Abstract
Green tea polyphenols (TEA) are known to exhibit antioxidative activity as well as tumor‐suppressing activity. In order to examine the tumor‐suppressing activity of TEA against adult T‐cell leukemia (ATL), we cultivated peripheral blood T lymphocytes of ATL patients (ATL PBLs), an HTLV‐I‐infected T‐cell line (KODV) and healthy controls (normal PBLs) for 3 days in the presence of TEA and its main constituent, epigallocatechin‐3‐gallate (EGCg), to measure cell proliferation and apoptosis, and to quantitate mRNAs of
HTLV‐I pX
and
β‐actin
genes of the cultured cells. Growth of ATL PBLs was significantly inhibited by 9–27 μg/ml of TEA and EGCg, in contrast to minimal growth inhibition of T cells of normal PBLs. Inhibition of KODV was intermediate between ATL PBLs and normal PBLs. The ATL PBLs and KODV treated with 27 μg/ml of either TEA or EGCg induced apoptotic DNA fragmentation, producing terminal deoxynucleotidyl transferase‐mediated dUTP‐biotin nick end labeling (TUNEL)‐positive cells, while the normal PBLs treated with the same concentration of TEA or EGCg produced a negligibly small number of TUNEL‐positive cells, in which apoptotic DNA fragmentation was not detectable. Expression of HTLV‐I pX mRNA was suppressed more than 90% in ATL PBLs by treatment with 3–27 μg/ml of either TEA or EGCg, while expression of β‐actin mRNA was much less suppressed by treatment with the same concentration of TEA or EGCg. These results indicate that TEA and EGCg inhibit growth of ATL PBLs, as well as HTLV‐I‐infected T‐cells, by suppressing
HTLV‐I pX
gene expression and inducing apoptotic cell death.
