Ageing and bad habits weaken the body and allow the cancer to win the victory over healthy tissues – this, not gene mutations is the main reason for the formation of malignant tumors.
History of Cancer
The first descriptions of malignant tumors in the history of mankind were made by ancient Egyptians, and the term for the disease – cancer – suggested the ancient Greek doctor Hippocrates. The first operations to remove cancerous lesions were carried out about the I century BC.
However, despite all attempts to diagnose and fight the disease, for many centuries, they remained unsuccessful. Only at the end of the XVIII century, there were clear and detailed “instructions” for the removal of different types of cancers. And detailed study of malignant tumors became possible only with the appearance of the first advanced microscopes and the development of pathological anatomy in the second half of 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, the study of environmental factors and lifestyle began.
Mutation theory of carcinogenesis
At present, the mutational theory of carcinogenesis is common in scientific circles. According to this hypothesis, the cause of malignant tumors are mutations accumulated in the genome of cells. Proof of the theory of mutational carcinogenesis is the discovery of special cells – protooncogens and genes-suppressors.
In order to understand what these cells are and how they are related to 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 mutation genome. At present, scientists know several tens of genes that start to produce cancer-causing proteins by mutation. These genes are called oncogenes, and many anti-cancer drugs are designed to suppress their work.
A protoncogen is a normal healthy gene that can turn into an oncogene and start producing deadly proteins under the influence of a variety of factors. On the contrary, the activity of suppressor genes is aimed at the production of proteins that prevent tumor formation. It turns out that the system of interaction between protooncogenes and suppressors is a kind of scales, on one cup of which there are cells causing the tumor, and on the other – cells that are trying to resist it.
A mutation of one gene can be a push that will lead to an avalanche-like mutation process in other cells. The accumulation of three to six genetic damages already leads to the “overweight” of the cancer bowl and the emergence of a malignant tumor.
The theory of mutational carcinogenesis described above is proved by numerous scientific studies, but still scientists have answers to not all questions. For example, until now, the researchers could not explain the so-called Peto’s paradox. Its essence is the following: 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, which means that the chances of a whale getting cancer should be many times greater than in the case of mice. However, for some reason, this is not the case: both mice and whales suffer from cancer at about the same rate, and some rodent breeds “outrun” the whales by this indicator.
In addition, scientists argue that most of the mutations accumulate during the first half of life – around the time when a man or animal stops growing. However, cancer most often occurs in old age. As a result of aging and under the influence of bad habits, the healthy tissues of our body deteriorate and at some point the body is inferior to the stronger cancer cells.