title: Anti-erbB2 treatment induces cardiotoxicity by interfering with cell survival pathways.
abstract: BACKGROUND
  Cardiac dysfunction is among the serious side effects of therapy with recombinant humanized anti-erbB2 monoclonal antibody. The antibody blocks ErbB-2, a receptor tyrosine kinase and co-receptor for other members of the ErbB and epidermal growth factor families, which is over-expressed on the surface of many malignant cells. ErbB-2 and its ligands neuregulin and ErbB-3/ErbB-4 are involved in survival and growth of cardiomyocytes in both postnatal and adult hearts, and therefore the drug may interrupt the correct functioning of the ErbB-2 pathway.
  
  
  METHODS
  The effect of the rat-anti-erbB2 monoclonal antibody B-10 was studied in spontaneously beating primary myocyte cultures from rat neonatal hearts. Gene expression was determined by RT-PCR (reverse transcription polymerase chain reaction) and by rat stress-specific microarray analysis, protein levels by Western blot, cell contractility by video motion analysis, calcium transients by the FURA fluorescent method, and apoptosis using the TUNEL (terminal uridine nick-end labelling) assay.
  
  
  RESULTS
  B-10 treatment induces significant changes in expression of 24 out of 207 stress genes analyzed using the microarray technique. Protein levels of ErbB-2, ErbB-3, ErbB-4 and neuregulin decreased after 1 day. However, both transcription and protein levels of ErbB-4 and gp130 increased several fold. Calreticulin and calsequestrin were overexpressed after three days, inducing a decrease in calcium transients, thereby influencing cell contractility. Apoptosis was induced in 20% cells after 24 hours.
  
  
  CONCLUSIONS
  Blocking ErbB-2 in cultured rat cardiomyocytes leads to changes that may influence the cell cycle and affects genes involved in heart functions. B-10 inhibits pro-survival pathways and reduces cellular contractility. Thus, it is conceivable that this process may impair the stress response of the heart.
authors.affiliation: The Cardiovascular Research Center, Heart Institute, Hadassah-Hebrew University Medical Center, Jerusalem, Israel. pthea@hadassah.org.il
authors.forename: Thea
authors.initials: T
authors.lastname: Pugatsch
authors.forename: Suzan
authors.initials: S
authors.lastname: Abedat
authors.forename: Chaim
authors.initials: C
authors.lastname: Lotan
authors.forename: Ronen
authors.initials: R
authors.lastname: Beeri
mesh_terms: D000818:Animals; D000831:Animals, Newborn; D000911:Antibodies, Monoclonal / Q000009:adverse effects* / Q000276:immunology; D017209:Apoptosis / Q000187:drug effects*; D002470:Cell Survival / Q000187:drug effects; D002478:Cells, Cultured; D015870:Gene Expression; D006331:Heart Diseases / Q000276:immunology*; D009200:Myocardial Contraction / Q000187:drug effects; D032383:Myocytes, Cardiac / Q000187:drug effects*; D020411:Oligonucleotide Array Sequence Analysis; D051381:Rats; D018719:Erb-b2 Receptor Tyrosine Kinases / Q000235:genetics / Q000276:immunology*
chemical_list: D000911:Antibodies, Monoclonal; D018719:Erb-b2 Receptor Tyrosine Kinases