Homing in on the Fat and Cancer Connection

C ancer researchers worldwide are increasingly focusing on the link between obesity and cancer. epi demiological studies over the past 30 years have consistently shown that diabetics and obese people have a higher risk of getting cancer than lean healthy people, and when they do get it their risk of dying from it is greater. But not all fat tissue is the same. Now researchers are focusing on how two types of fat tissue—white adipose tissue (WAt) and brown adipose tissue (BAt)—may affect cancer growth. White Adipose Tissue once considered a mere energy storage depot, adipose tissue has revealed itself to be more than just an innocent bystander in promoting chronic disease. White adipose tissue secretes adipokines that include hor mones such as insulin and leptin, cytokines and growth factors that may stimulate or inhibit cell growth and cause systemic inflammation. For example, insulin and insulinlike growth factor (IGF), a related hormone, play a role in fueling a range of cancers including breast, prostate, and blad der. Because obese people have more WAt than healthy people, they also have higher levels of certain circulating adipokines. Studies in animal models have shown that tumors can take advantage of adipokines. While systemi cally circulating adipokines may be important, studies also point to neighboring adipose tis sue as a potential contributor. " the tumor microenviron ment is very important and understudied, " explained mikhail Kolonin, Ph.D., associate professor at the Center for Stem Cell and regenerative medicine at the university of texas health Science Center in houston. In some tumors, the majority of cells are not malignant, he said, they are rather infil trating stromal and vascular cells of mixed origin. the problem for researchers has been that in humans, there is no sure way to identify the cells' origins. Some research groups have been able to show in animal models and cell culture that mesenchymal stem cells (mSCs) appear to be recruited by tumors in response to inflammatory and hypoxia signals. At tumor sites, they engage in tissue remodeling aimed at normal organ repair. While bone marrow is certainly a source of these progenitor cells, three years ago Kolonin came up with a hypothesis that adipose tissue may also contribute to can cers associated with obesity. " most of the focus has been on bone marrow as a source of progenitor cells, " said at the european Institute of oncology in milan, …