Abstract 327: MARK2/MARK3/MARK4 kinases are therapeutic targets for human head and neck squamous cell carcinoma with co-dependencies of YAP-TEAD pathway.

Abstract Background: Head and neck squamous cell carcinoma (HNSCC) requires the identification of new therapeutic targets to improve treatment outcomes. This study investigated the biological significance of Microtubule Affinity-Regulating Kinases (MARKs), a family of serine-threonine kinases that regulate microtubule-associated proteins (MAPs). Because MARK activity influences cell structure, intracellular transport, and proliferation, these kinases may represent promising therapeutic targets. Materials and Methods: Protein expression levels of MARK family genes were evaluated in 20 human HNSCC cell lines. Cisplatin and docetaxel-resistant models were established by gradually escalating cisplatin and docetaxel concentrations up to 4 μM and 15 nM, respectively in CA9-22 and YD-8 cells. Cell viability was determined using WST assays. CRISPR/Cas9 genome editing was employed to generate MARK2/3/4 knockout cell lines. In addition, the anticancer efficacy of several newly developed MARK2/3/4 hits was assessed. Results: MARK2/3/4-knock-out cells demonstrated significantly reduced proliferation and impaired matrigel invasion compared with wild-type controls. MARK kinase loss was associated with suppression of the MAPK- and PI3K-AKT signaling pathways. Because MARK proteins are known to interfere with MST/SAV and LATS complex formation through phosphorylation-dependent mechanisms, we further showed that MARK4 depletion reduced nuclear YAP/TAZ localization and decreased expression of YAP/TEAD transcriptional targets. Collaborative screening identified multiple candidate molecules for MARK-specific inhibition at the hit-compound stage; notably, one lead compound exhibited strong antiproliferative activity in HNSCC cells, including cisplatin-resistant models. Conclusions: MARK proteins function as negative regulators of the HIPPO kinase cascade, thereby enhancing YAP/TAZ oncogenic activity in HNSCC. Loss of MARK function reduces tumorigenic phenotypes, supporting MARKs as promising therapeutic targets for future drug development. Citation Format: Se Eung Oh, Hwan Jung Lim, Seong Jun Park, Sang Uk Han, Jee Hung Kim, Seo Young Lee, Hei-Cheul Jeung. MARK2/MARK3/MARK4 kinases are therapeutic targets for human head and neck squamous cell carcinoma with co-dependencies of YAP-TEAD pathway abstract. In: Proceedings of the American Association for Cancer Research Annual Meeting 2026; Part 1 (Regular Abstracts); 2026 Apr 17-22; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2026;86(7 Suppl):Abstract nr 327.