High cholesterol levels increase breast cancer risk

Degradation product of cholesterol is said to promote the development of breast cancer tumors

11/29/2013

A breakdown product of cholesterol could increase the risk of breast cancer and metastases. The US researchers found out in the context of animal experiments. Thus, the substance 27-hydroxy-cholesterol (27HC) mimics the hormone estrogen and drives the growth of breast cancer tumors. The results should also be transferable to humans.

High cholesterol levels are detrimental to cure prognosis for breast cancer
The link between obesity and breast cancer has been known for some time. Which mechanism, however, is responsible for the fact that overweight women have an increased risk for tumors in the chest, was previously regarded as an unsolved mystery. US researchers led by Donald McDonnell at Duke University Medical School, Durham, North Carolina, may have found an explanation. Like the scientists in the magazine „Science“ The cholesterol degradation product 27HC is responsible for the fact that elevated cholesterol levels increase the risk of breast cancer and the formation of metastases and worsen the chances of recovery.

„Many studies show a link between obesity and breast cancer and, in particular, that elevated cholesterol levels are linked to breast cancer risk, but so far no mechanism has been discovered, "McDonnell cites in a statement from his institute. „We have now found a molecule - not cholesterol itself, but a common degradation product called 27HC - that mimics the hormone estrogen and drives the growth of breast cancer. "Around a quarter of breast cancer tumors have an increased sensitivity to the sex hormone.

Enzyme makes breast cancer more aggressive
As shown in mice with breast cancer, 27HC not only promotes the development of breast tumors, they also metastasize more. Antiestrogens, on the other hand, have an inhibiting effect on the cholesterol degradation product.

The results of the researchers were confirmed in studies on human breast cancer cells. In the process, another substance was discovered that also makes the tumors more aggressive: The enzyme CYP27A1 breaks down cholesterol to 27HC and activates the cancer cells. Therefore, estrogen inhibitors may fail in some cases of hormone-sensitive breast cancer.

„In human breast cancer samples, CYP27A1 levels correlated with tumor grade. In tumors of higher grade, both tumor cells and tumor associated macrophages displayed high levels of the enzyme“, the researchers write in the magazine.

„This is a very important finding, "McDonnell is further quoted in the Institute's message. „Because human breast tumors produce this enzyme to produce 27HC, they produce an estrogen-like molecule that can promote tumor growth. The tumors have developed a mechanism that allows them to use a different source of fuel. "

To lower breast cancer cholesterol levels
The researchers' conclusion: A cholesterol-conscious diet or drug control of cholesterol levels is very likely to reduce breast cancer risk. In addition, such measures could result in improved efficacy of cancer therapies with aromatase inhibitors or tamoxifen in pre-existing disease.

„So far, it has been known that there is a link between high cholesterol and breast cancer risk, "said Professor Klaus Parhofer from the University of Munich Großhadern hospital told the news agency „dpa“. „One has not understood the connection. This study proves the causality and also shows the mechanisms. "According to the endocrinologist, the results of the researchers are transferable to humans, but the extent of the effect must be clarified in further investigations.

Breast cancer is the most common type of cancer among women. About every eighth woman is ill today. As frightening as the diagnosis may be for the patient, it is no longer equivalent to a death sentence, thanks to major advances in diagnostics and therapy. According to the German Society of Senology (DGS), about 80 percent of ill women today can be successfully treated. Basically, the earlier a tumor is discovered, the greater the chance of recovery. (Ag)