Genetic therapy for breast cancer reaches the drawing board.

cytogenetic approaches to cancer. One such approach, fluorescence in situ hybridization (FISH), he said, enables scientists to assess the number of copies of specific genes in individual cells by staining them with fluorescently labeled DNA probes. They can then map the distribution of specific abnormalities within a tumor. In some cases, FISH reveals an "amazing amount of heterogeneity" in the number of copies in solid tumors, Gray noted. The technique is ideal for studying genes already known to be involved in cancer, but most investigators suspect that a lot more genes are out there, perhaps even more important than those that are now known.