Abstract: Objective To investigate the effect of circular RNA (circRNA) circ_ 0061140 on the proliferation, cell cycle and apoptosis of non-small cell lung cancer cells via targeting miR-6838- 5p. Methods Reverse transcription-quantitative polymerase chain reaction (RT-qPCR) was used to detect the expression levels of circ_ 0061140 and miR-6838-5p in the non-small cell lung cancer cells. The NCI-H1299 non-small cell lung cancer cells were divided into 7 groups: the si-circ _ 0061140 group (transfected with si-circ_ 0061140, circ_ 0061140 lowly expressed), the si-NC group (transfected with si-NC, the negative control), the NC group (blank control with no transfection of miRNA), the miR-6838-5p group ( transfected with miR-6838-5p mimic, miR-6838-5p highly expressed), the miR-NC group ( transfected with miR-NC, the negative control), the si-circ_ 0061140 + anti-miR-NC group (co-transfected with si-circ_ 0061140 and anti-miR-NC), the si-circ_ 0061140 + anti-miR-6838-5p group ( co-transfected with si-circ_ 0061140 and anti-miR-6838-5p). Western blotting was used to detect the expression levels of cyclin D1 and cleaved cysteinyl aspartate specific proteinase-3 ( cleaved-caspase-3). The proliferation of cells was detected by MTT method. The cell cycle and cell apoptosis was detected by the flow cytometry. Dual luciferase reporter assay was used to verify the relationship between circ_ 0061140 and miR-6838-5p. Results The expression level of circ_ 0061140 in the non-small cell lung cancer tissues and the cell lines NCI-H1299, NCI-H2170, NCI-H1975 were all higher than that in the adjacent tissues and the BEAS-2B normal lung epithelial cells, while the expression level of miR-6838-5p in the non-small cell lung cancer tissues and the lung cancer cells was lower than that in the adjacent tissues and BEAS-2B cells (all P < 0. 05). the expression level of cyclin D1 protein, the proliferation rate, and the ratio of S phase cells in cells of the si-circ_ 0061140 group and the miR-6838-5p group were lower than those of the NC group, while the expression level of cleaved-caspase-3 protein, the ratio of G0 / G1 phase cells, the apoptosis rate, and the mortality rate were higher than those of the si-NC group and the miR-NC group when compared with the NC group (all P< 0. 05). circ_ 0061140 targeted regulates the expression of miR-6838-5p. Co-transfection of anti- miR-6838-5p and si-circ_ 0061140 could attenuate the effect of si-circ_ 0061140 on the proliferation, cell cycle and apoptosis in non-small cell lung cancer cells. Conclusion The down-regulation of circ _ 0061140 in non-small cell lung cancer cells can suppress the proliferation of cells, block the cells in the G0 / G1 phase, and increase the apoptosis of cells by targeting miR-6838-5p.

Key words: circ _ 0061140, non-small cell lung cancer, miR-6838-5p, cell proliferation; cell cycle, cell apoptosis