Cancer is generally a disease of tissue growth regulation. All together for an ordinary cell to change into a disease cell, the qualities that control cell development and separation must be adjusted. The affected genes are separated into two general classifications. Oncogenes are genes that promote cell growth and proliferation. Tumor silencer genes are genes that repress cell division and survival. Dangerous change can happen through the development of novel oncogenes, the improper over-articulation of typical oncogenes, or by the under-expression or disabling of tumor silencer genes. Commonly, changes in multiple genes are required to transform a typical cell into a disease cell.