ATR–Chk1 signaling pathway and homologous recombinational repair protect cells from 5-fluorouracil cytotoxicity

Fujinaka, Y. et al. (2012) ATR–Chk1 signaling pathway and homologous recombinational repair protect cells from 5-fluorouracil cytotoxicity. DNA Repair, 11(3), pp. 247-258. (doi: 10.1016/j.dnarep.2011.11.005)

Abstract

5-Fluorouracil (5-FU) has long been a mainstay antimetabolite chemotherapeutic drug for the treatment of major solid tumors, particularly colorectal cancer. 5-FU is processed intracellularly to yield active metabolites that compromise RNA and DNA metabolism. However, the mechanisms responsible for its cytotoxicity are not fully understood. From the phenotypic analysis of mutant chicken B lymphoma DT40 cells, we found that homologous recombinational repair (HRR), involving Rad54 and BRCA2, and the ATR–Chk1 signaling pathway, involving Rad9 and Rad17, significantly contribute to 5-FU tolerance. 5-FU induced γH2AX nuclear foci, which were colocalized with the key HRR factor Rad51, but not with DNA double-strand breaks (DSBs), in a dose-dependent manner as cells accumulated in the S phase. Inhibition of Chk1 kinase by UCN-01 increased 5-FU-induced γH2AX and enhanced 5-FU cytotoxicity not only in wild-type cells but also in Rad54- or BRCA2-deficient cells, suggesting that HRR and Chk1 kinase have non-overlapping roles in 5-FU tolerance. 5-FU-induced Chk1 phosphorylation was significantly impaired in Rad9- or Rad17-deficient cells, and severe γH2AX nuclear foci and DSBs were formed, which was followed by apoptosis. Finally, inhibition of Chk1 kinase by UCN-01 increased 5-FU-induced γH2AX nuclear foci and enhanced 5-FU cytotoxicity in Rad9- or Rad17-deficient cells. These results suggest that Rad9- and Rad17-independent activation of the ATR–Chk1 signaling pathway also significantly contributes to 5-FU tolerance.

• Item Type: Articles
• Status: Published
• Refereed: Yes
• Glasgow Author(s) Enlighten ID: Gillespie, Professor David
• Authors: Fujinaka, Y., Matsuoka, K., Iimori, M., Tuul, M., Sakasai, R., Yoshinaga, K., Saeki, H., Morita, M., Kakeji, Y., Gillespie, D.A., Yamamoto, K., Takata, M., Kitao, H., and Maehara, Y.
• College/School: College of Medical Veterinary and Life Sciences > School of Cancer Sciences
• Journal Name: DNA Repair
• ISSN: 1568-7864
• ISSN (Online): 1568-7856
• Published Online: 20 December 2011