ERBB2 and breast cancer: As observed in Fig. 1, PAK4 levels are high in MDA-MB-468, SUM159, BT-549 and MDA-MB-231 (all triple negative), MCF7 (ER+/PR+), SkBr-3 (HER2+), and BT-474 (PR+/HER2+) breast cancer cell lines.