Dietary cholesterol has been shown to promote and accelerate mammary tumor formation in mice. Mice fed a high cholesterol diet in one study developed larger tumors that were faster growing and metastasized more easily compared to animals on a control diet. In addition, circulating cholesterol levels have been observed to be reduced during tumor development, providing evidence for increased use of cholesterol by tumors.

These findings suggest that an increase in cholesterol might accelerate the development of breast tumors and increase their aggressiveness. In fact, high cholesterol has been reported to increase breast cancer risk in women. However, there is also some evidence that low cholesterol is also associated with heightened breast cancer risk. Now a new study has reported that normal breast cells respond to oxidized low-density lipoprotein (LDL, the "bad" cholesterol) by increasing proliferative and pro-inflammatory signaling, thereby setting the stage for breast cancer development.

Latest research finds LDL cholesterol can increase inflammation and proliferation

The study referenced at the beginning of this news article was designed to investigate the effects of oxidized LDL in normal human breast cells. High cholesterol is characterized by enhanced production of oxidized LDL, the "bad" cholesterol. Oxidation occurs when LDL cholesterol reacts with free radicals. To conduct the study, the authors used MCF-10A human mammary epithelial cells, which is a non-cancerous breast cell line.

The MCF-10A cells readily internalized oxidized LDL. Through a series of experiments and measurements, the authors demonstrated that the cells responded to oxidized LDL by upregulation of proliferative signaling. In fact, the cells demonstrated increasing proliferative response to oxidized LDL in a dose-dependent manner. In addition, the cells responding to oxidized LDL by upregulation of pro-inflammatory signaling.