Abstract 848: Inhibition of RTK fusion condensates enhances signal perception and promotes drug tolerance

Abstract

Abstract Drug resistance remains a significant obstacle in the successful treatment of cancer, highlighting the critical need to understand how oncogenes and cancer drugs impact cell physiology and resistance development. EML4-ALK is a receptor tyrosine kinase (RTK) fusion oncogene that drives 3-7% of lung cancer. Despite potent ALK inhibitors, EML4-ALK+ cancers frequently develop resistance during therapy. Recently, it was discovered that EML4-ALK and other RTK fusions form cytoplasmic protein condensates, and that condensate formation was required for oncogenic signaling. However, whether oncogenic condensates play a role in drug responses is unclear. In this study, we applied an optogenetic technique called ‘functional profiling’ to understand how EML4-ALK condensates impact cell signal transmission and drug response. Using light-stimulated RTKs, we found that EML4-ALK condensates strongly suppress signaling through transmembrane RTKs, including through EGFR, a central receptor in resistance development. Strikingly, treatment with ALK inhibitors (ALKi) rapidly restored and hypersensitized RTK signaling. We found that EML4-ALK condensates suppress RTK signals through sequestration of the downstream adapter Grb2, which is essential for signaling through EGFR and other RTKs. The release of Grb2 from condensates resensitized RTKs within 10s of minutes of ALKi addition. Resensitized RTKs, in turn, caused sporadic RTK activation pulses throughout the cell population, and pulses originated from paracrine RTK signals released by apoptotic neighbors. We found that these paracrine signals counteracted ALK inhibitor therapy and promoted survival and drug tolerance. Blocking paracrine signals through co-treatment of ALKi with inhibitors of either EGFR or matrix metalloproteases enhanced cell killing and minimized long-term drug tolerance. Our study uncovers a role for oncogenic condensates in drug resistance signaling, reveals a novel mechanism for oncogene-induced suppression of RTK signaling, and suggests novel co-therapies to more effectively treat cancers driven by EML4-ALK and possibly other RTK fusions. Our work also demonstrates the potential of functional optogenetic profiling for drug discovery to promote cancer therapy. Citation Format: David Gonzalez-Martinez, Lee Roth, Thomas Mumford, Yael Mosse, Asmin Tulpule, Trever Bivona, Lukasz Jan Bugaj. Inhibition of RTK fusion condensates enhances signal perception and promotes drug tolerance [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 848.