ERBB2 and neoplasm: While a study by Zhu et al. suggests that PTPN13 regulates ErbB2 function directly by de-phosphorylating the ErbB2 signal domain [24], we have not found that in our system suggesting that PTPN13 and activated ErbB2 alone cannot account for the enhanced downstream signaling, tumor growth, and invasion evident in our published studies [23].