MMP9 and neoplasm: SNAIL may enhance the expression of interstitial-space–related genes, such as MMP9 and ZEB1. A variety of MAPK pathways, such as ERK1 and -2, JNK, and p38 kinase cascades, participate in the expression of MMP1 caused by tumor necrosis factor alpha (TNF-α) by upregulating EGR1 and promote tumor invasion and metastasis (39).