SASS6 Promotes Proliferation of Esophageal Squamous Carcinoma Cells by Inhibiting the p53 Signaling Pathway

Abstract

SASS6 encodes for the Homo sapiens SAS-6 centriolar assembly protein and is important for proper centrosome formation. Although centrosomes are amplified in a wide variety of tumor types, abnormally high SASS6 expression had previously only been identified in colon cancer. However, the role of SASS6 in esophageal squamous cell carcinoma (ESCC) pathogenesis has not yet been elucidated. The aim of this study was to investigate the role and mechanisms of SASS6 in ESCC. The expression level of PNCK mRNA was detected in specimens of ESCC (n = 20) and paired paracancerous tissues (n = 20) by qPCR, and that of PNCK protein was detected in specimens of ESCC paraffin tissue (n = 316) and corresponding paraffin paracancerous tissue (n = 94) by immunohistochemistry. The correlations of PNCK protein expression level with clinical stage and survival prognosis in ESCC patients were also investigated, respectively. Celigo Cell Counting and MTT assay were used to measure cell viability. Apoptosis and colony formation were detected by flow cytometric analysis and colony assay. The bioluminescence imaging was used to evaluate the effects of SASS6 knockdown on tumor growth using a xenograft animal model. The global gene expression profile was determined in wild type and SASS6-depleted ESCC cells via transcriptomics analysis. Mechanically, the changes of p53 signaling pathway were detected by Western blotting. We found that the mRNA and protein levels of SASS6 were increased in human ESCC samples. In addition, SASS6 protein expression was associated with the esophageal cancer stage and negatively impacted survival of patients with ESCC. Furthermore, silencing of SASS6 inhibited cell growth and promoted apoptosis of ESCC cells in vitro and inhibited xenograft tumor formation in vivo. A genetic cluster and pathway analysis showed that SASS6 regulates the p53 signaling pathway. Western blot analysis demonstrated that CCND2, GADD45A, and EIF4EBP1 protein expression decreased and that TP53 protein expression increased in the shSASS group when compared with the control group. SASS6 promoted the proliferation of esophageal cancer by inhibiting the p53 signaling pathway. Thus, SASS6 has potential as a novel tumor marker and therapeutic target for ESCC.