Obesity promotes cancer progression regardless of diet

Washington - Researchers have shed light on why obese patients with cancer often have a poorer prognosis compared with those who are lean.

Mikhail Kolonin, Ph.D., associate professor at the Institute of Molecular Medicine at the University of Texas Health Science Center at Houston and his colleagues evaluated how obesity promotes cancer progression.

“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,” he said.

Their initial results confirmed this hypothesis: In obese and lean mice that ate the same diet, tumours grew much faster in obese mice than they did in lean mice. The researchers also observed that there were far more white adipose tissue cells (called adipose stromal cells) in obese mice than in lean mice and thus turned their focus on the role of these cells.

Detailed analyses indicated cancer induced mobilization of adipose stromal cells into the circulation. Once in the tumours, some of these cells developed into fat cells, while others were incorporated into tumour-associated blood vessels.

Tumour-associated blood vessels support tumour growth by bringing in oxygen and nutrients vital for cancer cell survival and proliferation. Kolonin noted that the ability of adipose stromal cells to contribute to the formation of tumour-associated blood vessels is likely one of the main reasons that the excess of these cells in tumours was associated with increased malignant cell proliferation and tumour growth.

“Our data provide the first in vivo evidence of recruitment of cells from endogenous fat tissue to tumours,” said Kolonin.

“The fact that these cells are present in tumours is still an emerging concept. We have shown that not only are they present, but they are also functional and affect tumour growth. Identifying the signals that cause these cells to be recruited to tumours and finding ways to block them might provide a new avenue of cancer treatment,” he added.

The findings were reported in Cancer Research, a journal of the American Association for Cancer Research.