• 9/13/2007
  • web-based article
  • Katherine Bourzac
  • Digital Pathology Blog (tissuepathology.typepad.com)

Researchers at the University of Texas are developing a microfluidics device that detects oral-cancer cells in 10 minutes and is simple and cheap enough for use in the dentist’s office. The device could be adapted to test for other cancers, including cervical cancer. It works well on cancer cells grown in the lab and is currently being tested on biopsies from oral-cancer patients.

Many oral cancers are painless or, in their early stages, resemble dental disease, so patients and doctors may overlook them, says Carter Van Waes, chief of head and neck surgery at the National Institute on Deafness and Other Communication Disorders. The National Cancer Institute estimates that, this year, 22,560 people will be diagnosed with oral cancer, and more than 5,000 will die of the disease. “Even though oral cancer is not common, it’s usually advanced when it’s diagnosed,” says Spencer Redding, chair of dental-diagnostic science at the University of Texas Health Science Center, in San Antonio. Redding is helping test the new device, which was developed by John McDevitt, professor of chemistry at the University of Texas at Austin.

“The goal is to identify patients earlier,” when the survival rate is about 90 percent, says Redding. Patients diagnosed in the later stages of the disease don’t respond well to treatment, and only about 50 percent survive. McDevitt and Redding envision a compact device that would be standard in dental offices. Any suspicious-looking sores in a patient’s mouth could be scraped and tested for signs of cancer while the patient is still in the dentist’s chair.

The device, made of acrylic, has a small reaction chamber fed and cleaned via tiny inlet and outlet channels. A solution of scrapings from a patient’s mouth enters through the inlet and is strained through a cell-catching filter. Caught cells are then flooded with a solution containing fluorescent protein tags. The tags stick to a protein, called a cancer biomarker, that’s made in much greater quantities by oral-cancer cells than by normal cells. Under a fluorescence microscope, cancer cells caught in the device have an intense green halo. The entire test can be performed in less than 10 minutes.

The test has the potential to be very cheap. Cells are exposed to a tiny volume of liquid–only about four microliters–and all cell preparation happens inside the device. Traditional methods for detecting cancer-cell biomarkers are expensive and complex and require trained technicians, so they are available only at hospitals with sophisticated equipment. At the moment, the results of the new test still have to be read under an external fluorescence microscope, but McDevitt’s lab is developing a small prototype machine that incorporates both the microfluidics device and a simplified fluorescence-imaging system.

A 10-minute test is 10 times faster than traditional methods for detecting tumor biomarkers, says Van Waes. “The speed is really important,” says Linda Pilarski, Canada Research Chair in biomedical nanotechnology at the University of Alberta’s Cross Cancer Institute. “Ideally, you want the result while the patient is still there, so they don’t go away and not come back.” Starting treatment even a few weeks earlier can make a difference for cancer patients. And the speed, ease, and cost of the test could mean that more patients get screened, says Pilarski.

“Biomarkers are becoming the whole basis for cancer care,” says Pilarski. She hopes that cheap, fast tests like McDevitt’s will eventually make even finer distinctions. Patients with the same diagnosis can have cancers that differ subtly at the molecular level, she says, and “molecular tests can stratify patients” into subgroups with different treatment needs. Breast-cancer patients, for example, are already screened for a biomarker called HER2 to determine whether they should be given the drug Herceptin.

McDevitt is also working to incorporate the cell-screening technology with a test for cancer biomarkers in saliva. Adding more biomarkers to the test should increase its sensitivity and specificity, says Redding. The test might also be adapted for cervical cancer: the scraping of cells in a Pap smear is similar to that in an oral-cancer biopsy