No less important is the question of studying the carcinogenic activity of chemical compounds.

Intensification of the carcinogenic effect is also characterized by changes in other parameters of carcinogenesis (localization, variety of histological types), which depend on the route of entry and specific properties of the modifier (toxic, allergic, etc.), animal species.

The dependence of the modifying effect on the mode of administration of toxic and carcinogenic agents:

the most dangerous is the simultaneous action of a carcinogen and a toxicant, in which the activation of blastomogenesis is most intense in all qualitative and quantitative parameters of carcinogenesis; administration of carcinogenic substances in different sequences have different effects on carcinogenesis depending on the substance under study and the route of administration (tendency to inhibit carcinogenesis with oral administration of phenolic compounds before and after the carcinogen, tendency to activation by inhalation and inoculation of animals lack of modification when exposed to a carcinogen).

The combined effect of all substances at the level of their maximum concentration limits for the environment does not enhance carcinogenesis.

The dose-effect dependence of the carcinogenic effect on the action of the “carcinogen-modifying substance” complex indicates that the most effective measure of primary prevention of malignant tumors in the population is compliance with the hygienic standards of these substances.

No less important is the study of cocancerogenic activity of chemical compounds. Some substances that do not have carcinogenic activity by themselves, when entering the body, can activate the action of weak doses of carcinogenic substances that have entered the body in one way or another.

Continuation of research in this direction is necessary to expand and deepen ideas about the mechanism of influence of modifiers on carcinogenesis, on the one hand, and to improve the methodology of hygienic regulation of environmental factors taking into account their combinatorial and complex effects on the body , on the other.

Investigation of the influence of oncogenic factors on biocenoses

Nowadays, the problems of oncoecology are becoming especially relevant, where studies of the influence of oncogenic factors on biocenoses are being conducted. This new approach involves the study of the population effects of circulating carcinogens in order to integratedly assess the state of various ecosystems, identify organisms that are indicators of environmental pollution by carcinogens and control their content.

Determining the effects of carcinogenic compounds in ecosystems is carried out using basic methods of bioecological analysis of organisms, populations and biocenoses. Among freshwater and marine aquatic organisms, mussels, mesoplankton and some species of algae that have a great ability to accumulate surfactants are of the greatest interest.

Epidemiological analysis of tumor diseases among some fish populations allows to link the increase in the incidence of tumors with the degree of contamination of water bodies with industrial and domestic wastewater, petroleum products, to identify natural fish populations most sensitive to carcinogenic factors in aquatic ecosystems. Similar studies give an idea of ​​the integral action of all both blastomogenic and modifying factors over the long term, while the physicochemical analysis of water samples can detect only certain substances.

In the soil microbiocenosis, the most sensitive to the influence of benzo (a) pyrene (BP) (as the most common carcinogen) are soil fungi, actinomycetes, and spore bacteria, the number of which decreases as the concentration in the soil increases. Irreversible changes in the soil microbiocenosis develop under long-term exposure to small doses of carcinogens. As phytoindicators of surfactant biosphere pollution, it is proposed to use pine needles, the degree of pollution of which correlates with the concentration of the latter in the atmosphere.

An urgent task of oncoecology is to study the role of the physicochemical environment of habitats and living organisms in the circulation of carcinogens. The formation and circulation of carcinogens is well studied on the example of some abiogenic carcinogens (surfactants), biogenic (mycotoxins), anthropogenic (blastomogenic nitroso compounds), herbicides and pesticides.

Scheme 2. Scheme of carcinogenic circulation in the environment

Scheme 3

Scheme 4. The main ways of transport of chemicals (including carcinogens) in the environment and ways of their entry into the human body

General principles of research of blastomogenic activation of potentially toxic chemicals

Specially issued guidelines regulate the conditions and methods of research of blastomogenic substances. The biotesting of chemical compounds includes screening (selection) of substances with acceptable carcinogenicity and verification of their activity. The main selection criteria are:

chemical structural similarity with known chemical carcinogens (taking into account the similarity of metabolic pathways in the body and the relationship of the structure of the chemical compound with the transforming effect); the presence of hormone-like growth-stimulating properties, the ability to alkylate cell molecules and cytostatic properties; prevalence in the main components of ecosystems (soil, water, air); the presence of epidemiological data on the increase in the incidence of malignant tumors in organisms (including humans) in contact with certain substances.

Establishing a correlation between mutagenic and carcinogenic properties of blastomogenic factors has contributed to the development of short-term tests for carcinogens based on the registration of gene mutations, chromosomal aberrations, DNA-damaging effects in prokaryotic and eukaryotic organisms, plants, Drosophila and vitrophiles in culture.

Among the rapid tests, the most developed and widespread is the Ames test, which uses Salmonellae tiphymurium as the object of influence, which makes it possible to register both direct and reverse mutations. To test those chemical compounds whose transforming effect is manifested only after their metabolic activation, test systems supplemented with activators of carcinogen metabolism (liver microsomes) or mammalian cell cultures (rat hepatocytes) are used. A comparative analysis of the most famous modern rapid tests is given in table 1.

Table 1. Short-term tests to detect mutagenic and carcinogenic chemicals

Widely used methods

General brief data about the method

Advantages of the test

Disadvantages of the test

Markets of mutagenic action of tested chemicals

Mutagenicity tests using bacteria

Use. Salmonella typhimurium / or Escherichia coli / microsomes.

. There are 3 classes of bacterial tests:

1) those that allow to detect reverse mutations;

2) those that allow the detection of direct mutations;

3) those who have insufficient DNA repair.

 

1) rapid division of unicellular organisms; 2) well-studied genetics and biochemistry of bacteria; 3) a high degree of availability of the bacterial genome; 4) a positive result indicates that the substance is potentially mutagenic or carcinogenic to mammals

1) the absence of an unconditional correlation between mutagenicity and carcinogenicity of factors;

2) inability to detect chemicals that cause cancer not as a result of DNA damage;

3) does not detect genomic disorders;

4) artificiality of the method, which takes place in vitro and with the use of S9, which do not reflect the real metabolic situation in the liver.

Mutation his- to his + for Salmonella typhimurium and trp- to trp + for Escherichia coli: 1) replacement of base pairs; 2) shift the reading frame

Genotoxicity studies using yeast

Yeast Saccharomyces cerevisiae and Saccharomyces pombe are used

1) eukaryotic organization of chromosomes; 2) the ability to assess many end events; 3) low cost of the test at high efficiency

1) the need for modeling metabolic processes in mammalian cells, 2) consideration of the structure of the yeast cell

Genetic events: 1) point mutations in chromosomes and mitochondrial genes; 2) recombination (both inter- and intragenic); 3) aneuploidy in the process of meiosis and mitosis, there are visual changes in the color of the colonies, which are easily detected

Unscheduled DNA synthesis in mammalian cells under test

The method consists in culturing mammalian cells (usually rat hepatocytes or primary fibroblasts + microsomal liver enzymes) on slides, treating their DNA with a damaging agent in an environment where there is H3-thymidine and subsequent observation of the inclusion of radioactive labeling in the process … excisional repair) in the cell

1) rapid visual detection of lesions of the genome of mammalian cells; 2) speed and convenience of the test

1) does not allow to detect initial violations; 2) does not allow to establish the consequences of reparations

PSD (unscheduled DNA synthesis during excisional repair and inclusion of a radioactive label) – visualization of grains obtained during certain processing of the drug and autoradiography

Cytogenetic disorders and sister chromatid exchanges in vitro

CHO-primary line of fibroblasts isolated from Chinese hamster ovaries or human peripheral blood lymphocytes is used

1) the speed of the test; 2) clarity

1) high dependence on staff qualifications; 2) high dependence on the quality of drugs

Identification of chromosomal aberrations, calculation buy a comparison essay online now of SHO

Tests for induction of mutations in cells in vitro

Many cell types (human, rat, mouse, hamster) cells and various selective systems are used.

1) the speed of the test; 2) the ability to perform the test directly on human cells

The complexity of reproduction in vitro – both qualitatively and quantitatively – metabolic activation that occurs in tissues in vivo.

Direct and reverse mutations

Use of higher plants to detect mutagenic chemicals

More often 10 species of higher plants are used in 25 different test systems: 1) tests for induction of damage of mitotic chromosomes (somatic cells of the ends of roots or pollen tubes of barley, horse beans, onions, tradescantia); 2) tests for induction of meiotic chromosome aberrations (pollen stem cells) 3) tests for induction of gene mutations in specific or multiple loci (mutations of the “waxy” locus in Zea mays, mutations in chlorophyll deficiency Hordeum vulgare, somatic mutations in Trad

1) cytogenetic tests on plants are characterized by speed and cheapness; 2) they do not require complex laboratory equipment; 3) allow you to detect a variety of genetic disorders

1) a significant part of the tested chemical compounds showed its mutagenic effect in only one plant test system, 2) there is insufficient data on non-mutagenic substances; 3) little data on the metabolism of xenobiotics in the plant; 4) the presence of fundamental differences in the structure of plant cells and mammalian cells (the presence of a strong cellulose shell in plant cells); 5) the difference between meiosis and gametogenesis in plant cells and mammalian cells

Damage to mitotic chromosomes (somatic cells of root or pollen tubes), aberrations of meiotic chromosomes (pollen stem cells), mutations in specific or multiple loci (mutations of the wax locus in Zea mays, mutations in chlorophyll deficiency in Hordeum vultia)

Test for sex-linked recessive lethal mutations in Drosophila

 Drosophila melanogaster tests for X-linked recessive lethalities, which take into account

1) the criterion for determining the occurrence of mutations is very objective: the conclusions are based on whether one of the classes of males in the F2 generation is present or absent; 2) lethal mutations occur much more often than non-genetic disorders of other types; 3) this test is multilocal and covers most of the Drosophila genome

1) the test takes a long time compared to the tests on the bacteriumand lower eukaryotes; 2) possible misclassification of substances as a result of incorrect tests

Calculation of induced lethal mutations

In vivo cytogenetic tests: metaphase analysis of bone marrow cells and micronucleus test

Studies are performed using the bone marrow of Chinese hamsters, mice, rats of young adult animals

1) the conditions of in vivo research are much closer to the situation in humans; 2) there is no need to model metabolic processes occurring in mammalian cells.

1) microscopic analysis of chromosomal aberrations in metaphase cells is to some extent subjective; 2) in vivo methods are not as sensitive as in vitro tests

1) chromosomal aberrations in the metaphases of mitotic cell division of proliferating tissues; 2) shallow nuclei in the interphase, formed from centric fragments of chromosomes or whole chromosomes

Test for induction of dominant lethal mutations

Fertilized eggs from females mating with young adult male mice treated with the tested chemicals

1) lethal mutations occur much more often than non-genetic disorders of other types; 2) this test is multilocal and covers most of the Drosophila genome

1) the test takes a long time compared to tests on bacteria and lower eukaryotes;

1) analysis of postimplantation mortality; 2) taking into account post- and pre-implantation losses