MMP1 and breast cancer: Interestingly, it has also been demonstrated that human epidermal growth factor receptor 2 (HER-2) induces MMP-1 expression through the enhanced regulation of the transcription factor/proto-oncoprotein Ets-1, suggesting that (contrary to the protective role of MMP-8 neutrophil collagenase [20]) the interstitial collagenase MMP-1 may significantly affect the metastatic behavior of BC cells [33].