title: Loss of distal 11q is associated with DNA repair deficiency and reduced sensitivity to ionizing radiation in head and neck squamous cell carcinoma.
abstract: About 45% of head and neck squamous cell carcinomas (HNSCC) are characterized by amplification of chromosomal band 11q13. This amplification occurs by a breakage-fusion-bridge (BFB) cycle mechanism. The first step in the BFB cycle involves breakage and loss of distal 11q, from FRA11F (11q14.2) to 11qter. Consequently, numerous genes, including three critical genes involved in the DNA damage response pathway, MRE11A, ATM, and H2AFX are lost in the step preceding 11q13 amplification. We hypothesized that this partial loss of genes on distal 11q may lead to a diminished DNA damage response in HNSCC. Characterization of HNSCC using fluorescence in situ hybridization (FISH) revealed concurrent partial loss of MRE11A, ATM, and H2AFX in all four cell lines with 11q13 amplification and in four of seven cell lines without 11q13 amplification. Quantitative microsatellite analysis and loss of heterozygosity studies confirmed the distal 11q loss. FISH evaluation of a small series of HNSCC, ovarian, and breast cancers confirmed the presence of 11q loss in at least 60% of these tumors. All cell lines with distal 11q loss exhibited a diminished DNA damage response, as measured by a decrease in the size and number of gamma-H2AX foci and increased chromosomal instability following treatment with ionizing radiation. In conclusion, loss of distal 11q results in a defective DNA damage response in HNSCC. Distal 11q loss was also unexpectedly associated with reduced sensitivity to ionizing radiation. Although the literature attributes the poor prognosis in HNSCC to 11q13 gene amplification, our results suggest that distal 11q deletions may be an equally significant factor.
authors.affiliation: Department of Human Genetics, University of Pittsburgh Graduate School of Public Health, Pittsburgh, PA 15261, USA.
authors.forename: Rahul A
authors.initials: RA
authors.lastname: Parikh
authors.forename: Jason S
authors.initials: JS
authors.lastname: White
authors.forename: Xin
authors.initials: X
authors.lastname: Huang
authors.forename: David W
authors.initials: DW
authors.lastname: Schoppy
authors.forename: Bora E
authors.initials: BE
authors.lastname: Baysal
authors.forename: Rajasekaran
authors.initials: R
authors.lastname: Baskaran
authors.forename: Christopher J
authors.initials: CJ
authors.lastname: Bakkenist
authors.forename: William S
authors.initials: WS
authors.lastname: Saunders
authors.forename: Lih-Ching
authors.initials: LC
authors.lastname: Hsu
authors.forename: Marjorie
authors.initials: M
authors.lastname: Romkes
authors.forename: Susanne M
authors.initials: SM
authors.lastname: Gollin
mesh_terms: D064007:Ataxia Telangiectasia Mutated Proteins; D002294:Carcinoma, Squamous Cell / Q000235:genetics*; D018797:Cell Cycle Proteins / Q000235:genetics; D045744:Cell Line, Tumor; D002872:Chromosome Deletion; D002880:Chromosomes, Human, Pair 11; D049914:DNA Repair-Deficiency Disorders / Q000235:genetics*; D004268:DNA-Binding Proteins / Q000172:deficiency / Q000235:genetics; D005784:Gene Amplification; D006258:Head and Neck Neoplasms / Q000235:genetics*; D006657:Histones / Q000172:deficiency / Q000235:genetics; D006801:Humans; D017404:In Situ Hybridization, Fluorescence; D000076228:MRE11 Homologue Protein; D017346:Protein Serine-Threonine Kinases / Q000172:deficiency / Q000235:genetics; D011839:Radiation, Ionizing; D025521:Tumor Suppressor Proteins / Q000172:deficiency / Q000235:genetics
chemical_list: D018797:Cell Cycle Proteins; D004268:DNA-Binding Proteins; C468783:H2AX protein, human; D006657:Histones; C121766:MRE11 protein, human; D025521:Tumor Suppressor Proteins; C576324:ATM protein, human; D064007:Ataxia Telangiectasia Mutated Proteins; D017346:Protein Serine-Threonine Kinases; D000076228:MRE11 Homologue Protein