Targeting HDAC11 to combat hepatocellular carcinoma and regulate alternative RNA splicing

PROJECT SUMMARY Liver cancer incidence and mortality continue to rise, and new therapeutic targets are needed. This fellowship application will explore how the enzyme histone deacetylase eleven (HDAC11) drives liver cancer, and tests HDAC11 as a potential new target for therapy. HDAC11 acts primarily as a lysine fatty acid (KFA)

hydrolase, an enzyme that removes fatty acids from proteins (de-KFA). HDAC11 is expressed at low levels in most healthy tissues, but is increased in liver cancer, and high levels are significantly correlated with poor patient outcomes. Proteomic studies have implicated HDAC11 in alternative mRNA splicing, which is prevalent

in most cancers. The overall goal of this application is to understand the role of HDAC11 in liver cancer and assess the potential of new, highly specific HDAC11 small molecule inhibitors. In two aims, this application will test the hypothesis that HDAC11 promotes hepatocellular carcinoma through de-KFA of the splicing factor

SF3B2, and that inhibiting HDAC11 will block hepatocellular carcinoma progression. In Aim 1, SF3B2 will be authenticated as an HDAC11 substrate in established hepatocellular carcinoma cell lines using a click chemistry-based approach. Preliminary data confirms the feasibility of this technique and establishes that

SF3B2 can be lysine fatty acylated. Proposed studies will test if HDAC11-mediated de-KFA of SF3B2 changes its nuclear localization, thereby changing its ability to regulate RNA splicing in the nucleus and resulting in alternative mRNA expression. To detail the alternative splicing outcomes driven by HDAC11, mRNA isoform

specific long read sequencing will be conducted. The abundance of isoform specific alternative mRNAs in HDAC11 wild type versus knockout and inhibitor-treated liver cancer will be quantified. In Aim 2, HDAC11 specific small molecule inhibitors will be tested to establish HDAC11 inhibition as a potential cancer treatment

approach. Preliminary data show that HDAC11 inhibition specifically decreases colony formation and increases drug sensitivity, leading to the inference that HDAC11 may promote cancer cell stemness characteristics such as self-renewal and drug resistance. Oncogenesis in vivo will be tested following wildtype, knockout, and

inhibitor treatments with disease progression monitored by luminescence imaging. This study will provide new knowledge on the molecular functions of HDAC11 in alternative mRNA splicing and liver cancer progression, and evaluate clinically-relevant small molecule inhibitors for potential liver cancer treatment. Completion of the

proposed project will develop necessary research and professional skills that are essential for a career as a cancer investigator.