1. ¹Department of Oral and Maxillofacial Sciences, Gifu University, Graduate School of Medicine, 1-1 Yanagido, Gifu 501-1194, Japan
2. ²Department of Tumor Pathology, Gifu University, Graduate School of Medicine, Gifu 501-1194, Japan

Correspondence: Dr K Kato, E-mail: keizo@gifu-u.ac.jp

³These authors contributed equally to this work.

Received 9 November 2007; Revised 23 June 2008; Accepted 30 June 2008; Published online 29 July 2008.

Abstract

RECK is a novel tumour suppressor gene that negatively regulates matrix metalloproteinases (MMPs) and inhibits tumour invasion, angiogenesis and metastasis. In the present study, we investigated the effects of epigallocatechin-3-gallate (EGCG), a major polyphenol in green tea, on the methylation status of the RECK gene and cancer invasion in oral squamous cell carcinoma cell lines. Our results showed that treatment of oral cancer cells with EGCG partially reversed the hypermethylation status of the RECK gene and significantly enhanced the expression level of RECK mRNA. Inhibition of MMP-2 and MMP-9 levels was also observed in these cells after treatment with EGCG. Interestingly, EGCG significantly suppressed cancer cell-invasive ability by decreasing the number of invasive foci (P<0.0001) as well as invasion depth (P<0.005) in three-dimensional collagen invasion model. Although further investigation is required to assess the extent of contribution of RECK on MMPs to the suppression of invasive behaviour, these results support the conclusion that EGCG plays a key role in suppressing cell invasion through multiple mechanisms, possibly by demethylation effect on MMP inhibitors such as RECK.