Genetic link between low alcohol tolerance and oral cancers found

An international team of scientists has found that the genes that help the body break down alcohol also influence a person's risk of developing cancers of the mouth, throat and oesophagus. The study, published in the journal Nature Genetics, looked at six variants of the alcohol dehydrogenase genes and compared their frequency in nearly 4000 cancer patients and just over 5, 000 healthy people from Europe and Latin America. They found that people with two of these variants were less likely to develop these cancers.

Alcohol is a toxin and excessive drinking is associated with several types of cancer. In particular, alcohol, along with smoking, is a known risk factor in oesophageal cancer and more than 70 per cent of people diagnosed with mouth cancer drink more than the recommended alcohol limit. In the body, alcohol is broken down by an enzyme called alcohol dehydrogenase, which detoxifies the alcohol and helps remove it from the system. There are seven known alcohol dehydrogenase genes in humans and different variants of these genes affect how fast a person is able to break down alcohol. This, in turn, affects how well that person can take the effects of alcohol - people with fast-acting alcohol dehydrogenase variants do not get drunk as quickly as those with slow-acting variants.

The new study, led by the International Agency for Research on Cancer, based in Lyon, France, found that two-fast acting variants called rs1229984 and rs1573496 also offered protection against the cancers in question, and were even more powerful in combination. The study showed that people who carry both gene variants were 55 per cent less likely to develop the cancers in this study. The researchers believe that this is because alcohol is detoxified faster by these people, so their mouths and throats are less exposed to its damaging effects. Team member Dr Tatiana Macfarlane, from Aberdeen University, explained that 'the study showed that your risk of getting oral cancers is linked to genetics as well as lifestyle'. She added: 'We found that, in particular, the risk depends on how fast your body metabolises alcohol. The results suggest that the faster you metabolise it, the lower your risk'.

The researchers also found that the protective effect was more notable in people who drank more, but they warned that this does not mean that having these gene variants is a licence to drink heavily. Dr Macfarlane emphasised that 'these results provide the strongest evidence yet that alcohol consumption is strongly linked to oral cancers'. Hazel Nunn, from Cancer Research UK, told BBC News Online that 'people with these genetic variants who drink alcohol are still at higher risk of these cancers than non-drinkersÉ the best practical advice for reducing the risk of cancers of the mouth, pharynx, larynx and oesophagus remains to stop smoking and drink less alcohol'.