Globally 25% of hepatocellular carcinoma (HCC or liver cancer) is thought to be attributable to the hepatitis C virus (HCV). The exact link between HCV infection and liver cancer is unclear. There is still doubt as to whether the HCV actually causes HCC. The current medical view is that HCV most probably creates the conditions for HCC to develop.
These conditions are:
- The presence of HCV in the liver causes a high turnover of liver cells. There are two causes for this. Firstly the virus constantly kills cells and so to try to make up for the loss of these cells, other liver cells multiply. The second cause is the programmed destruction of liver cells by the immune system. This is done to try and stop the virus spreading. This constant turnover of liver cells can give rise to accumulation of random DNA mutations in cells. Some of these mutations may affect the parts of the cell that regulate cell growth and reproduction. This may lead to uncontrolled growth of these defective cells.
- It is thought that part of the hepatitis C virus might interfere with the mechanism that repairs damage to DNA within cells.
- Recent research has indicated that HCV destroys a key protective tumour-suppressing gene. People usually have two copies of this cancer-fighting gene. Even if one copy of the gene mutates, the other good copy can normally (but not always) compensate for the defective gene. But if the remaining good copy is deleted through a second mutation the ability of the protein to destroy tumours is lost completely.
All these changes can lead to the transformation of some liver cells into malignant, cancerous cells.