The mechanism by which certain vegetables can slow the growth of cancer cells was detailed in a recent article in the scientific journal Carcinogenesis. The article’s author, Leslie Wilson, is a professor of biochemistry and pharmacology at UCSB. His research discovered how the compounds from broccoli and other cruciferous vegetables - that is, edible plants in the family Brassicaceae, which also includes many leafy greens - work on a cellular level to inhibit the growth of breast cancer.
“There are many active cancer-fighting agents in these vegetables,” Wilson said. The cancer-fighting compounds, known as isothiocyanates, come from a substance known as glucoraphanin, which is particularly abundant in broccoli and cauliflower. It is especially prevalent in the young sprouts of these two vegetables, but is also present in many cruciferous vegetables including cabbage, kale, and collard greens. When the vegetables are chewed, the isothiocyanates are produced.
The particular compound Wilson’s lab studied was sulforaphane, an isothiocyanate originally discovered in 1992. “Our goal here is to figure out how things work,” Wilson said. He found that sulforaphane acts in a similar way to powerful anticancer drugs already on the market, such as Taxol and Vinblastine, which are also derived from plants. The difference between sulforaphane and these drugs is that it is much weaker and therefore less toxic. Wilson said that there were no observable side effects in his study.
According to Wilson’s research, sulforaphane reduces the growth of breast cancers cells by causing cell death. He explained that all animal cells, including tumor cells, divide by a process called mitosis. During mitosis, the cells are divided by structures called microtubules to become two separate cells. Sulphoraphane acts to hinder these essential microtubules, and when the dividing cells can’t separate, they die. It therefore “inhibits proliferation and kills precancerous cells,” according to Wilson.
While his research focused on breast cancer, Wilson said that the evidence suggests sulforaphane might inhibit the proliferation of many rapidly growing tumor cells. He mentioned its potential in treating lung, colon, and prostate cancers, although he said the evidence is fragmentary. Stomach and pancreatic cancers, on the other hand, don’t respond to this kind of treatment, he said.
Although no full-scale clinical trials have been conducted with breast cancer patients, Wilson said, “My hope is that this can stimulate interest in clinical trials.” He added that there is still much work to be done, as is often the case with this kind of research.
Sulforaphane is also known to have antioxidant properties, as are other compounds found in these vegetables. It has also been reported to have antidiabetic and antimicrobial properties.
The best way to get sulforaphane, together with other isothiocyanates, is in vegetables, according to Wilson. “If you eat a lot over time, you get a lot of activity of those compounds,” he said. He added that this activity is lost by extensive cooking of the vegetables. He recommended eating them raw or lightly steamed instead. Other research suggested that while boiling resulted in a loss of these compounds, steaming, microwaving, and stir-frying the vegetables did not result in a significant loss.