Thymineless Death by the Fluoropyrimidine Polymer F10 Involves Replication Fork Collapse and Is Enhanced by Chk1 Inhibition.

Thymineless Death by the Fluoropyrimidine Polymer F10 Involves Replication Fork Collapse and Is Enhanced by Chk1 Inhibition. Neoplasia. 2018 Nov 12;20(12):1236-1245 Authors: Mani C, Pai S, Papke CM, Palle K, Gmeiner WH Abstract We are developing the fluoropyrimidine polymer F10 to overcome limitations of 5-fluorouracil (5-FU) that result from inefficient metabolism to 5-fluoro-2'-deoxyuridine-5'-mono- and tri-phosphate, the deoxyribonucleotide metabolites that are responsible for 5-FU's anticancer activity. F10 is much more cytotoxic than 5-FU to colorectal cancer (CRC) cells; however, the mechanism of enhanced F10 cytotoxicity remains incompletely characterized. Using DNA fiber analysis, we establish that F10 decreases replication fork velocity and causes replication fork collapse, while 1000-fold excess of 5-FU is required to achieve similar endpoints. Treatment of HCT-116 cells with F10 results in Chk1 phosphorylation and activation of intra-S-phase checkpoint. Combining F10 with pharmacological inhibition of Chk1 with either PF-477736 or prexasertib in CRC cells enhanced DNA damage relative to single-agent treatment as assessed by γH2AX intensity and COMET assay. PF-477736 or prexasertib co-treatment also inhibited upregulation of Rad51 levels in response to F10, resulting in reduced homologous repair. siRNA knockdown of Chk1 also increased F10-induced DNA damage assessed and sensitized CRC cells to F10. However, Chk1 knockdown ...
Source: Neoplasia - Category: Cancer & Oncology Authors: Tags: Neoplasia Source Type: research