Abstract 3935: The polymeric fluoropyrimidine CF10 overcomes limitations of 5-FU in pancreatic ductal adenocarcinoma cells through increased replication stress
Authors: DiNiro Roberto , Haber Alex O. , Jeong Kang J. , Park Soon Y. , Mills Gordon B. , Gmeiner William H. , Brody Jonathan R. 
Published: June 2022

Abstract
Pancreatic ductal adenocarcinoma (PDA) is a lethal disease that will soon become the second leading cause of cancer deaths in the US. Beside surgery, current therapies have narrow clinical benefits for this devastating disease, and in the majority of cases, only improve survival by a few months. Moreover, systemic toxicities are a harsh reality of these treatments. FOLFIRINOX is the drug regimen of choice, one component of which is 5-Fluorouracil (5-FU) which causes serious gastrointestinal and hematopoietic toxicities and is vulnerable to resistance due, in part, to thymidylate synthase (TS) overexpression. The Gmeiner lab has pioneered the development of polymeric fluoropyrimidines, named F10 and CF10, which unlike 5-FU, are in principle completely converted to the TS inhibitory metabolite FdUMP, without generating appreciable levels of ribonucleotides that cause systemic toxicities and while displaying much stronger anti-cancer activity. Here, we further confirm the potency of CF10 and investigate enhancement of its efficacy through combination with inhibitors targeting replication stress, a hallmark of PDA cells. We show that, consistent with our previous studies in PDA cells, CF10 is much more potent as a single agent than 5-FU, by an average 308x fold, and was effective in the nM range (GI50 range 3.13 - 336 nM) in 5 PDA cell lines tested. We also found that CF10 induces increased replication stress as assessed by phosphorylation of ATR, which appears as early as 8 hours after treatment and increases in intensity over 48 hours, consistent with the kinetics of FdU being released from CF10 and incorporated into DNA, a process requiring several hours. Importantly, phosphorylation of ATR induced by CF10 was significantly higher than with 5-FU. This is especially striking because compounds for this assay were used at their IC50 concentrations, with for example MiaPaCA2 cells being exposed to 899 time more 5-FU than CF10, yet at this concentration 5-FU induced less ATR phosphorylation. Further, we find that the activity of CF10, but not 5-FU can be enhanced through combination with inhibitors of ATR and Wee1 that regulate the S and G2 damage checkpoints. Our results indicate CF10 has potential to supersede the established benefit of 5-FU in PDA treatment and indicate novel combination approaches that may be beneficial compared to well-established regimens used currently for 5-FU.
Citation Format: Roberto DiNiro, Alex O. Haber, Kang J. Jeong, Soon Y. Park, Gordon B. Mills, William H. Gmeiner, Jonathan R. Brody. The polymeric fluoropyrimidine CF10 overcomes limitations of 5-FU in pancreatic ductal adenocarcinoma cells through increased replication stress [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 3935.