Oncogenes: present status.

Oncogenes are genes associated with causation of cancer. They were originally associated with the ability of retroviruses to cause tumors in animals. These viral oncogenes (V-onc) have their cellular counterparts (C-onc) called Proto oncogenes. Function of Proto oncogenes is to maintain cellular growth and development. Activation of these proto-oncogenes can occur due to mutation which leads to uncontrolled cell growth. The Proto oncogenes can be grouped into different categories based on their protein products, i.e. protein kinases, growth factors, growth factor receptors, and DNA binding proteins. There are also genes that normally suppress malignant transformation and these are called anti oncogenes. Loss of their suppressor activity leads to unimpeded growth. Oncogene abnormalities are seen in pediatric leukemias, lymphomas, and various solid tumors. Anti oncogenes are associated with retinoblastoma (Rb gene), Wilms' tumor, rhabdomyosarcoma and neuroblastoma, etc. Identification of these abnormalities have diagnostic, prognostic and therapeutic implications. The utility of oncogenes in classification of human cancer and monitoring cancer therapy is quite clear, but the future of these for therapeutic interventions remains uncertain. Role of c-abl oncogene in chronic myeloid leukemia (CML), bcl-2, in lymphomas, N-myc in neuroblastomas and retinoblastoma (Rb) gene in retinoblastomas is well understood and used in designing proper therapeutic approaches. Since oncogenes also control normal cellular function, their use for therapy may be limited by the amount of damage to normal cells. Their maximum therapeutic benefit may be realized only when used in combination with other modalities.