MMP14 and breast cancer: This study confirmed the role of β1 integrin in the MMP-2 activation response of breast cancer cells to Col I. This work has demonstrated that abrogation of β1 integrin caused down-regulation of MT1-MMP, α2 and α3 integrins, and reduced MMP-2 activation in response to Col I. The reduction in MMP-2 activation required the most complete abrogation of β1 integrin, suggesting that an important threshold may exist for the level of β1 integrin required to mediate Col I-stimulated MMP-2-activation.