Trastuzumab-treated Invasive Lobular Carcinoma patients have a differently expressed protein tyrosine phosphatase receptor type H, PTPRH

Trastuzumab, a monoclonal antibody that targets the human epidermal growth factor receptor 2 (HER2), isused to treat human breast cancer1,2. However, a thorough knowledge of how trastuzumab therapy modulatestumor signal transduction is inadequate. We discovered that the protein tyrosine phosphatase receptor type H,encoded by PTPRH, was among the genes most differentially expressed in the primary tumors of patientstreated with trastuzumab, and expressed at lower levels in the tumors of patients treated with trastuzumab, bymining published and public microarray and gene expression data3,4 from the primary tumors of patientstreated with trastuzumab. Thus, trastuzumab treatment in breast cancer patients is linked to lower primarytumor expression of a protein tyrosine phosphatase, whose deficit in pediatric solid tumors identifies a riskphenotypeand whose expression is reduced in colorectal cancer.