• 6/20/2007
  • London, England
  • staff
  • medicexchange.com

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.

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 per cent of head and neck cancer patients are cured of the disease. While late-stage HNSCC has a poor prognosis, cure rates exceed 80 per cent 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 per cent 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 per cent 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.

According to Dr. Franzmann, an oral rinse sample contains enough cells to determine the presence of hypermethylated DNA. A pilot study showed that hypermethylation could be found in oral rinse samples from nine out of 11 head and neck cancer patients who had low levels of soluble CD44 from the original study.

“If put into practice, an oral rinse screening test for head and neck squamous cell cancer could be more effective than the PSA test for prostate cancer,” Dr. Franzmann said. “Many lives could be saved through a test that is no more invasive than gargling.”

Researchers at George Mason University are investigating a remarkable use of nanotechnology that might change the way doctors monitor patients for cancer-indicating biomarkers. These hydrogel nanoparticles, less than one tenth the size of a red blood cell, could function like ‘smart’ sponges, designed to soak up specific proteins in the bloodstream.

According to the researchers, it is conceivable in the future to inject these nanoparticles in the bloodstream, allow them to run through the circulatory system and then harvest them by simple blood withdrawal for analysis. While the nanoparticles are considered to be biologically inert, proper safety trials will have to be performed before their use in patients. In the meantime the particles can be used to harvest candidate biomarkers from a tube of blood drawn from patients.

“There is a tremendous need to identify cancer biomarkers but the biggest problem is that they are usually present in only very minute amounts in the blood,” Alessandra Luchini, Ph.D., a post-doctoral researcher at George Mason University’ Center for Applied Proteomics and Molecular Medicine. “We can engineer hydrogel nanoparticles to look for a single biomarker, or a multitude of selected molecules, amid a relatively vast volume of blood.”

The hydrogel nanoparticles are built as a lattice of plastic individual components, arranged at the nanoscale, about a millionth of a meter long. The nature of the individual components allows the researchers to modify the size of the holes in the lattice to form sponge-like pores small enough to catch a single protein biomarker.

To entice biomarkers into the pores, Luchini and her colleagues are using ‘bait’ that is specific for either a class of molecules or an individual biomarker. The bait could consist of an electrical charge that can pull the biomarker into an engineered pore or it could consist of sticky molecule, like an antibody, that is designed to adhere to the biomarker’s unique shape.

Once it has captured a biomarker and been removed from the patient through a simple blood withdrawal, the hydrogel can be electrically treated to coax biomarkers out of the particles.