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Based on analyses of cDNA microarrays and protein power-blots, our laboratory and others demonstrated that a number of genes showed altered expression during development of cisplatin resistance (CP-r) in human cancer cells, including genes associated with DNA damage-repair, proto-oncogenes, apoptosis, stress-response, and transcription factors, etc. To verify these results and find genes that are directly responsible for CP-r, as opposed to reflecting a secondary response induced by cisplatin treatment, we constructed a retroviral cDNA library in the vector pLNCX2 from KB-CP.5 (KCP.5), a cell line selected in one step after expose to cisplatin at 0.5 ug/ml. Using a large library of cDNAs (1.8x 106 cDNAs), and a programmed (intermittent) cisplatin selection system to allow more effective functional cloning, eleven expressed cDNAs were associated with CP-r in a primary pool of near 105 transfected cell clones. Interestingly, a metallothionein and a heat shock protein were among these 11 genes found in the transfectants after CP selection, indicating that the application of our retroviral cDNA KCP.5/pLNCX2 library and programmed CP selection are effective for functionally cloning genes able to confer CP-r. In addition, several other genes, including those encoding ribosomal proteins were also found in the CP-selected clones and are being further characterized.

[Proc Amer Assoc Cancer Res, Volume 46, 2005]