Heterogeneous liver cancer development promoted by PTEN regulated beta-catenin and SOX9 signal Jingyu Chen, Ni Zeng, Anketse Debebe, Taojian Tu, Lina He and Bangyan Stiles Pharmacology and Pharmaceutical Sciences, University of Southern California, School of Pharmacy, Los Angles, CA90089 Liver cancer is a heterogeneous group of malignancies that include hepatocellular carcinoma (HCC) and intrahepatic cholangiocyte carcinoma (iCCA) as the two most common types. The high degree of heterogeneity in liver cancer presents a significant challenge to therapeutic interventions. We studied liver cancer heterogeneity in mouse models lacking PTEN (phosphatase and tensin homologue deleted on chromosome 10) in different liver cell types. The tumor suppressor, PTEN, is under expressed in up to 70% of liver cancers due to LOH or miRNA regulation in addition to mutations. Heterogeneous HCC and iCCA composed of mixed lineage cells are observed when PTEN is lost regardless if the deletion is targeted to hepatocytes, cholangiocytes or both. In these models, we showed that steatosis is required to establish the niche for tumor growth. Steatosis promotes the upregulation of Wnt and well as Notch signals in the tumor environment. Blocking steatosis reduces both Wnt and Notch signals in these mice. We explored the role Wnt/beta-catenin signal using inhibitor for beta-catenin transcriptional activity and discovered that blocking b-catenin transcriptional activity attenuate the growth of tumors and reduces TIC populations in this context of steatosis driven tumors. In addition, we found that Notch signal leads to upregulation of SOX9 (Sex determining region Y-box9). As beta-catenin was reported to bind to SOX9 and leads to its degradation. Our observation suggests that PTEN loss disrupts this relationship and leads to concurrent upregulation of beta-catenin and SOX9. This concurrent upregulation of Wnt/beta-catenin and Notch/Sox9 may be necessary for tumor transformation regulated by PTEN tumor suppressor and steatosis.