办事指南

Cancer killer - A hormone in soya beans starves tumour cells to death

点击量:   时间:2018-02-10 07:01:11

By Andy Coghlan BIOCHEMISTS in the US have worked out how a key ingredient in soya beans thwarts cancer. They have shown that genistein, a plant oestrogen, plays a pivotal role in suppressing the growth of cancerous cells. Asian diets high in soya have been linked with low incidence of cancers, particularly breast, colon and prostate cancers. This link has been reinforced by evidence that when Asians migrate to the US and abandon the high-soya diet, their risk of developing these cancers increases. Amy Lee of the University of Southern California in Los Angeles has discovered that genistein is a key factor in this. It works by weakening cancer cells’ response to the stresses that usually impel them to grow faster. “When a cancer cell is growing at full blast, the cells soon run out of oxygen and glucose that are normally supplied in blood,” says Lee. To compensate, they send out a chemical SOS which triggers formation of new vessels to nourish the tumour, a process called angiogenesis. In earlier experiments on tissue cultures, Lee and others proved that genistein can blunt the response of cancer cells to stress. Now, they know the exact mechanism. She and her colleague Yanhong Zhou have shown that genistein blocks the action of a transcription factor known as CCAAT binding factor. This protein normally binds to an important genetic “motif” in DNA and triggers the stress genes. Genistein adds phosphorus to the binding factor, neutralising it before the switch is tripped, so the cancer cell starves, withers and dies (Journal of the National Cancer Institute, vol 90, p 381). “This is preliminary evidence, but genistein really stands out as the ingredient that’s most active in stopping cancer growth and angiogenesis,” says Lee. Crucially, the researchers found that genistein has no effect on normal, healthy cells which are not dividing rapidly like cancer cells. “It doesn’t shut off the normal synthesis of this protein in healthy cells,