Abstract:

Objective To investigate the effect of miR?217 on gefitinib resistance in non?small cell lung cancer （NSCLC）， and to explore the downstream target genes and related pathways. Methods qRT?PCR was used to detect the expression of miR?217 in human lung normal epithelial cell lines BEAS?2B， NSCLC cell lines A549， HCC827， PC9， NCI?H1975 and gefitinib resistant strain PC9/GR. PC9/GR cells were selected and the cells of control group， NC?mimic group， miR?217 mimic group， miR?217 mimic + si?NC group， and miR?217 mimic + si?FOXO3 group were constructed using liposome transfection technique. CCK8 and clonal formation assay were used to detect changes in cell proliferation capacity， flow cytometry was used to detect changes in cell apoptosis capacity， and western blot was used to detect protein expression related to PI3K/AKT signaling pathway. The Targetscan bioinformatics website predicted the downstream target genes of miR?217， and the correlation between miR?217 and the target gene FOXO3 was detected by dual luciferase assay. Results Compared with BEAS?2B cells， the expression of miR?217 in A549， HCC827， PC9 and NCI?H1975 cells was significantly decreased （P < 0.05）. With the increase of gefitinib concentration， the expression of miR?217 gene in PC9 cells was gradually decreased （P < 0.05）， and the expression of miR?217 in PC9/GR cells was lower than that in PC9 （P < 0.05）. Compared with the control group and NC?mimic group， the cell proliferation capacity of miR?217 mimic group was significantly decreased （P < 0.05）， the number of apoptosis was increased （P < 0.05）， and the expression levels of p?PI3K and p?AKT were decreased （P < 0.05）. Dual luciferase reporter gene assay proved that FOXO3 is the target of miR?217. Compared with miR?217 mimic group and miR?217 mimic + si?NC group， the cell drug resistance of miR?217 mimic + si?FOXO3 group was increased （P < 0.05）， the proliferation ability was significantly increased （P < 0.05）， and the number of apoptosis was decreased （P < 0.05）. The expression levels of P?PI3K and P?AKT were increased （P < 0.05）. Conclusion Overexpression of miR?217 reversed the resistance of PC9/GR to gefitinib in NSCLC cells and inhibited the proliferation and accelerated apoptosis of PC9/GR cells， which may be related to the regulation of PI3K/AKT signaling pathway by targeting FOXO3.

Key words: NSCLC, miR?217, FOXO3, PI3K/AKT signaling pathway