Adipose tissue cells (called adipose stromal cells) which expand in obese people promote and support tumor growth, researchers at the Institute of Molecular Medicine at the University of Texas Health Science Center at Houston reported in the journal Cancer Research. The authors believe they have discovered why obese cancer patients usually have poorer prognoses compared to slim people.
These are fat progenitor cells, the authors explained. Cells that can turn into various types of cells. They fortify the vessels that provide essential blood to tumors.
Mikhail Kolonin, Ph.D. explained that population studies have clearly shown that there is an association between obesity and cancer rates. Indeed, for a number of cancers, obesity is linked to poorer prognoses.
According to WHO (World Health Organization), there were over 1.4 billion obese adults in 2008 globally, and 7.6 million registered cancer deaths.
Kolonin and team set out to determine how obesity promotes the progression of cancer. Kolonin said “Our earlier studies led us to hypothesize that fat tissue called white adipose tissue, which is the fat tissue that expands in individuals who are obese, is itself directly involved and that it is not just diet and lifestyle that are important.”
Their hypothesis was confirmed by their initial results. They had two groups of mice, obese and lean ones. They were fed the same diet, however, tumors grew much faster in the fat mice.
They also noticed that there were many more adipose stromal cells in the obese mice compared to the lean ones. This made them pursue the role of these cells.
They found that cancer appears to induce mobilization of adipose stromal cells into the circulation. As soon as they entered the tumors, many of them turned into fat cells, while others became parts of the blood vessel network that fed the tumor.
Adipose stromal cells contributed to tumor angiogenesis – the formation of new blood cells that provided the tumor with oxygen and nutrients vital for its growth and survival. Kolonin and team believe that the abundance of these types of cells in obese people is what drives tumor growth and malignant cell proliferation. Tumors emit a signal which attracts the progenitor cells from white adipose tissue in the mice.
“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.”
Obesity has been associated with poor prognosis in many types of cancer. Below are some data from five different studies:
- Prostate cancer – researchers from Duke University Medical Center explained at the American Urological Association Annual Meeting in 2011 that obese patients with prostate cancer have a considerably higher risk of the cancer growing and spreading, even if hormone therapy is administered.
- Breast cancer – severely obese women have a 39% higher risk of developing estrogen receptor-positive breast cancer and a 35% greater risk of triple-negative breast cancer compared to women of the same age of normal weight, scientists from the Fred Hutchinson Cancer Research Center reported in May 2011.
- Ovarian cancer outcomes – obese women with ovarian cancer are more likely to die from the disease than ovarian cancer patients of normal weight, scientists from the Cedars-Sinai Medical Center announced in August 2006. They added that fat cells excrete a hormone that encourages tumor growth.
- Colorectal cancer – obesity raises the risk of developing colorectal cancer, the American College of Gastroenterology announced in March 2012.
- Renal cell cancer – obesity may increase the risk of developing the most common form of renal cell cancer, researchers from the Memorial Sloan-Kettering Cancer Center in New York revealed in January 2010.
Written by Christian Nordqvist