Simultaneous activation of Kras–Akt and Notch pathways induces extrahepatic biliary cancer via the mTORC1 pathway.

Biliary tract cancer (BTC) has poor prognosis. The Notch receptor is aberrantly expressed in extrahepatic cholangiocarcinoma (eCCA). However, the role of Notch signaling in the initiation and progression of eCCA and gallbladder (GB) cancer remains unknown. Therefore, we investigated the functional role of Notch signaling during tumorigenesis of the extrahepatic bile duct (EHBD) and GB. Activation of Notch signaling and oncogenic Kras resulted in the development of biliary intraepithelial neoplasia (BilINs) in the EHBD and GB, which were premalignant lesions that progressed to adenocarcinoma in mice. The expression of genes involved in the mTORC1 pathway was increased in biliary spheroids from Hnf1b‐CreERT2; KrasLSL‐G12D; Rosa26LSL‐NotchIC mice and inhibition of the mTORC1 pathway suppressed spheroid growth. Additionally, simultaneous activation of the PI3K–AKT and Notch pathways in EHBD and GB induced biliary cancer development in mice. Consistent with this, we observed a significant correlation between activated NOTCH1 and phosphorylated Ribosomal Protein S6 (p‐S6) expression in human eCCA. Furthermore, inhibition of the mTORC1 pathway suppressed the growth of Notch‐activated human biliary cancer cells in vitro and in vivo. Mechanistically, the Kras/Notch–Myc axis activated mTORC1 through TSC2 phosphorylation in mutant biliary spheroids. These data indicate that inhibition of the mTORC1 pathway could be an effective treatment strategy for Notch‐activated human eCCA. © 2023 The Pathological Society of Great Britain and Ireland. [ABSTRACT FROM AUTHOR]