A report from the annual meeting of the American Association for Cancer Research suggests that cells lining the mouth reflect the molecular damage done to the lungs by smoking. This means that examining these cells could save patients being checked for lung cancer from invasive and uncomfortable procedures.
Manisha Bhutani and colleagues, from the University of Texas, looked at the lining of the mouth and lung epithelium of 125 long-term smokers enrolled in a large cancer prevention study. They examined the status of two crucial tumor-suppressing genes . The genes, p16 and FHIT, are known to be damaged or silenced very early in the process of cancer development. There is substantial damage long before cancer appears.
Study participants gave both an oral and lung sample initially and then another at three months. The researchers tracked whether either p16, FHIT or both had been silenced by methylation - the attachment of a chemical methyl group to crucial spots in a gene that shut down its function. Patterns of methylation were compared between the tissues.
The baseline tissue comparison showed methylation of p16 in the lungs of 23 percent of study participants, of FHIT in 17 percent and of either of the two genes in 35%. The percentages were similar in oral tissue, with p16 methylated in 19%, FHIT in 15% and one of the two in 31%.
Strong correlations were observed between methylation patterns in both tissues. When methylation of either gene was considered positive, 37 of the 39 individuals (95%) with p16 and/or FHIT promoter methylation in the oral samples had promoter methylation in at least one matched bronchial sample. This compared with only 59 of the 86 (69%) individuals without the promoter methylation in the oral samples. Similar correlations were seen at the three-month analysis.
This is the first time that accessible tissue has been used to monitor molecular events in less accessible tissue, according to the authors of the study. There is apparently the potential to use similar techniques to monitor for other smoking-related cancers, such as bladder, pancreatic and head and neck cancers.
