MARGARET SHIPP, MD: A gene chip is a way of being able to understand the message system of a cell. If you think about the way that a cell knows how it should behave, there is basic genetic information encoded in DNA. DNA is then turned into RNA, and RNA is made into protein, and the protein in a cell is actually what makes a cell do -- it's the instructions -- makes a cell do what it should do. What a gene chip allows you to do is to examine those genetic instructions for many of the different genes in the body with a single approach. So the way that this works is that you make from a type of cell that you're interesting in evaluating RNA, and then you have a platform, which is the chip, and that platform has on it representations -- DNA -- for thousands of genes. This is represented in a size that's probably smaller than a quarter. What you can do is you can take the RNA from a tumor cell and overlay it on this chip that has thousands of genes represented, wash it and scan it with a special camera, and get a computer representation of the expression of those thousands of genes just by looking at the information on that chip.
WAYNE FREEDMAN: What do you mean by expression?
MARGARET SHIPP, MD: Expression is an indication of how much of a specific gene product exists in a certain cell, so you get an idea of how active that gene is in a cell. Is it high? Are the levels high? Are the levels low? So you can begin to put together the genetic information by understanding which genes are expressed at high levels, which genes are expressed at low levels, and understand what types of genes are active in different cell types.
WAYNE FREEDMAN: You always get a different road map depending on the tumor?
MARGARET SHIPP, MD: Yes, almost certainly we do.