A microarray chip doesn’t look revolutionary. Nor does it look particularly high-tech.
The patented Affymetrix GeneChip is roughly the size of a business card. Its facade is broken by a black square cavity and computerized bar code. Its white label is laced with fine print: an expiration date, an identification number and the warning, “For Research Use Only.”
Still, the chip’s plastic case looks more like a cumbersome hotel key card than a potential medical breakthrough.
But researchers and medical doctors across the country have heralded microarray chips as having the potential to save lives, diagnose disease and improve patient care. They’re also capable of reducing everything from medical costs and liability suits to the bad side effects of drugs, according to experts.
For instance, the chips are slated to guide cancer therapies and help doctors decide how aggressively to proceed after a biopsy. By analyzing the genetics of a patient’s tumor, the technology may even rule out chemotherapy treatments for some survivors.
Greg Yap is vice president of DNA products for Affymetrix, a Santa Clara, Calif., company that produces the GeneChip and is a seminal force in microarray technology. Yap sees incredible possibilities in the small chips.
A revolution in care
“Microarrays will revolutionize the way that medical care is delivered in this world,” he said. The company vice president also sees a long, albeit bright road ahead.
He follows his bold statement with an equally strong caveat: Don’t expect miracles any time soon. “These things have enormous promise,” Yap said, “but it will take a long time for the full impact of this to be felt.”
In fact, even though microarray technology has been around since 1989, most doctors are still awaiting a formal introduction.
At the most basic level, microarrays are glass slides affixed with pieces of DNA or RNA. Even more, they are pocket-sized descriptions of entire organisms that have been translated into the language of genetics. The chips typically represent one organism, be it human, animal, plant or a disease.
Human microarrays require human genes from either a simple cheek swab or blood sample. In some instances, as with the investigation of cancer, doctors may need to biopsy a patient’s tumor to test his RNA.
A person’s genetic information, when isolated, is purified and then inserted into the square cavity of a human microarray chip. Sans the sticky scientific details, what happens next is that a laser and computer work together to analyze the chip and generate a corresponding computerized image. The image usually is a dark, gridded canvas that, to the non-geneticists of the world, looks as though it has been spattered with white paint.
These specks actually are a highly ordered arrangement of nearly 3 billion bases of DNA or RNA. The intensity of their whiteness translates into a significant molecular signature that can inform researchers what’s happening to a person at the genetic level.
Today researchers use the chips to quickly and thoroughly analyze genomes of single organisms and, even better, to compare the interactions between two organisms, such as humans and disease agents.
An array of possibilities
This translates into a plethora of possibilities. For instance, microarrays can accurately and rapidly diagnose viral and bacterial infections. A single chip can distinguish between the SARS virus in Toronto and the slightly different SARS virus in Hong Kong. Another chip could identify anthrax in a municipal water system, and yet another could diagnose your next-door neighbor with the common cold.
But microarrays are not a medical panacea. They cannot inform researchers in situations where diet, environment or upbringing contribute heavily to an illness. In terms of understanding cancer and inherited diseases such as diabetes, though, “genetics has a very strong role and a role that doctors haven’t been able to understand before,” Yap said.
Soon doctors may get their chance.
“The technology is just now starting to reach the clinic,” said Rex Chisholm, who as the director of the Center for Genetic Medicine at Northwestern University has fielded the microarray demands of university researchers for five years. As the technology continues to develop, it likely will move into doctor’s offices and contribute to daily medical practice, he said.
Stephen Kralovic is a medical epidemiologist at the VA Medical Center in Cincinnati who specializes in the diagnosis and treatment of infectious diseases. He is eager and still waiting to work with the chips in a clinical setting.
“Microarray technology holds much promise for future use,” he offered. “It will not only take into account the individual genetic make-up of the patient, but it will take into account the genetic make-up of the infecting organism and allow a highly individualized therapy.”
In a world where everyone is unique and medical care is expensive, on-target treatment is an elusive gold standard. So is the correct, rapid diagnosis of disease.
Pharmaceutical companies spend billions of dollars annually trying to identify in what individuals and at what dose a drug is most effective. Today these companies are using microarray technology to better understand how genetics influences a drug’s performance.
“If you could understand a person’s genetics and understand which versions of the genes that they have, you could pick the right drug instead of giving them the wrong drug,” Yap said. “That’s not just beneficial in terms of economics; that could be the difference between a person living or dying.
“It’s all about giving the right drug to the right person at the right time.”
