Abstract: Objective To investigate the effects of the SH3 binding glutamic acid⁃rich protein like (SH3BGRL) on the proliferation and migration of gastric cancer cells and its mechanism. Methods Based on TCGA, GTEx and GEO databases, the expression of SH3BGRL in gastric cancer and normal gastric mucosal epithelial tissue was analyzed by bioinformatics. The expression profiles of SH3BGRL protein in gastric cancer tissue and normal gastric mucosal epithelial tissue was obtained by HPA database. Furthermore, the expression level of SH3BGRL was divided into high and low groups based on TCGA database to analyze its effect on prognosis, immune cell infiltration and immunotherapy in gastric cancer patients. The expression of SH3BGRL protein in gastric cancer was observed by IHC staining of clinical specimens. The expression level of SH3BGRL in gastric cancer cell line and normal gastric mucosal epithelial cells GES⁃1 was detected by RT⁃qPCR. Gastric cancer cells HGC⁃27 and NCI⁃N87 were transfected with siRNA and divided into si⁃NC group (negative transfection control group) and si⁃SH3BGRL group (silent SH3BGRL group), and the successfulness of transfection was verified by RT⁃qPCR and Western blot. Cell proliferation and migration ability were detected by CCK⁃8 and Transwell assay, and then THP⁃1 monocytes were induced to differentiate into M0 macrophages. The differentiated M0 macrophages and transfected gastric cancer cells were co⁃cultured, and the changes of M2 macrophage markers were detected by RT⁃qPCR and cellular immunofluorescence after co⁃culture , and RT⁃qPCR was used to detect the expression level of CSF1 in SH3BGRL⁃silenced gastric cancer cells. Results The results of bioinformatics analysis showed that compared with normal gastric mucosal epithelial tissues, the expression of SH3BGRL was up⁃regulated in gastric cancer tissues (all P<0.01), and the overall survival and progression⁃free survival of patients with high SH3BGRL expression were shorter than those with low SH3BGRL expression (all P<0.01). In addition, the proportion of M2 macrophage infiltration was higher in patients with high SH3BGRL expression, which was associated with low response rate to immunotherapy (all P<0.01). The results of IHC staining showed that the expression of SH3BGRL protein was up⁃regulated in gastric cancer tissues (P<0.001). Compared with GES⁃1 cells, mRNA expression levels of SH3BGRL in gastric cancer cells HGC⁃27 and NCI⁃N87 were significantly up⁃regulated (all P<0.01). Compared with si⁃NC group, the proliferation ability of gastric cancer HGC⁃27 and NCI⁃N87 cells was significantly decreased after SH3BGRL silenced (all P<0.01), and migration ability of HGC⁃27 cell was significantly decreased (P<0.01). After co⁃culture of M0 macrophages with SH3BGRL⁃silenced gastric cancer cells HGC⁃27 and NCI⁃N87, M2 macrophage markers CD163, CD206 and Arg1 were down⁃regulated (all P<0.01). After SH3BGRL silenced in HGC⁃27 and NCI⁃N87 cells, the target gene CSF1 of the NF⁃κB signaling pathway was significantly down⁃regulated (all P<0.01). Conclusions The expression of SH3BGRL is up⁃regulated in gastric cancer, and the silencing of SH3BGRL inhibits the proliferation and migration of gastric cancer cells, which may be related to inhibiting the polarization of M2 macrophages and forming immunosuppressive tumor microenvironment.

Key words: Gastric cancer, SH3 binding glutamic acid?rich protein like, Proliferation, Migration, Tumor microenvironment, M2 macrophage polarization