The impact of FANCD2 deficiency on formaldehyde-induced toxicity in human lymphoblastoid cell lines

Abstract

Formaldehyde (FA), a major industrial chemical and ubiquitous environmental pollutant, has recently been classified by the International Agency for Research on Cancer as a human leukemogen. The major mode of action of FA is thought to be the formation of DNA-protein crosslinks (DPCs). Repair of DPCs may be mediated by the Fanconi anemia pathway; however, data supporting the involvement of this pathway is limited, particularly in human hematopoietic cells. Therefore, we assessed the role of FANCD2, a critical component of the Fanconi anemia pathway, in FA-induced toxicity in human lymphoblast cell models of FANCD2-deficiency (PD20 cells) and FANCD2-sufficiency (PD20-D2 cells). After treatment of the cells with 0-150 μM FA for 24 hours, DPCs were increased in a dose-dependent manner in both cell lines, with greater increases in FANCD2-deficient PD20 cells. FA also induced cytotoxicity, micronuclei, chromosome aberrations, and apoptosis in a dose-dependent manner in both cell lines, with greater increases in cytotoxicity and apoptosis in PD20 cells. Increased levels of γ-ATR and γ-H2AX in both cell lines suggested the recognition of FA-induced DNA damage; however, the induction of BRCA2 was compromised in FANCD2-deficient PD20 cells, potentially reducing the capacity to repair DPCs. Together, these findings suggest that FANCD2 protein and the Fanconi anemia pathway are essential to protect human lymphoblastoid cells against FA toxicity. Future studies are needed to delineate the role of this pathway in mitigating FA-induced toxicity, particularly in hematopoietic stem cells, the target cells in leukemia.

Complementation of hypersensitivity to DNA interstrand crosslinking agents demonstrates thatXRCC2is a Fanconi anaemia gene

“…Sensitivity to formaldehyde and other aldehydes has been observed in a variety of cell lines with deficiencies in FA proteins. 32 33 40-43 900677A cells, with or without complementation by XRCC2, display no defect in FANCD2 monoubiquitination or foci formation. Since monoubiquitination of FANCI by the FA core complex is essential for FANCD2 monoubiquitination and assembly into foci, 15 16 FANCD2 is a reliable indicator that XRCC2 does not function early in the FA-BRCA pathway, but instead functions late.…”

Inhaled formaldehyde induces DNA–protein crosslinks and oxidative stress in bone marrow and other distant organs of exposed mice

“…DPC are lost by spontaneous hydrolysis which can induce mutations [Quievryn and Zhitkovich, 2000]. The FANC-BRCA pathway is essential to counteract DPCs caused by FA [Jacquemont and Taniguchi, 2007;Ridpath et al, 2007;Ren et al, 2013] and genetic variants in these genes could influence individual susceptibility to develop leukemia. Recent studies in primary lung fibroblasts and lung epithelial cells showed that FA-induced DPC, but not DNA-adducts, triggered an S-phase-dependent p53-mediated stress response through a replication inhibition due to stalling of replicative helicases by the intact, superbulky DPC [Wong et al, 2012].…”

Re-evaluation of the WHO (2010) formaldehyde indoor air quality guideline for cancer risk assessment

“…Additionally, a tolerance pathway also exists, allowing replication across unrepaired DPX lesions that may include strand breaks (potentially causing genomic rearrangements) followed by strand ligation (Stingele et al 2015). Not least, the Fanconi anaemia pathway is important in the repair of inter-strand DNA cross-links and DPX (Ren et al 2013; Kirsch-Volders et al 2014; McHale et al 2014; Schneider et al 2015). …”