PTEN and breast carcinoma: Consistent with this hypothesis, Zhang et al. reported that loss of PTEN contributed to resistance to Trastuzumab treatment in erb-b2 receptor tyrosine kinase 2 (ERBB2)-overexpressing breast cancer cell lines and xenograft models by directly dephosphorylating and activating the proto-oncogene and nonreceptor tyrosine kinase (c-SRC) on tyrosine 416 [67].