DNA Chips to Predict Treatment Responses

A University of Houston scientist has developed a chemical process for building a device that could help doctors predict a patient's response to drugs or to screen them for diseases-all with one simple lab test.

The DNA chip - similar to a computer chip but imbedded with DNA molecules instead of electronic circuitry - is designed to probe a tissue sample for genetic information that indicates whether the person has a genetic predisposition for certain diseases or conditions.

"We have put thousands of strands of DNA onto a chip that can screen for the genes linked to breast cancer, cystic fibrosis or prostate cancer," says Xiaolian Gao, a professor of biochemistry at the University of Houston. "This highly parallel technology allows us to do thousands or tens of thousands of experiments all at once."

The process which Gao's team developed to make the DNA chip involves the use of thousands of micromirrors to project tiny light patterns - less than the diameter of a human hair - onto each postage stamp-sized DNA chip.

Controlled by a computer, the light hits the chip at different spots, where it triggers a chemical reaction. Individual DNA strands are then built up on these locations one by one in a grid-like pattern. The researchers then put specific "probes" on the chip which determine if a person has or doesn't have the genetic codes present.

"Your genetic code may determine whether you have the ability to degrade a certain drug, or how well you will respond to a certain drug," says Gao. "Some people have better responses than others to hypertension drugs, or chemotherapy, for example. This drug screening process can help tell us why one drug is more effective than another."

Gao says there are currently many other biochip technologies available or in development, and the ultimate applications of biochips are similar - genetic screening, disease diagnosis and new drug development-all tailored for the specific genetic makeup of individual patients.

SOURCE:
The Lancet, October 27, 2001; 358:1389-1399

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