Downregulation of PDIA3 inhibits gastric cancer cell growth through cell cycle regulation

Aims: Protein disulfide isomerase A3 (PDIA3) promotes the correct folding of newly synthesized glycoproteins in the endoplasmic reticulum. Emerging evidences have indicated that PDIA3 play an important role in tumor progression in variety of cancer and might be identified as a biomarker for cancer prognosis and cancer immunotherapy. However, the functional role of PDIA3 in gastric cancer (GC) needs to be unfolded. Therefore, the aim of our study was to detect the expression level of PDIA3 in gastric cancer and its association with gastric cancer development as wells as the underlying mechanism.Methods: The Cancer Genome Atlas (TCGA) database was used to analyze the expression of PDIA3 in gastrointestinal (GI) cancers. The correlation of PDIA3 expression to GC patient survival was further investigated. Chemically synthesized control siRNA (siNC) and PDIA3-specific siRNA (siPDIA3) were transferred into GC cells TMK-1 and AGS to knock down the expression of PDIA3. CRISPR-cas9 system was utilized to established PDIA3-knockout cell lines. Cell viability, invasion, migration and cell cycle assays were performed on GC cell lines after knockdown and knockout of PDIA3. In addition, subcutaneous tumor xenograft was established in nude mice to analyze the role of PDIA3 in gastric carcinogenesis and development in vivo. The differentially expressed genes, KEGG pathway enrichment and GO functional enrichment was analyzed based on RNA sequencing (RNA-seq) technology to find downstream targets of PDIA3 in GC cells.Results: Significantly increased expression level of PDIA3 were found in GI cancer tissues and GC cells. PDIA3 expression was negatively correlated with the three-year survival rate of GC patients. Down-regulation of PDIA3 by siRNA or CRISPR-cas9 significantly inhibited proliferation, invasion and migration of GC cells, with cell cycle arrested at G2/M phase. Meanwhile, decreased PDIA3 significantly inhibited growth of tumor xenograft in vivo. It was found that cyclin G1 (encoded by CCNG1 gene) expression was decreased by downregulation of PDIA3 in GC cells both in vitro and in vivo. In addition, protein level of other cell cycle related factors including cyclin D1, CDK2, and CDK6 were also significantly decreased which might contribute to the cell cycle arrest as well as the restriction of GC growth.Conclusion: PDIA3 plays an oncogenic role in GC. Our findings unfolded the functional role of PDIA3 in association with GC development and highlighted a novel target for cancer therapeutic strategy.