Abstract: Objective To investigate the effect of combining anlotinib with gefitinib on the proliferation of gefitinib-resistant human non-small cell lung cancer (NSCLC) PC9/GR cells and its possible mechanism. Methods The PC9/GR cells were divided into anlotinib group, gefitinib group, anlotinib combined with gefitinib group and control group, respectively, according to different drug administrations. MTT assay was used to detect the cell proliferation. Flow cytometry was used to analyze the distribution of cell cycle. The protein expression levels of p-ERK1/2 and p-AKT were detected by Western blot. Results The half inhibitory concentrations (IC₅₀) of anlotinib and gefitinib in PC9/GR cells for 72 h were (1.91±0.18) μmol/L and (4.83±0.15) μmol/L, respectively. Both drugs showed anti-proliferation effects of dose-dependent, and the combination of the two drugs showed obvious synergistic effects, with a combination index (CI) less than 1. The anlotinib and gefitinib could arrest PC9/GR cells at G0/G1 phase (all P<0.05). Compared with the single drug group, the G0/G1 phase arrest in the combination group wer more significant, significantly down-regulating the protein expression of p-ERK1/2 and p-AKT (all P<0.05). Conclusions The anlotinib combined with gefitinib has synergistic anti-proliferation effect on non-small cell lung cancer PC9/GR cells, and can improve the sensitivity of gefitinib. The synergistic anti-tumor mechanism may be related to the induction of cell cycle arrest and down-regulation of p-ERK1/2 and p-AKT protein expressions.

Key words: Non-small cell lung cancer, Drug resistance, Gefitinib, Anlotinib