PTEN and breast cancer: SKBR3 is a HER2-enriched breast cancer cell line that overexpresses the HER2 gene product64, and is KRAS, HRAS, NRAS, BRAF, PTEN, PI3KCA, and MAP2K4 wild type63,65,66, and also negative for AKT1 activation, and AKT2 and AKT3 amplification63.