March 30, 2006
A team of NIDCR grantees reported last year that people with oral squamous cell carcinoma have elevated levels of mitochondrial DNA, or mtDNA, in their saliva. The mitochondria are our cells’s energy sources, and they contain their own unique DNA. Following up on this discovery, the scientists wondered whether cells with altered mtDNA remain in the body’s aerodigestive tract (mouth, pharynx, larynx, and esophagus) and continue to be found in the saliva after the primary squamous cell carcinoma tumor has been surgically removed. To find the answer, they examined the saliva of 76 head and neck cancer patients before and after treatment for the common mtDNA genes called Cox I and Cox II. As published in the March 1 issue of the journal Clinical Cancer Research, the scientists reported the salivary mtDNA content was significantly decreased in these patients after treatment, which one would expect following the removal of their tumors. They found that the decrease was most pronounced in those who had never smoked and in patients who had undergone postoperative radiation therapy. However, the mtDNA continued to be harvested in the saliva, an indication that some of these altered cells are still present postoperatively and most commonly in current smokers. “The lack of decrease in current smokers implies that there is a significant population of residual epithelial cells with elevated mtDNA . . .”