Molecular messages and signals circulating in blood or contained in cells lining the airway can identify early stage cancer, according to research reported at the 2007 Annual Meeting of the American Association for Cancer Research.
Scientists looking to apply basic science knowledge to medical practice are developing tests that diagnose, predict or monitor cancer risks, without invasive tissue sampling. Such tests could benefit all, particularly underserved populations, such as the poor, who often wait until symptoms appear before seeing a doctor.
Lung carcinogenesis tracked by DNA methylation mapping from exhaled breath of ambulatory subjects: Abstract 827
A series of quietly exhaled breaths might indicate whether or not a patient is at risk for lung cancer, according to researchers from the New York State Department of Health. Using DNA recovered from exhaled breath, researchers can examine the state of cells that line the lungs, and potentially detect cancer at an early stage, when treatment may be most successful.
"Early detection of lung cancer is vital, yet there is no current non-invasive means of identifying cancer in a clinical setting," said Simon Spivack, M.D., M.P.H, research physician in the Human Toxicology & Molecular Epidemiology Laboratory at the New York State Department of Health's Wadsworth Center. "We have found that exhaled breath contains DNA, we believe from the cells lining the lungs, which may then tell us whether that person is at risk for cancer."
Condensed exhaled breath has been used previously to detect small volatile molecules that could indicate both non-malignant and malignant, lung diseases. Dr. Spivack and his colleagues have shown, in a pilot study, that the large molecule DNA could also be recovered albeit in trace amounts in exhaled breath condensate.
In particular, the researchers looked to see if the DNA they captured had been methylated, that is, tagged by a molecular "methyl" fragment, which blocks activation of the genes. The researchers analyzed the detailed methylation patterns of six tumor suppressor gene promotors, regions of DNA that serve as regulators of gene transcription. When those promoter regions become methylated, the cell can no longer activate its tumor suppressor genes.
It is not necessary to methylate every promoter region to induce cancer, the researchers say, so they study detailed variations in the patterns of methylation among selected gene promoters in different patients. Dr. Spivack and his colleagues believe that categorizing patients according to these methylation patterns can potentially evaluate a patient's predisposition to lung cancer. The pilot study of 33 individuals showed statistically apparent differences between never-smokers, former and current smokers, and those with lung cancer.
According to Dr. Spivack, their findings could represent a considerable advance in the early detection of lung cancer. He posits a scenario in which breath or other non-invasive tests such as CT scans can serve as cost-effective pre-screening tools for lung cancer, and could allow for treatment at early stage when the patient would theoretically have the best chance of success.
CD44 Expression in Oral Rinses: A Potential Early Detection Strategy for Head and Neck Cancer: Abstract 3506
A simple oral rinse could detect the early development of head and neck squamous cell carcinoma, according to researchers at the University of Miami's Sylvester Comprehensive Cancer Center. Their strategy involves the detection of CD44, a protein biomarker for HNSCC tumors, combined with the detection of cancer-related altered DNA, and could reliably distinguish cancer from benign diseases.
Currently, only 50 percent of head and neck cancer patients are cured of the disease. While late-stage HNSCC has a poor prognosis, cure rates exceed 80 percent if caught early enough.
"Head and neck cancers are devastating for all patients. They are particularly challenging for the poor and disadvantaged, who often do not have the adequate, regular care that makes early detection more likely," said Elizabeth Franzmann, M.D., assistant professor of otolaryngology at Miami. "Our study has shown that an oral rinse test, simple enough to be administered at any community health center, is likely to detect cancer about 90 percent of the time."
While CD44 appears on the surface of cells in healthy tissue, it is elevated at least seven- fold times in head and neck cancer. Dr. Franzmann and her colleagues theorized that CD44 could be detected in an oral rinse, which would flush out the CD44 protein by washing over the cellular membranes of interest in the throat and mouth.
According to Dr. Franzmann, their study began with an attempt to find if soluble CD44, alone, was sufficient to distinguish between cancer and other diseases. They collected oral rinses from 102 head and neck cancer patients and 69 control patients with benign diseases and history of tobacco or alcohol use. The test detected two patients with cancer or precancer before the disease was clinically evident. Furthermore, the study detected few false positives among the control group. However, they were only able to detect elevated levels of CD44 in 62 percent of cancer patients.
So, Dr. Franzmann and her colleagues looked for another potential marker of cancer: the hypermethylation of promoter genes. In many cancer cells, DNA can be chemically modified without changing the actual DNA sequence. This hypermethylation process can encourage the growth of cancer by effectively shutting down the genes that control the cell's growth cycle.