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Researchers have made great progress in understanding how
certain changes in DNA can cause normal cells to become cancerous. DNA
is the chemical in each cell that carries our genes -- the instructions
for how our cells function. We look like our parents because they are
the source of our DNA. But DNA affects more than the way we look. Some
genes have instructions for controlling when our cells grow and divide.
Certain genes that promote cell division are called oncogenes. Others
that slow down cell division or cause cells to die at the right time
are called tumor suppressor genes. Cancers can be caused by DNA
mutations (defects) that turn on oncogenes or turn off tumor suppressor
genes.
Mutations of 2 tumor suppressor genes are responsible for many
inherited cases of neuroendocrine tumors and neuroendocrine cancers.
Most inherited cases are due to changes in the MEN1 gene. A
smaller number are caused by inherited changes in the NF1 gene.
Most cases of neuroendocrine tumors and neuroendocrine cancers
are caused by sporadic mutations of oncogenes or tumor suppressor
genes. Mutations are called sporadic
if they occur after a person is born, rather than having been
inherited. The mutations that cause carcinoid tumors often affect the MEN1 gene, the same
gene that is responsible for most familial neuroendocrine tumors and
neuroendocrine cancers. In many other types of cancer, researchers have
shown that these acquired mutations are the result of cancer-causing
chemicals in our environment, diet, or tobacco smoke. Relatively little
is known, however, about factors that cause new mutations in genes that
lead to neuroendocrine tumors and neuroendocrine cancers.
Doctors do know that carcinoid tumors start out very small and
grow slowly. When patients have parts of their stomach or small
intestine removed to treat other diseases, taking a close look under
the microscope often shows small groups of neuroendocrine cells that
look like tiny carcinoids. Researchers still do not know why some
remain so small and others begin to grow and become large enough to
cause symptoms.
Last Medical Review: 06/19/2009
Last Revised: 06/19/2009
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