CASK regulates Notch pathway and functions as a tumor promoter in pancreatic cancer.

Calcium/calmodulin-dependent serine protein kinase (CASK), a member of membrane-associated guanylate kinase (MAGUK) super-family, is implicated in regulating cell proliferation, cytoskeletal remodeling, and cell metastasis. Our study aimed to investigate the effect of CASK on the malignant behaviors of pancreatic cancer cells and to determine the signaling pathway involved. CASK expression in pancreatic cancer tissues based on the TCGA database was analyzed using GEPIA online tool. The overall survival (OS) and disease-free survival (DFS) in patients with pancreatic cancer based on CASK expression was also analyzed using GEPIA. KEGG pathway enrichment analysis was used to show the association of 1522 CASK-related genes and signaling pathways. The expression of CASK, Notch1 and Hey1 was detected by Western blot. Cell proliferation, colony number, invasion, and apoptosis were detected by CCK-8, colony formation assay, Transwell invasion assay, and flow cytometry analysis, respectively. Results showed that CASK was upregulated in pancreatic cancer tissues and cells. Pancreatic cancer patients with high CASK expression showed shorter OS and DFS than patients with low CASK expression. KEGG pathway enrichment analysis proved that CASK and 1522 CASK-associated genes were primarily associated with the Notch pathway. CASK silencing inhibited cell proliferation, colony formation ability, and invasion and elicited apoptosis in pancreatic cancer cells. Additionally, we confirmed that CASK silencing inhibited the Notch pathway in pancreatic cancer cells. Overexpression of Notch1 resisted the anti-tumor functions of CASK knockdown in pancreatic cancer cells. In conclusion, CASK knockdown suppressed the malignant behaviors of pancreatic cancer cells by inactivating the Notch pathway.