When premalignant epithelial cells from the tumors were exposed to the substances secreted by mammary-gland fat from isolated mice, they began to proliferate more rapidly, suggesting that the isolated animals' fat could secrete substances that boost tumor growth.
There is growing recognition that "fat cells secrete substances that act on neighboring cell types and that the particular location of the fat in the body matters," Conzen said, "These various fat 'depots' function with highly tissue-specific roles. Different types of fat tissues respond differently to stress, diet and exercise."
The changes in fat cell gene expression were most pronounced at 15 weeks of age, just before a tumor mass could be easily detected in the mice. At this point, the tumors were classified as "carcinoma in situ," a precursor to an invasive malignancy. When a biopsy reveals carcinoma in situ, women are typically encouraged to have a lumpectomy.
"Because the change in fat cell behavior precedes malignancy, there may be ways to intervene and thereby slow or prevent the development of a subsequent more serious breast cancer," Conzen said. "We could use drugs to block the production or secretion of the fat signals to proliferate. There may even be ways, including diet and exercise, to manipulate breast fat metabolism."
Why is breast fat particularly sensitive to the effects of social isolation? Scientists don't yet understand how this response fits into the larger picture of the deleterious effects of stress on an organism, but "it will be an important avenue to pursue, particularly when so much human disease appears to be negatively impacted by social stressors, diet, and other factors causing metabolic derangement," Conz
|Contact: John Easton|
University of Chicago Medical Center