Link between Obesity and Breast Cancer Identified

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Leptin, the growth factor associated with weight gain, has been found to promote breast cancer cell growth, according to research published in the Nov. 20 issue of the Journal of the National Cancer Institute. The research also found a lack of leptin or its receptor is associated with a lack of breast tissue development in mice.

Previous research identified an association between obesity and breast cancer, but scientists were unsure of what was responsible for linking these two diseases. New research, led by University of Minnesota researcher Margot Cleary, Ph.D., may close that gap in understanding.

“These findings may explain why weight gain, which is accompanied by higher than expected leptin concentrations, also has been associated with increased breast cancer risk,” said Cleary. “Preventive measures need to be taken to control these deadly diseases.”

Obesity is considered a risk factor for breast cancer, and women who are obese tend, at the time of diagnosis, to have more aggressive disease with a poorer prognosis. Increased leptin levels have been tied to increased body fat levels and obesity.

Research conducted at the University of Minnesota’s Hormel Institute, in collaboration with researchers at the Mayo Clinic, found that leptin enhanced the proliferation of both normal and cancerous breast cells.

The study shows that, in the presence of leptin, the number of cancerous breast cells increased 150 percent as compared to 50 percent for normal breast cells. In addition, leptin receptors, the docking sites responsible for signaling various metabolic activities within the cells, were identified.

In a test used to assess the cells’ ability to form tumors, it was found that only the breast cancer cell line exposed to leptin responded, supporting the idea that leptin can promote tumor growth and development. Evidence that leptin promotes breast cancer tumor development provides an explanation of why obesity and breast cancer are associated.

Future studies should focus on determining whether the presence of leptin receptors in breast tumors is associated with those factors commonly assessed during breast cancer diagnosis, such as hormonal receptors, said Cleary.