Inhibition of colorectal cancer cells 'in vitro': an investigation of the chemo-preventative action of common culinary spices

Baker, Tibbie (2012) Inhibition of colorectal cancer cells 'in vitro': an investigation of the chemo-preventative action of common culinary spices. (MSc(R) thesis), Kingston University, .


Colorectal cancer (CRC), a leading cause of cancer deaths, is characterised by two early molecular events: the expression of cyclo-oxygenease-2 (COX-2) and aberrant Wnt signalling. Culinary spices and their constituent polyphenols have been shown to inhibit both COX-2 expression and cancer cell growth in vitro. However, there is relatively little data on the effect of culinary spices on CRC cells. Thus, the aim of this study was two-fold: to investigate the impact of a selection of commonly used culinary spices (cinnamon, clove, ginger, nutmeg and turmeric) on the growth of CRC cell lines HCT116 (a COX-2 negative cell line) and HT29 (a COX-2 positive cell line); and to identify whether the measured inhibition is underpinned by their effect on ß-catenin (a central signal transducer of the Wnt pathway and a marker of uncontrolled proliferation) and/or COX-2. Growth . inhibition studies indicated that all the spices tested were able to inhibit CRC cell proliferation in vitro and that their potency was influenced by the extraction solvent used and the cell line; the 50% inhibitory concentration (ICso) ranged from 3.5 gallic acid equivalents (GAE) Ilg/ml (clove) to 18.4 GAE Ilg/ml (cinnamon). Analysis of the data indicated that the amount of actual ground spice needed to achieve the ICso, for aqueous extracts only, did not exceed the amounts used in the preparation of food. Immunoblot analysis indicated that the spice extracts (SEs) did not have an effect on Wnt signalling via ß-catenin and their impact on COX-2 could not be determined. In conclusion, this study shows that whole spice extracts inhibited the growth of colorectal cancer cells in vitro at quantities that can be achieved in the diet, and can thus be considered as promising dietary chern 0- preventative agents. However, further experiments are required for the elucidation of their mode of action. Interactions that occur between the constituent polyphenols of these spices may provide further insight into their chemo-preventative properties and also the chemo-therapeutic potential of their constituents.

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