To investigate the potential role of PYK2 in migration and invasion of HER2+/ER−/PR- breast cancer cells and in response to metformin (1 mM), SkBr3 and MDA-MB-453 PYK2 knockdown cell lines were generated (Fig. 2a and b, Additional file 1: Figure S1B and C). Here, ERBB2 is linked to breast cancer.