ABSTRACT
@#[Abstract] Objective: To investigate the expression of tight junction protein claudin-7 (CLDN-7) in pancreatic cancer and its correlation with the clinicopathological features and prognosis of pancreatic cancer patients. Methods: Oncomine, GEPIA and GEO databases were used to comprehensively analyze the mRNA expression level of CLDN-7 in pancreatic cancer, and Kaplan-Meier Plotter database was used to analyze the relationship between the expression of CLDN-7 and the survival prognosis of pancreatic cancer patients. Immunohistochemical staining was used to detect the protein level of CLDN-7 in 44 cases of pancreatic cancer tissues and 31 cases of para-cancerous tissues resected in the Department of General Surgery of the Second Hospital of Lanzhou University from 2015 to 2018, and the relationship between CLDN-7 expression and clinicopathological characteristics and prognosis of patients was also analyzed. GO (Gene Ontology) analysis and KEGG (Kyoto Encyclopedia of Genes and Genomes) pathway enrichment analysis were conducted to analyze the possible signaling pathways that CLDN-7 may involve in and their main functions, which were further verified in TCGA and GEPIA databases. Results: Analysis of both the databases and the clinical samples showed that CLDN-7 was significantly over-expressed in pancreatic cancer tissues, and its high expression was correlated with clinical prognosis of pancreatic cancer patients; moreover, CLDN-7 expression was an independent factor affecting the overall survival time of pancreatic cancer patients (all P<0.05). GO analysis and KEGG pathway enrichment analysis confirmed that CLDN-7 was involved in DNA damage repair and glucose metabolism in pancreatic cancer patients. TCGA and GEPIA database validation showed that CLDN-7 expression in pancreatic cancer was significantly and positively correlated with the expression of DNA damage repair related genes (POLD4, SMUG1, NTHL1) and glucose metabolism related genes (ALDOA, TALDO1, PGLS) (all P<0.01). Conclusion: CLDN-7 is highly expressed in pancreatic cancer and indicates a worse clinical prognosis; moreover, CLDN-7 is associated with DNA damage repair and intratumoral glucose metabolism in pancreatic cancer.