OBJECTIVE: To explore the clinical efficacy and mechanism of sunitinib on gefitinib resistant nonsmall cell lung cancer. METHODS: Seventy-five patients with non-small cell lung cancer admitted to Inner Mongolia Autonomous Region People’s Hospital from Jan. 2017 to Jan. 2019 were extracted

and the patients’ tumor tissues were resected. The cancer cells were extracted for primary culture

and the total cell RNA was extracted and its purity and concentration were determined. The inhibition of sunitinib on proliferation of geffitinib resistant non-small cell lung cancer cells was determined by MTT. Western blot was used to detect the levels of multi-drug resistant protein（ MDR）

transcription factor κB（ NF-κB）

vascular endothelial growth factor（ VEGF） and platelet-derived growth factor（ PDGF） in geffitinib resistant cells treated with sunitinib. RESULTS: The IC50 value of 1. 5 μmol/L sunitinib on gefitinib resistant cells was（ 30. 57 ± 1. 86） μmol/L

significantly lower than that of IC50 value of 0 μmol/L sunitinib on gefitinib resistant cells [（ 45. 62 ± 1. 79） μmol/L]. Sunitinib could significantly increase the sensitivity of resistant cells to gefitinib and reduce the IC50 value of gefitinib. In addition

sunitinib also significantly reduced the expression levels of MDR

NF-κB

VEGF and PDGF in resistant cells

with the most significant effects of 44. 38%reduction in PDGF protein expression. CONCLUSIONS: Geffitinib and sunitinib have synergistic effect

which can reverse the efficacy of geffitinib resistant non-small cell lung cancer

and provide more theoretical basis for clinical application

and its mechanism still needs the further study.