title: DNA strand breaks and cell cycle perturbation in herceptin treated breast cancer cell lines.
abstract: BACKGROUND
  Herceptin is a humanized antibody that binds to the product of the HER-2 oncogene. Clinical studies have indicated that treatment with Herceptin may slow disease progression in tumors expressing high levels of the HER-2 antigen. However, the mechanism of this action is not known.
  
  
  METHODS
  Four different cell lines were used that had different levels of HER-2 expression. Treated and nontreated cells were analyzed for DNA strand breaks and cell cycle perturbation using standard flow cytometry methods.
  
  
  RESULTS
  In this study we found that cell lines expressing high levels of HER-2, when treated with Herceptin, exhibited marked increases in DNA strand breaks as measured by the TUNEL assay, and that these cells also exhibited slowed growth. BT-474 and SKBR-3 cell lines, both of which express high levels of the HER-2 antigen, had significant increases in labeled nucleotide expression at 3 and 6 day time points following exposure to Herceptin at a concentration of 10 microg/ml. Similar treatment of MCF-7 and MDA-231 cell lines, both of which express low levels of HER-2, had little effect on the level of labeled nucleotide expression at either the 3 or 6 day time points. Following 4 days of Herceptin treatment, BT-474 and SKBR-3 cell lines had significant decreases in the percentage of cells in the S phase of growth. This effect was not seen in either the MCF-7 or MDA-231 cell lines.
  
  
  CONCLUSIONS
  Herceptin has a biological effect only on cells that contain high levels of HER-2. This effect is a decrease in cell proliferation that is coincident with, and may be caused by an increase frequency of DNA strand breaks.
authors.affiliation: Wake Forest University Cancer Center, Winston-Salem, NC 27157-1072, USA.
authors.forename: S
authors.initials: S
authors.lastname: Mayfield
authors.forename: J P
authors.initials: JP
authors.lastname: Vaughn
authors.forename: T E
authors.initials: TE
authors.lastname: Kute
mesh_terms: D000911:Antibodies, Monoclonal / Q000494:pharmacology* / Q000627:therapeutic use; D061067:Antibodies, Monoclonal, Humanized; D000970:Antineoplastic Agents / Q000494:pharmacology* / Q000627:therapeutic use; D001943:Breast Neoplasms / Q000188:drug therapy* / Q000235:genetics / Q000473:pathology; D002453:Cell Cycle / Q000187:drug effects*; D002455:Cell Division / Q000187:drug effects; D004249:DNA Damage; D006801:Humans; D018719:Erb-b2 Receptor Tyrosine Kinases / Q000032:analysis / Q000096:biosynthesis; D000068878:Trastuzumab; D014407:Tumor Cells, Cultured / Q000187:drug effects
chemical_list: D000911:Antibodies, Monoclonal; D061067:Antibodies, Monoclonal, Humanized; D000970:Antineoplastic Agents; D018719:Erb-b2 Receptor Tyrosine Kinases; D000068878:Trastuzumab