Hbx/Il-6/Stat3 Signaling in Oct4 Protein Stability and Cancer Stemness Properties in Hbv-Related-Hcc: the Role of Senp1 and Its Clinical Impact

The molecular pathogenesis of hepatocellular carcinoma (HCC) is heterogeneous with diverse etiologies and complex signal activation. Chronic hepatitis B virus (HBV) hepatitis is highly associated with HCC development that continues to be a great challenge in clinical practice. However, the lacking of effective individual targeting on HBV-related HCC dramatically hindered the therapeutic efficacy. The cancer stemness properties are associated with poor prognosis, metastasis, recurrence and treatment resistance. OCT4 is a pluripotent regulator which closely associated with cancer stemness, including recurrence and drug resistance in HCC. Hepatitis B Virus X protein (HBx) was been reported to induce cancer stemness properties, such as up-regulation OCT4 and NANOG protein levels, in HCC but with unclear mechanism. Unraveling the molecular mechanisms of HBx-derived cancer stemness in HBV-related HCC tumorigenesis will be of crucial importance in clinical therapeutic targeting on drug resistance and HCC early recurrence. We have previously demonstrated an important role of the SUMO1 (the small ubiquitin-like modifier) peptidase, SENP1, in stabilizing OCT4 protein stability and regulating the drug resistance in human embryonic carcinoma cells (2012, Cancer Research). Our previous studies showed that a positive correlation of inflammatory cytokine IL-6 and OCT4 expression. The highly expression of OCT4 is correlated with short disease-free survival (DFS) and poor prognosis, especially in HBV-related HCC (2015, Clinical Cancer Research). Our extension studies showed a high positive correlation between OCT4 and SENP1 expressions in human HCC tissues. Furthermore, the expression level of OCT4 protein in HCC cells was reduced when silencing SENP1 expression in vitro. However, the regulatory mechanism of SENP1 is unclear. As SENP1 has been hypothesized to be a regulator for OCT4 protein, thus this proposal aims to identify that HBx regulate SENP1 expression through IL-6/STAT3 signaling pathway and the role of HBx-induced SENP1 in cancer stemness properties through OCT4 regulation in HBV-related HCC. Results in basic research will be correlated the clinical significance and prognosis of HCC patients. Findings in this research will not only identify the molecular mechanism for HBV-induced cancer stemness properties through SENP1 regulation in HBV-related HCC but also facilitate clinical targeting on individual therapy against this intractable cancer. Three specific aims will be addressed: Aim 1: To identify the role of HBx in OCT4 protein stability through SENP1 regulation and cancer stemness-related properties in HBV-related HCC. Aim 2: To examine the mechanisms of HBx-IL-6/STAT3 signaling pathway in SENP1 expression and OCT4 protein stability in HBV-related HCC. (using a HBx-GFP or an active form STAT3Y640F overexpression HCC cells in vitro cell model and in vivo mouse model). Aim 3: To verify the clinical association of serum IL-6 levels, SENP1, OCT4, EMT regulators, drug resistance factors, and tumor early recurrence of HBV-related HCC (using HCC serum samples, tissue microarrays, and frozen samples)