How Asthma Can Protect Against Brain Tumors
The stereotypical depiction of asthmatics in pop culture is not very flattering, but new research can change that. Asthma can actually be a protective armor in some cases — against brain tumors, no less. A study, published earlier this month in Nature Communications, explains why people with asthma seem to develop fewer brain tumors.
Global epidemiological studies noted the curious link a while ago, Science Alert noted. But now, scientists may have finally confirmed that the link does indeed exist, and have narrowed down a potential cause. According to the new paper, the key is a protein derived from T-cells (the body’s immune cells), called decorin.
The findings help scientists understand the two conditions much better, and provide key insights into just how intricately the minutiae of our bodies are connected. In other words, “what’s bad news for the airways may be good news for the brain,” as the press release put it. It could also potentially help shape new treatments for brain tumors in asthma patients.
To go a few steps back, T-cells drive both respiratory inflammation that causes asthma, and they also interact with optic nerve fibers to cause brain tumors. But for people whose T-cells caused asthma, there was a correspondingly lower risk of developing brain tumors as per data collected over the years. “Prior case-controlled clinical studies have revealed a reduced incidence of brain tumors in children with T-cell-mediated disorders, including asthma,” the paper stated.
Scientists were able to observe the phenomenon using litters of mice, all of which were genetically modified to become prone to brain tumors. They then induced asthma using house dust mites in some of them. Results showed that in the mice with asthma, there was no brain tumor formation, whereas the mice without asthma went on to develop brain cancer.
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Here is where decorin enters the picture. This protein, when it shows up in T-cells was found to be associated with asthma in mice — and the connection between decorin and asthma has also been established for a while. But the new study shows that this same protein could also have anti-carcinogenic effects in the brain.
The mice with asthma were found to have higher levels of decorin — corroborating previous research that showed that inhibiting decorin in mice actually reduces the incidence of asthma. But decorin, while evidently bad for the lungs, may be good for the brain.
Increased decorin in mice’s optic nerves, the researchers found, prevented the activation of another set of immune cells known as microglia, which are associated with the growth of cancerous tumors.
This doesn’t mean that the way forward is to induce asthma for everyone, researchers say. “[A]sthma can be a lethal disease… But what if we could trick the T-cells into thinking they’re asthma T-cells when they enter the brain, so they no longer support brain tumor formation and growth?” said neurologist David Gutmann from Washington University, and an author of the study.
“Collectively, the findings presented in this report suggest a model in which brain cancer risk is modified by alterations in circulating T-cell function,” the researchers write.
With the link between decorin (responsible for asthma) and its inhibition with microglia (responsible for brain tumors) more clearly established, researchers can now find ways of lowering the risk of tumors in people who are genetically predisposed to developing them — even potentially treating them — in humans.
The present research applies to a specific type of brain tumor — what’s known as the optical pathway glioma. “The next step for us is to see whether this is also true for other kinds of brain tumors,” Gutmann said. And that’s not all; scientists are also investigating the role of eczema — another inflammatory disease, it also involves T-cells and could have similar implications.
“As we understand this communication between T-cells and the cells that promote brain tumors better, we’ll start finding more opportunities to develop clever therapeutics to intervene in the process,” Gutmann concluded.