Key mechanisms of carcinogenesis

Abstract

The main characteristics of a malignant tumor are uncontrolled growth, cellular atypia, invasion, and metastasis. Autonomous, or uncontrolled, growth is the primary characteristic of tumors. However, tumor autonomy does not mean complete independence from the host organism. Tumor cells require nutrients and oxygen to grow, proliferate, and invade. If the tumor's blood supply is impaired, areas of necrosis develop, accompanied by tissue breakdown. Furthermore, tumor cells are constantly exposed to the influence of normal cells, elements of the endocrine microenvironment, the immune system, and various cytokines. Tumor cells themselves also constantly produce various metabolites, toxic substances, oncoproteins, growth factors, and hormones that affect the host organism. Tumor cell autonomy is based on disruption of intercellular interactions due to the auto-, para-, and endocrine effects of oncoproteins and cytokines (growth factors, tumor necrosis factors, interferons). One of the main causes of disruption of intercellular interactions during tumor growth is genomic and/or epigenomic rearrangements in the tumor cell, leading to changes in the cell's structure and function. The nature of disruption of intercellular interactions in a tumor constantly changes during tumor progression. Tumor autonomy reaches its maximum at the metastatic stage.