okadaic-acid and Intestinal-Neoplasms

The study of green tea polyphenols as a cancer preventative is approaching a new era, with significant results accumulating rapidly. This paper briefly reviews four topics related to mechanisms of action of tea polyphenols: (I) identification of the genes commonly affected by EGCG, as demonstrated by Clontech's Atlas cDNA Expression Array; (II) the significance of heterogeneous nuclear ribonucleoprotein B1 (hnRNP B1) as a new biomarker for early detection of lung cancer, and inhibition of its expression by EGCG; (III) the synergistic or additive effects of EGCG with the cancer preventive agents, sulindac and tamoxifen, on induction of apoptosis in PC-9 cells and on inhibition of intestinal tumor development in multiple intestinal neoplasia (Min) mice; (IV) the results of a 10 year prospective cohort study demonstrating the effectiveness of daily consumption of green tea in preventing cancer, and a prototype study for developing green tea beverage as cancer preventive.

Topics: Animals; Anticarcinogenic Agents; Biomarkers, Tumor; Carcinoma, Squamous Cell; Catechin; Chemoprevention; Cohort Studies; Drug Synergism; Female; Gene Expression Profiling; Gene Expression Regulation, Neoplastic; Heterogeneous-Nuclear Ribonucleoprotein Group A-B; Heterogeneous-Nuclear Ribonucleoproteins; Humans; Intestinal Neoplasms; Japan; Lung Neoplasms; Male; Mice; Mice, Mutant Strains; Okadaic Acid; Oligonucleotide Array Sequence Analysis; Prospective Studies; Ribonucleoproteins; Sulindac; Tea; Tumor Cells, Cultured

Two non-transformed intestinal epithelial cell lines (RIE-1 and IEC-6) and three intestinal carcinoma cell lines (HT-29, T84 and MCA-38) were used to detect the toxic effects due to okadaic acid in the presence of mussel tissue homogenates. Cytotoxicity was assessed by measurement of the metabolic conversion of 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyl tetrazolium bromide to its corresponding formazan dye. All of the cell lines were sensitive to okadaic acid, with HT-29, RIE-1 and IEC-6 showing the greatest response. Dilutions of whole mussel tissue homogenates caused some loss of viability in most of the cell lines but had no significant effect on the viability of RIE-1 cells. In no case did the mussel homogenate compromise the dose-response curve to okadaic acid when data were normalized to the appropriate control value. These intestinal epithelial cell lines may prove useful in the bioassay of okadaic acid and related toxins.

Topics: Animals; Bivalvia; Cell Line; Cell Survival; Epithelial Cells; Epithelium; Ethers, Cyclic; Humans; Intestinal Mucosa; Intestinal Neoplasms; Mice; Mitochondria; Okadaic Acid; Phosphoprotein Phosphatases; Rats; Succinate Dehydrogenase; Tumor Cells, Cultured