Abstract LB035: Targeting cytoplasmic condensates in the stress response of cancer cells

Abstract RNA-binding proteins (RBPs) constitute a large and diverse class of proteins (>1400 human proteins) that control RNA metabolism and function. RBPs bind sequence and/or structural motifs in single- or double-stranded RNA using RNA-binding domains (RBDs) to assemble ribonucleoprotein (RNP) complexes. RNPs regulate gene expression and non-coding RNA (ncRNA) function by organizing RNA-protein networks affecting the biogenesis, transport, translation, and degradation of bound RNAs. RNPs known as processing-bodies (P-bodies) and stress granules (SGs) form cytoplasmic membraneless condensates to compartmentalize cellular processes that facilitate survival of cancer cells in the tumor microenvironment and mediate resistance to anticancer treatments. The composition and dynamic regulation of RNPs and how these molecular features of RNA granules are regulated to promote cancer cell adaptation and progression remains poorly understood. Perturbing RBPs is a viable path towards RNP pharmacology but small molecules for this ‘undruggable’ class of proteins are currently lacking. Here, we described utilization of sulfonyl-triazoles (SuTEx chemistry) for disruption of cytoplasmic condensate through covalent binding of tyrosines to enable pharmacology of RNP function in cancer cells. A chemoproteomics platform founded on SuTEx chemistry was deployed for chemical biology and therapeutic investigation of P-bodies and SGs. Key findings to be presented include: (i) establishing a SuTEx-enabled screening platform for accessing ligandable tyrosine (Y)/lysine (K) residues in stressed cancer cells, (ii) identification of a set of SuTEx ligands capable of preventing or inducing SG and P-body formation in stressed cells, (iii) Discovery of a SuTEx ligand for the hyper-reactive EDC3 Y475 site for P-body modulation and (iv) validation of G3BP1 Y40 as a ligandable site that can disrupt arsenite-induced SG formation in cells. We will also describe unpublished work on efforts to advance discovery of new condensate modulators using global proteomic methods. Collectively, we describe a tractable means to reveal and ultimately target cancer vulnerabilities by disrupting tumor-specific stress coping mechanisms found in dynamic cellular compartments for therapeutic translation. Citation Format: Ku-Lung Hsu, Anthony M. Ciancone, Kyung W. Seo, Miaomiao Chen, Adam L. Borne, Adam H. Libby, Dina L. Bai, Ralph E. Kleiner. Targeting cytoplasmic condensates in the stress response of cancer cells [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 2 (Late-Breaking, Clinical Trial, and Invited Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(7_Suppl):Abstract nr LB035.