A particular gene variation appears to significantly increase the risk that individuals with cirrhosis of the liver will go on to develop hepatocellular carcinoma (HCC), a liver tumor that is the third leading cause of cancer death.
In the January 2 Journal of the American Medical Association, researchers from Massachusetts General Hospital (MGH) Cancer Center and colleagues in France describe finding that a single alteration in the epidermal growth factor (EFG) gene may greatly increase the risk of developing HCC.
“If these results are confirmed, this EGF variation could be used to determine which cirrhotic patients should be screened more intensively for tumor development,” says Kenneth Tanabe, MD, chief of Surgical Oncology at the MGH Cancer Center, the study's lead author. “In addition, the molecular pathway controlled by EGF and its receptor EGFR – which is known to be important in several types of cancer – appears to be an excellent target for chemoprevention studies. This is a deadly cancer and so progress in prevention and early detection is critically important.”
HCC is the sixth most common solid tumor worldwide and most commonly develops in individuals with cirrhosis, which may be caused by infection with the hepatitis B or C viruses. There are currently no effective treatments for most HCC patients, so there is considerable interest in strategies that may prevent development of the tumor.
EGF's normal function is to stimulate tissue growth. Animal studies have shown that elevated levels of this protein in the liver lead to tumor development and that blocking the protein's receptor can prevent development of liver cancer. The current study was designed to determine whether cirrhotic patients with higher EGF levels are at greater risk for liver cancer and to determine the influence of a particular inherited gene on EGF levels in cirrhotic patients.
The researchers focused on a known variation in the EGF gene – the presence of the nucleotide guanine (G) instead of the more common adenine (A) in a particular location – which has been shown to increase EGF secretion in blood cells and raise the risk for malignant melanoma. Individuals inherit one copy of the gene from each parent and therefore have this gene with either two copies of A (A/A), two copies of G (G/G), or one copy of each (A/G). Genetic analysis of liver tumor cell lines showed that messenger RNA transcribed from DNA strands with the G allele was more stable that that transcribed from the A version, which could explain why cells with two G copies tend to secrete higher levels of EGF.