Gene Expression Profiling with DNA Microarrays Revolutionary Tools to Help Diagnosis, Prognosis, Treatment Guidance, and Drug Discovery

DNA microarrays are small solid supports on the surface of which DNA probes for thousands of genes have been orderly arrayed. Hybridization of labeled RNA from tissues or tumors allows evaluation of the relative amount of any specific mRNA present in the samples, depicting its gene expression profile. During development and progression of breast cancers, specific genetic programs are activated, which can be assayed on DNA microarrays. Studies performed so far show that the gene expression profile of a tumor defines its biology, its invasive and metastatic potential, and its responsiveness to treatments. Classification of breast cancer by expression profiling appears a very powerful approach, outperforming all commonly used methods of classification. However, much work has to be done before microarray will give robust information for clinical decisions and become routine practice.