Two reasons
Scientists have found confirmation of a 75-year-old hypothesis about the causes of cancer
Svetlana Maslova, Hi-tech+
Scientists have shown that one habitual cancer risk factor — oncogenic mutation or exposure to a carcinogen — is not enough for the development of a tumor. Their findings are based on an analysis of the mechanisms of lung cancer, but it is possible that other types of tumors adhere to similar mechanisms.
The work of a team from the Francis Crick Institute is based on a study by Israeli biochemist Isaac Berenblum 75 years ago. Then Berenblum studied how air pollution contributes to lung cancer in non-smokers. Later he formed his theory of cancer development.
Before talking about Berenblum's discovery, it should be recalled that modern science is of the opinion that most tumors develop from healthy cells that at a certain time received DNA damage due to mutations. For example, tobacco smoke is believed to lead to lung cancer by damaging DNA in lung cells.
Meanwhile, studying non-carcinogenic oils, Berenblum came to the conclusion that some cancers require two triggers for tumor development. He called the first one an "initiating factor", and the second one a "promotion factor". At the first stage, an unspecified factor causes a healthy cell to become a latent tumor, and at the second stage it begins to form a malignant tumor. At the same time, we can pass a long time between these stages.
Scientists decided to find out whether polluted air could be a "promotion factor" and awaken latent cancer cells. The conclusions of the authors were told by the press release Scientists reveal how air pollution can cause lung cancer in people who have never smoked.
Studying epidemiological data covering almost half a million people, the researchers found more frequent cases of lung cancer with mutations in the EGFR gene in areas with a higher concentration of suspended particles in the air measuring 2.5 microns. In mice, these particles also led to tumor growth.
Meanwhile, a study of healthy lung tissue samples showed that 15% of them contained EGFR mutations, and another 50% contained KRAS mutations — another risk factor for lung cancer.
"Air pollution should wake up the right cells at the right moment for cancer to develop," said co—author William Hill. But scientists do not yet know exactly how exposure to suspended particles activates latent cancer cells.
According to one hypothesis, the signal molecule beta-interleukin causes stimulation. This has yet to be tested, although the beta-interleukin-1 inhibitor, designed to reduce the risk of cardiovascular disease, has previously shown a strange side effect - a low rate of lung cancer.
In conclusion, the scientists added that the results revive Berenblum's hypothesis, which many have already forgotten. Probably, in the coming years, a bilateral mechanism of cancer development will be discovered for other types of tumors.
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