The first appeared in The American Journal of Pathology this month:
Role of Cholesterol in the Development and Progression of Breast Cancer, The American Journal of Pathology, January 2011
The PyMT mouse was used because its cancer is similar to human breast cancer. Mice were fed either a diet mimicking the standard American diet or a control diet.
Control Chow diet:
There were more breast tumors, they were larger, they appeared sooner, and they metastasized more easily in the mice eating the higher-fat diet:
"In summary, administration of a Western-type diet resulted in accelerated tumor onset, and increased tumor incidence, multiplicity, and burden. These data suggest an important role for dietary cholesterol in tumor formation."They also found a link to lung cancer:
"The results suggest a trend toward an increased number of metastases in the lungs of PyMTg mice fed a Western diet compared with mice fed a chow diet."
The second appeared in the same journal last month:
A Western-Type Diet Accelerates Tumor Progression in an Autochthonous Mouse Model of Prostate Cancer, The American Journal of Pathology, December 2010
Here's a Jeff press release:
High Dietary Fat, Cholesterol Linked to Increased Risk of Prostate Cancer, Thomas Jefferson University - Kimmel Cancer Center, December, 2010
The TRAMP mouse was used in this case because its cancer parallels human prostate cancer. The mice were fed diets similar to those above. Again, there were larger tumors that grew faster and metastasized more easily to the lungs:
"They found that the Western diet accelerated prostate tumor development and progression. These tumors also produced increased levels of receptors that bind to lipoprotein carriers of cholesterol, and they were more aggressive. The researchers further discovered that the TRAMP mice fed a Western diet appeared to experience greater incidence of cancer metastasis to the lungs, compared to the control group."This was interesting ... In both studies, mice experienced a sudden drop in serum cholesterol after tumors formed, suggesting uptake and use of cholesterol by the tumor. Another hypothesis is an alteration of fat metabolism by the liver after cancer develops.
The leader of the team, Dr. Philippe Frank, said:
"Cells need cholesterol to produce androgen hormones, and androgen hormones promote prostate cancer growth,” he explains. “Perhaps more importantly, we also believe that tumors feed on cholesterol, and the more blood cholesterol is accessible, the more is available for tumor growth."