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We don't know what causes each case, but we do know
many of the risk factors for these cancers and how some of them cause
cells to become cancerous.
Recently, scientists have begun to understand how these risk
factors produce certain changes in the DNA of cells, causing them to
grow abnormally and form cancers. DNA is the genetic material that
carries the instructions for nearly everything our cells do. We usually
look like our parents because they passed their DNA on to us. But DNA
affects more than our outward appearance. Some genes (parts of our DNA)
contain instructions for controlling when cells grow and divide.
- Genes that promote cell division are called oncogenes.
- Genes that slow down cell division or cause cells to die at
the appropriate time are called tumor
suppressor genes.
It is known that cancers can be caused by DNA mutations
(defects) that activate (turn on) oncogenes or inactivate (turn off)
tumor suppressor genes. Some people inherit DNA mutations from their
parents that greatly increase their risk for developing breast,
ovarian, colorectal and several other cancers. But inherited oncogene
or tumor suppressor gene mutations are not believed to cause very many
cancers of the larynx or hypopharynx.
Oncogene and tumor suppressor gene mutations related to these
cancers usually start during life rather than before birth like an
inherited mutation does. Every time a cell prepares to divide into 2
new cells, it must duplicate its DNA. This process is not perfect and
copying errors occur.
Fortunately, cells have repair enzymes that proofread the DNA,
but some errors may slip past. Some people may have faulty DNA repair
mechanisms that make them especially vulnerable to cancer-causing
chemicals and radiation. Acquired mutations in cells often result from
exposure to cancer-causing chemicals -- like those found in tobacco
smoke. Acquired changes in genes, such as the p53 tumor
suppressor gene, are thought to be important in the development of
larynx and hypopharynx cancer.
Inherited mutations of oncogenes or tumor suppressor genes
rarely cause these cancers, but some people seem to inherit a reduced
ability to detoxify (break down) certain types of cancer-causing
chemicals and may be more susceptible to the cancer-causing effects of
tobacco and alcohol.
Others may inherit an increased tendency to activate
carcinogens, making them even more dangerous. These people are more
sensitive to the cancer-causing effects of tobacco smoke and certain
industrial chemicals. Researchers are developing tests that may help
identify such people, but these tests are not yet reliable enough for
routine use. Therefore, doctors recommend that all people avoid tobacco
smoke and hazardous industrial chemicals.
With additional damage, the cells begin to invade (spread into
neighboring tissue) and metastasize (spread to distant organs). See the
section, "What's
new in laryngeal and hypopharyngeal cancer research and treatment?"
to learn more about recent genetic discoveries in this type of cancer.
Last Medical Review: 05/07/2009
Last Revised: 05/07/2009
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