title: Heat induces gene amplification in cancer cells.
abstract: BACKGROUND
  Hyperthermia plays an important role in cancer therapy. However, as with radiation, it can cause DNA damage and therefore genetic instability. We studied whether hyperthermia can induce gene amplification in cancer cells and explored potential underlying molecular mechanisms.
  
  
  METHODS
  (1) Hyperthermia: HCT116 colon cancer cells received water-submerged heating treatment at 42 or 44°C for 30 min; (2) gene amplification assay using N-(phosphoacetyl)-L-aspartate (PALA) selection of cabamyl-P-synthetase, aspartate transcarbarmylase, dihydro-orotase (cad) gene amplified cells; (3) southern blotting for confirmation of increased cad gene copies in PALA-resistant cells; (4) γH2AX immunostaining to detect γH2AX foci as an indication for DNA double strand breaks.
  
  
  RESULTS
  (1) Heat exposure at 42 or 44°C for 30 min induces gene amplification. The frequency of cad gene amplification increased by 2.8 and 6.5 folds respectively; (2) heat exposure at both 42 and 44°C for 30 min induces DNA double strand breaks in HCT116 cells as shown by γH2AX immunostaining.
  
  
  CONCLUSIONS
  This study shows that heat exposure can induce gene amplification in cancer cells, likely through the generation of DNA double strand breaks, which are believed to be required for the initiation of gene amplification. This process may be promoted by heat when cellular proteins that are responsible for checkpoints, DNA replication, DNA repair and telomere functions are denatured. To our knowledge, this is the first study to provide direct evidence of hyperthermia induced gene amplification.
authors.affiliation: Department of Radiation Oncology, University of Mississippi Medical Center, Jackson, MS 39213, USA. yanbin@mercyhealth.com
authors.forename: Bin
authors.initials: B
authors.lastname: Yan
authors.forename: Ruoyun
authors.initials: R
authors.lastname: Ouyang
authors.forename: Chenghui
authors.initials: C
authors.lastname: Huang
authors.forename: Franklin
authors.initials: F
authors.lastname: Liu
authors.forename: Daniel
authors.initials: D
authors.lastname: Neill
authors.forename: Chuanyuan
authors.initials: C
authors.lastname: Li
authors.forename: Mark
authors.initials: M
authors.lastname: Dewhirst
mesh_terms: D017766:Acid Anhydride Hydrolases / Q000235:genetics; D001221:Aspartate Carbamoyltransferase / Q000235:genetics; D001224:Aspartic Acid / Q000031:analogs & derivatives / Q000494:pharmacology; D053903:DNA Breaks, Double-Stranded; D004080:Dihydroorotase / Q000235:genetics; D005784:Gene Amplification; D015972:Gene Expression Regulation, Neoplastic; D045325:HCT116 Cells; D006358:Hot Temperature / Q000009:adverse effects*; D006801:Humans; D006979:Hyperthermia, Induced / Q000009:adverse effects*; D009369:Neoplasms / Q000235:genetics* / Q000628:therapy*; D010746:Phosphonoacetic Acid / Q000031:analogs & derivatives / Q000494:pharmacology; D000097024:Acylphosphatase
chemical_list: D017766:Acid Anhydride Hydrolases; D001221:Aspartate Carbamoyltransferase; D001224:Aspartic Acid; D004080:Dihydroorotase; D010746:Phosphonoacetic Acid; D000097024:Acylphosphatase; C013195:sparfosic acid