Alternative spliced transcripts as cancer markers

Eukaryotic mRNAs are transcribed as precursors containing their intronic se quences. These are subsequently excised and the exons are spliced together to form mature mRNAs. This process can lead to transcript diversification t hrough the phenomenon of alternative splicing. Alternative splicing can tak e the form of one or more skipped exons, variable position of intron splici ng or intron retention. The effect of alternative splicing in expanding pro tein repertoire might partially underlie the apparent discrepancy between g ene number and the complexity of higher eukaryotes. It is likely that more than 50% of human genes produce more than one transcipt form. Many cancer-a ssociated genes, such as CD44 and WT1 are alternatively spliced. Variation of the splicing process occurs during tumor progression and may playa major role in tumorigenesis. Furthermore, alternatively spliced transcripts may be extremely useful as cancer markers, since it appears likely that there m ay be striking contrasts in usage of alternatively spliced transcript varia nts between normal and tumor tissue than in alterations in the general leve ls of gene expression.