Serial Analysis of Gene Expression (SAGE) is a sequence-based approach to the identification of differentially expressed genes by comparative analyses. SAGE is a powerful tool, one of the more comprehensive methods available for detailed analysis of large numbers of cellular transcripts, leading to a profile of the expressed genes.1 SAGE provides an accurate quantitative analysis of the relative levels of genes expressed in a specimen. The ability to count many thousands of genes allows the detection of genes that are expressed at very low levels in a high-throughput manner. A three-step molecular approach, the SAGE process allows simultaneous analyses of sequences derived from various cell populations or tissues.2
In 1995, Victor Velculescu first described SAGE, a pioneering approach to gene expression analysis that enabled a detailed characterization of expression patterns without prior knowledge of previously isolated genes. The method was originally developed to investigate genes that might be differentially expressed in colon cancer.4
Cancer research remains the focus of the vast majority of SAGE studies. The identification of novel markers for cancer progression and prognosis as in the case of uterine cancer, in which early stage I detection can be difficultis critical for successful treatment. The SAGE method can identify potential targets for therapeutic intervention and find key biochemical pathways. This application is well suited for gene expression analysis of any tissue from any organism.
SAGE is based on the principle that once isolated from a defined position within a transcripta sequence tag of 9 or 10 base pairs (bp) provides sufficient information to identify a transcript. These tags can be serially analyzed by ligating or concatenating them to form longer chains. After they are sequenced, software