Inhibition of urinary bladder carcinogenesis by broccoli sprouts

“The bladder is like a storage bag, and cancers in the bladder occurs almost entirely along the inner surface, the epithelium, that faces the urine, presumably because this tissue is assaulted all the time by noxious materials in the urine,” said senior author Yuesheng Zhang, M.D., Ph.D, professor of oncology at Roswell Park Cancer Institute. “The ITCs in broccoli sprout extracts after oral ingestion are selectively delivered to the bladder epithelium through urine excretion.”

Using a rat model of bladder cancer, Zhang and his colleagues found that freeze-dried aqueous extract of broccoli sprouts significantly, and dose-dependently, inhibited bladder cancer development. The incidence, multiplicity, size and progression of bladder cancer were all inhibited by the extract, while the extract itself caused no observable changes in the bladder. This protective effect of the extracts was associated with a significant increase in the bladder of several enzymes that are known to protect against oxidants and carcinogens, Zhang says.

In the body, ITCs are metabolized to dithiocarbamates (DTCs). The researchers measured the levels of ITCs and DTCs in the blood, tissue and urine of the rats fed with the extracts. More than 70 percent of the ITCs present in the extracts were excreted into the urine as ITC equivalents (ITCs + DTCs) in 12 hours after a single oral dose, indicating high bioavailability and rapid urinary excretion.

What is more striking, Zhang says, is that the concentrations of ITC equivalents in the urine of extracts-treated rats were two to three orders of magnitude higher than those in plasma, indicating that the bladder epithelium is most exposed to orally dosed ITCs. Indeed, tissue levels of ITC equivalents in the bladder were significantly higher than in the liver, demonstrating that the ITCs in the extracts are efficiently and selectively delivered to the bladder epithelium through urinary excretion, Zhang concludes.-American Association for Cancer Research