PSMB2 knockdown suppressed proteasome activity and cell proliferation, promoted apoptosis, and blocked NRF1 activation in gastric cancer cells.

Abstract

Proteasome 20S Subunit Beta 2 (PSMB2) has been suggested to play several roles in cancer. However, the role of PSMB2 and its underlying mechanisms in gastric cancer have not been studied. In this study, qRT-PCR was employed to detect the expression of genes that encode for 26s proteasome subunit proteins. PSMB2 expression and its prognostic ability were assessed by collecting patient tissue samples and reviewing the TCGA and Kaplan-Meier Plotter databases. Immunofluorescence and western blotting experiments were performed to evaluate the expression of PSMB2 in human gastric cancer cells and normal gastric epithelial cells. Subsequently, PSMB2 was knocked down in HGC-27 and SNU-1 cells and overexpressed in N-87 and AGS cells. Proteasome activity assays, 5-Ethynyl-2'-deoxyuridine staining, and TUNEL assays were used to assess proteasome activity, cell proliferation, and apoptosis. Tumor xenograft assays were conducted to evaluate PSMB2 function in vivo. Our results showed that a total of 8 genes encoding for the 26s proteasome subunit protein were highly expressed in a variety of gastric cancer cells. Next, PSMB2 was selected as the focus of subsequent studies which showed that PSMB2 was highly expressed in samples of gastric cancer tissue. Furthermore, a review of the TCGA database revealed that a high level of PSMB2 expression was associated with a poor clinical prognosis. Our results indicated that PSMB2 overexpression promoted proteasome activity, cell proliferation, and suppressed the apoptosis of gastric cancer cells, while those effects were reversed by treatment with a proteasome inhibitor (MG132). In contrast, PSMB2 knockdown produced the opposite effects and also blocked NRF1 activation. Moreover, PSMB2 knockdown inhibited tumor growth in vivo, decreased PSMB2 expression and cell proliferation, and promoted apoptosis in tumor tissues. Our findings revealed the role played by PSMB2 in gastric cancer and suggest PSMB2 as a new target molecule for use in diagnosing and treating gastric cancer.