The pathogenesis of malignancies
Oncology / / May 10, 2016
pathogenesis of tumors - the emergence and reproduction in the body of genetically modified tumor cells with specific properties.Tumor cells are genetically modified in the sense that they are able to transmit their descendants pathological properties: daughter cells formed by dividing tumor cells, at least part of which retains tumor properties.Such a transfer of tumor cells properties descendants may occur in an infinite number of generations.Tumor cell division in most cases is the main way of growth of the primary tumor nodules.The primary components of many types of human and animal tumors are clones, ie. E. All of the descendants of the node cells are a source of tumor cells.Transfer of the tumor cells to other tissues and reproduction leads to the formation of metastatic tumor nodules in these tissues.
The experiment can be transplanted tumor cells arising in one body to another body;the recipient of the transplanted cells developed a new tumor site.The first successful transplantation of tumor
Tumor cells in transplantation usually retain many morphological, biochemical and immunological features of the original tumor cells.In particular, the preserved characteristic of original tissue histocompatibility antigens.Therefore, tumor cells tend to give strong growth only at their transplantation of genetically identical animals.When transplanting animal of another genotype of the tumor tissue, as well as any other foreign tissue transplantation induces immunity, leading to the death of the transplanted cells.In some tumor strains after long occurred direct selection of cells resistant to transplant immunity.Such strains can be successfully transplanted even animals other genotypes.
Tumor tissue also stores the original tissue specific antigens.Therefore, successful transplantation of tumors other animal species (geterotransplantatsiya) is only possible if the recipient prevented or weakened immune responses.This can be achieved in several ways:
a) transplanting cells into the tumor tissue with weak immune responses induced by, for example, in the anterior chamber or into the brain;
b) introducing the recipient immunosuppressive drugs;
c) using as recipient animals with genetic defects in the immune response.
Applying these methods weaken immunity, it managed to carry out a successful geterotransplantatsiyu some human tumors animals.
tumor cells it is also possible to grow long and passaged in tissue culture.Among human tumor lines, long grown in tissue culture, most widespread HeLa cell line;This line is derived from the cultivation of cervical carcinoma cells.Cultured normal cells (fibroblasts, epithelial cells) after exposure to tumor substances or carcinogenic viruses can undergo malignant transformation: A certain percentage of transformed cells in culture tumor.In culture, there is also a spontaneous transformation of tumor cells;after prolonged passaging in culture without additional cells may be tumor effects.Tumour characteristics of cells grown in culture, identifying, by transplanting these cells into syngeneic animals or athymic mice.Properties
tumor cell population may change during the growth of the primary tumor and the secondary nodes, and in the passage of transplantable tumors.These changes appear to result from the fact that the tumor tissue may generate new genetic variants of tumor cells with properties different from those of the majority of the cell population.If these options are any cells or "benefit" to the tumor site by most cells, the result of selection, the cells will accumulate in the tumor tissue.Stable irreversible changes one or more properties of the tumor tissues is called tumor progression.Each tumor progression may be a multi-stage: in the process of tumor growth and it can successively predominate several different tumor cell variants.Under normal conditions, each additional stage of progression of tumor tissue increases the contrast of the original normal tissue.For example, during the progression may ability of tumor cells to disappear to give the tissue structure, with structures similar to normal tissue;disappear biochemical characteristics typical of the original tissue.Disappears normal sensitivity to hormones that control reproduction of the original normal cells;appears and enhanced ability to invasive growth and metastasis.Just predict the time of a particular tumor progression and changes in the nature of its progression can not be: the progression of each tumor is individually.Apparently, such a tumor progression individuality due to the fact that the new genetic variants in tumor tissue result from a random process of variability.The tumor cell cultures can be created special conditions under which the cells will accumulate variant, at least different from normal cells than most cell culture.Such variants are called revertant.Detection reversion process is of fundamental importance since it shows that the genetic variation is in all directions in the tumor tissue, both in cells modified by more and more towards normal cells.Which option will receive any benefit - it depends on the selection criteria.