Although several risk factors for hepatocellular cancer are known (see "What are the risk factors for liver cancer?"), exactly how these may lead normal liver cells to become cancerous is only partially understood.
Cancers develop when a cell's DNA 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. But DNA affects more than how we look.
Some genes have instructions for controlling when cells grow, divide into new cells, and die. Some genes that tell cells to grow and divide 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 TP53 tumor suppressor gene, which normally works to prevent cells from growing too much. Damage to the TP53 gene 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 might lead to cancer.
Liver cancer clearly has many different causes, and there are undoubtedly many different genes involved in its development. It is hoped that a more complete understanding of how liver cancers develop will help doctors find ways to better prevent and treat them.