As the age increases, the probability of becoming cancer rises because the function of the immune system deteriorates.

"Two hit hypotheses" that carcinogenesis occurs when both of the alleles of the tumor suppressor gene are caused to lose their function by mutation or deficiency, in 1971Alfred George Knudson JrFrom 2018 to the present as a dominant idea in carcinogenesis. However, in a new study, the role of the immune system to suppress cancer, not the allele, has been noted.

As we age, cancer rates go up as immune system winds down | Ars Technica

Thymic involution and rising disease incidence with age | Proceedings of the National Academy of Sciences

As cell mutation occurs at the time of division, the more the cell divides, the more likely the mutation will occur. Therefore, the probability of carcinogenesis with age has been thought to increase as opportunities for mutation of "2 hits" to increase as cells divide.

The main evidence to prove this two hit hypothesis comes from cases of retinoblastoma. Children with hereditary retinoblastoma are primarily geneticRb geneIt holds an abnormality of, and when a second abnormality of some kind happens to it there is carcinogenesis. Many children with genetic mutations are said to have tumors in their eyes before they are five years old.


Currently being doneMade to Order MedicalIt focused on this 2 hit model. Treatment is done by identifying key mutations that cause cancer and aiming and defying them, but treatment may be successful or failed. Also, not all cancer has a definite gene to be targeted, and it seems that there are many cases where the tumor grows contrary to medicine.

On the other hand, in recent years,T cellsAs a "killer T cell" that attacks the tumor and kills cancer cells by proliferation and activationImmunotherapyIt is effective. In general, tumors have proteins on the surface that activate T cells, but this protein also has a mechanism that interferes with the human immune system. Immunotherapy of cancer eradicates this disturbance, and it carries out treatment to unleash the T cell which fights the tumor.

In the latest study, the relationship between the immune system and tumor cells was analyzed, and the function of such an immune system can be used not only as a basis for a therapeutic approach but also as "why people become more prone to carcinogenic as they get older It was shown to explain what "is?"

T cellsThymusThis thymus is the largest in childhood, becomes smaller little by little as the age grows, and the number of T cells to be produced also decreases. According to the contents indicated by the mathematical model, the probability that cancer mutation causing cancer will occur is almost the same throughout life, but as young there are numerous T cells existing in the early stage to clear out the early cancer cells and it is difficult to get sick Thing.

However, as the number of T cells decreases with age and the number of cancer cells increases, the immune system becomes overwhelmed and becomes a form of disease. It is to explain not only the carcinogenesis of such function of the immune system but also the phenomenon that human beings are more prone to infectious diseases to get older. Researchers believe that the prevalence of cancer is higher in men than in females because of the large number of T cells that women enter into the circulatory system and because the rate of decrease in T cells due to aging is small.

byPolygon Medical Animation

In addition, 90% of cancer patients conforming to the new model shown in this study have some sudden change around the end of their 50s, so it is recommended to conduct strict examinations in the late 50's .

It is important to note that this study showed that carcinogenesis is not explained by "2 hit hypothesis" alone. Mutation of genes is, of course, an important factor in the mechanism of carcinogenesis, but even if there is a mutation, it was shown that the cancer can be prevented by opposing the immune system.

in Science, Posted by logq_fa