Abstract/Summary

Colon cancer is the third most diagnosed type of cancer globally and prostate cancer is the most common type of cancer in men. Consumption of diets containing fruits and vegetables is associated with a reduction in risk of both types of cancer. This may be due to the presence of various beneficial bioactive compounds and micronutrients in these foods. The precise mechanism(s) of protection are not well characterised. In this thesis, I focused on the anti-cancer effect of blueberry polyphenols on models of colon and prostate cancer. I hypothesised that the parent phytochemicals present in blueberries and their metabolites generated by in vitro digestion and fermentation would suppress molecular pathways associated with the progression of prostate and colon cancer in cell culture based models of carcinogenesis. The human colon adenocarcinoma cell lines, HT-29 and CaCo-2, were used as colon cancer models. I found that delphinidin and malvidin and crude methanol/water blueberry extract reduced oxidative DNA damage (comet assay), inhibited growth (DAPI-staining), and suppressed cell cycle activity through G,/M arrest (PI/flow cytometry). No improvement in epithelial integrity (TER assay) were observed. The human cell lines, WPE1-NA22 and WPE1-NB26 were used to represent benign and advanced stages of prostate cancer respectively. Similarly, these findings demonstrated that delphinidin and malvidin and crude methanol/water blueberry extract reduced oxidative DNA damage (comet assay). These compounds also inhibited cell migration (wound healing assay). It should be noted that the metabolites from blueberry were less protective on prostate cancer than they were on the colon cancer cells The in vitro digestion and fermentation models do not fully represent the metabolic fate of phytochemicals in vivo. Therefore, ileal fluid samples were collected from ileostomy patients following consumption of raspberries and these samples were used in in vitro fermentation models to assess the production of bioactive phenolic acids in the colon from polyphenol precursors. The pattern of major phenolic acids formed by the micro biota, consisted of benzoic acid derivatives e.g. benzoic acid, 4-hydroxybenzoic acid and phenyl propionic acid derivatives e.g. 3-(phenyl) propionic acid, 3(3' -hydroxyphenyl) propionic acid and 3(4' -hydroxyphenyl) propionic acid. These observations were in agreement with previous findings from our collaborators. Considerable inter-individual variation in the distribution of phenolic acids was observed, possibly due to variable transit times along GIT and the physical condition of each volunteer. We found that theses benzoic acid dervatives protected against H,O,-induced DNA damage in CCD841, colon epithelial cells, suggesting a potential for these compounds to reduce the risk of DNA mutation in colon cells. Therefore, these breakdown products may provide a colonic health benefit; however, this requires further investigation. In the final part of the thesis as a minor objective, Selenium (Se) was investigated for its effect(s) on cell death and survival using the CaCo-2 human adenocarcinoma cell line. We hypothesised that Se may induce the expression of genes involved in endoplasmiC reticulum (ER) stress-induced apoptosis as measured by real-time qPCR. No evidence that Se significantly induced the expression of caspase 3, a key gene in the apoptotic pathway via ER stress pathway was found. Similarly, glutathione peroxidase 1, a detoxifying enzyme belonging in selenoprotein family was not significantly up-regulated after the treatment of physiologically-relevant concentrations of Se. In conclusion, the in vitro studies completed in this thesis with blueberry extract and its metabolites as well as the major individual berry anthocyanidins had preventative effects in colon and prostate cancer cell models through multiple mechanisms. Se also seems to be a potential candidate for cancer prevention in colon cell model; however, further research is necessary to clarify the mechanism of action. This thesis provides further mechanistic evidence for the protective effects of berry phenolics and their metabolites in reducing the risk of colon and prostate cancer.