Obesity linked to breast cancer cell growth and tumor size

New research suggests that the obesity status of a woman may determine the rate of breast cancer cell growth and tumor size. This is according to a study published in the journal Breast Cancer Research.

Obesity is known to be a major risk factor for breast cancer in post-menopausal women, say researchers from the Tulane School of Medicine in New Orleans, LA.

According to a previous study published in JAMA of more than 80,000 registered nurses, women who gained 55 pounds or more after the age of 18 were found to have a 50% increased risk of developing breast cancer.

But the researchers note that obesity, particularly abdominal obesity, and its relationship with fat stem cells and breast cancer has not previously been studied.

Therefore, the research team analyzed a series of fat stem cell lines that had been taken from 24 women who were undergoing elective liposuction.

Researchers say that a woman's obesity status, particularly fat in the abdomen area, may determine the rate of breast cancer cell growth and tumor size.

One stem cell line from each woman was taken from the abdomen, while another was taken from a non-abdominal area. For comparison, cells were taken from both obese and non-obese women, as determined by their body mass index (BMI).

The fat stem cells were grown in a laboratory alongside breast cancer cells. These cells were then injected into the mammary glands of mice, and an estrogen pellet was placed under their skin.

Obesity 'increases expression of leptin'

On examining the tumor growth from the samples, the researchers found that the cells taken from women who were obese increased cancer cell numbers and tumor growth, and this detection was more significant in cell lines taken from abdominal fat.

The researchers say that this finding may be due to the exposure of the fat cells to estrogen. They say that this boosts the production of a hormone called leptin, which increases the number of cancer cells and tumor growth.

Explaining the findings, Bruce A. Bunnell, a senior author from the Center for Stem Cell Research and Regenerative Medicine and the Department of Pharmacology at Tulane University, told Medical News Today:

"It was determined that obesity alters the stromal cells (connective tissue cells of organs) and increases their expression of leptin.
Functionally, the altered stromal cells affect proliferation through several key molecular factors. Together, this would suggest that obesity alters stromal cell function, which in turn alters breast cancer cells to increase their growth and progression."

Potential targets for therapeutic intervention

Bunnell added that these findings are important, as they provide evidence to support the role of obesity at the "cellular and molecular level" in breast cancer development and progression.

"While previous epidemiological studies have shown a link, we are one of the first to show the effects of altered stromal cells on the gene signature of breast cancers cells," Bunnell told Medical News Today.

"Furthermore, by identifying the differences between the stromal cells from obese women and lean women, we may be able to discover novel targets for therapeutic intervention."

Bunnell noted that these findings should prompt women, particularly those who are at higher risk of breast cancer, to maintain a healthy body weight. He referred to previous studies, in which women who were enrolled in a strict diet and exercise regime had a better breast cancer prognosis, compared with women who did not follow the regime.

The next step from this research, Bunnell said, is to determine the process by which obesity alters stromal cells.

"While we know that obesity leads to chronic, low-grade inflammation, identifying the particular mechanisms involved may help us limit the effects on the stromal cells and in turn the support these cells provide to the tumor," he added.

"Furthermore, identifying whether or not these leptin-altered stromal cells affect other aspects of breast cancer will be interesting to investigate. The results will provide additional evidence for the mechanism by which obesity enhances breast cancer incidence and mortality."