In this study, the authors investigated the mechanism of antiproliferative and apoptotic actions exerted by tea polyphenols on human papilloma virus-18-positive HeLa cervical cancer cells. Treatment of HeLa cells with green tea polyphenol (-)-epigallo-catechin gallate (EGCG) and black tea polyphenol theaflavins (TF) in showed a marked concentration- and time-dependent inhibition of proliferation and induced sub-G1 phase in a dose-dependent manner after 24 h. There was an attenuation of mitochondrial membrane potential with the increase of reactive oxygen species generation, p53 expression, Bax/Bcl-2 ratio, cytochrome-c release, and cleavage of procaspase-3 and -9 and poly(ADP-ribose)-polymerase, indicating the participation of a mitochondria related mechanism. In addition, EGCG as well as TF inhibited activation of Akt and nuclear factor-kappaB (NF-kappaB) via blocking phosphory-lation and subsequent degradation of inhibitor of kappaBalpha and kappaBbeta subunits, thereby downregulating cyclooxygenase-2. Additionally, the protein level of cyclin D1, a transcriptional target of NF-kappaB, was also reduced significantly.

Singh et al. Oncology Research; 2011;19:245-57.