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, or metastasis, reducing the survival rate by 33% at diagnosis.
Although the link between cigarette smoking and cancer is well known, the role of nicotine, a non-carcinogenic chemical found in tobacco, in breast-lung metastasis is an area where more research is needed.
Now, scientists at Wake Forest School of Medicine have discovered that nicotine stimulates the spread of breast cancer cells into the lungs.
The study is published in the January 20, online edition Nature Communication.
“Our data show that nicotine exposure creates an environment in the lungs that is ripe for metastatic growth,” said Kounosuke Watabe, Ph.D., lead author of the study and professor of cancer biology at the School Wake Forest Medicine, part of Wake Forest Baptism Health.
This environment is called a pre-metastatic niche, which attracts pro-tumor neutrophils, a type of immune cell. The pre-metastatic niche releases a protein called STAT3-activated lipocalin 2 (LCN2) from the neutrophils to stimulate metastatic growth.
For the study, the Watabe team first studied 1,077 breast cancer patients and found that normal or post-smokers have a higher incidence of lung metastasis compared to patients who have never smoked.
Then, using a mouse model of breast cancer metastasis, the researchers found that continued exposure to nicotine generates an inflammatory microenvironment in the lungs characterized by an influx of activated neutrophils to a pre-metastatic niche. to create.
Even after nicotine discontinuation for 30 days, the frequency of distant metastasis was not reduced, suggesting a persistent risk for breast cancer patients who had previously smoked.
Watabe and colleagues were also looking for a drug that could inhibit this accumulation of neutrophils and identified salidroside, a natural fertilizer found in the plant Rhodiola rosea. This fertilizer, which has anti-inflammatory, anti-cancer and anti-viral properties, significantly reduced the number of pro-tumor neutrophils and subsequently reduced the frequency of lung metastases in mice.
“Based on these findings, breast cancer patients should choose smoking cessation programs that do not use nicotine replacement products,” Watabe said. “Furthermore, our findings indicate that salidroside may be a promising therapeutic drug to help prevent lung metastasis of breast cancer, although more research is needed.”
Source:
Wake Forest Baptist Medical Center