Abstract: Objective To investigate the effects of circular RNA APLP2 (circAPLP2) on the proliferation, migration, and invasion of human colorectal cancer (CRC) cell lines by regulating microRNA-455-3p (miR-455-3p)/Stathmin1 (STMN1) axis. Methods RT-qPCR was used to detect the expression of circAPLP2, miR-455-3p and STMN1 in CRC and normal colorectal cell lines and the optimal cell line was screened. Proliferation, migration and invasion were detected by MTT assay, scratch assay and Transwell assay, respectively. The relationship between circAPLP2 and miR-455-3p, between miR-455-3pand STMN1 was confirmed by dual Lucifer's reporter gene assay. Results CircAPLP2 and STMN1 were highly expressed in CRC cells, miR-455-3p showed a low expression. Knocking down circAPLP2 resulted in a decrease in rate of survival and of scratch healing rate and invasion of SW620 cells, An up regulation of miR-455-3p expression, a down regulation of STMN1, cyclin D1, N-cadherin protein expression and an up regulation of E-cadherin protein expression were also found (P＜0.05). Inhibition of miR-455-3p expression reversed inhibitory effect of knocking down circAPLP2 on SW620 cell proliferation, migration, and invasion, up-regulated the STMN1, cyclin D1 and N-cadherin protein expression, and down-regulation of E-cadherin protein expression (P＜0.05). Dual luciferase reporter gene assay showed that circAPLP2 targeted at negative regulation of miR-455-3p expression, while miR-455-3p targeted at negative regulation of STMN1 expression. Nude mouse transplantation experiment found that knocking down circAPLP2 affected the growth of transplanted tumors, while miR-455-3p expression was up-regulated and STMN1 expression was down-regulated(P＜0.05). Conclusions CircAPLP2 inhibits the proliferation, migration and invasion of colorectal cancer cell lines by regulating the miR-455-3p/STMN1 axis.

Key words: circular RNA APLP2, miR-455-3p, Stathmin1 (STMN1), colorectal cancer, proliferation