MMP1 and neoplasm: We found that PMA (50 ng/mL), which is a strong tumor inducer, significantly enhanced MMP-1, -3, and -9 mRNA expressions, whereas pre-treatment with C2 ceramide resulted in an inhibition of the MMP-1, -3, and -9 expressions in both the U87MG and U373MG cells (Figure 1A–D).