induced by the synergistic effect of low-dose arsenic and Ptpn11D61G/+ mutation was pre-vented by mTOR pathway inhibition via rapamycin. Conclusion: This study found that metabolic reprogramming, particularly mitochondrial hyperactivation, is a core mechanism underlying tumorigenesis induced by the synergistic effect of Ptpn11(D61G/+ )mutation and arsenic exposure. Furthermore, these findings suggested mTOR is a therapeutic target for Ptpn11-associated cancers.