A second erb-B receptor tyrosine kinase, ERBB4, is differentially expressed in the tumors of breast cancer patients treated with trastuzumab.
HER2, the human epidermal growth factor receptor 2, is encoded by the ERBB2 gene (1). Trastuzumab, a monoclonal antibody that targets HER2, is utilized for the treatment of breast cancer (2). We recently reported that trastuzumab treatment paradoxically increases HER2 expression in the primary tumors of patients with breast cancer (3). We report here, using analysis of published microarray data (4, 5), that a second erb-B receptor tyrosine kinase, ERRB4, is also differentially expressed in the tumors of patients with breast cancer treated with trastuzumab. Trastuzumab treatment appears to be associated with the up-regulation of two members of the erb-B receptor tyrosine kinase family in human breast cancer.