Cancer is mostly a matter of bad luck, because in 66 percent. depends on whether the cells of our tissues develop carcinogenic mutations, which we have no control over either a healthy lifestyle or avoiding addictions, US scientists said in an article in the prestigious journal Science. However, the results of these analyzes were challenged by an American biologist who saw that the researchers misread their own results.
A team of scientists from the Johns Hopkins Kimmel Cancer Center working under the supervision of prof. Bert Vogelstein and prof. Cristiana Tomasetti decided to investigate the causes of neoplasms, or rather the differentiation of tissues that leads to neoplasm. It is known that cancer is favored by mutations that constantly occur in cells when they differentiate and divide. The John Hopkins researchers wanted to investigate the causes of these mutations. As noted by prof. Vogelstein, cancer is a combination of bad luck, heredity and the environment, so we developed a model to determine to what extent each of these three factors is involved in cancer.
According to the scientists, the model showed that in 2/3 of cases, i.e. about 66 percent. the development of specific mutations that make it possible to produce cancer is the result of bad luck. These mutations occur when stem cells divide and are non-directional. The remaining 1/3 would depend on heredity and environment. In the development of cancer, it would be like on a battlefield – a bullet can hit us, miss us by a hair or a kilometer – such a model was presented by scientists.
According to prof. Vogelstein, the impact of bad luck can be increased or decreased, e.g. for long-term smokers the risk will be greater if there is a family history of lung or laryngeal cancer. However, if they have good genes, i.e. such cancers have not been found in the family, they are less likely to develop the disease than other smokers. Similarly, in the case of a contaminated environment – in the case of living in such contaminated areas, the value of the bad luck factor increases many times.
As noted by prof. Tomasetti means that if two-thirds of cancer cases are due to non-directional mutations when stem cells divide, then changing to a healthier lifestyle will significantly reduce the risk of cancer in some cases, and not help at all in others. So we need to focus on developing tests and tools to diagnose cancer as early as possible, because you never know when they will occur – he added.
66 percent chance of mutation
According to the research report in Science, scientists analyzed 31 basic types of tissue that exist in everyone’s life. In the replication of DNA in stem cells, which differentiate depending on the type of tissue, errors – mutations occur. Most of them are harmless, but some promote cancer formation. Especially if mutations start to accumulate, because then the risk of cancer increases.
Scientists felt it necessary to study the frequency of these errors and their impact on cancer. To do this, they cataloged the number of stem cell divisions in 31 types of tissue and compared it with lifetime cancer risk. After the database was created and the relationship was presented graphically, the relationship between the total number of stem cell divisions and the cancer risk was established at 0.804. This means that the more divisions, the higher the cancer risk. As prof. Vogelstein, this relationship can be seen, for example, in colorectal cancer, which requires four times more stem cell division than small-cell intestinal cancer; it is also more common.
Hence the scientists’ conclusion about bad luck, because after a statistical calculation of what percentage of cancer risk can be explained by the number of cell divisions, the final value is almost 66%. that is 2/3. According to scientists, as many as 22 types of cancer in tissues can be mostly explained by bad luck, i.e. the number of stem cell divisions, or rather errors that occur during them. However, in the case of 9 types, the incidence of neoplasms is higher than unlucky. These cancers are likely to depend more on environmental and genetic factors in each individual.
This group includes, for example, lung cancer, which is largely dependent on smoking, or melanoma, associated with frequent exposure to intense sunlight without any protective factors. This means that cancer is protected neither by good genes nor by a healthy lifestyle, but only by tests that can detect its occurrence at an early stage, when it is curable. Cancer is largely a matter of chance.
Or maybe mistakes were made …
However, the work of the team from John Hopkins was taken by prof. Bob O’Hara, statistician and biologist at Biodiversitat und Klima Forschungzentrum in Germany. He quickly discovered that US scientists misread their analyzes. Indeed, in a diagram showing the number of stem cell divisions and the incidence of tumors in individual tissues, the relationship is evident, as described by the Vogelstein-Tomasetti syndrome. But why exactly this bad luck, i.e. the dependence of cancer incidence on the number of cell divisions, was calculated at 2/3?
O’Hara noted that the risk of bad luck from cancer should always be the same, no matter what the overall risk of a particular type of cancer is. It is known that breast and lung cancer is more common than, for example, thymic cancer. And as it turns out from the work of the team from John Hopkins, there is no such correlation.
O’Hara plotted the results on his chart and found that in some cases of both low-risk and high-risk cancers, the amount of stem cell division is small and the risk of cancer is medium to high. This means that such types of cancer are very little dependent on stem cell division, so the rate calculated by the Vogelstein-Tomasetti team is certainly not 66%.
The argument about the special role of DNA mutations in the division of stem cells for the development of cancer must fail too, argues O’Hara. According to the latest data from the US governmental agency to combat CDC disease, lung cancer affects smokers 18 times more often than non-smokers. The dependence of this cancer on smoking is so high that it leaves no room for other causes, especially since non-smokers diagnosed with this cancer were most often passive smokers, with 1-2 smokers in their immediate family. There is a relationship between the occurrence of neoplasms and the division of stem cells in tissues. But it is definitely not 66 percent. Says O’Hara.
So the conclusion from the sensational research of John Hopkins scientists is simple. It pays to change your lifestyle to a healthier one, eat better, move around and sleep and rest more. And get tested regularly. Then we will deal with the threat of cancer.
Tekst: Marek Mejssner