Effects of serum- and glucocorticoid-inducible kinase 1 (SGK-1) inhibition on epidermal growth factor receptor (EGFR) signaling in non-small cell lung cancer

Oncogenic activation of epidermal growth factor receptor (EGFR) signaling exists in non-small cell lung cancer (NSCLC). Increased expression of Serum and Glucocorticoid Inducible Kinase 1 (SGK-1) in NSCLC cells was found related to proliferation and migration. Relationship between EGFR signaling and a SGK-1 substrate, NDRG1, was also shown in pancreas and colon cancer. In this study, we analyzed the effects of SGK-1 inhibitor GSK650394 on cell proliferation and EGFR signaling in A549 and H1299 human NSCLC cell lines for the first time. Incubation with GSK650394 (8 and 16 µM) significantly decreased cell proliferation and colony formation in A549 and H1299 cells (p<0.05). This result points out that NSCLC cells need SGK-1 activity for proliferation. SGK-1 activity was sensitive to GSK650394 in NSCLC cells. Phosphorylation of NDRG1 (p<0.001) and GSK3was suppressed (p<0.01) in H1299 and A549 cells respectively. We evaluated effects of SGK-1 inhibition on EGFR signaling together with alteration in NDRG1 phosphorylation. Although significant NDRG1 phosphorylation decrease in H1299 cells, any significant change in expression and activation of EGFR wasn't observed in both cell lines. In conclusion, possible mechanisms could be enlightened by evaluating effects on EGFR after increasing NDRG1 expression in NSCLC cells. SGK-1 inhibitors could be a remarkable alternative in combination treatments with their effects on NSCLC cell proliferation.