The transformation of normal cells into cancerous neoplastic cells is induced by physical, chemical and biological agents collectively called carcinogens; they lose the property of contact inhibition.
| Viral Oncogenes |
Cellular Oncogenes |
| These are the genes present in the oncogenic viruses, which effect oncogenic transformation of the cells they infect. |
These are the genes present in normal cells and code for growth factors; when activated under certain conditions, can cause oncogenic transformation of the cell. |
