Abstract 5874: Phenotypic plasticity of TKI resistance reprograms cytoskeleton organization through cadherin-catenin and integrin pathways

The acquired resistance to EGFR tyrosine kinase inhibitors (TKIs) restricts its clinical utility. Clinically, acquired resistance has been highly associated with epithelial-mesenchymal transition (EMT) traits. In this study, we characterized shared phenotypic plasticity features of TKI-resistant cells and aimed to find its key driver in three different cell lines harboring mutant EGFR. In vitro resistance cell lines were generated by dose-escalation exposure to osimertinib, a 3rd generation TKI, for more than 2 months. We employed canonical markers (E-cadherin, vimentin, pan-cytokeratin, and N-cadherin) along with additional markers (EpCAM and fibronectin) to define the EMT status of resistant cells. Moreover, cytoskeleton architecture (F-actin and Vimentin) was utilized to clarify the types of cell motility. Transcriptomics analysis illustrated enriched pathways at focal adhesion and adherens junction. Loss of adherens junction-related catenin (α-E-catenin, β-catenin, γ-catenin, p120 catenin) and aberrant activation of focal adhesion-related protein (p-FAK Y397 and Y576/57, p-Src Y416) confirmed the transcriptomics analysis of reduced contact inhibition and cell polarity. The resulting migration mode of resistant cells highly resembles ameboid movement. Mechanistically, we identified that YTHDF3, a metastasis-promoting regulator of mRNA methylation, destabilizes the mRNA of E-cadherin. Depletion of YTHDF3 in resistant cells reversed the cadherin-catenin pathway and distribution of vimentin and f-actin. In conclusion, resistant cells display ameboid-like movement resulting from loss of contact inhibition and aberrant activation of focal adhesion. Mechanistically, we identified that YTHDF3, a metastasis-promoting regulator of mRNA methylation, destabilizes the mRNA of E-cadherin. Depletion of YTHDF3 in resistant cells reversed the cadherin-catenin pathway and distribution of vimentin and f-actin. YTHDF3 serves as an RNA epitranscriptomic regulator that destabilizes CDH1 mRNA, thereby disrupting adherens junction formation and reducing integrin-mediated focal adhesion stabilization. Citation Format: Chun Ma, Jerry Chieh-Yu Chen, Mong-Lien Wang. Phenotypic plasticity of TKI resistance reprograms cytoskeleton organization through cadherin-catenin and integrin pathways [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(6_Suppl):Abstract nr 5874.