title: DNA fragile site breakage as a measure of chemical exposure and predictor of individual susceptibility to form oncogenic rearrangements.
abstract: Chromosomal rearrangements induced by non-radiation causes contribution to the majority of oncogenic fusions found in cancer. Treatment of human thyroid cells with fragile site-inducing laboratory chemicals can cause preferential DNA breakage at the RET gene and generate the RET/PTC1 rearrangement, a common driver mutation in papillary thyroid carcinomas (PTC). Here, we demonstrate that treatment with non-cytotoxic levels of environmental chemicals (benzene and diethylnitrosamine) or chemotherapeutic agents (etoposide and doxorubicin) generates significant DNA breakage within RET at levels similar to those generated by fragile site-inducing laboratory chemicals. This suggests that chronic exposure to these chemicals plays a role in the formation of non-radiation associated RET/PTC rearrangements. We also investigated whether the sensitivity of the fragile RET region could predict the likelihood of rearrangement formation using normal thyroid tissues from patients with and without RET/PTC rearrangements. We found that normal cells of patients with thyroid cancer driven by RET/PTC rearrangements have significantly higher blunt-ended, double-stranded DNA breaks at RET than those of patients without RET/PTC rearrangements. This sensitivity of a cancer driver gene suggests for the first time that a DNA breakage test at the RET region could be utilized to evaluate susceptibility to RET/PTC formation. Further, the significant increase of blunt-ended, double-stranded DNA breaks, but not other types of DNA breaks, in normal cells from patients with RET/PTC-driven tumors suggests that blunt-ended double-stranded DNA breaks are a preferred substrate for rearrangement formation, and implicate involvement of the non-homologous end joining pathway in the formation of RET/PTC rearrangements.
authors.affiliation: Department of Biochemistry and Molecular Genetics, University of Virginia, 1340 Jefferson Park Avenue, Charlottesville, VA 22908-0733, USA and.
authors.forename: Christine E
authors.initials: CE
authors.lastname: Lehman
authors.affiliation: Department of Biochemistry and Molecular Genetics, University of Virginia, 1340 Jefferson Park Avenue, Charlottesville, VA 22908-0733, USA and.
authors.forename: Laura W
authors.initials: LW
authors.lastname: Dillon
authors.affiliation: Department of Pathology and Laboratory Medicine, University of Pittsburgh, Pittsburgh, PA 15261, USA.
authors.forename: Yuri E
authors.initials: YE
authors.lastname: Nikiforov
authors.affiliation: Department of Biochemistry and Molecular Genetics, University of Virginia, 1340 Jefferson Park Avenue, Charlottesville, VA 22908-0733, USA and.
authors.forename: Yuh-Hwa
authors.initials: YH
authors.lastname: Wang
mesh_terms: D001554:Benzene / Q000633:toxicity; D002277:Carcinoma / Q000235:genetics* / Q000473:pathology; D002291:Carcinoma, Papillary; D002869:Chromosome Aberrations / Q000187:drug effects; D043283:Chromosome Fragile Sites / Q000235:genetics*; D053903:DNA Breaks, Double-Stranded / Q000187:drug effects; D004249:DNA Damage / Q000235:genetics; D004052:Diethylnitrosamine / Q000633:toxicity; D006801:Humans; D009154:Mutation; D015514:Oncogene Proteins, Fusion / Q000235:genetics; D000072081:Patched-1 Receptor / Q000235:genetics*; D051096:Proto-Oncogene Proteins c-ret / Q000235:genetics*; D000077273:Thyroid Cancer, Papillary; D013964:Thyroid Neoplasms / Q000235:genetics* / Q000473:pathology
chemical_list: D015514:Oncogene Proteins, Fusion; D000072081:Patched-1 Receptor; D004052:Diethylnitrosamine; D051096:Proto-Oncogene Proteins c-ret; C099282:RET protein, human; D001554:Benzene