This was further confirmed by demonstrating a correlation between reduced survival in pure HER2 breast cancer patients and expression of PYK2 and the stem cell marker CD44. Although clinical trials are ongoing, testing this possibility in the future using samples from metformin-treated breast cancer patients and when available, will certainly shed light on potential induction of cancer invasion by metformin in treated patients. This evidence concerns the gene ERBB2 and breast carcinoma.