FANCD1/BRCA2 Plays Predominant Role in the Repair of DNA Damage Induced by ACNU or TMZ

Natsuko Kondo,Minoru Suzuki,Akihisa Takahashi,Masatoshi Hasegawa,Eiichiro Mori,Shinichiro Masunaga,Koji Ono,Thomas Helleday,Larry H Thompson,Małgorzata Z Zdzienicka,Takeo Ohnishi,Yuko Kinashi,Taichi Noda,Marcel P Van Der Brug

doi:10.1371/journal.pone.0019659

Abstract

Nimustine (ACNU) and temozolomide (TMZ) are DNA alkylating agents which are commonly used in chemotherapy for glioblastomas. ACNU is a DNA cross-linking agent and TMZ is a methylating agent. The therapeutic efficacy of these agents is limited by the development of resistance. In this work, the role of the Fanconi anemia (FA) repair pathway for DNA damage induced by ACNU or TMZ was examined. Cultured mouse embryonic fibroblasts were used: FANCA−/−, FANCC−/−, FANCA−/−C−/−, FANCD2−/− cells and their parental cells, and Chinese hamster ovary and lung fibroblast cells were used: FANCD1/BRCA2mt, FANCG−/− and their parental cells. Cell survival was examined after a 3 h ACNU or TMZ treatment by using colony formation assays. All FA repair pathways were involved in ACNU-induced DNA damage. However, FANCG and FANCD1/BRCA2 played notably important roles in the repair of TMZ-induced DNA damage. The most effective molecular target correlating with cellular sensitivity to both ACNU and TMZ was FANCD1/BRCA2. In addition, it was found that FANCD1/BRCA2 small interference RNA efficiently enhanced cellular sensitivity toward ACNU and TMZ in human glioblastoma A172 cells. These findings suggest that the down-regulation of FANCD1/BRCA2 might be an effective strategy to increase cellular chemo-sensitization towards ACNU and TMZ.

Highlights

IntroductionNitrosourea drugs such as ACNU in Japan and central Europe, or carmustine [1,3-bis(2chloroethyl)-1-nitrosourea; BCNU], in the United States were the standard of care in addition to radiation [1,2]
FANCG2/2 and FANCD1mt cells exhibited a striking hypersensitivity to ACNU
The genetic background of FANCAwt, FANCCwt, FANCA/Cwt and FANCD2wt were almost the same, it is definitely clear that ACNU-induced DNA-DNA cross-links might be repaired by FANCA, FANCC and FANCD2 which are components of Fanconi anemia (FA) nuclear core complex

Summary

Introduction

Nitrosourea drugs such as ACNU in Japan and central Europe, or carmustine [1,3-bis(2chloroethyl)-1-nitrosourea; BCNU], in the United States were the standard of care in addition to radiation [1,2] This has changed since TMZ was shown to deliver benefits which were accompanied by lower levels of toxicity [3]. A recent meta-analysis suggested the existence of a significant survival gain with the use of ACNU in newly diagnosed high-grade gliomas [4]. Even if these alkylating agents are used for the treatment for high-grade gliomas, the therapeutic efficacy of these agents is limited by the development of resistance to these agents, and the underlying mechanisms leading to the development of this resistance is still unknown

Methods

Results

Conclusion