Consuming broccoli does not induce genes associated with xenobiotic metabolism and cell cycle control in human...

Epidemiological studies suggest that a diet rich in broccoli can reduce the risk of cancer at several sites. The anticarcinogenic activity has been largely attributed to the biological activity of sulforaphane (SF), the isothiocyanate derived from 4-methylsulphinylbutyl glucosinolate, which accumulates in broccoli. SF induces xenobiotic metabolizing genes in both cell cultures and animal models and induces genes associated with cell cycle arrest and apoptosis. However, it is not known whether these genes are induced in humans after consumption of broccoli. Sixteen subjects were recruited into a randomized, 3-phase crossover dietary trial of standard broccoli, high glucosinolate broccoli, and water. Global changes in gene expression that occurred 6 h after consuming broccoli soups or water were quantified in gastric mucosal tissue, using Affymetrix whole genome microarrays (n = 4), and in selected genes by real-time RT-PCR in the other individuals. Consumption of high glucosinolate broccoli resulted in up-regulation of several xenobiotic metabolizing genes, including thioredoxin reductase, aldoketoreductases, and glutamate cysteine ligase modifier subunit, which have previously been reported to be induced in cell and animal models after exposure to SF. Only 1 such gene was significantly up-regulated after consumption of standard broccoli. The consequences of these results in relation to the potential anticarcinogenic action of broccoli are discussed.