Cooperation of Co-Amplified Genes in Hepatocellular Carcinoma

PROJECT 2: SUMMARY Hepatocellular carcinoma (HCC) is a highly fatal disease with an alarming increase in incidence and mortality. Obesity-induced non-alcoholic steatohepatitis (NASH) is a leading cause of HCC. Immune checkpoint inhibitors (ICIs) have been approved for HCC treatment, but patients with HCC and underlying NASH (NASH-

HCC) do not respond as well to ICIs. The lack of effective treatment for advanced HCC mandates that novel players regulating HCC be identified that might be targeted to develop effective combinatorial therapies. The oncogene MYC plays a key role in the development and progression of HCC, including NASH-HCC, and the

MYC gene is frequently amplified in HCC patients. TATA-box binding protein associated factor 2 (TAF2) gene shows the highest co-amplification with MYC. As yet, there are no studies analyzing the role of TAF2 in cancer, including HCC. Our preliminary studies unravel overexpression of TAF2 in human HCC and a significantly

strong negative correlation between TAF2 expression levels and HCC patient survival. In mouse liver, overexpression of MYC alone induced HCC with a variable degree; TAF2 alone did not induce tumors, but the combination of TAF2 and MYC generated robust HCC, indicating that these co-amplified genes cooperate to

promote aggressive HCC. Interaction was observed between MYC and TAF2, and RNA-sequencing revealed significant modulation of MYC-mediated gene regulation upon TAF2 overexpression. TAF2 knockdown in human HCC cells profoundly inhibited migration and invasion, and a hepatocyte-targeted nanoparticle delivering TAF2 siRNA inhibited mouse HCC allografts in syngeneic mice. Interestingly, knocking down TAF2

in human HCC cells conferred increased susceptibility to MYCi975, a specific MYC inhibitor that synergistically enhances ICI efficacy. Based on these findings, it is hypothesized that 1) as transcriptional regulators, MYC and TAF2 cooperate to promote HCC by inducing a global change in transcription, 2) TAF2 is required for the

maintenance of HCC, and 3) combined inhibition of MYC and TAF2 augments ICI therapeutic efficacy, thus serving as an efficient way to counteract HCC. These hypotheses will be interrogated by investigating the molecular mechanism by which MYC and TAF2 promote HCC and the role of TAF2 during HCC development

and progression using a conditional TAF2 knockout mouse, and by evaluating combined inhibition of MYC and TAF2 along with ICI as a therapeutic strategy in endogenous mouse models of HCC and NASH-HCC. This proposal is innovative and has important mechanistic and translational significance with the potential to affect

survival for scores of patients with HCC.