Molecular mechanism of regulating miR-223-3p/RHOB expression by circRNA SAMD8 to inhibit progression of pancreatic ductal adenocarcinoma

Objective To investigate the potential mechanism of circRNA SAMD8(circ-SAMD8) in development of pancreatic ductal adenocarcinoma (PDAC).

Methods The expression profile of circRNAs in PDAC tissues was analyzed based on Microarray data (GSE79634). Quantitative real-time polymerase chain reaction (qRT-PCR) was used to verify the expression of circ-SAMD8 (hsa_circ_0006148) in PDAC tissues and cells (CFPAC-1 and PANC-1).The target microRNA (miRNA) of circ-SAMD8 and its downstream mRNA were predicted by bioinformatics analysis, and identified by double luciferase reporter gene assay. The proliferation ability of PDAC cells was detected by MTT assay and colony formation assay. The expression levels of anti-apoptotic protein Bcl-2 and pro-apoptotic protein Bax were detected by Western blot. The percentage of apoptotic cells was detected by flow cytometry.

Results The expression levels of circ-SAMD8 in PDAC tissues and cells were significantly lower than those in paracancer tissues and normal cells (P < 0.05). Overexpression of circ-SAMD8 could effectively promote apoptosis of PDAC cells and inhibited proliferation of PDAC cells.Dual luciferase reporter gene experiments showed that miR-223-3p was a potential interacting molecule of circ-SAMD8, and the downstream mRNA target of miR-223-3p was RHOB. The miR-223-3p was abnormally overexpressed in PDAC tissues and cells, accompanied by low RHOB expression. In PDAC cells transfected with miR-223-3p mimics or sh-circ-SAMD8, RHOB expression was significantly decreased, proliferation ability was enhanced, and apoptosis rate was decreased.

Conclusion Circ-SAMD8 regulates the expression of RHOB downstream by sponging miR-223-3p, and effectively inhibits the occurrence and development of PDAC.