The colon cancer mutator genes are another notable discovery. These genes inhibit the DNA repair process, thus promoting and accelerating oncogenesis. Genes have also been found that affect the invasive and metastatic behavior of tumors. Genes analogous to tumor suppressor genes may affect many steps in the metastatic cascade. Adhesion molecules and protease inhibitors affect the metastatic process.
Some genes alter the extracellular environment.
For example, a gene has been discovered that controls the number of adenomas that occur in familial adenomatous polyposis. It has been proposed that an absence of this enzyme leads to increased fat in the gut, which may cause anaerobic bacteria to increase production of free radicals, which are mutagenic and carcinogenic. The clinical implications of these discoveries are profound and complex. This process, termed apoptosis, or programmed cell death, is essential to normal cell development in the way that loss of the tail is essential in the development of a tadpole into a frog. Under normal circumstances, these processes are genetically programmed and regulated in such a way that homeostasis is maintained.