Most miRNAs participate in the regulation of the synthesis of a single MMP; however, miRNA-29b regulates MMP-2 synthesis in prostate cancer cells and MMP-9 expression in osteosarcoma, while miRNA-34a controls MMP-9 and MMP-14 production in tongue squamous cell carcinoma [41,42,43]. This evidence concerns the gene MMP9 and prostate cancer.