It is possible that the pronounced impact of PTPRO specifically in HER2-positive disease could be due to the fact that HER2 itself is a direct substrate of PTPRO phosphatase activity [11]; specifically, loss of PTPRO was shown to increase HER2 phosphorylation and HER2-induced proliferation and transformation of breast cancer cell lines. The gene discussed is ERBB2; the disease is breast carcinoma.