[Effects of Proteasome 20S Subunit Beta 8 on Proliferation,Migration,and Invasion of Clear Cell Renal Cell Carcinoma Cells via Mitogen-Activated Protein Kinase Kinase/Extracellular Signal-Regulated Kinase Signaling Pathway]

Abstract

Objective To explore the effects of proteasome 20S subunit beta 8 (PSMB8) on the proliferation,migration,and invasion of clear cell renal cell carcinoma (ccRCC) cells and whether PSMB8 promotes tumor progression by activating the mitogen-activated protein kinase kinase (MEK)/extracellular signal-regulated kinase (ERK) signaling pathway. Methods The Cancer Genome Atlas was employed to analyze the mRNA levels of PSMB8 in ccRCC and normal tissue,and the expression levels of PSMB8 in ccRCC tissue and cells were determined by real-time quantitative PCR,Western blotting,and immunohistochemistry.Furthermore,the cell lines with stable overexpression and knockdown of PSMB8 were constructed.The CCK-8 assay and colony formation assay were employed to examine the cell proliferation,and the wound healing assay and Transwell assay were employed to examine the invasion and migration of cells.Kyoto Encyclopedia of Genes and Genomes pathway enrichment was performed to analyze the co-expressed genes of PSMB8.Western blotting was used to measure the phosphorylation levels of the proteins in the MEK/ERK signaling pathway.Finally,the rescue experiment was carried out with the ERK agonist C16-PAF. Results Compared with the normal tissue,the ccRCC tissue showed up-regulated mRNA and protein levels of PSMB8 (both P<0.001),which were associated with the TNM stage of patients with ccRCC (P<0.001).Compared with the negative control group,overexpression of PSMB8 promoted the proliferation (P=0.021,P=0.039),migration and invasion (all P<0.001) of 786-O and ACHN cells,and the knockdown of PSMB8 inhibited the proliferation (P=0.022,P=0.005),migration and invasion (all P<0.001) of 786-O and ACHN cells.The pathway enrichment analysis of co-expressed genes of PSMB8 predicted the mitogen-activated protein kinase signaling pathway (P<0.001).After the knockdown of PSMB8,786-O and ACHN cells showed lowered phosphorylation levels of MEK1/2 (P=0.017,P=0.016) and ERK1/2 (P=0.010,P=0.040) and down-regulated transcription levels of ERK downstream factors c-Myc (P=0.043,P=0.038),c-Fos (P=0.025,P=0.008),and CyclinD1 (P=0.006,P=0.047).Compared with the ERK agonist C16-PAF group,the PSMB8 knockdown + C16-PAF group showed inhibited proliferation (P=0.003,P=0.002),migration and invasion (all P<0.001) of 786-O and ACHN cells. Conclusion PSMB8 may promote the proliferation,migration,and invasion of ccRCC cells by activating the MEK/ERK signaling pathway.

Keywords: clear cell renal cell carcinoma; mitogen-activated protein kinase kinase/extracellular signal-regulated kinase signaling pathway; proteasome 20S subunit beta 8.