How cholesterol can increase cancer growth

A new study published in Science this week has shown that when cholesterol is broken down, one of the products can contribute to the growth and spread of breast cancer.

It is known that obesity is a major risk factor for several types of cancer, including breast, bowel and womb, but this study provides a possible mechanism. One already known mechanism is that fat cells produces hormones like oestrogen, which fuel cancer growth. Researchers a few years ago found a similar effect with cholesterol: a product of cholesterol break-down, a molecule called 27HC (27-Hydroxycholesterol), seems to act in a similar way to oestrogen. Now researchers at Duke University Medical Centre have gone one step further to confirm its role in cancer.

The team found that human breast cancer cells grew faster when exposed to 27HC. They also found that feeding mice a high fat diet increased 27HC levels, and increased the size of tumours by 30% compared to mice on a normal diet. Interestingly, the 27HC also increases the rate of metastasis (spread of cancer to other organs).

Further evidence came from human breast tissue samples. The team found that more aggressive tumours expressed more of a certain enzyme, CYP27A1, than less aggressive samples. This enzyme converts cholesterol to 27HC, so the more aggressive tumours were producing and exposed to more 27HC. They also found that women with low levels of a different enzyme that breaks down 27HC were more likely to die earlier than those with high levels of this enzyme.

These findings are quite strong evidence that 27HC can contribute to cancer growth and might be how cholesterol has an effect. It raises the possibility that cholesterol-lowering drugs (like statins) could be used to prevent cancer, which there is some evidence for already. However, cancer charities are quick to advise against women taking statins as a precaution until more research has been done. This discovery also means that the CYP27A1 enzyme could be used in cancer treatment, to break down harmful 27HC.

Read more at: http://www.bbc.co.uk/news/health-25142026