MMP2 and breast cancer: A subsequent study found contradictory results regarding MMP2 [43] in which the role of ERK 1/2 was confirmed in breast cancer metastasis to the brain; however, blockade of this pathway with PD98059 suppressed the secretion of MMP2, which they suggest was the main mechanism by which ERK 1/2 increased metastatic potential due to MMP2 being a pivotal candidate in cell motility.