Abstract
Liver cancer comprises a group of malignant tumors, among which hepatocellular carcinoma (HCC) and intrahepatic cholangiocarcinoma (ICC) are the most common. ICC is especially pernicious and associated with poor clinical outcome. Studies have shown that a subset of human ICCs may originate from mature hepatocytes. However, the mechanisms driving the trans-differentiation of hepatocytes into malignant cholangiocytes remain poorly defined. We adopted lineage tracing techniques and an established murine hepatocyte-derived ICC model by hydrodynamic injection of activated forms of AKT (myr-AKT) and Yap (YapS127A) proto-oncogenes. Wild-type, Notch1flox/flox, and Notch2flox/flox mice were used to investigate the role of canonical Notch signaling and Notch receptors in AKT/Yap-driven ICC formation. Human ICC and HCC cell lines were transfected with siRNA against Notch2 to determine whether Notch2 regulates biliary marker expression in liver tumor cells. We found that AKT/Yap-induced ICC formation is hepatocyte derived and this process is strictly dependent on the canonical Notch signaling pathway in vivo. Deletion of Notch2 in AKT/Yap-induced tumors switched the phenotype from ICC to hepatocellular adenoma-like lesions, while inactivation of Notch1 in hepatocytes did not result in significant histomorphological changes. Finally, in vitro studies revealed that Notch2 silencing in ICC and HCC cell lines down-regulates the expression of Sox9 and EpCAM biliary markers. Notch2 is the major determinant of hepatocyte-derived ICC formation in mice.
Highlights
IntroductionThese authors contributed : Jingxiao Wang and Mingjie Dong
These authors contributed : Jingxiao Wang and Mingjie DongElectronic supplementary material The online version of this article contains supplementary material, which is available to authorized users.Primary liver cancer is the second most common cause of cancer mortality in the world, with increasing incidence globally [1, 2]
By adopting lineage tracing technology [6], we show that AKT/Yapinduced intrahepatic cholangiocarcinoma (ICC) formation is hepatocyte derived and this process depends on the canonical Notch signaling pathway
Summary
These authors contributed : Jingxiao Wang and Mingjie Dong. Primary liver cancer is the second most common cause of cancer mortality in the world, with increasing incidence globally [1, 2]. Hepatocellular carcinoma (HCC) and intrahepatic cholangiocarcinoma (ICC) are the two most prevalent liver tumor types. Most ICCs are diagnosed at advanced stage and only a few patients are suitable for surgery at the time of diagnosis. 3 307 Hospital of Academy of Military Medical Science, Beijing, China. EYFP was only expressed in hepatocytes, while surrounding mesenchymal cells did not show red fluorescence. Tumor is labeled as T and non-tumor is labeled as NT.
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