cancer index. mice injected with breast cancer cells make a lot of a long strand of RNA called Hotair developed 10 times more lung tumors as controls ( left ) did.
Adapted from Gupta et al., Nature, 464 (15 April 2010)
It has long been known that obesity women more prone to cancer brands breast, but the reasons are not clear. The researchers found that the tissue surrounding the breast cells is "more rigid" in mice and obese women, and that this difference of tissues in rodents spurs the growth of cancer cells. For women, the work suggests, weight loss can reshape fatty tissue and reduce the risk of cancer. Moreover, the growing practice of using fat from obese women for reconstructive surgery within them may present a risk which had been neglected until now.
Obesity is associated usually with cancer, but the link with breast cancer is particularly striking: In large recent study, the most overweight women had a risk 58% higher than normal weight women. One explanation is that fat tissue produces estrogen, which can fuel the growth of breast cancer cells after menopause, when the ovaries stop producing estrogen. But the mechanics of the scaffolding that surrounds the cells it within the extracellular matrix, may also matter.
Mice recent studies have found that a more rigid extracellular matrix triggers the production of proteins that promote cell growth of precancerous breast cancer. This may help explain why women with dense breasts are also at higher risk for breast cancer. Other studies have shown that when people become obese, their fat tissue tends to accumulate fibrous tissue scarlike pockets.
These studies did not address directly whether these fibrous pockets affect the local stiffness of the breast tissue, and if these changes lead to cancer growth. To explore this question, a team led by Cornell University biomedical engineer Claudia Fischbach first showed that female mice that were obese because of genetic or a diet high in fat, have more fibrous mammary fat pads with collagen fibers straighter than those observed in lean mice (see image). Mechanical tests have shown that straight fibers reflect more rigid extracellular matrix between breast cells. The researchers also found a surplus of myofibroblasts, a type of cell involved in wound healing that form the structure of collagen and other matrix proteins. When Cornell team human cells in breast cancer culture matrix filed by fat cells of obese mice derivatives, cancer cells grew faster than they did on the matrix thinner mouse cells .
The researchers found similar structural differences in adipose tissue biopsies of the breast obese and lean women, they report today in Science Translational Medicine . The results suggest that the most rigid extracellular matrix pockets in the breasts of obese women contribute to tumor growth as well as more aggressive cancers, Fischbach said, "People always think that it is all about the soluble factors, chemical products. It is also about the interaction with the physical parameters "
The news was not all bad. When the team of Fischbach put obese mice on a diet, their mammary fat had fewer myofibroblasts, suggesting weight loss could make the fat of a woman structure more normal tissues and reduce her risk of breast cancer. at the same time, the study raises questions using clean grease from a woman also in his body to reconstruct breasts after mastectomy. the adipose tissue of obese women may increase the risk of a recurrent tumor, Fischbach suggests.
Biochemist Valerie Weaver of the University of California, San Francisco, who previous studies conducted between tissue stiffness and breast growth, called the paper "very important" because it is a new mechanism linking obesity with breast cancer. mammograms often can not detect dense tissue in obese women because it is hidden by fat cells, said Fischbach. Small local areas of rigid tissue found in the new study are particularly likely to fail, she added. Thus, new detection methods may be needed to diagnose these hotspots of potential cancer-promoting.
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