Exploring the Prognostic Value and Biological Function of CPNE1 Gene in Hepatocellular Carcinoma
Authors: Su Jinfang , Huang Yongbiao , Wang Yali , Li Rui , Deng Wanjun , Zhang Hao , Xiong Huihua 
Published: September 2021

Abstract
BackgroundLiver hepatocellular carcinoma (LIHC), the major histology subtype of primary liver cancer, accounts for 70-80% proportion of total liver cancer cases. Copine1 (CPNE1), the first discovered CPNE1 family member, participates in the process of carcinogenesis and development of diverse tumors. Our study aimed to investigate the expression and prognostic value of CPNE1 gene in hepatocellular carcinoma (HCC), to explore its functional network in HCC and its effects on biological behaviors such as proliferation, migration and invasion of HCC cells, and to explore its related signaling pathways.METHODSHCCDB, CCLE and HPA online databases were used to explore the expression of CPNE1 gene in HCC tissues; LinkedOmics online database was used to analyze the co-expression network of CPNE1 in hepatocellular carcinoma, and gene set enrichment analysis (GSEA) was used for GO functional annotation, KEGG pathway enrichment analysis, kinase target enrichment, miRNA target enrichment and transcription factor target enrichment analysis. The expression levels of CPNE1 in normal hepatocytes and several hepatocellular carcinoma cell lines were detected by RT-qPCR, and finally HepG2 and MHCC-97H cells were selected to construct CPNE1 knockdown cell lines by transfection with siRNA, and the knockdown efficiency was detected by Western Blot and RT-qPCR. The effect of CPNE1 knockdown on the proliferation of hepatocellular carcinoma cells was examined by CCK8 assay and clone formation assay; the effect of CPNE1 knockdown on the migration ability of hepatocellular carcinoma cells was assessed by cell scratch assay and Transwell cell migration assay; finally, the expression of related signaling pathway proteins was examined by Western Blot. The correlation of CPNE1 expression with immune infiltration and immune checkpoint molecules in HCC tissues was analyzed using TIMER online database.RESULTSAnalysis in several databases showed that CPNE1 was highly expressed in HCC tissues and significantly correlated with sex, age, cancer stage and tumor grade. Overall survival (OS) was significantly lower in patients with high CPNE1 expression than in patients with low CPNE1 expression, and CPNE1 could be used as an independent prognostic indicator for HCC. GSEA analysis showed that co-expressed genes of CPNE1 were mainly involved in biological processes such as establishment of protein localization to membrane, ribonucleoprotein complex biogenesis and lipid localization. Q-PCR showed that CPNE1 expression was upregulated in HCC cells compared with normal hepatocytes, and knockdown of CPNE1 gene inhibited the AKT/P53 pathway, resulting in decreased proliferation, migration and invasion of HCC cells. The level of CPNE1 expression in HCC was significantly and positively correlated with the level of infiltration of B cells, CD8+ T cells, CD4+ T cells, macrophages, neutrophils, and dendritic cells (p<0.001), and with the expression of immune checkpoint molecules PDCD1, CD274, CTLA4, LAG3, HAVCR2, and TIGIT.CONCLUSION﻿The expression of CPNE1 was significantly higher in HCC tissues than in normal liver tissues, and high CPNE1 expression was associated with poor prognosis. Knockdown of CPNE1 inhibited AKT/P53 pathway activation and suppressed HCC cell proliferation and migration. There was a significant correlation between CPNE1 expression and tumor immune infiltration in HCC.