ß-catenin deficiency in hepatocytes aggravates hepatocarcinogenesis driven by oncogenic ß-catenin and MET.

ABSTRACT

Both activating and inactivating mutations in catenin ß1 (ctnnb1), which encodes ß-catenin, have been implicated in liver tumorigenesis in humans and mice, although the underlying mechanisms are not fully understood. Herein, we show that deletion of endogenous ß-catenin in hepatocytes aggravated hepatocellular carcinoma (HCC) development driven by an oncogenic version of ß-catenin (CAT) in combination with the hepatocyte growth factor receptor MET proto-oncogene receptor tyrosine kinase (MET). Although the mitogenic signaling and cell cycle progression was modestly impaired after CAT/MET transfection, the ß-catenin-deficient livers displayed changes in transcriptomes, increased DNA damage response, expanded Sox9+ cells, and up-regulation of protumorigenic cytokines, including interleukin-6 and transforming growth factor ß1. These events eventually exacerbated CAT/MET-driven hepatocarcinogenesis in ß-catenin-deficient livers, featured by up-regulation of extracellular signal-regulated kinase (Erk), protein kinase B (Akt), and Wnt/ß-catenin signaling and cyclin D1 expression. The resultant mouse tumors showed similar transcriptomes to human HCC samples with concomitant CTNNB1 mutations and MET overexpression. CONCLUSION: These data argue that while dominantly activating mutants of ß-catenin are oncogenic, inhibiting the oncogenic signaling pathway generates a pro-oncogenic microenvironment that may facilitate HCC recurrence following a targeted therapy of the primary tumor. An effective therapeutic strategy must require disruption of the oncogenic signaling in tumor cells and suppression of the secondary tumor-promoting stromal effects in the liver microenvironment. (Hepatology 2018;671807-1822).