Cells lining the mouth reflect the molecular damage that smoking does to the lining of the lungs, researchers at The University of Texas M. D. Anderson Cancer Center report today at the annual meeting of the American Association for Cancer Research.
Examining oral tissue lining the mouth to gauge cancer-inducing molecular alterations in the lungs could spare patients and those at risk of lung cancer from more invasive, uncomfortable procedures used now, said senior researcher Li Mao, M.D., professor in M. D. Anderson's Department of Thoracic/Head and Neck Medical Oncology.
"We are talking about just a brushing inside of the cheek to get the same information we would from lung brushings obtained through bronchoscopy," said study presenter and first author Manisha Bhutani, M.D., a post-doctoral fellow in Thoracic/Head and Neck Medical Oncology.
The team examined the oral and lung lining tissue - called the epithelium - in 125 chronic smokers enrolled in a large, prospective lung cancer chemoprevention study.
The status of two crucial tumor-suppressing genes was analyzed. 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 there is cancer," Mao said.
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 percent. The percentages were similar in oral tissue, with p16 methylated in 19 percent, FHIT in 15 percent and one of the two in 31 percent.