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Posted: April 16, 2007
Hydrogel nanoparticles act as 'smart' sponges in cancer blood tests
(Nanowerk News) Molecular messages and signals circulating in blood or contained in cells lining the airway can identify early stage cancer, according to research reported today 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 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.
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.
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.