According to a study of laboratory mice conducted by researchers at the Kimmel Cancer Center at Jefferson University, elevated fat and cholesterol levels found in a typical American-style diet play an important role in the growth and spread of breast cancer.
The study results, published in the January issue of The American Journal of Pathology, show that mice who are predisposed to develop mammary tumors and are fed a Western diet, can develop larger tumors that are faster growing and metastasize more easily, compared to animals eating a control diet.
Breast cancer rates are five times higher in Western countries than in other developed countries and people in countries with a low rate who later adopt a Western diet show an increased rate of the cancer. “These facts suggest strong environmental influence on breast cancer development,” said the research team leader Philippe G. Frank, Ph.D., Assistant Professor in the Department of Stem Cell Biology and Regenerative Medicine at Thomas Jefferson University.
According to the authors, fat and cholesterol in the diet have been shown to be risk factors in the development and progression of a number of tumor types, but diet-based studies in humans have reached contradictory conclusions.
In this study, mice were placed on a diet that contained 21.2 percent fat and 0.2 percent cholesterol, which the researchers believe is reflective of a typical Western diet. A control group of mice was fed a diet of only 4.5 percent fat and negligible amounts of cholesterol.
The mice fed the higher fat and cholesterol food developed tumors quickly, with the number of tumors almost doubled, and 50 percent larger than those in mice that ate a normal diet. Researchers also noted a trend towards an increased number of lung metastases in mice fed the fatty diet.
Even though they were eating a higher cholesterol diet, the mice with tumors had a lower level of cholesterol in their blood. Dr. Frank observed that this suggests that tumor formation was responsible for the reduction in blood cholesterol levels. He explained that cholesterol may provide the building blocks for tumor growth and that a drop in blood cholesterol may signify that some tumors are growing as cholesterol provides support for breast cancer growth.
Dr. Frank suggested that the use of cholesterol-lowering drugs, such as statins, might both protect against breast cancer as well as treat patients with tumors. Since researchers also found that blood cholesterol levels dropped significantly as tumors began to develop, the researchers believe that measuring blood cholesterol levels may also be an effective method of screening cancer development.