CircCUL2 suppresses retinoblastoma cells by regulating miR-214-5p/E2F2 Axis

The aim of this study was to investigate the effect of circCUL2 on the proliferation, invasion and migration of retinoblastoma cells by regulating the miR-214-5p/E2F2 axis. qRT-PCR and western blot were performed to detect the expressions of circCUL2, miR-214-5p and E2F2 in tumor tissues and adjacent normal tissues from retinoblastoma patients, and in normal human retinal epithelial cells ARPE-19 and human retinoblastoma cells Y79 and SO-Rb50. qRT-PCR and western blot were performed for the detection of RNA levels of circCUL2 and miR-214-5p and the mRNA and protein levels of E2F2, 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide assay for cell proliferation ability, Transwell assay for cell invasion ability, and scratch assay for cell migration ability. Luciferase dual reporter assay was used to detect the targeting relationship between circCUL2 and miR-214-5p, and between miR-214-5p and E2F2. CircCUL2 and E2F2 were lowly expressed, while miR-214-5p was highly expressed in retinoblastoma tumor tissues and cells. Transfection with pcDNA3.1-CUL2 or miR-214-5p inhibitor inhibited the proliferation, invasion and migration of Y79 and SO-Rb50 cells compared with the negative control; while transfection with sh-CUL2 or miR-214-5p mimics promoted the proliferation, invasion and migration of Y79 and SO-Rb50 cells. CircCUL2 negatively regulated miR-214-5p, while miR-214-5p negatively regulated E2F2. Overexpression of miR-214-5p or silencing of E2F2 in SO-Rb50 cells partially reversed the inhibitory effect of circCUL2 on the proliferation, invasion and migration of retinoblastoma cells. CircCUL2 inhibited the proliferation, invasion and migration of retinoblastoma cells by regulating the miR-214-5p/E2F2 axis.