Improved potency of F10 relative to 5-fluorouracil in colorectal cancer cells with p53 mutations

Aim:Resistance to fluoropyrimidine drugs(FPs)is a major cause of mortality in colorectal cancer(CRC).We assessed the potency advantage of the polymeric FP F10 relative to 5-fluorouracil(5-FU)in four human CRC cell lines that differ only in TP53 mutational status to determine how p53 mutations affect drug response and whether F10 is likely to improve outcomes.Methods:HCT-116 human CRC cells(p53^(+/+))and three isogenic variants(p53^(-/-),R248W/+,R248W/-)were assessed for drug response.Resistance factors were derived from cell viability data and used to establish the relative potency advantage for F10.Rescue studies with exogenous uridine/thymidine determined if cytotoxicity resulted from DNA-directed processes.Results:Significant resistance to 5-FU resulted from p53-loss or from gain-of-function(GOF)mutation(R248W)and was greatest when GOF mutation was coupled with loss of wild-type p53.F10 is much more potent than 5-FU(137-314-fold depending on TP53 mutational status).F10 and 5-FU induce apoptosis by DNA-and RNA-directed mechanisms,respectively,and only F10 shows a modest enhancement in cytotoxicity upon co-treatment with leucovorin.Conclusion:TP53 mutational status affects inherent sensitivity to FPs,with p53 GOF mutations most deleterious.F10 is much more effective than 5-FU regardless of TP53 mutations and has potential to be effective to CRC that is resistant to 5-FU due,in part,to TP53 mutations.