Medical Genetics - V. M. Zaporozhan 2005

Fundamentals of Oncogenetics
General characteristics of genes responsible for tumor development

The formation of malignant tumors is associated with several groups of genes: oncogenes and Proto-oncogenes, tumor suppressor genes, and Mutator Genes.

Oncogenes are cellular or viral genes (introduced into a Cell by a virus) whose expression can lead to The Development of a neoplasm.

Proto-oncogenes are normal cellular genes whose enhanced or modified Functions turn them into oncogenes. Normally, proto-oncogenes promote cell mitosis. Activated or modified proto-oncogenes (oncogenes) significantly accelerate cell proliferation. Such Mutations are dominant, meaning that a single oncogene is sufficient to alter the phenotype.

Tumor Suppressors (anti-oncogenes) are genes that inhibit cell proliferation. The inactivation of these genes increases the likelihood of neoplasm formation, whereas the restoration of their function, conversely, suppresses tumor cell growth. Mutations that reduce Gene activity are recessive, so alterations in both gene copies are required to change the phenotype.

In 1989, Nobel laureate J. M. Bishop wrote regarding proto-oncogenes and suppressor genes: “Two Types of genes govern cell multiplication: proto-oncogenes, which act as the accelerators of division, and suppressor genes, which function as the brakes. Jam the accelerator and release the brakes, and The Cell, like something unleashed, will begin to divide incessantly.”

Mutator genes may not directly affect cell growth, but the disruption of their function increases The rate of mutations and/or other genetic alterations. This significantly raises the probability of various oncogenic mutations, ultimately making tumor formation only a matter of time.