July 2001

DNA Chips Target Cancer

Continued from page 2

By Marc Wortman

Perfecting Detection

Once researchers know the fingerprints of different cancers, they'll be able to craft customized DNA chips that doctors can use to diagnose patients with previously unheard-of accuracy. Says Staudt, "The textbooks on cancer diagnostics are going to be rewritten over the next three to four years.[DNA-chipbased diagnostics] will very soon become routine technology."

But the ability to read subtle genetic changes could allow doctors to do more than pinpoint the exact identity of a cancer; it could also help them read early warning signs that normal cells are about to turn cancerous-long before such changes are evident to a pathologist. That's what University of South Florida cancer geneticist Melvyn Tockman is hoping, anyway.He and his colleagues are working on an early-detection method for lung cancer-a method that could make John Leventhal's scar a relic of the medical dark ages.

The researchers take sputum samples from ex-smokers and use DNA chips to analyze which genes are active in the lung cells. By comparing the genetic profile of these damaged cells to profiles from both healthy and cancerous lung cells, Tockman hopes to find the fingerprint that indicates a cancer is just about to form. In the future a patient at risk for lung cancer might take a simple DNA-chip-based test for this genetic fingerprint each time he went for his regular checkup.

That's a few years in the future, but the initial payoff of DNA chips in detecting cancer may come even sooner. Researchers are already using the chips to identify telltale proteins that can be detected by conventional cancer-screening tools. "If a cancer has one hundred uniquely expressed genes," explains Mohan Iyer, the vice president of business development at Santa Clara, CAbased diaDexus, "the home run hit is to find one [of the proteins those genes code for] that can be used in a simple blood test to screen individuals for cancer." If a protein were found to be unique to a certain cancer, says Iyer, standard hospital equipment could easily detect it in a blood sample.

With DNA-chip tools now helping to identify the proteins associated with breast, lung, colon and ovarian cancer, to name a few, Incyte Genomics, Corning and a handful of other companies are developing new protein-based screening methods for diagnosis of the diseases. These new tests should begin to reach diagnostic laboratories in the next two years or so.