Hepatocellular carcinoma (HCC) is one of the few cancers that continues to rise in incidence and fatalities each year and will soon be the second leading cause of cancer deaths in the US. Overall response rates to current HCC drugs remain low, highlighting the need for more effective and targeted therapeutics to treat this cancer type. Although HCC has been characterized as genetically heterogeneous, several key drivers of the disease have been identified. Notably, mutations in β-catenin (encoded by CTNNB1), occur in ~30% of cases and are of therapeutic interest as these mutations are necessary for cancer growth. However, the upregulated β-catenin pathway in these tumors has thus far remained undruggable. Given the lack of selective and mutant specific CTNNB1 inhibitors or known drug targets without significant on-target toxicity for the Wnt/β-catenin pathway, Arvin Dar and Ernesto Guccione sought to identify small molecules that displayed specific cancer cell-toxicity in models of mutant CTNNB1. Through chemical genetic screens in tumor organoids, they identified a selective antagonist of CTNNB1-mutant HCC, which they named WNTinib, that is effective in vivo and in human-derived model systems.
In this ASPIRE award, Dar and Guccione will work to identify the mechanism of action of WNTinib; in particular, they will identify both the targets and anti-targets of the compound. They will use two complementary approaches; one based on genetic and functional screens, and a second based on chemical proteomics combined with biophysical approaches to measure drug-target engagement in vivo. These studies will employ a library of WNTinib analogs, chemical probes that will be used to enrich direct targets, and detection methods for the identification of specific binders. The integration of such data with functional genetic screens will provide deep mechanistic insights into WNTinib and its precise mode of action. Ultimately, the approaches that they will use to advance target and anti-target discovery could be applied to any compound of interest, allowing for broad utility and impact.