Signaling pathway differences between EGFR TKI-sensitive and -resistant non-small cell lung cancer cells.

Abstract

e13510 Background: Epidermal growth factor receptor (EGFR) tyrosine kinase inhibitors (TKIs) have showed dramatic clinical benefits in advanced non-small cell lung cancer (NSCLC), but the biggest problem is resistance. How to overcome resistance is still a serious problem to clinical practice. The aims of this studies was to analyse the signaling pathway differences between the EGFR TKI-sensitive and resistant NSCLC cell lines and to seek potential molecular targets for tumor treatment after resistance. Methods: We selected four types of NSCLC cell lines: PC-9(exon19 del), PC9GR (gefitinib-acquired resistant cell), H1650(exon19 del), H1975 (L858R+T790M), signaling pathway differences between PI3K/Akt/mTOR,MAPK and STAT3 were analysed through western blot, immunoprecipitation and confocal microscope. Results: Activation status of EGFR super signaling pathways: PI3K-Akt, Erk and STAT3 between EGFR TKI- sensitive and resistant NSCLC cells was different under basic state. The phosphorylation levels of Akt ser473, FOXO1 and Erk in EGFR TKI-resistant cells, especially in H1650 cell, were more higher than that in PC9 cell except for p-STAT3. p-STAT3 expression in PC9 was higher than that in resistant NSCLC cells. The further analysis showed that cellular localizations of p-STAT3 between sensitive and resistant cells were different through confocal microscope, p-STAT3 in PC9 and H1975 cells was almost in nucleus, while in PC9GR and H1650 cells was almost in cytoplasm. The assay of mTORC2 kinase activities in vitro showed that mTORC2 kinase activities in the resistant cells were obviously higher than that in sensitive cells. Conclusions: we found that EGFR TKI-sensitive and resistant NSCLC cells had different activation status of signaling pathways especially mTOR associated signaling pathways and different mTORC2 kinase activities. These results indicated that targeting mTOR with specific mTOR inhibitors would be a good strategy for NSCLC treatment after EGFR TKI resistance.