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Cancerogenesis
Carcinogenesis and hereditary predisposition: process resulting in the formation of a cancer.
Carcinogenesis can be defined as the acquisition by cells of certain properties that make them immortal and which endow them with the capacity for unlimited proliferation. The number of divisions that a human cell can generate is limited by a mechanism called senescence. Tumour cells also become insensitive to signals intended to inhibit proliferation. In addition, they acquire the capacity of neoangiogenesis (the process by which new blood vessels grow from existing ones. The cancerous mass is irrigated by blood vessels that supply the oxygen and food necessary to the survival of the cancer cells) and that of the invasion or infiltration of neighbouring and remote tissues. Cancer cells can pass into a blood vessel and be transported to another organ where they can generate a second cancer (metastasis).
The main cause of cancer is the mutation of genes only in the diseased cells. A cancer has at least 5 to 10 modified genes in one cell. Also, only 5-10% of human cancers are associated with a constitutional mutation of a gene; in this case we speak of family cancers of a hereditary nature and genetic predisposition.
In the case of predisposition to a cancer, as with all multifactorial diseases, genetic heredity and inter-individual genetic variability are not the only factors involved. The relations of the organism with its environment also influence the development or not of a cancer.
On the contrary, individuals exposed to a similar environment do not all run the same risk.
A large number of chemical, biological and physical agents in the environment can affect genes and cause their mutation, thus having an impact on their functioning and on carcinogenesis.