Abstract 4367: PTEN/AKT signal promotes cholangiocyte fate in liver tumorigenesis by inducing SOX9 overexpression and crosstalk with Notch activation

Abstract Cholangiocarcinoma (CCA) is the second most dominant primary liver malignancy next to hepatocellular carcinoma (HCC), and among the most mortal among human cancers. The PI3K/AKT signaling pathway was considered a permissive signal for the development of CCA. To explore how the PI3K/AKT signal contributes to CCA development, we deleted Pten, the lipid phosphatase that negatively regulates the PI3K/AKT signal in the liver. The Lv-PTEN (PtenloxP/loxP; Alb-Cre+) mice developed a mixed HCC and CCA tumor phenotype with all mice developing CCA by 12-month age. Treatment of Lv-PTEN mice with DDC at 3 months to obstruct the bile duct leads to an earlier CCA oncogenesis. Deletion of Akt2 in the Lv-PTEN mice (Lv-DM, Akt2loxP/loxP; PtenloxP/loxP; Alb-Cre+) significantly attenuates tumor development. Compared with the Lv-PTEN mice, loss of AKT2 in Lv-DM mice robustly and significantly reduced the expression of SOX9, a cholangiocyte gene. This data suggests that the AKT signal may permit a cholangiocyte fate by inducing SOX9 expression. Supporting the role of PTEN/AKT in permitting a cholangiocyte fate, SOX9 expression is also induced in the livers of mice where Pten deletion is targeted to the hepatocytes via injection of AAV8-TGB-Cre (Hp-PTEN, PtenloxP/loxP; R26RYFP; AAV8-TBG-Cre). Similar to the Lv-PTEN mice, treatment with DDC induced early onset of CCA development in the Hp-PTEN mice. We next explore Notch signal for its crosstalk with PTEN loss that permits CCA development. Notch signal is robustly induced in the tumors of the Lv-PTEN mice and induced with DDC treatment in both Lv-PTEN and Hp-PTEN livers. We showed that exposure to Jag1 ligand-coated extracellular matrix or expression of NICD also induced the expression of SOX9 while DAPT time-dependently attenuated the expression of SOX9. In the Hp-Pten mice treated with DDC, inhibiting the Notch pathway with DAPT attenuated ductal reaction and led to downregulation of SOX9 in the Lv-PTEN livers, suggesting a positive regulatory role of Notch on SOX9. These data support that Notch activation regulates SOX9 and collaborates with PTEN loss to drive cholangiocyte fate and CCA development. Citation Format: Qi Tang, Jingyu Chen, Ni Zeng, Lina He, Shefali Chopra, Diala Alhousari, Phillip Nguyen, Guo Zhang, Bangyan L. Stiles. PTEN/AKT signal promotes cholangiocyte fate in liver tumorigenesis by inducing SOX9 overexpression and crosstalk with Notch activation abstract. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts) ; 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84 (6Suppl): Abstract nr 4367.