1. ¹UMR599 Inserm, Institut Paoli-Calmettes, Centre de Recherche en Cancérologie de Marseille, Département d'Oncologie Moléculaire, Marseille, France
2. ²UMR599 Inserm, Institut Paoli-Calmettes, Centre de Recherche en Cancérologie de Marseille, Département d'Oncologie Médicale, Marseille, France
3. ³Faculté de Médecine, Université de la Méditerranée, Marseille, France
4. ⁴Département de BioPathologie, Institut Paoli-Calmettes, Marseille, France

Correspondence: Dr D Birnbaum, UMR599 Inserm, 27 Bd. Leï Roure, 13009 Marseille, France. E-mail: birnbaum@marseille.inserm.fr

⁵These authors contributed equally to this work.

Received 6 January 2006; Revised 22 February 2007; Accepted 11 April 2007; Published online 21 May 2007.

Abstract

Breast cancers that overexpress the ERBB2 tyrosine kinase receptor may be treated with the recombinant humanized monoclonal anti-ERBB2 antibody trastuzumab (herceptin). However, resistance to this targeted therapy is frequent. We have determined the response of 18 breast tumor cell lines to trastuzumab and compared it with the ERBB2 phosphorylation status using antibodies directed against tyrosine residue 1248. We show that sensitivity to trastuzumab is frequently associated with the expression of a phosphorylated ERBB2 protein.