Although several risk factors for hepatocellular cancer are known (see "What are the risk factors for liver cancer?"), exactly how these factors cause normal liver cells to become cancerous is only partially understood.
Cancers develop when the DNA of cells is damaged. 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 have 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. Several different genes usually need to have changes for a cell to become cancerous.
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 thousands of genes in a liver tumor sample at the same time. It is hoped that a more complete understanding of how liver cancers develop will help doctors find ways to better prevent and treat them.
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