The healthcare community has known for some time that obesity significantly raises the risk of contracting type 2 diabetes, one of the most common chronic diseases in the developed world. But now scientists have found that obesity is also linked to the development of cancer. A recent study published in the journal Cancer Research has shown that the cells that create fat (adipose stromal cells) are the same ones that help supply nutrients and oxygen to cancerous tumors.
Obesity is the second-leading cause of cancer after smoking, according to experts from the World Cancer Research Fund. Researchers claim that obesity increases the risk of at least nine different types of cancer, including that of the breast, bowel, prostate, ovary, uterus, kidney, pancreas, gall bladder and esophagus.
There were 1.4 billion obese individuals worldwide in 2008, according to the World Health Organization, and the numbers have been climbing steadily since then. Statistics show that those who are obese have far worse prognoses for cancer survival than their leaner counterparts.
According to lead author of the study, Mikhail Kolonin, Ph.D., associate professor at the Institute of Molecular Medicine at the University of Texas Health Science Center in Houston, adipose stromal cells are fat progenitor cells. This means that they are a type of stem cell that can become different kinds of cells. In this case, they are recruited by a tumor to help feed it.
Kolonin and researchers performed the experiment on two groups of mice: one set of test subjects was fat and the other obese. Both sets of mice were fed the same diet. However, tumors grew faster in the obese mice. Researchers noted considerably more adipose stromal cells in the obese mice, so they explored the mechanisms that may have been responsible.
The scientists found that tumors emit a signal that attracts adipose stromal cells. These cells then either became fat cells in the tumor or turned into cells that became part of the network of blood vessels that supplied oxygen and nutrients to the tumor.
Dr. Kolonin said, “Our data provide the first in vivo evidence of recruitment of cells from endogenous fat tissue to tumors. The fact that these cells are present in tumors is still an emerging concept. We have shown that not only are they present, but they are also functional and affect tumor growth. Identifying the signals that cause these cells to be recruited to tumors and finding ways to block them might provide a new avenue of cancer treatment.”
This experiment was important in that it demonstrated that obesity in itself—not only poor diet and lack of exercise—may be a major contributor to cancer.