The basal levels of MMP-1 and MMP-9 are increased in various breast cancer cells, including MCF7, in response to heregulin-β1 via activation of MAPK/ERK pathway [127] and overexpression of Ets1 in ErbB2 expressing breast cancer cells increases the expression of MMP-1 [128]. This evidence concerns the gene ERBB2 and breast carcinoma.