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Abstract Liver cancer has seen an increase in mortality rate over recent decades due to limited targeted therapies and growth in specific etiologies. Lenvatinib, a multi-TKI inhibitor, is used as a first-line therapy for liver cancer patients who cannot receive immunotherapy, which is a component of the current standard of care. Unfortunately, lenvatinib efficacy is short. Understanding why liver cancers become resistant and identifying interventions to restore sensitivity can help prolong the clinical efficacy of lenvatinib. A panel of 20 liver cancer lines was screened to identify four lenvatinib-sensitive lines. These lines were subsequently conditioned to grow under increasing lenvatinib concentrations to generate lenvatinib-resistant (LR) models. One such model, Hep3B LR, exhibited a stable resistance to lenvatinib for up to 12 weeks in culture. Hep3B LR showed cross-resistance to selective inhibitors of FGFR4 and FGFR1 but not of MAPK14 and PDGFR, suggesting that the resistance phenotype may result from FGFR dysfunction. Unlike parental Hep3B, Hep3B LR exhibited a 3. 4X increase in migration. Western blot detected an increase in pAKT, a survival marker. Additionally, proteins associated with cancer drug resistance were higher in Hep3B LR cells: Notch receptors and ligands, pStat3, and Axl. To identify means of overcoming lenvatinib resistance in Hep3B LR, a Cell-Titer Glo high-throughput assay was developed to measure the growth inhibition of candidate drugs in the presence and absence of lenvatinib. Preliminary results from the first 24 drugs screened reproduced known drug sensitivities associated with lenvatinib resistance (i. e. , MEK/ERK, EGFR, GPX4 inhibition) but also identified novel sensitivities to inhibition of PKMYT1 or γ-secretase, the latter a cleavage enzyme involved in Notch signaling activation. Validation of these candidate hits using a grid-based titration of both drugs showed additive growth inhibition of lenvatinib in combination with ERK, EGFR, or GPX4 inhibitors but not with PKMYT1 or γ-secretase inhibitors in resistant cells. Interestingly, EGFRi and lenvatinib were substantially synergistic in parental cells, suggesting that an upfront combination of these inhibitors could potentially be used before the emergence of lenvatinib resistance in liver cancer. We have established a lenvatinib-resistant liver cancer cell model and validated a drug screening assay to identify potential combinatorial therapies to overcome lenvatinib resistance in liver cancer. Citation Format: Kevin Chau, Martina S. McDermott, KeWei Gong, Dennis J. Slamon. High-throughput screening identifies potential combinatorial therapies to overcome lenvatinib resistance in liver cancer abstract. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts) ; 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84 (6Suppl): Abstract nr 4662.
Chau et al. (Fri,) studied this question.