For the first time, UK scientists have reported direct evidence that taking up smoking results in epigenetic changes associated with the development of cancer.
The results were reported at the 35th Congress of the European Society for Medical Oncology (ESMO) in Milan, Italy.
The link between smoking and cancer has been established for decades, explained Dr Yuk Ting Ma from the Cancer Research UK Institute of Cancer Studies, Birmingham, who presented the results. Smoking is the single biggest cause of cancer in the world, and years of research have confirmed that carcinogenic substances in tobacco smoke can damage DNA.
Scientists have also suspected that smoking causes so-called epigenetic changes, such as methylation, which alter gene expression without causing changes to the actual DNA sequence.
"Until now, however, there has been no direct evidence that smoking induces DNA methylation in humans," Dr Ma said. "Cross-sectional surveys restricted to patients with cancer have revealed that aberrant methylation of several tumor suppressor genes is associated with smoking. But such surveys cannot distinguish those epigenetic changes that are a consequence of the disease process from those which are directly attributable to smoking."
In a study funded by Cancer Research UK, the British team set out to clarify the link between smoking and methylation in a cohort of 2,011 healthy young women aged 15-19 who were originally recruited as part of a study of pre-cancerous changes to cells of the cervix.
"For this particular study we have identified all the women from that cohort who had normal smears and who also tested negative for human papillomavirus throughout follow-up," Dr Ma explained. "In this subgroup of disease-free women we have then tested the cervical smears of all the women who first started to smoke following study entry for p16 methylation, and compared them to women who were never smokers."
|Contact: Vanessa Pavinato|
European Society for Medical Oncology