Inflammatory marker predicts breast cancer risk in obese post-menopausal women

Imperial researchers have shed new light on the link between obesity and breast cancer in post-menopausal women.

“The link between obesity and breast cancer in post-menopausal women has been identified, but is not fully understood,” says Dr Marc Gunter, from Imperial’s School of Public Health, who led the research.

“Obesity is associated with higher levels of the hormones insulin and oestrogen, and these are already linked to breast cancer development, but we wanted to dig deeper to see if we were missing something else, something specific to the condition of obesity that had not been spotted yet.”

Fat – or adipose tissue – secretes a variety of hormones and inflammatory proteins known as adipokines and obese individuals have higher circulating levels of inflammatory markers in their blood.  

The study, in collaboration with Albert Einstein College of Medicine in New York, Dr Gunter analysed blood samples from 1,718 postmenopausal women, measuring seven adipokines known to be associated with breast cancer development in experimental models.

They also measured the samples for C-reactive protein (CRP) – a generic inflammatory marker, to see if they could find a specific link between adipokines and inflammation and the women who developed the disease.

The blood samples were collected in the 1990s as part of a large US study called the Women’s Health Initiative Observational Study (WHI-OS) which is recording detailed, long-term health information of some 93,000 women.  

Of the 1,718 samples, 875 were from women who went on to develop breast cancer after several years or more and the team wanted to compare these with the 839 samples from women who remained breast cancer free.  

The results, published in the Journal of the National Cancer Institute (JNCI), showed that only the presence of relatively high levels of CRP was a significant predictor of which women would go on to develop breast cancer. In fact, women with higher levels of CRP had approximately double the risk of developing breast cancer compared to those with lower levels.

“We were surprised that the adipokines were not implicated as a risk factor in their own right,” says Dr Gunter. “The results show that those we detected in the blood samples simply correlate with insulin and oestrogen levels and if they are contributing to breast cancer development, it’s likely through these other hormones. We were even more surprised to discover that the only significant risk factor was high levels of CRP, as this is something that is easily detected in routine blood tests.”

He continues: “As fat cells accumulate in the body, they generate inflammatory markers, causing the body to flood the area with inflammatory cells, which produces more inflammation, in a vicious cycle. We need more research to find out exactly what’s happening, but it’s possible that this prolonged state of inflammation could partly explain the association between obesity and breast cancer in post-menopausal women. And a simple CRP blood test could be a useful tool to monitor risk for a large number of women.”

REFERENCE

Gunter et al 2015, “Circulating Adipokines and Inflammatory Markers and Postmenopausal Breast Cancer Risk” JNCI J Natl Cancer Inst (2015) 107(9): djv169, doi: 10.1093/jnci/djv169