Otsuka T. Ogo T. Eto T. Asano Y. Suganuma M. Niho Y. Institution
First Department of Internal Medicine, Faculty of Medicine, Kyushu University, Fukuoka, Japan.
Growth inhibition of leukemic cells by (-)-epigallocatechin gallate, the main constituent of green tea.
Life Sciences. 63(16):1397-403, 1998. Abstract
In this report, we presented the results that EGCG, the main constituent of the polyphenols present in Japanese green tea inhibited growth of leukemic cell lines of both human and mice. The proliferation of human leukemic cell lines and mouse NFS60 cell line was inhibited by EGCG. Sensitivity of each line to EGCG was different, and more than 50% of DNA synthesis was reduced in all the cell lines in the presence of 50 microM EGCG. On the other hand, normal hematopoietic progenitor cells retained their natural function of supplying mature cells of various lineages in the presence of less than 10 microM EGCG in vitro. Even in the presence of 100 microM EGCG, half the colonies containing all the lineages of cells were developed. All the dead cells of each line showed characteristics of apoptosis, which might be due to inhibition by EGCG of growth factors' signaling. Besides anticarcinogenic activity, EGCG is expected to have a new function for leukemia therapy without side effects.
Nakachi K. Suemasu K. Suga K. Takeo T. Imai K. Higashi Y. Institution
Department of Epidemiology, Saitama Cancer Center Research Institute. Title
Influence of drinking green tea on breast cancer malignancy among Japanese patients. Source
Japanese Journal of Cancer Research. 89(3):254-61, 1998 Mar. Abstract
Inhibitory effects of green tea on
carcinogenesis have been investigated in numerous laboratory studies using (-)-epigallocatechin gallate (EGCG) or crude green tea extract, and there is also some epidemiologic evidence. Further, EGCG has been reported to inhibit the growth of cancer cells, lung metastasis in an animal model, and urokinase activity. In this study, we first examined the association between consumption of green tea prior to clinical cancer onset and various clinical parameters assessed at surgery among 472 patients with stage I, II, and III breast cancer. We found that increased consumption of green tea was closely associated with decreased numbers of axillary lymph node metastases among premenopausal patients with stage I and II breast cancer and with increased expression of progesterone receptor (PgR) and estrogen receptor (ER) among postmenopausal ones. Since these are potential prognostic factors, we then investigated the prognosis of breast cancer with special reference to consumption of green tea, in a follow-up study of these patients. We found that increased consumption of green tea was correlated with decreased recurrence of stage I and II breast cancer (P < 0.05 for crude disease-free survival); the recurrence rate was 16.7 or 24.3% among those consuming > or = 5 cups or < or = 4 cups per day, respectively, in a seven-year follow-up of stage I and II breast cancer, and the relative risk of recurrence was 0.564 (95% confidence interval, 0.350-0.911) after adjustment for other lifestyle factors. However, no improvement in prognosis was observed in stage III breast cancer. Our results indicate that increased consumption of green tea prior to clinical cancer onset is significantly associated with improved prognosis of stage I and II breast cancer, and this association may be related to a modifying effect of green tea on the clinical
characteristics of the cancer.
Imai K. Suga K. Nakachi K.
Department of Epidemiology, Saitama Cancer Center Research Institute, Japan. Title
Cancer-preventive effects of drinking green tea among a Japanese population.
Preventive Medicine. 26(6):769-75, 1997 Nov-Dec. Abstract
BACKGROUND: Laboratory studies have revealed the cancer preventive effects of green tea, so the association between
green tea consumption and cancer was
examined in a human population. METHODS: The association between green tea consumption and cancer incidence was studied in our prospective cohort study of a Japanese population. We surveyed 8,552 individuals over 40 years of age living in a town in Saitama prefecture on their living habits, including daily consumption of green tea. During the 9 years of follow-up study (71,248.5 person-years), we identified a total of 384 cases of cancer in all sites. RESULTS: We found a negative association between green tea consumption and cancer incidence, especially among females drinking more than 10 cups a day. The slowdown in increase of cancer incidence with age observed among females who consumed more than 10 cups a day is consistent with the finding that increased consumption of green tea is associated with later onset of cancer. Age-standardized average annual incidence rate was significantly lower among females who consumed large amounts of green tea. Relative risk (RR) of cancer incidence was also lower among both females (RR = 0.57, 95% CI = 0.33-0.98) and males (RR = 0.68, 95% CI = 0.39-1.21) in groups with the highest consumption, although the preventive effects did not achieve statistical significance among males, even when stratified by smoking and adjusted for alcohol and dietary variables. CONCLUSION: Our epidemiological study showed that green tea has a potentially preventive effect against cancer among humans.