Pathogenesis of cancer

Сергей Шалин Pathogenesis of cancer

We can talk about the pathogenesis of cancer only by determining the primary mutation of the nuclear DNA of the genome of the precursor cell of the cancer cell. It is possible to theoretically substantiate which cell can lay claim to the role of a precursor cell of a cancer cell if we take into account the functional abilities of the cancer cell received from a somatic cell and the pathological state of the tissues that created optimal conditions for the emergence of a malignant stem cell, the growth and development of the malignant process. Key words: initiation, promotion, monocyte, malignant stem cell, mutation.

Key words: initiation, promotion, monocyte, malignant stem cell, mutation.

INTRODUCTION

Carcinogenesis or oncogenesis is a multi-stage mechanism of the emergence, growth and development of a malignant process. According to the modern theory of carcinogenesis, the occurrence of a malignant tumor is the result of the sequential accumulation of mutations in the somatic cells of the body that are not inherited. When the number of mutations becomes critical, the formation of a primary malignant stem cell occurs. The weak link of this theory is the absence of a cancer cell precursor cell. In a morphological study, it looks like this: a healthy normal cell, next to it a malignant cell, there is no transitional variant or precursor cell to a cancer cell.

MALIGNANT DISEASES

All human malignant diseases are divided into two main groups: hemoblastoses and solid tumors. The principle of division is based on the different localization of the malignant process and some similarity between malignant cells and normal cells of the microenvironment. The cytogenesis of malignant diseases of hematopoietic and lymphoid tissue is considered the most studied, which is based on the doctrine of stem and semi-stem precursor cells of hematopoiesis. Cytogenesis of solid tumors has not yet been studied; there is no clear idea from which progenitor cells malignant cells arise. That is why we will mainly consider issues related to solid tumors, drawing a possible analogy with hemoblastoses.

General signs of hemoblastoses and solid tumors.

1. Etiology: chemical agents (endo- and exocarcinogens), ionizing radiation.

2. Pathogenesis: nuclear DNA mutations and epigenetic changes — damage to the structure of the cell membrane and chemical processes in the cytoplasm of the cell. 3. Diagnostics: clinical, laboratory and instrumental research methods with mandatory morphological verification of the diagnosis (histological and cytological studies).

4. Complications: infectious, thrombotic, disruption of the normal mechanism of osteogenesis, gastrointestinal complications (nausea, vomiting, hiccups, constipation, diarrhea and mucositis), intoxication and psychological changes (anxiety, depression, aggressiveness and suicide).

5. Principles of pathogenetic therapy: influences that suppress the proliferation of malignant cells (X-ray, chemotherapy, hormone therapy and immunotherapy); vitamin therapy; auxiliary therapy (blood transfusion, relief of infection, treatment of thrombosis and bleeding); bone marrow transplantation.

6. Causes of death: cachexia, secondary infection, severe anemia, thromboembolic complications, massive bleeding and hemorrhage.

7. The main symptoms of a malignant neoplasm: transmission of all properties by inheritance, preservation of the principle of malignant progression, uncontrolled cell division, invasive growth and metastasis. Thus, the general similarity of hemoblastoses and solid tumors is established at the genetic level. General signs of hemoblastoses and solid tumors.

Differences between haemoblastosis and solid tumours

Let us consider each group of malignant diseases separately and also split haemoblastosis into two sub-groups: leucosis and lymphoma. Based on studies of the onsets of all malignant diseases, we can draw the following conclusions:

Leucosis is a numerous and heterogeneous group of malignant diseases, which emerge from haemopoietic (blood forming) cells and affect red marrow.

— the precursors of malignant stem cells are pluripotent or unipotent stem cells of the foci of myelo- or lymphopoiesis in the red marrow;

— both stages (initiation and promotion) of the “birth” of a malignant stem cell take place in the same location — in the red bone marrow;

— the basis of a malignant stem cell “birth” is the block of differentiation and transformation of a pluripotent or unipotent stem cell of myelo- or lymphopoiesis;

— the mechanism of a malignant stem cell “birth” lies in the genotype and epigenetic changes of a pluripotent or unipotent stem cell of myelo- or lymphopoiesis following the carcinogenic impact;

— the malignant process starts from the “birth” of one malignant stem cell, which then forms a clone of malignant cells;

— the disease is manifested through growth of the malignant process in the red marrow, but at that time a primary malignant focus is absent;

— the malignant process develops by the proliferation of malignant cells within the red marrow, and by haematogenous and lymphogenous spread in the host body;

— the malignant process impacts haemopoiesis, homeostasis, immunity etc.

Lymphoma is a group of malignant haematological diseases of lymphatic tissue characterised by malignant transformation of lymphoid cells;

— the precursors of malignant stem cells are pluripotent or unipotent stem cells of lymphopoiesis located in the red marrow;

— the first stage (initiation) of the “birth” of a malignant stem cell takes place in the red marrow, the second stage (promotion) in the location of the primary malignant focus;

— the basis of a malignant stem cell “birth” is a block of differentiation and transformation of a pluripotent or unipotent stem cell of lymphopoiesis;

— the mechanism of a malignant stem cell “birth” is the genotype and epigenetic changes of a pluripotent or unipotent stem cell of lymphopoiesis following the carcinogenic impact;

— the malignant process starts from the “birth” of one malignant stem cell, which then forms a clone of malignant cells;

— the malignant process is manifested through forming the primary malignant focus located in the lymph nodes (nodal involvement) or in any other organs and tissues (extra nodal involvement);

— the malignant process is developed by lymphogenous spread in the host body, sometimes cells of lymphoma are detected in the blood, but usually they tend to form thick tumours in the lymphatic system or in the internal organs (liver, stomach, nervous system or in other places);

— the malignant process impacts haemopoiesis, homeostasis, immunity etc.

Solid Tumours are the largest in quantity, heterogeneous group of malignant diseases, which develop through multi-stage malignant transformation of a normal proliferating somatic cell into a malignant stem celclass="underline"

— the origins of malignant cells are not known, as the precursor of the malignant stem cells is not known. It is supposed that the precursors are normal somatic proliferating cells — cambial cells, which are located in the area of the crypts’ floor, glands’ neck, periosteum and perichondrium, along the blood vessels’ flow and also in the area of intense restorative proliferation;

— it is not known where and how both stages (initiation and promotion) of the “birth” of a malignant stem cell take place. It is supposed, in the area of intensive proliferation of cells;

— also it is not known what process underlies the “birth” of a malignant stem cell. It is supposed that a normal somatic proliferating cell transforms into the malignant stem cell;

— the mechanism of the “birth” of a malignant stem cell is not known. It is supposed that following the carcinogenic impact the genotype and epigenetic changes of a normal proliferating somatic cell take place, and these are a launching mechanism for its transformation into the malignant stem cell;