Identification of amplified genes from SV40 large T antigen-induced rat PNET cell lines by subtractive cDNA analysis and radiation hybrid mapping

Primitive neuroectodermal tumors (PNETs) such as human medulloblastomas are genetically heterogeneous and therefore poorly understood, In a rat model the SV40 large T antigen was used to induce neoplasms with characteristic f eatures of PNETs, Tumor development requires a latency period of 8-11 month s implicating secondary genetic alterations. To identify such secondary alt erations we performed comparative analyses of two phenotypically identical PNET-derived eel lines. Indeed, these cell Lines displayed distinct high-le vel amplification sites. Using a combination of subtractive cDNA analysis a nd radiation hybrid mapping we have now identified genes in the amplicon re gions of the two cell lines. Interestingly, one of these genes encodes the rat homolog of a cytosolic branched chain aminotransferase (BCAT(C)) previo usly shown to be amplified in a mouse teratocarcinoma cell line. We propose that this simple cloning strategy may serve as a powerful tool for the iso lation of genes implicated in known chromosomal aberrations in primary tumo rs and tumor cell lines.