Abstract 1130: CETSA interaction proteomics define specific RNA modification pathways as key components of fluorouracil based cancer drug cytotoxicity

Abstract Introduction: Our current understanding of the mechanism of action (MoA) of many cancer drugs is still incomplete. This hampers efforts in establishing efficient personalised medicine regimens, the optimisation of combination therapies, and the development of next generation drugs. Results: Here, we apply a high-resolution implementation of the proteome-wide cellular thermal shift assay (CETSA) to follow protein interaction changes induced by the antimetabolite 5-fluorouracil (5-FU) and related nucleosides. We focus on the relatively early drug effects, up to 12 hours, when this time frame is less accessible to other omics methods, while critical for defining drug MoAs. We confirm anticipated effects on the known main target, thymidylate synthase (TYMS), and enzymes in pyrimidine metabolism and DNA damage pathways. However, most interaction changes we see are for proteins previously not associated with the MoA of 5-FU, including wide-ranging effects on RNA modification and processing pathways. Attenuated responses of specific proteins in a resistant cell model identify key components of the 5-FU MoA, where intriguingly the abrogation of TYMS inhibition is not required for cell proliferation. Conclusions: When 5-FU is one of the most used and studied cancer drugs, this novel information significantly expands our understanding of the 5-FU MoA and will be important to direct further work towards dissecting its complete MoA. Furthermore, the CETSA responses of several proteins now provide ideal readouts for directly monitoring whether the required 5-FU effects are accomplished and can now be examined as CETSA-based candidate biomarkers in clinical studies. Together, this work also validates an efficient strategy for dissecting the MoA of cancer drugs, which could be broadly applicable to other cancer drugs in clinical use or in development. Citation Format: Smaranda Bacanu, Ying Yu Liang, Anderson D. Ramos, Nayana Prabhu, Pär Nordlund. CETSA interaction proteomics define specific RNA modification pathways as key components of fluorouracil based cancer drug cytotoxicity [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 1130.