Breast cancer
Having high cholesterol can place women at greater risk of developing breast cancer, a new study says.USAG-Humphreys/Flickr

Having high cholesterol can place women at a greater risk of developing breast cancer, says a new study.

Researchers from Duke University in the US conducted experiments on mice and found that a by-product of cholesterol known as 27HC (hydroxycholesterol) imitated the hormone oestrogen and led to the development and spreading of breast cancer to other organs.

Though oestrogen plays a major role in the important functions of the body, it has long been associated with the development of cancer in the breast and uterus.  According to reports, nearly 75 percent of all breast cancer cases are caused by the oestrogen hormone.

"A lot of studies have shown a connection between obesity and breast cancer, and specifically that elevated cholesterol is associated with breast cancer risk, but no mechanism has been identified," senior author Donald McDonnell, said in a statement. "What we have now found is a molecule - not cholesterol itself, but an abundant metabolite of cholesterol - called 27HC that mimics the hormone estrogen and can independently drive the growth of breast cancer."

The authors found that taking antiestrogens or stopping 27HC supplementation helped prevent the activity of the 27 hydroxycholesterol.

To confirm the mice-based findings, researchers collected and examined breast cancer tissue from humans. They found that the number of enzymes which produce the 27HC molecule went high with an increase in the aggressiveness of the tumour. Results also showed that increased 27HC can negatively affect breast cancer treatment using aromatase inhibitors.

While explaining their findings, the researchers cited previous gene expression studies that highlighted how 27HC exposure increased resistance to tamoxifen that is widely used to treat breast cancer. 

"This is a very significant finding," McDonnell said. "Human breast tumors, because they express this enzyme to make 27HC, are making an estrogen-like molecule that can promote the growth of the tumor. In essence, the tumors have developed a mechanism to use a different source of fuel."

Interestingly, risk of developing breast cancer can be reduced by keeping the cholesterol low, by following a healthy diet or by taking statins.

The findings have been reported in the journal Science.