First, the human NSCLC cells PC9ER and HCC827ER were generated by exposing cells to increasing concentrations of erlotinib over 6 months...we constructed GBP1‑knockdown and GBP1‑overexpressing cells to determine the IC50 value of erlotinib, to perform an apoptosis assay and to examine cell cycle distribution...In the present study, GBP1 was significantly upregulated in erlotinib‑resistant cells, compared with erlotinib‑sensitive cells. In vitro and in vivo experiments showed that upregulated GBP1 expression contributed to erlotinib resistance, while decreased GBP1 expression had the opposite effect.