Breast cancer patients are 60 percent more likely to die of cancer after surviving a heart attack, according to a new study published in Nature Medicine.
Researchers reported that heart attacks, by blocking blood flow through arteries, trigger a specific, pro-cancer immune reaction. The team of scientists included University of Illinois cancer researcher Erik Nelson and was led by New York University’s Grossman School of Medicine.
Designed by evolution to attack invading bacteria and viruses, the immune system also recognizes cancer cells as abnormal and worthy of attack, the authors said. But heart attacks, along with other blood flow-reducing events like stroke and heart failure, were found to come with changes to immune cells that rendered them less able to respond to tumors.
Researchers have known about a link between breast cancer and cardiovascular disease for some time, which was largely ascribed to the negative effects of chemotherapy. While searching the literature, the team was surprised to find that no lab had yet examined whether heart attacks in turn worsen cancer progression.
“This study shows that patients who survived early stage breast cancer but then experienced a cardiovascular event, were far more likely to develop recurrent breast cancer, and die of that recurrence,” said Erik Nelson, associate professor in the Department of Molecular and Integrative Physiology at the University of Illinois School of Molecular and Cellular Biology.
The new work also found that mice with breast cancer saw a two-fold increase in tumor volume over 20 days after ligation (cutting off) of blood flow in the coronary artery, which simulated a heart-attack, when compared to mice with cancer but normal blood flow.
“By blunting the immune system’s assault on cancer cells, a heart attack appears to provide an environment that enables tumor growth,” said corresponding author Kathryn Moore, the Jean and David Blechman Professor of Cardiology, and Director of the Cardiovascular Research Center at NYU Langone Health. “While further studies will be needed, our results provide support for the aggressive clinical management of cardiovascular risk factors, not only to reduce risk of cardiovascular disease, but possibly breast cancer progression.”
As one in eight American women will develop breast cancer during their lifetimes, and with nearly three million breast cancer survivors in the United States, the need for a better understanding of the interplay between cancer and cardiovascular disease is urgent, Moore said.
“This is another example of how the immune system can be misguided into fueling cancer,” Nelson said. “Now that we know about this link, we can start developing strategies to help protect this group of patients.”
The Nelson lab researches how the immune system is regulated, and its members are developing strategies to ‘re-educate’ the immune system to attack cancer, rather than promote it. They are particularly interested in how cholesterol metabolism influences the immune system.
“Given the evidence of cross-talk between cardiovascular disease and breast cancer, measures that lower the risk for a cardiovascular event, such as exercise and treating high cholesterol and high blood pressure, warrant further study as potential ways to keep patients’ cancer from getting worse,” said postdoctoral researcher Graeme Koelwyn, who led the study in Moore’s lab.
Funding for the work came from National Institutes of Health. The work was also supported by American Heart Association grant 19POST34380010, and by the Canadian Institutes of Health Research.