[Oncogenes and tumor-suppressor genes]

Abstract

Tumors arise as a result of a chain of genetic alterations that impair normal cell functions and lead to invasion and development of metastases. These genetic alterations may result either in qualitative or quantitative changes in genes that play a key role in normal cell function, called proto-oncogenes, or in inactivation of genes that normally inhibit cell growth, called tumor suppressor genes. Whatever the mechanism involved, responses of the cell to changes in the environment become inappropriate. This paper successively reviews the various categories of proto-oncogenes, the mechanisms by which proto-oncogenes can be activated, and several examples of tumor suppressor genes. The various genetic factors involved in cell transformation probably act together to create a network of molecular interactions that results in tumor progression.