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Although several risk factors for hepatocellular cancer are
known, the exact way in which these factors cause normal liver cells to
become cancerous is only partially understood.
Cancers develop when damage occurs to the DNA of cells. 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. It also can influence our risk for developing
certain diseases, such as some kinds of cancer.
Some genes 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 right time
are called tumor
suppressor genes. Cancers can be caused by DNA changes
that turn on oncogenes or turn off tumor suppressor genes.
Certain chemicals that cause liver cancer, such as aflatoxins,
are known to damage the DNA in liver cells. For example, studies have
shown that aflatoxins can damage the p53 tumor suppressor gene, which
normally works to prevent cells from growing too much. Damage to p53
DNA can lead to increased growth of abnormal cells and formation of
cancers.
Infection of liver cells with hepatitis viruses can also
damage
DNA. These viruses have their own DNA, which carries
instructions on how to infect cells and produce more viruses. In some
patients, this viral DNA can insert itself into a liver cell's DNA,
where it may affect the cell's genes. But scientists still don't know
exactly how this leads to cancer.
Although scientists are starting to understand how liver
cancer develops, much more must be learned. Liver cancer clearly has
many different causes, and there are undoubtedly many different genes
involved in its development. In recent years, scientists have created
new tools that allow them to look at the activity of thousands of genes
in a liver tumor sample at the same time. This is likely to have a
major effect on the study of liver cancer in the near future. It is
hoped that a more complete understanding will help doctors develop ways
to better prevent and treat liver cancers.
Last Medical Review: 11/05/2009
Last Revised: 11/05/2009
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