Involvement of 67 kDa Laminin Receptor on Cellular Uptake of Green Tea Polyphenol Epigallocatechin-3-O-Gallate in Caco-2 Cells

Abstract

The major polyphenol in green tea, (−)-epigallocatechin-3-O-gallate (EGCG) has been shown to prevent carcinogenesis. Most recently, we have identified the metastasis-associated 67 kDa laminin receptor (67LR) as a cell surface receptor that mediates the anti-cancer and anti-allergic activities of EGCG. We have established human colon cancer Caco-2 cells expressing elevated or reduced 67LR by transfecting with the 67LR gene or 67LR-specific siRNA. Enhanced expression of 67LR in Caco-2 cells increased the growth inhibitory activity of EGCG correlating with the EGCG binding to the cell surface, whereas the 67LR-downregulated cells have lost the ability to bind EGCG and the response to the EGCG activity. We evaluated the levels of cellular uptake of EGCG in these cells to investigate an involvement of 67LR on EGCG cellular uptake. As a result, the enhanced 67LR-expression reduced the uptake level of EGCG, whereas the 67LR-downregulated cells have increased it. These results suggest that 67LR associates with the cellular uptake of EGCG in Caco-2 cells.