Photodynamic therapy in combination with green tea polyphenol EGCG enhances antitumor efficacy in human papillomavirus 16 immortalized tumor cells

A constituent of green tea, (-)-epigallocatechin-3-gallate (EGCG), or polyphenol (GTP) has been known to possess anti-cancer properties. Our goal was to investigate the enhanced anti-tumor effects of photodynamic therapy (PDT) plus green tea extract in TC-1 tumor cells implanted into mice. The MTT assay, Western blot analysis and tumor growth inhibition study were evaluated at various time intervals after the PDT plus EGCG or GTP. Following Radachlorin injection after 3 hr, the tumors were then treated with external light treatment (300 J/ cm2), and then, EGCG or GTP was administered daily for 20 days. PDT or EGCG was found to be more effective compared to control groups. Moreover, the PDT combined with EGCG demonstrated a significant suppression of tumor growth in vitro and in vivo. The tumor growth by the PDT combined with EGCG was significantly reduced. The PDT combined with GTP was also suppressed the tumor size compared with the control group. However, the tumor volume after EGCG treatment was significantly suppressed compared to GTP. In addition, EGCG lowered the uptake of Radachlorin. Thus, an EGCG supplement prior to photodynamic irradiation is not desirable. The PDT combination with EGCG in vitro and in vivo led to a significant decrease in levels of COX-2 at 48 hr post PDT plus EGCG combination treatment. These data suggest that EGCG plus PDT can induce a significant tumor suppression response compared with PDT alone. Also, it can be an effective approach to induce anti-cancer therapy strategy. KEY WORDS: Photodynamic therapy; Radachlorin; (-)-epigallocatechin-3-gallate; EGCG; Green Tea Polyphenol