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

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Abstract
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 features of PNETs. Tumor development requires a latency period of 8-11 months implicating secondary genetic alterations. To identify such secondary alterations we performed comparative analyses of two phenotypically identical PNET-derived cell lines. Indeed, these cell lines displayed distinct high-level amplification sites. Using a combination of subtractive cDNA analysis and radiation hybrid mapping we have now identified genes in the amplicon regions of the two cell lines. Interestingly, one of these genes encodes the rat homolog of a cytosolic branched chain aminotransferase (BCAT(C)) previously 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 isolation of genes implicated in known chromosomal aberrations in primary tumors and tumor cell lines.