The role of apoptosis in the modulation of colon carcinogenesis by dietary fat and by the organoselenium compound 1,4-phenylenebis(methylene)selenocyanate.

Studies in laboratory animals have demonstrated that dietary supplements of organoselenium, 1,4-phenylenebis(methylene)selenocyanate (p-XSC) inhibit colon carcinogenesis. Diverse chemopreventive agents and clinically used anticancer drugs have been shown to induce apoptosis in colonic tumors. Inducing apoptosis is a key mechanism for the effectiveness of some chemopreventive agents; however, failure of apoptosis is now believed to contribute to the development of human cancer. In this study, we determined the number of apoptotic bodies in the colon tumors of rats fed a low-fat (LF) or a high-fat (HF) diet with or without p-XSC treatment. At 5 weeks of age, male F344 rats were divided into four groups, which were then maintained on one of the following diets: LF, 5% corn oil; HF, 23.5% corn oil; and LF and HF supplemented with 20 ppm p-XSC. In addition, the LF or HF diet with p-XSC supplements was administered either during the initiation stage or postinitiation. At 7 weeks of age, all rats except those intended for vehicle (normal saline) treatment were given 15 mg/kg of body weight of azoxymethane once weekly for 2 weeks. The animals were sacrificed 38 weeks after carcinogen treatment, and their colonic tumors were examined for appearance of apoptosis. The LF diet significantly increased the percentage of apoptosis as compared to the HF diet; the percentage of apoptosis in LF and HF diets were 12.4 and 2.9. The colon tumors that were present in the groups fed p-XSC together with a LF or a HF diet after carcinogen administration (postinitiation period) had a higher number of apoptotic bodies than those that were present in the animals fed p-XSC before carcinogen treatment (initiation period). The extent of apoptosis was weak when p-XSC was given with a HF diet (4.4%) during the initiation phase, but it was high significant when p-XSC was administered with LF diet (25.2%). Taken together, our data suggest that administration of LF diet supplemented with p-XSC increases apoptosis as compared to a HF diet alone.

Modulation of apoptosis by sulindac, curcumin, phenylethyl-3-methylcaffeate, and 6-phenylhexyl isothiocyanate: apoptotic index as a biomarker in colon cancer chemoprevention and promotion.

Recent evidence supports the theory that tumor growth in vivo depends on evasion of normal homeostatic control mechanisms that operate through induction of cell death by apoptosis. This study tested the hypothesis that several potential chemopreventive agents share the ability to induce apoptosis and that inhibition of apoptosis is a mechanism of tumor promoters. The present study was designed to investigate whether the chemopreventive properties of sulindac, curcumin, and phenylethyl-3-methylcaffeate (PEMC) and the tumor-promoting activity of 6-phenylhexyl isothiocyanate (PHITC) that were observed in our previous studies are associated with the induction or inhibition of apoptosis in azoxymethane (AOM)-induced colon tumors in male F344 rats. At 5 weeks of age, groups of rats were fed control (modified AIN-76A) diet or diets containing 320 ppm of sulindac, 2000 ppm of curcumin, 750 ppm of PEMC, or 640 ppm of PHITC. At 7 weeks of age, all rats except those intended for vehicle (normal saline) treatment were given AOM (15 mg/kg body weight) once weekly for 2 weeks. To study the effect of sulindac administered during promotion/progression stage, the rats were fed the control diet initially and then fed the experimental diet containing 320 ppm of sulindac 14 weeks after the second AOM treatment. The rats were sacrificed 52 weeks after carcinogen treatment, and their colonic tumors were subjected to histopathological evaluation and the appearance of apoptosis. In the current study, chronic administration of sulindac, curcumin, and PEMC or sulindac given only during promotion/progression significantly increased the apoptotic index (percentage of apoptosis) as compared to administration of the control diet; the apoptotic indices in the control, sulindac, curcumin, and PEMC diets were 8.3, 17.6, 17.7, and 18.5%, respectively, and in sulindac administered during promotion/progression stage, the apoptotic index was 19.1%. However, dietary PHITC blocked the process of apoptosis during colon carcinogenesis. The apoptotic index in PHITC diet was 7.0%. Taken together, our data show that chemopreventive properties of agents are correlated with the degree of apoptosis. Therefore apoptosis seems to be a reliable biomarker for the evaluation of potential agents for cancer prevention.

Evaluation of cell death in EBV-transformed lymphocytes using agarose gel electrophoresis, light microscopy and electron microscopy. I. Induction of classic apoptosis by the bile salt, sodium deoxycholate.

In this study, we examined the effect of different concentrations of sodium deoxycholate (NaDOC), a secondary bile salt, on an Epstein-Barr virus transformed human lymphoid cell line (NC-37). We found that NaDOC induces classic apoptosis in a dose-dependent manner at 0.1-0.4 mM doses, and necrosis at much higher concentrations (0.8-3.1 mM). This is the first demonstration that a bile salt can induce apoptosis in any cell type. The mode of cell death was determined using morphologic methods (light and electron microscopy) as the gold standard. Standard agarose gel electrophoretic techniques were applied to identify the "ladder" of DNA fragments that have been associated with apoptosis in certain cell types. Although DNA fragmentation was observed during the apoptotic death of NC-37 cells, we were not able to identify a "ladder" pattern of fragmentation. Two other types of cells, however, that previously have been reported to display a characteristic "ladder" pattern of DNA fragmentation, glucocorticoid-treated WEHI7.2 cells and isolated human neutrophils, did display the "ladder" pattern. This study emphasizes the need to examine morphology when identifying the mode of cell death induced by a new agent.