The Effect And Mechanism Of Blocking EGFR And MTOR Signaling Pathway In Nasopharyngeal Carcinoma Resistant To EGFR-TKI

Objective To clarify the combined effect and mechanism of the epidermal growth factorreceptor (EGFR) inhibitor gefitinib and the mammalian target of rapamycin (mTOR)inhibitor everolimus in nasopharyngeal carcinoma resistant to gefitinib in vitro.Methods The effect of cell growth inhibition through a single agent or combined treatmentof human nasopharyngeal carcinoma cell line HONE1was measured by MTT assay. Flowcytometry was applied to assess the cell cycle and apoptosis when HONE1were incubatedwith drugs alone or in combination at48h or72h. Western Blot was used to detect the expression of total and phosphorylated levels of AKT and S6K in HONE1, at basalcondition and after treatment with monotherapy or combination therapy for48h.Result The effect of inhibition in cell growth of both gefitinib and everolimus in theHONE1cell lines was dose-dependent. The IC50value for gefitinib in HONE1cells was17.92μmol/L, and the IC50value for everolimus in HONE1cells was2.46nmol/L, thecombined effect of gefitinib and everolimus in the HONE1cell lines did not show asignificant synergistic effect(p>0.05). Gefitinib and everolimus were found to induceapoptosis and G0/G1cell cycle arrest in the HONE1cell lines in time-dependent manner.But the combined effect of the two drugs did not show a significant advantage than the drugalone. AKT activation appeared to remain persistent in the HONE1cell lines for48h ofgefitinib exposure. Phospho-S6K expression was downregulated in the HONE1cell linesfollowing exposure to everolimus for48h, however, followed by upregulation of phospho-AKT. Nevertheless, the inhibitory effect of combined treatment with p-S6K and p-AKTexpression was not significantly stronger than the single drug.Conclusion The mTOR inhibitor everolimus could not reverse geftinib sensitivity inresistant nasopharyngeal carcinoma cell line HONE1. The mechanism of the EGFR/AKTsignaling pathway and the mTOR signaling pathway in nasopharyngeal carcinoma cells ispresently being explored by our research group.