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The BBC reports on a new development in understanding why nonsmokers can develop lung cancer [1]
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Date: 2022-09-10
Ever hear the phrase "There's something in the air"? It turns out that may be a factor in why cancer turns up in people who are non-smokers - but the full story is more complicated.
The BBC reports on research looking at how lung cancer turns up in people who are nonsmokers in a finding which has implications for understanding what triggers cancer in the first place. Health and science correspondent James Gallagher looks at a mechanism which has just been reported.
Cancer is understood to be the result of cells with damaged DNA that begin to replicate and grow out of control. DNA damage can come from exposure to toxic chemicals, radiation, viral infections, and can also be influenced by genetics that put some people at higher risk of developing cell mutations that lead to cancer. Some lifestyle habits may also be a factor.
A study by a team at the Francis Crick Institute in London showed that rather than causing damage directly, air pollution was waking up old damaged cells. That is, the cells were already present and damaged, but seemingly inert until exposure to air pollution triggered a response by the body that led to cancer.
The type of cancer in question was lung cancer, and the riddle the team was trying to solve was why people who do not smoke were developing lung cancer. they knew air pollution was a factor but they wanted to look deeper.
The discovery came from exploring why non-smokers get lung cancer. The overwhelming majority of lung cancers are caused by smoking but still, one in 10 cases in the UK is down to air pollution. The Crick scientists focused on a form of pollution called particulate matter 2.5 (known as PM2.5), which is far smaller than the diameter of a human hair.
Through a series of detailed human and animal experiments they showed: Places with higher levels of air pollution had more lung cancers not caused by smoking
Breathing in PM2.5 leads to the release of a chemical alarm - interleukin-1-beta - in the lungs
This causes inflammation and activates cells in the lungs to help repair any damage
But around one in every 600,000 cells in the lungs of a 50-year-old already contains potentially cancerous mutations
These are acquired as we age but appear completely healthy until they are activated by the chemical alarm and become cancerous Crucially, the researchers were able to stop cancers forming in mice exposed to air pollution by using a drug that blocks the alarm signal. The results are a double breakthrough, both for understanding the impact of air pollution and the fundamentals of how we get cancer.
What the team appears to have found is that the body’s own efforts to respond to damage from air pollution has the effect of triggering cells that are damaged but seemingly inert into full-blown cancer. Blocking the immune response in this case seems to prevent that from happening.
There are three reasons why this is important:
The kind of air pollution examined in the study is a serious problem around the world. It’s becoming even more of one as climate change leads to more wildfires. The idea that taking a pill can ameliorate some of the consequences of exposure opens up a new line of research and has implications for public health.
It shows that genetic damage alone does not fully explain why people develop cancer. The researchers expect to find many other such links now that they know what to look for.
While not specifically mentioned in the article, it suggests that exposure to carcinogens may not immediately result in cancer — but subsequent events can cause it to manifest. This has implications for epidemiology — and for liability lawsuits.
Doctors have already trialled an interleukin-1-beta drug in cardiovascular disease and found, by complete accident, they cut the risk of lung cancer. The latest findings are being presented to scientists at a conference of the European Society for Medical Oncology. Speaking to the BBC from the conference, Prof [Charles] Swanton said: "Pollution is a lovely example, but there are going to be 200 other examples of this over the next 10 years." And he said we needed to rethink how even smoking causes cancer - is it just the known DNA damage caused by the chemicals in tobacco or is the smoke causing inflammation, too? Curiously, the idea that mutated DNA is not enough and cancers need another trigger to grow was first proposed by scientist Isaac Berenblum in 1947.
NOTE: Smoking remains the biggest cause of lung cancer. This research does not mean that someone can smoke safely if they just take a pill.
It’s also important not to overgeneralize.
While a drug may have been found to cut the risks of developing lung cancer in this study, that does not mean the same drug will also work on other types of cancer. It just means there are new avenues to explore in understanding how cancer develops, in effect treating cancer before it becomes cancer. Understanding that the body’s own immune response to what it encounters can be a factor in the onset of cancer has some interesting implications.
While we look to science for answers, what truly drives science forward is asking questions — and finding out which are the right questions to ask.
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https://www.dailykos.com/stories/2022/9/10/2121984/-The-BBC-reports-on-a-new-development-in-understanding-why-nonsmokers-can-develop-lung-cancer
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