Breast cancer is the second most common cancer among women in the United States, and cigarette smoking is associated with a higher incidence of breast cancer spread, or metastasis, lowering the survival rate by 33% at diagnosis.
While cigarette smoking’s link to cancer is well-known, the role of nicotine, a non-carcinogenic chemical found in tobacco, in breast-to-lung metastasis is an area where more research is needed.
In a new study, researchers found that nicotine promotes the spread of breast cancer cells into the lungs.
They found that nicotine exposure creates an environment in the lungs that is ripe for metastatic growth.
The research was conducted by scientists at Wake Forest School of Medicine.
In the study, the team first examined 1,077 breast cancer patients and found that current smokers or former smokers have a higher incidence of lung metastasis compared to patients who never smoked.
Then, using a mouse model of breast cancer metastasis, they discovered that persistent exposure to nicotine generates an inflammatory microenvironment in the lungs characterized by an influx of activated neutrophils to create a pre-metastatic niche.
Even after quitting nicotine for 30 days, the incidence of distant metastasis was not reduced, suggesting an ongoing risk for breast cancer patients who are former smokers.
The team also looked for a drug that might block this accumulation of neutrophils and identified salidroside, a natural compound found in the plant Rhodiola rosea.
This compound, which has anti-inflammatory, anti-cancer and anti-viral properties, strongly decreased the number of pro-tumor neutrophils and subsequently reduced the incidence of lung metastases in mice.
Based on these findings, the team says breast cancer patients should opt for smoking cessation programs that do not use nicotine replacement products.
One author of the study is Kounosuke Watabe, Ph.D.
The study is published in Nature Communications.
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