title: Radiosensitivity of human fibroblasts is associated with amino acid substitution variants in susceptible genes and correlates with the number of risk alleles.
abstract: OBJECTIVE
  Genetic predictive markers of radiosensitivity are being sought for stratifying radiotherapy for cancer patients and risk assessment of radiation exposure. We hypothesized that single nucleotide polymorphisms in susceptible genes are associated with, and the number of risk alleles has incremental effect on, individual radiosensitivity.
  
  
  METHODS
  Six amino acid substitution variants (ATM 1853 Asp/Asn G>A, p53 72 Arg/Pro G>C, p21 31 Ser/Arg C>A, XRCC1 399 Arg/Gln G>A, XRCC3 241 Thr/Met C>T, and TGFbeta1 10 Leu/Pro T>C) were genotyped by direct sequencing in 54 fibroblast strains of different radiosensitivity.
  
  
  RESULTS
  The clonogenic survival fraction at 2 Gy range was 0.15-0.50 (mean, 0.34, standard deviation, 0.08). The mean survival fraction at 2 Gy divided the cell strains into radiosensitive (26 cases) and normal (28 controls). A significant association was observed between the survival fraction at 2 Gy and ATM 1853 Asn, XRCC3 241 Met, and TGFbeta1 10 Leu alleles (p = 0.05, p = 0.02, and p = 0.02, respectively). The p53 72 Arg allele showed a borderline association (p = 0.07). The number of risk alleles increased with increasing radiosensitivity, and the group comparison showed a statistically significant difference between the radiosensitive and control groups (p < or = 0.001).
  
  
  CONCLUSIONS
  The results of our study have shown that single nucleotide polymorphisms in susceptible genes influence cellular radiation response and that the number of risk alleles has a combined effect on radiosensitivity. Individuals with multiple risk alleles could be more susceptible to radiation effects than those with fewer risk alleles. These results may have implications in predicting normal tissue reactions to radiotherapy and risk assessment of radiation exposure.
authors.affiliation: Radiation Biology Laboratory, Department of Biomedical Physics, King Faisal Specialist Hospital and Research Centre, Riyadh, Saudi Arabia. galsbeih@kfshrc.edu.sa
authors.forename: Ghazi
authors.initials: G
authors.lastname: Alsbeih
authors.forename: Medhat
authors.initials: M
authors.lastname: El-Sebaie
authors.forename: Najla
authors.initials: N
authors.lastname: Al-Harbi
authors.forename: Muneera
authors.initials: M
authors.lastname: Al-Buhairi
authors.forename: Khaled
authors.initials: K
authors.lastname: Al-Hadyan
authors.forename: Nasser
authors.initials: N
authors.lastname: Al-Rajhi
mesh_terms: D000483:Alleles; D019943:Amino Acid Substitution / Q000235:genetics*; D064007:Ataxia Telangiectasia Mutated Proteins; D018797:Cell Cycle Proteins / Q000235:genetics; D004268:DNA-Binding Proteins / Q000235:genetics; D005347:Fibroblasts / Q000528:radiation effects*; D005819:Genetic Markers; D006801:Humans; D020641:Polymorphism, Single Nucleotide / Q000235:genetics*; D017346:Protein Serine-Threonine Kinases / Q000235:genetics; D016283:Proto-Oncogene Proteins p21(ras) / Q000235:genetics; D011829:Radiation Dosage; D011836:Radiation Tolerance / Q000235:genetics*; D016212:Transforming Growth Factor beta / Q000235:genetics; D014410:Tumor Stem Cell Assay; D016159:Tumor Suppressor Protein p53 / Q000235:genetics; D025521:Tumor Suppressor Proteins / Q000235:genetics; D000076105:X-ray Repair Cross Complementing Protein 1
chemical_list: D018797:Cell Cycle Proteins; D004268:DNA-Binding Proteins; D005819:Genetic Markers; D016212:Transforming Growth Factor beta; D016159:Tumor Suppressor Protein p53; D025521:Tumor Suppressor Proteins; D000076105:X-ray Repair Cross Complementing Protein 1; C110901:X-ray repair cross complementing protein 3; C000619371:XRCC1 protein, human; C576324:ATM protein, human; D064007:Ataxia Telangiectasia Mutated Proteins; D017346:Protein Serine-Threonine Kinases; D016283:Proto-Oncogene Proteins p21(ras)