MMP9 and metastatic prostate carcinoma: A recent study found that L-theanine had the therapeutic potential for metastatic prostate cancer (PCa), since L-theanine inhibited the epithelial-mesenchymal transition process of PCa by downregulating matrix metallopeptidase 9 (MMP9), N-cadherin, Vimentin, and Snail, and upregulating E-cadherin (70).