Green tea polyphenols modulate secretion of urokinase plasminogen activator (uPA) and inhibit invasive behavior of breast cancer cells.

Many epidemiological studies have suggested that consumption of green tea may decrease the risk of cancer. The chemopreventive effect of green tea polyphenols (GTP) has been demonstrated through the inhibition of cell proliferation and angiogenesis in cell culture and animal models of breast cancer. Metastasis of breast cancer is the major reason for the high mortality of breast cancer patients and is directly linked to the invasive behavior of breast cancer cells. Cancer metastasis consists of several interdependent processes including cancer cell adhesion, cancer cell migration, and invasion of cancer cells. In this study, we evaluated the effect of GTP on human breast cancer cells, and we show that in addition to inhibiting cell growth, GTP also suppressed the invasive behavior of MDA-MB-231 cells. These anti-invasive effects of GTP were the result of the inhibition of constitutively active transcription factors AP-1 and NF-kappaB, which further suppressed secretion of urokinase plasminogen activator (uPA) from breast cancer cells. Based on these results, it can be hypothesized that GTP treatment resulted in the inhibition of formation of signaling complexes responsible for cell adhesion and migration (uPA, uPA receptor, vitronectin, integrin receptor) and cell invasion (uPA, uPA receptor). Our results indicate that GTP may contribute to the anticancer effects of green tea by inhibiting the invasive behavior of cancer cells.