Abstract 4673: DCLK1 promotes hepatocellular carcinoma via atypical β-catenin-regulated signaling and immune suppression

Abstract

Abstract Introduction: Genetic lineage tracing in mouse model has revealed that mature hepatocytes are the cell of origin of injury-induced hepatocellular carcinoma (HCC), the second most common cause of cancer-related deaths worldwide. Hepatocyte plasticity, defined as the ability to change cellular identity, plays a critical role in the repair process following liver injury. Inflammatory liver diseases often lead to cirrhosis and HCC. The molecular mechanisms that regulate the decision between hepatocyte injury repair and neoplastic initiation are unclear. Doublecortin-like kinase 1 (DCLK1), a microtubule-associated kinase, is expressed during liver injury, cirrhosis, and HCC, but not in normal liver. Here, we demonstrate a novel mechanism by which DCLK1 regulates injury-associated hepatocyte plasticity and immunosuppression in HCC. Methods: Cell culture, DEN/CCl4-induced injury in mouse livers, and humanized mouse model were used for analyzing hepatocyte plasticity and DCLK1+ cells-induced changes in hepatic cells and macrophages. Results: DCLK1-overexpressing primary human hepatocytes formed spheroids in 3D culture. DCLK1-overexpressing hepatoma cells exhibited a 48-kDa active β-catenin with preserved hypophosphorylated N-terminus, which interacted with TCF-4, resulting in enhanced luciferase reporter activity and cyclin D1 expression. Downregulation of DCLK1 using siRNAs inhibited expression of this β-catenin fragment. DCLK1 overexpression increased phosphorylation of GSK-3β at Ser9, thus preventing its complete proteasomal degradation. Liver tissues from patients with cirrhosis and HCC expressed the 48-kDa active β-catenin, DCLK1, cyclin D1, and 80-kDa E-cadherin ectodomain, suggesting a change in epithelial polarity. DCLK1-overexpressing primary human hepatocytes transplanted into FRG mice demonstrated β-catenin activation in the transplanted hepatocytes. Injury-induced DCLK1+ epithelial cells in mouse livers expressed PD-L1. DCLK1+ human hepatoma cells induced CD206 in macrophages in a dual co-culture assay. Conclusions: DCLK1 enhances hepatocyte plasticity, clonogenicity, and tumorigenic signaling via atypical β-catenin-dependent mechanism. DCLK1+ cells show ability to suppress the host anti-tumor immunity by expressing PD-L1 and inducing macrophage polarization. Citation Format: Naushad Ali, Parthasarathy Chandrakesan, Michael S. Bronze, Courtney W. Houchen. DCLK1 promotes hepatocellular carcinoma via atypical β-catenin-regulated signaling and immune suppression [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 4673.