|
The exact cause of most cases of nasopharyngeal cancer (NPC)
is not known. However, scientists have found that the disease is linked
with certain dietary habits, infections, and inherited characteristics
that are described in the section "What
are the risk factors for nasopharyngeal cancer?" Research is
being done to learn more about these causes.
Over the past few years, scientists have learned how the
Epstein-Barr virus (EBV) may cause cells in the nasopharynx to become
cancerous, but much still remains to be learned. In developed
countries, most people infected with EBV develop only infectious
mononucleosis, and their immune system is able to recognize and destroy
the virus. These people recover without any long-term problems. But in
some cases, pieces of viral DNA mix with the DNA of cells in the
nasopharynx.
DNA is the chemical in each of our cells that makes up our genes -- the
instructions for how our cells function. We usually look like our
parents because they are the source of our DNA. However, DNA affects
more than how we look. Some genes contain instructions for controlling
when cells grow and divide. Viruses such as EBV also contain DNA. When
a cell is infected with the virus, the viral DNA may mix with the
normal human DNA. EBV DNA may instruct the cells of the nasopharynx to
divide and grow in an abnormal way.
But as mentioned in the section on risk factors, EBV infection
only rarely results in NPC, so other factors probably play a role in
whether or not it causes cancer. Eating a diet high in salt-cured fish
and meat seems to increase the ability of EBV to cause NPC. Studies
indicate that foods preserved in this way may produce chemicals that
can damage DNA. The damaged DNA alters the cells' ability to properly
regulate their growth and replication.
Some studies suggest that inheriting certain tissue types may
contribute to a person's risk of developing NPC. Because the tissue
type plays a role in the function of the immune system, some scientists
suspect that an abnormal immune reaction to EBV infection may be
involved. The details of how certain tissue types might increase NPC
risk are still being worked out.
Last Medical Review: 01/21/2009
Last Revised: 01/21/2009
|
