Plasma and tissue levels of tea catechins in rats and mice during chronic consumption of green tea polyphenols.

To understand the relationship between tea consumption and its biological effects, plasma and tissue levels of (-)-epigallocatechin-3-gallate (EGCG), (-)-epigallocatechin (EGC), and (-)-epicatechin (EC) were measured after rats and mice were given a 0.6% green tea polyphenol preparation as the drinking fluid for different periods of time. EGC and EC levels in rat plasma increased over time and reached peak values (3 times the Day 1 values) on Day 14. Then the plasma levels of tea catechins decreased, to Day 1 values on Day 28. The plasma concentrations of EGCG were much lower than those of EGC or EC. High levels of EGC and EC were found in urine, whereas high levels of EGCG were found in feces. The changes in the urinary and fecal excretions of tea catechins could not account for the above-described changes in the plasma levels. The amounts of catechins in different tissues reflected the ingestion, absorption, and excretion pattern. When the green tea polyphenol preparation was given to mice, the "increase-and-then-decrease" pattern of catechin levels was also observed in the plasma, lung, and liver; the EGCG levels were much higher than in the rats. The results suggest that consumption of tea by rodents could induce adaptive responses affecting blood and tissue levels of tea catechins with time and that investigation of a similar phenomenon in humans is warranted.

Molecular alterations of p73 in human esophageal squamous cell carcinomas: loss of heterozygosity occurs frequently; loss of imprinting and elevation of p73 expression may be related to defective p53.

p73 is structurally and functionally related to p53 and is possibly a tumor suppressor gene. Using 15 surgically resected frozen esophageal specimens containing both squamous cell carcinomas (ESCC) and neighboring normal epithelia, we studied p73 gene alterations and mRNA expression. Loss of heterozygosity of the p73 loci was found in nine of 14 informative cases (64%). A polymorphism at codon 173 (Thr) of p73 was identified (eight samples had ACC and seven had ACT), but mutation was not detected in tumor samples. Nine of the 15 ESCC samples (60%) displayed significantly elevated expression of p73 over the neighboring normal epithelium; of these nine samples, four displayed loss of imprinting (LOI) and one switched the expressed allele. Hypermethylation of exon 1 of the p73 gene was not detected, using the bisulfite modification method, in normal or tumor samples. Twelve of the 15 (80%) ESCC samples contained p53 defects, including missense mutation, non-frameshift small deletion or insertion, non-detectable transcripts and protein accumulation. The ESCC samples with p53 defects were significantly correlated with those which had elevated expression of p73 (Fisher's exact test, P < 0.05). The results suggest that increased expression of p73, including that by LOI, could be a partial compensatory mechanism for defective p53.

Inhibition of 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone-induced lung tumorigenesis by dietary olive oil and squalene.

Epidemiological studies have suggested that frequent olive oil consumption may be a protective factor against lung cancer formation. Squalene, a characteristic compound in olive oil, is an inhibitor of 3-hydroxy-3-methylglutaryl coenzyme A reductase activity and has been proposed to inhibit the farnesylation of ras oncoproteins. The present study investigated the effect of dietary olive oil and squalene in a mouse lung tumorigenesis model. Female A/J mice were fed AIN-76A diets containing 5% corn oil (control), 19.6% olive oil, or 2% squalene starting at 3 weeks before a single dose of 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK) (103 mg/kg, i.p.). Animals were maintained on their respective diets throughout the study. At 16 weeks after NNK administration, 100% of the mice in the control group had lung tumors with a tumor multiplicity of 16 tumors per mouse. The olive oil and squalene diets significantly (P < 0.05) decreased the lung tumor multiplicity by 46 and 58%, respectively. The squalene diet significantly (P < 0.05) decreased lung hyperplasia by 70%. In mice fed a diet containing 2% squalene for 3 weeks, the activation of NNK was increased by 1.4- and 2.0-fold in lung and liver microsomes, respectively, but its relationship to the inhibition of carcinogenesis is not clear. These results demonstrate that dietary olive oil and squalene can effectively inhibit NNK-induced lung tumorigenesis.

Characterization of early pulmonary hyperproliferation and tumor progression and their inhibition by black tea in a 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone-induced lung tumorigenesis model with A/J mice.

The pathogenesis of pulmonary tumors induced by a tobacco carcinogen, 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK), and its inhibition by black tea have been characterized. Female A/J mice (6 weeks old) were treated with a single dose of NNK (103 mg/kg of body weight, i.p.) on day 0, and the cell proliferation index was measured by the incorporation of bromodeoxyuridine (BrdUrd) immunohistochemically. The number of BrdUrd-labeled cells increased in the bronchiolar epithelium from day 2 to day 14, with the highest proliferation rate observed on day 5. By day 35, the BrdUrd-labeling index returned to the level of the control group. Further examination of the day 35 samples revealed the presence of foci of hyperproliferative cells in the bronchiolar epithelium, particularly in the bronchiolalveolar regions. These proliferating bronchiolar epithelial cells (Clara cells) may be the initiated sites for pulmonary tumorigenesis. In this short-term model, administration of black tea polyphenols (0.3%) through the drinking water starting 24 h after NNK treatment significantly inhibited NNK-induced early bronchiolar cell proliferation on day 5. In long-term studies, adenomas were observed in 100% (15 of 15) of the mice at week 16, with 7.8 +/- 0.8 tumors per mouse. At week 52, a malignant tumor incidence of 80% (41 of 51 mice) and a malignant tumor multiplicity of 2.39 +/- 0.19 were observed. The growth patterns of the malignant tumors, which included solid, papillary, and mixed types, may be associated with the cellular origin of the tumor. The cell proliferation indices, as measured by proliferating cell nuclear antigen immunohistochemistry, were significantly higher in dysplasia within adenoma than in adenoma, and significantly higher in adenoma at week 52 than in adenoma at week 16. Administration of black tea, starting 16 weeks after a single dose of NNK, inhibited the progression of adenoma to adenocarcinoma as determined by both malignant tumor incidence and multiplicity. The cell proliferation rate in adenomas was also suppressed by black tea treatment. The present work demonstrates the antiproliferative activities of black tea and its polyphenols. Such activities, at the early and late stages of lung tumorigenesis, may be important for the cancer-chemopreventive activities of black tea.

Black tea constituents, theaflavins, inhibit 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK)-induced lung tumorigenesis in A/J mice.

The present study investigated the inhibitory activity against lung tumorigenesis by a group of characteristic black tea polyphenols, theaflavins. In a short-term study, female A/J mice were treated with a single dose of 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK; 103 mg/kg b.w., i.p.) on day 0, and 0.1 and 0.3% theaflavins were administered as the sole source of drinking fluid starting 24 h after NNK treatment. The proliferation index of the lung tissues was measured by the incorporation of bromodeoxyuridine (BrdU) immunohistochemically. The highest NNK-induced proliferation rate of bronchiolar cells, observed on day 5, was significantly decreased by 0.3% theaflavins (proliferation index, 1.51 +/- 0.08 versus 2.35 +/- 0.16). In a long-term lung tumorigenesis study, pulmonary adenomas were observed in 100% (30/30) of the mice at week 16 after NNK treatment. Administration of theaflavins (0.1%) as the sole source of drinking fluid, starting 2 days after the NNK treatment until the termination of the experiment, significantly reduced the tumor multiplicity and volume by 23% (8.5 +/- 0.6 versus 6.5 +/- 0.6 tumors/mouse) and 34% (0.08 versus 0.05 mm3 per tumor), respectively. The proliferation index in lung adenomas was also significantly inhibited by theaflavins. The present work demonstrates the inhibitory action of theaflavins against NNK-induced pulmonary hyperproliferation and tumorigenesis.