Parallel drug development strategies for fibrolamellar hepatocellular carcinoma and proteasome-dependent multiple myeloma

Fibrolamellar Hepatocellular carcinoma (FLC) is a rare liver cancer which occurs primarily in young adults and children under the age of 40. In FLC, a deletion of 400,000 base pairs occurs in one chromosome 19 copy, leading to the formation of a fusion protein comprised of a domain of the heat shock protein DNAJB1 and the catalytic subunit of Protein Kinase A (DNAJB1-PRKACA). Patients are typically asymptomatic at early stages, and 5-year survival remains below 50%. With surgery as the only partially effective treatment and no approved systemic therapies, there is a critical need for new therapeutics. The primary model compound of this project, Napabucasin, is a naphthoquinone natural product that has shown wide spectrum anti-cancer activities. Napabucasin was found to be a top hit in drug screening showing potency against FLC patient derived xenografts (PDX) models and direct-from-patient FLC tumor cells. Napabucasin is known to work in multiple signaling pathways including protein translation, the generation of reactive oxygen species, suppression of tumor cell stemness, and blocking tumor cell apoptotic escape. We anticipate the organic synthesis and development of optimized Napabucasin analogues, along with the evaluation of their cytotoxicity and proliferation effectiveness compared to the parent compound, Napabucasin, will result in compounds with improved bioavailability and efficacy, particularly in FLC model cell lines (Huh7-Chimera). In an additional approach to cancer drug development, we are evaluating the efficacy of promising next generation proteasome inhibitors. In eukaryotic cells, protein homeostasis is maintained through controlled synthesis and degradation, with the Ubiquitin Proteasome System (UPS) serving as the major pathway for regulated proteolysis. Cancer cells increase UPS activity to manage proteotoxic stress from rapid proliferation, leading to degradation of tumor-suppressive proteins and activation of oncogenic pathways. Targeted inhibition of UPS function causes accumulation of ubiquitinated proteins, G2/M arrest, and apoptosis, establishing the proteasome as a validated anticancer target. The 20S core of proteasome contains three catalytic beta subunits (beta1, beta2, beta5). Among all three, the chymotrypsin-like beta5 activity remains the primary driver of cytotoxicity for clinically approved inhibitors such as bortezomib, carfilzomib; however, their therapeutic use is limited by toxicity. Peptidic beta-lactones (the cystargolide family), are promising next-generation proteasome inhibitors. This project evaluates newly synthesized cystargolide analogs for cytotoxicity, bioavailability, and proteasome inhibition in RPMI-8226 myeloma cells. Using cell-based assays and IC₅₀ determination, we aim to establish structure activity relationships and advance optimized beta-lactone inhibitors with improved therapeutic potential.