A University of Texas M. D. Anderson Cancer Centre team, led by an Indian researcher, has revealed that mouth can convey the extent of damage caused to lungs by smoking.
The researchers said that cells lining the mouth could reflect the molecular damage that smoking does to the lining of the lungs.
"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 Manisha Bhutani, study presenter, first author and a post-doctoral fellow in Thoracic/Head and Neck Medical Oncology.
The team, also including Dr Li Mao, senior researcher and professor in M. D. Anderson's Department of Thoracic/Head and Neck Medical Oncology, conducted the study over 125 chronic smokers enrolled in a large, prospective lung cancer chemoprevention study where they analysed the oral and lung lining tissue - called the epithelium.
The status of two crucial tumour- suppressing genes p16 and FHIT was analysed. Both the genes 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.
The participants gave both an oral and lung sample at initially and then another at three months.
The researchers tracked whether 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.
They found methylation of p16 in the lungs of 23 percent of the participantsf 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.
"Our study provides the first systematic evidence that accessible tissue, the oral epithelium, can be used to monitor molecular events in less accessible tissue," said Bhutani.
"This provides a convenient biomonitoring method to provide insight into the molecular events that take place in the lungs of chronic smokers," she added.
"We hope that our findings encourage researchers to test an increasing compendium of biomarkers to confirm the reliability of oral epithelium not only in lung cancer chemoprevention but also in therapeutic settings" said Dr. Ashutosh Kumar Pathak, another key study author and a post-doctoral fellow in Surgical Oncology.
Dr Mao said that 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.
The study was presented at the annual meeting of the American Association for Cancer Research.