A recent study published in the June 2020 issue of the Journal of Experimental Medicine has found that nicotine may facilitate the spread of lung cancer to the brain.
Nicotine by itself, while highly addictive, is not carcinogenic, contrary to popular belief. The hundreds of other chemicals in tobacco are. Smoking tobacco releases these carcinogenic chemicals into the lungs, which can eventually lead to the development of cancer. But although nicotine does not cause cancer, scientists at Wake Forest School of Medicine found that it may promote the spread of lung cancer cells to the brain.
The study
The team of researchers, led by Kounosuke Watabe, Ph.D, professor of cancer biology at Wake Forest School of Medicine, examined 281 patients with lung cancer and were surprised to find that those who smoked cigarettes had a “significantly higher incidence” of brain cancer in addition to their lung cancer when compared to those who had never smoked or were former smokers. After digging deeper, the researchers decided to test the effects of nicotine on the brain of a mouse. They discovered that nicotine was able to enhance metastasis (spread of cancer) by crossing the blood-brain barrier and weakening the microglia (a protective immune cell found in the brain). After being exposed to nicotine, the weakened microglia no longer showed a protective effect against cancer. Rather, it encouraged the growth of brain tumors.
“Based on our findings, we don’t think that nicotine replacement products are the safest way for people with lung cancer to stop smoking,” said Watabe.
A new way to stop cancer’s spread?
After some research, Watabe and his team came across a drug called parthenolide, which was able to block the cancer cells from spreading to the brain in mice. The researchers believe that this drug may be effective in preventing the spread of cancer from the lungs to the brain (because there is no nicotine involved), particularly for cancer patients who still use tobacco. Parthenolide is a naturally occurring compound in feverfew, a medicinal herb native to Asia. If lung cancer patients who still choose to smoke were to consume a daily extract of feverfew, they might be able to shield their brains from the cancerous cells present in their lungs.
Watabe says parthenolide could even supplement chemotherapy as a treatment against brain metastasis. “Currently, the only treatment for this devastating illness is radiation therapy,” he said. “Traditional chemotherapy drugs can’t cross the blood-brain barrier, but parthenolide can, and thus holds promise as a treatment or possibly even a way to prevent brain metastasis.” Watabe is hoping to work with oncologists at the Wake Forest School of Medicine to set up a clinical trial in order to test the effects of parthenolide on cancer patients.
To sum up
When examining lung cancer patients, researchers found that those who smoked tobacco had higher incidences of brain cancer. They then discovered that nicotine–an active chemical in tobacco–helped encourage the spread of cancer from the lungs to the brain, although the chemical is non-carcinogenic (but highly addictive). The researchers also came across a naturally occurring compound called parthenolide, which appeared to stop the brain metastasis because it does not contain nicotine.
Written by Natan Rosenfeld
References
- Nicotine promotes brain metastasis by polarizing microglia and suppressing innate immune function | Journal of Experimental Medicine | Rockefeller University Press
- Chemicals in Tobacco Products and Your Health | FDA
- Harmful and Potentially Harmful Constituents (HPHCs) | FDA
- Scientists Discover that Nicotine Promotes Spread of Lung Cancer to the Brain | Atrium Health Wake Forest Baptist