Wildlife biologist Marissa Irwin had no idea that cells in her body had gone haywire. In response to scrambled protein signaling pathways, certain cells turned cancerous and grew into tumors that took over the 37-year-old woman's ovaries. Though her doctors settled on a diagnosis of ovarian cancer, they could not determine what kind of neoplasia was causing the tumor growth--an important factor in determining the proper treatment.
Daniel Chan is one of a growing number of researchers who are trying to change all that. As director of the Biomarker Discovery Center at Johns Hopkins School of Medicine, Chan works with a relatively new and still developmental tool in his quest to make Such diagnoses more straightforward and to provide an early screening method. He works with protein-detecting microarrays.
The latest developments with these microarrays make it possible for researchers such as Chan to survey tens to thousands of proteins in biological samples simultaneously. If the technology works as advertised, it could illuminate the protein makeup, or proteome, of cells and body fluids, as well as the interplay between these proteins. That, in turn, could provide scientists with a better understanding of disease pathology and development, cell signaling, and other complex cellular processes. Researchers have a number of kinks to work out, however, if protein chips are to move from the research lab into the clinic.
MICROARRAYS EXPLAINED Protein arrays, like their precursor DNA microarrays, enable a massively parallel experimental approach. In a DNA microarray or biochip thousands of distinct DNA sequences, each representing a single gene, are printed on a solid substrate such as a glass microscope slide. Incubation with a labeled sample, such as mRNA from tissue, reveals which of the genes represented on the array are expressed in the sample, and their relative levels, thus producing a snapshot of the tissue's global gene expression pattern.
Panoramic though such pictures are, they reveal little about the actual biology of the cell. "It's the proteins that really carry out the function of cells. It's not the DNA or the RNA," says Mark Schena, visiting scholar at Sunnyvale, …