Identification of PROZ as a Cancer-related Gene in Hepatocellular Carcinoma under Hypoxia Condition

Abstract

Background: Hepatocellular carcinoma (HCC) is a common human malignancy. In recent years, the study of biomarkers for HCC progression has become a hot topic. This study focused on identifying the key gene protein Z (PROZ) associated with the tumorigenesis of HCC by bioinformatics methods, and exploring its function and regulatory mechanism. Methods: Differentially expressed genes (DEGs) in HCC cells under hypoxia condition and normoxia condition were analyzed with the data of GSE15366 and GSE41666. The genes associated with the prognosis of HCC patients were analyzed in the Human Protein Atlas (HPA) database and intersected with hypoxia-related DEGs in HCC to obtain key genes. Gene Expression Profiling Interactive Analysis database was used to analyze the relationship between expressions of the above key genes in HCC and the prognosis of patients. The mRNA expression level of PROZ was analyzed by qPCR. Immunohistochemical staining results of PROZ in HCC were obtained from the HPA database. The cell viability and apoptosis were testified by CCK-8 and TUNEL methods. The glucose consumption and lactic acid production of cells were also detected. LinkedOmics database was used to analyze the relevant signaling pathways regulated by PROZ in HCC. Western blot was adopted to detect expressions of Hexokinase 2 (HK2) protein, cyclin D1 (cyclin B1) and Notch signaling pathway-related proteins including notch receptor 1 (Notch1) and Hes family BHLH transcription factor 1 (Hes1). Results: PROZ was greatly down-regulated in HCC cells (HepG2 and Hep3B) in hypoxia condition. PROZ overexpression in HepG2 cell lines inhibited cell proliferation and glycolysis, and promoted apoptosis; PROZ knockdown worked oppositely. In terms of mechanism, PROZ inhibited the expression levels of cell cycle-related proteins, Notch1 and Hes1. Conclusions: PROZ inhibits HCC cell proliferation and glycolysis, and promotes apoptosis by inhibiting cell cycle and Notch signaling pathways. PROZ could be a potential biomarker/therapy target for HCC.