Our whole life is a fight against cancer

Yana Khlyustova, Newspaper.Ru 

Aging and bad habits weaken the body and allow cancer to win over healthy tissues – this, and not gene mutations, is the main cause of the formation of malignant tumors. Scientists told the science department of "Gazeta.En", how to beat cancer and why the cells of our body can be compared to dinosaurs.

The first descriptions of malignant tumors in the history of mankind were compiled by the ancient Egyptians, and the term for the disease – cancer – was proposed by the ancient Greek physician Hippocrates. The first operations to remove cancers were carried out from about the I century BC.

However, despite all attempts to diagnose and combat the disease, for many centuries they have remained unsuccessful. It was only at the end of the XVIII century that clear and detailed "instructions" for the removal of various types of cancerous tumors appeared. 

A detailed study of malignant formations became possible only with the advent of the first advanced microscopes and the development of pathological anatomy in the second half of the XIX century. 

At the beginning of the last century, doctors came closer to understanding the processes that cause cancer: the viral nature of some sarcomas was revealed, the carcinogenic effect of X-ray and ultraviolet radiation was revealed, and the study of the influence of environmental factors and lifestyle began. At the moment, the theory of cancer formation generally accepted in scientific circles is the mutational theory of carcinogenesis. According to this hypothesis, the cause of malignant tumors are mutations accumulated in the genome of the cell. The proof of the theory of mutational carcinogenesis is the discovery of special cells – proto-oncogenes and suppressor genes. 

In order to understand what these cells are and how they are associated with the formation of cancer, it is necessary to remember that in the vast majority of cases, a malignant tumor arises from just one cell with a mutated genome. At the moment, scientists know several dozen genes that, when mutated, begin to produce cancer-causing proteins. Such genes are called oncogenes, and many anti-cancer drugs are aimed at suppressing their work.

A proto–oncogene is an ordinary healthy gene that, under the influence of various factors, can turn into an oncogene and begin to produce deadly proteins. The activity of suppressor genes, on the contrary, is aimed at the production of proteins that prevent the formation of a tumor. It turns out that the system of interaction of proto-oncogenes and suppressors is a kind of scales, on one side of which there are tumor–causing cells, and on the other - cells that are trying to resist this. 

A mutation of one gene can become an impetus that will lead to an avalanche-like mutation process in other cells. The accumulation of three to six genetic damages already leads to a "preponderance" of the cancer bowl and the appearance of a malignant tumor.

The theory of mutational carcinogenesis described above has been proven by numerous scientific studies, but still scientists do not have answers to all questions. For example, until now, researchers have not been able to explain the so-called Peto's paradox. Its essence is as follows: if the theory of mutational carcinogenesis is correct, it means that theoretically any cell can become malignant. The number of cells in the body of a whale exceeds the number of cells in the body of a mouse by about a million times, and whales live about 50 times longer than rodents – this means that the chances of a whale getting cancer should be several times higher than the risk in the case of mice. However, in fact, for some reason this is not the case: both mice and whales suffer from cancer with approximately the same frequency, and some rodent breeds completely "overtake" whales by this indicator.

In addition, scientists claim that most mutations accumulate during the first half of an organism's life – around the time when a person or animal stops growing. Nevertheless, cancer most often occurs in old age. 

Researchers from the University of Colorado School of Medicine in Denver Andriy Rozhoka and James Degregori have proposed a new, experimentally confirmed theory describing the causes of cancer formation and explaining the Peto paradox. The scientists' article was published in the journal PNAS (Andrii I. Rozhoka and James DeGregori, Towards an evolutionary model of cancer: Considering the mechanisms that govern the fate of somatic mutations). Explaining what the essence of the hypothesis is, James Gregory said: "Let's mentally fast forward to 65 million years ago, at a time when dinosaurs lived on our warm and humid planet, and at the same time a small number of the first mammals lived with them.

Then a giant meteorite hit the planet, there were other changes in the habitat of animals that disrupted the existing ecosystem. As a result, warm-blooded mammals have become dominant on Earth."

The fact that dinosaurs have become extinct does not mean that they have become weaker or unsuitable for life, or that mammals were able to somehow get the better of them. The habitat has changed, which was a natural impetus for the change of the "leader". According to the authors of the study, similar processes occur in the human body: 

as a result of aging and under the influence of bad habits, the condition of healthy tissues of our body deteriorates and at some point the body gives way to stronger cancer cells.

Of course, cancer cells have some special properties, for example, they can live and successfully reproduce in tissues with a low oxygen content, but this does not make them some kind of "super cells". This property will give mutated genes an advantage only if the tissue is really poor in oxygen, which is atypical for a healthy person. Oncogenetic (that is, mutations capable of provoking cancer) are almost always present in the body, but the protective systems keep them under control – until the moment when the entire "ecosystem" does not change. It was to this conclusion that Andrei Rozhok and James Degregory came after conducting numerous experiments on mice. 

James DeGregory answered a few questions from the Newspaper.Ru", telling in more detail about the results of the work.

– James, please tell me, do your findings mean that changing the state of body tissues makes a greater "contribution" to the formation of cancer than the accumulation of mutations? 

- Yes. This is proved both by the mathematical models constructed by us and by experiments. 

– Does this mean that specialists should start working on the creation of new methods for the diagnosis and treatment of cancer? 

– I wouldn't say that. Nevertheless, our theory shows that the focus should not be on preventing mutation of the cell genome, but on how "advantageous" the environment in which they live is for cancer cells. It is necessary to understand how this or that therapy will affect the condition of healthy tissue: if it is damaged during treatment, these damages will help the remaining cancer cells develop, and the disease will return. Conversely, therapy that makes healthy tissue more "hardy" will slow down the development of the tumor. This problem can be perceived as an ecological one: if you want to preserve the lemur population in Madagascar, you will not cut down the forest in which they live!

– In this case, what can people do to slow down the aging and deterioration of their own body tissues? 

– Well, aging cannot be canceled, but it can be slowed down – and a healthy lifestyle will help in this. We all know that proper nutrition, sports and smoking cessation do not allow certain diseases to develop, now we have proved that this is true in the case of cancer. 

– Your theory may give the impression that cancer is an unavoidable disease of its kind, and humanity can do very little in the fight against it. Is it so? 

– No, of course not. I have already explained how a proper lifestyle can significantly reduce the risk of developing a tumor. Yes, aging is inevitable, but it is possible to extend the period of time during which a person retains health. However, to some extent our life depends on the case, so cancer can also appear in someone who cares about health. However, this does not mean that we should give up!

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24.07.2015