Interaction between Nrf2 and EGFR signaling in the proliferation of NSCLC cells.

Abstract

e21062 Background: We previously demonstrated that transcription factor Nrf2 promotes cancer cell proliferation and resistance to anticancer drugs in NSCLC cells. The activation of Nrf2 is regulated negatively by its cytoplasmic inhibitor Keap1 and positively by kinase-mediated phosphorylation. Since Nrf2 and EGFR are abundantly expressed in NSCLC cells, we examined the interaction between Nrf2 activation and EGFR signaling in NSCLC cell lines. Methods: Two human NSCLC cell lines, A549 cells and NCI-H292 cells were treated with EGF. We preliminarily clarified that Nrf2 is constitutively activated in A549 cells because of dysfunctional mutation in the Keap1 gene. NCI-H292 cells possess wild-type Keap1. Cell growth was analyzed by MTT assay. Activation of Nrf2 and the level of phosphorylated EGFR and its downstream signal transducers, p-Akt and p-ERK, were analyzed by immunoblotting. Results: Nrf2 was activated by stimulation with EGFR in NCI-H292 cells. EGFR- mediated activation of Nrf2 was inhibited by EGFR-TKI AG1478 in these cells. Nrf2 was constitutively activated, and the activation was not inhibited by AG1478 in A549 cells. EGFR-mediated activation of Nrf2 was inhibited by a MEK inhibitor U0126, but not by a PI3K inhibitor LY294002 in NCI-H292 cells. EGFR-mediated cell proliferation was significantly inhibited by knockdown of Nrf2 with its specific siRNA. Conclusions: In NCI-H292 cells that possess wild-type Keap1, Nrf2-mediated cell proliferation may be regulated by the EGFR/MAPK signaling pathway. On the other hand, in A549 cells, cell proliferation is not affected by EGFR signaling because of constitutive activation of Nrf2 due to dysfunction of Keap1. Thus, Keap1 gene mutation is a predictable factor for efficacy of EGFR-TKI. No significant financial relationships to disclose.