Objective      To determine the role of Rab25 to erlotinib (ER) in acquired resistance of non-small cell lung cancer (NSCLC).       Methods      PC9 cells and the erlotinib acquired resistance cells (PC9/ER) were subcultured to evaluate erlotinib resistance index using CCK-8 assay. After treated with series concentrations of erlotinib (0.1

0.2 and 0.3 μmol/L)

the mRNA and protein levels of Rab25 were detected in the PC9 and PC9/ER cell

s by quantitative real-time PCR (qPCR) and Western blotting

respectively. Immunofluorescence assay was used to observe the subcellular localization of Rab25 in the cells. After knocking-down Rab25 in PC9/ER with siRab25

the changes of proliferation index (PI) and erlotinib IC

50

were detected by flow cytometry and CCK-8 assay respectively.       Results      The resistance index of PC9/ER to erlotinib was 68.82±21.42. The mRNA and protein levels of Rab25 were significantly higher in the PC9/ER cells than the PC9 cells after ER treatment for 48 h. In addition

the heaped Rab25 protein was mainly located in the cell membrane. Interestingly

the Rab25 protein level was progressively increased in a dose-dependent manner in PC9/ER cells

but not in PC9 cells. Erlotinib IC

50

and PI were much lower in the PC9/ER cells with Rab25 knockdown than the control cells (P＜0.05).       Conclusion       Rab25 is strongly expressed in acquired resistant NSCLC cells against ER

and it contributes to ER acquired resistance in the cells.