Expression patterns of claudins in cancer.

Claudins are four-transmembrane proteins, which were found in tight junctions. They maintain cell barriers and regulate cell differentiation and proliferation. They are involved in maintaining cellular polarity and normal functions. Different claudins show different expression patterns. The expression level and localization of claudins are altered in various cancers. They promote or inhibit proliferation, invasion, and migration of cancer cells through multiple signaling pathways. Therefore, claudins may serve as diagnostic markers, novel therapeutic targets, and prognostic risk factors. The important roles of claudins in cancer aroused our great interest. In the present review, we provide a summary of insights into expression patterns of claudins in cancer, which is more comprehensive and provides new ideas for further research.

Correlation of Claudin18.2 expression with clinicopathological characteristics and prognosis in gastric cancer.

OBJECTIVES: Claudin18.2 (Cldn18.2) is a tight junction protein expressed in gastric epithelial cells and is an emerging target for gastric cancer (GC). This study aimed to analyze the correlation between Cldn18.2 and clinicopathological parameters in GC patients undergoing radical surgery. METHODS AND RESULTS: This study included 426 GC patients who underwent radical gastrectomy. The expression of Cldn18.2 was analyzed by immunohistochemical staining and grading. The statistical results indicated that the expression of Cldn18.2 was correlated with T stage, TNM stage, Lauren classification, and the expression level of Mucin-2 (MUC2), Mucin-5AC (MUC5AC), Mucin-6 (MUC6), human epidermal growth factor receptor 2 (HER2), P53 and trefoil factor 2 (TFF2). In addition, through data mining of the Cancer Genome Atlas (TCGA) database, it is suggested that Cldn18.2 expression level is significantly correlated with the expression level of MUC5AC, MUC6, and TFF2. Besides, Cldn18.2 is related to tumor immune infiltration, programmed cell death protein 1 (PD 1) pathway, cell cycle and Wnt signaling pathway. CONCLUSIONS: The expression of Cldn18.2 was closely related to gastric-type GC, so gastric-type GC patients may benefit more from targeted drugs targeting Cldn18.2. In GC cells, depletion of Cldn18.2 may influence cell cycle and immune response by affecting Wnt signaling pathway and PD 1 pathway.