Biological Activity of Broccoli on Human Colon Caco-2 Cells

Animal and cell culture studies with isothiocyanates (ITCs) have shown they can induce gene and protein expression and physiological processes consistent with anticarcinogenic activity. However there is little evidence to show the effects of whole broccoli extract, despite the wealth of epidemiological studies on the benefits of broccoli consumption. In this study we report changes in global gene expression in Caco2 cells exposed to crude broccoli extracts, differentially cooked to change their isothiocyanate profile. We find that the greatest extent of changes in gene expression occurred following exposure to extracts which had the highest concentration of isothiocyanates. However, changes in genes involved in polyamine metabolism and TGFβ signalling occurred following exposure to all extracts, including those containing no glucosinolate degradation products. Subsequent studies demonstrated that exposing cells to these extracts increased putrescine and N-acetyl spermine concentration, and suppressed the induction of phosphorylated Smad 2 in the presence of the TGFβ1 ligand. In conclusion there are bioactive compounds in broccoli, independent of ITCs, that can perturb physiological and anticancer activities, including polyamine catabolism and TGFβ signalling.