The involvement of tumor suppressor genes (TSG) in cancer initiation and progression is well documented in several tumor types such as colon (APC, p53) and breast (BrcA1, BrcA2) cancers. Loss of heterozygosity of distinct chromosomal regions, which are thought to harbor as yet unidentified TSGs, have also been linked to many cancer types. Traditional research approaches such as positional cloning have greatly assisted in elucidation of these genetic factors, and continue to be critical in efforts to understand the nature and role of TSGs in human cancers. In parallel, molecular profiling is a new strategy for analysis of tumors that has emerged based on the information provided by the Human Genome Project and the development of several high-throughput technologies. This new research concept utilizes global measurements of mRNA and protein expression patterns in tumor cells and their normal counterparts in search of the genetic culprits responsible for tumorigenesis (1 ).