Carcinogens and cancer
Oncology / / May 10, 2016
In most cases, cancer in humans (80%) is caused by chemical carcinogens.In the environment, the atmosphere, food can be identified quite a number of such substances, which in animal experiments show carcinogenic properties.The atmosphere of the cities is significantly contaminated with polycyclic aromatic hydrocarbons.The presence of chemical carcinogens
number of compounds that cause cancer in animal experiments, is much greater than the number of compounds, which proved carcinogenic in humans.Currently, there are about 800 chemicals with carcinogenic in animal experiments, but only 25 of them turned out to be carcinogenic to humans.The chemical structure of these substances is very different.Among them are inorganic substances, metal salts.With many of these people contact in the labor process (asbestos, benzene, cadmium, chromium derivatives, nickel compounds, vinyl chloride);that is why here it is necessary to reckon with a long (years, and sometimes decades) exposure.Among the inorganic compounds is a well-studied biological activity of asbestos.
Asbestos - it generalizes the name by which is meant the compound hydrogenated silicates having a different chemical structure and physical properties.Asbestos fibers may be of cement, metal oxides, glass and ceramics, having a certain size, they cause lung cancer.Asbestosis upconverts lung tumors, especially in smokers.It is known that the raw material from which the synthetic substance produced polyvinyl chloride (vinyl chloride monomer), is not only toxic but also carcinogenic.In experimental animals, among other tumors, it also causes hepatic angiosarcoma.Among the workers of factories producing PVC, after prolonged exposure really cases of angiosarcoma of the liver were observed.
significant carcinogenic nitrosamines are group which, depending on the location of administration and the animal species can cause liver carcinoma, lung, kidney, stomach and bladder.The presence of nitrosamines could be detected in the environment, food, beverages.
Active hepatocarcinogs were aflatoxins - metabolic products of one of the species of fungi Aspergillus flavus;the most active among them, Aflatoxin B1.There is evidence that aflatoxin contamination of certain areas of tropical countries increased incidence of liver cancer is caused by aflatoxin.The group of carcinogenic alkylating agents include mustard, some epoxy compounds, lactones and ethylenimines.It is known that compounds of this type are widely used in cancer chemotherapy.
prove a carcinogenic effect of hormones in both animals and humans.Of great importance is the identification of carcinogenic effects of diethylstilbestrol.This hormone is used for the prevention of threatened abortion, and it has been observed that in such cases are often met in the offspring malformations of the vagina and carcinoma.This observation was evidence that transplacental carcinogenesis is a real danger not only to animals but also to humans.Prolonged estrogen administration can cause endometrial carcinoma in women.
Carcinogenic effects can not be limited to one particular molecular band, because they have organic and inorganic molecules with very different structure.In the result, even a small change in the structure of the molecule can vary and the localization of the tumor.
Malignant transformation involves a change in cell phenotype.Carcinogens, apparently, directly or indirectly, enter into interaction with macromolecules such that regulate cell renewal.It was proved that the majority of chemical carcinogens in the human environment not found in the active and in the form of so-called prekantserogennoy and only later in the body are converted into active chemical compound in the so-called complete carcinogens.From chemical carcinogens such as polycyclic aromatic hydrocarbons, aromatic amines, nitrosamines, aflatoxins activated by performing a so-called mixed function monooxygenases.Monooxygenases localized in microsomes, polycyclic aromatic hydrocarbons are converted to epoxy compounds, which are formed in a similar way and digidrodiomy are active carcinogenic metabolites, joins the cell macromolecules.