The PI3K pathway is a downstream effector of NRF2 activation in the esophagus

Mutations in nuclear factor erythroid 2-related factor 2 (NFE2L2 or NRF2) occur in 10-22 % of esophageal squamous cell carcinoma (ESCC) cases and result in NRF2 activation, promoting tumor progression, and therapeutic resistance. Although previous studies suggested a link between NRF2 and kinases, specific kinases responsive to NRF2 activation remain to be fully identified. Using protein phosphorylation profiling and kinase activity profiling, we identified phosphatidylinositol 3-kinase (PI3K) pathway as a downstream effector in NRF2^W24C-KYSE70 cells compared to isogenic NRF2^null-KYSE70 cells. AREG, pEGFR, PIK3CA, pAKT, p-S6, and p-PTEN were downregulated in NRF2 deficient cells. Notably, NRF2 deficiency sensitized ESCC cells to EGFR, PIK3CA, and AKT inhibitors. Co-treatment with Alpelisib (a PIK3CA inhibitor) and Pyrimethamine (an NRF2 inhibitor) synergistically suppressed the growth of NRF2^W24C-KYSE70 and NRF2^D77V-KYSE180 cells. In vivo, NRF2 activation in the esophageal epithelium of Keap1^-/- and Sox2CreER;LSL-Nrf2^E79Q/+ mice resulted in upregulation of pAKT, p-mTOR, and pS6. In human ESCC tissues, expression of pNRF2 (an active form of NRF2) was positively associated with that of pAKT and p-mTOR. Furthermore, co-treatment with Pyrimethamine and Alpelisib significantly inhibited hyperproliferation and hyperkeratinization in the esophageal epithelium of Sox2CreER;LSL-Nrf2^E79Q/+mice. Together, our data demonstrates the PI3K pathway as a downstream effector of NRF2 activation in the esophagus, and co-targeting of NRF2 and the PI3K pathway may offer a promising therapeutic strategy for NRF2^Mut ESCC.