RNA sequencing of Cd44-positive and Cd44-negative livers  isolated from Nf2 - mutant mice
Primary liver cancer is the third leading cause of cancer related death worldwide. An increasing body of evidence suggests that the Hippo tumor suppressor pathway plays a critical role in restricting cell proliferation and determining cell fate during physiological and pathological processes in the liver. Merlin (Moesin-Ezrin-Radixin-likeprotein), encoded by the NF2 (neurofibromatosis type 2) gene is an upstream regulator of the Hippo signaling pathway. Targeting of Merlin to the plasma membrane seems to be critical for fulfilling its major tumor-suppressive functions; this is facilitated by interactions with membrane-associated proteins, including CD44 (clusterofdifferentiation44). Indeed, mutations within the CD44-binding domain of Merlin were reported in many human cancers. In this study, we evaluated the relative contribution of CD44- and Merlin-dependent processes to the development and progression of liver tumors. To this end, mice with liver-specific deletion of the Nf2 gene were crossed with Cd44-deleted mice, and subjected to extensive histological, biochemical and molecular analyses. In addition, cells were isolated from mutant livers and subjected to in vitro assays. Deletion of Nf2 in the liver led to substantial liver enlargement and generation of hepatocellular carcinomas (HCCs), intrahepatic cholangiocarcinomas (iCCAs) as well as mixed hepatocellular cholangiocarcinomas. Deletion of Cd44 had no influence on liver size or primary liver tumor development but it significantly inhibited metastasis formation in Nf2-mutant mice. CD44 upregulates expression of integrin ß2 and promotes transendothelial migration of liver cancer cells which may facilitate metastatic spreading. Altogether, our results suggest that CD44 may be a promising target for interfering with metastatic spreading of liver cancer. Overall design: 6 samples in total: 3 samples CD44+/+, 3 samples CD44-/-