['Matrix metalloproteinases (MMPs) play pivotal roles in tumor progression. MMP-13 (collagenase-3) digests collagen and other extracellular components.', 'Reverse transcriptase-polymerase chain reaction (RT-PCR), immunohistochemistry and zymograph were used to study the roles of MMP-13 during the neoplastic process of oral squamous cell carcinoma (OSCC).', 'Increase of MMP-13 mRNA and protein expression in OSCC cell lines relative to cultivated normal oral keratinocytes was found. MMP-13 mRNA expression in OSCC was significantly higher than in non-cancerous match tissue (NCMT) in 36 tissue pairs. Esophageal squamous cell carcinoma also exhibited high MMP-13 mRNA expression. The percentage of OSCC exhibiting strong MMP-13 immunoreactivity was significantly higher than pre-invasive lesion and NCMT. Treatment with >5 microm epigallocatechin-3-gallate (EGCG) to OEC-M1 cells suppressed the expression and activity of MMP-13.'] Do increase of MMP-13 expression in multi-stage oral carcinogenesis and epigallocatechin-3-gallate suppress MMP-13 expression?