MMP9 and prostate cancer: CD44 (Cluster of Differentiation 44) is a transmembrane hyaluronic acid receptor that can act as the organizing platform for MMPs and can be cleaved by proteases resulting in extra- and intracellular forms, where the latter one was reported to bind to runt-related transcription factor 2 (RUNX2) and work as a co-transcriptional factor for metastatic-related genes, e.g., MMP9 in prostate cancer [28, 29].