Expression characteristics and biological functions of CGB5 gene in gastric cancer.

[OBJECTIVE] The chorionic gonadotropin (CG) subunit beta 5 (CGB5) gene is a member of the glycoprotein hormone β chain family, encoding the β5 subunit of CG, which has been shown to promote tumorigenesis and induce proliferation in various types of cancer including gastric cancer (GC). However, the mechanistic role of CGB5 in GC has not been fully elucidated. Therefore, this study investigated relevant genes that regulate GC through bioinformatics analysis.

[METHODS] Immunohistochemistry, immunofluorescence, and western blot (WB) detection methods were appropriately used to evaluate the expression pattern and clinical significance of CGB5 in 100 Chinese GC patients that were recruited from the Gaochun People's Hospital. The effect of small interfering ribonucleic acid (siRNA) on apoptosis, migration, and invasion of GC cells was investigated in vitro. Three-dimensional tumor spheres of these two types of GC cells (NCI-N87 cells and MKN45 cells) were constructed before investigation of the Calcein acetoxymethyl ester (AM)/ Propidium iodide (PI) staining, flow cytometric apoptosis, and apoptotic-related protein content of the tumor spheres after siRNA inhibition of CGB5 expression.

[RESULTS] It was observed that compared with adjacent normal gastric tissue, expression of CGB5 was significantly upregulated in GC tissue. The siRNA inhibited CGB5 expression in two GC cell lines (NCI-N87 cells and MKN45 cells). Also, it was discovered that CGB5 highly correlated with microsatellite instability (MSI) and immune cell activity in GC, thus revealing the greater research value of CGB5 gene. More importantly, CGB5 siRNA could inhibit invasion and migration of tumor cells, induce apoptosis of GC cells and GC tumor spheres, as well as the mechanism relating to regulation of apoptosis associated gene expression. Overall, the findings suggest that CGB5 may play a crucial role in the development of GC carcinogenesis. Thus, this research may contribute to design of potential drug targets for treatment of GC.