Identification of amplified and expressed genes in breast cancer by comparative hybridization onto microarrays of randomly selected cDNA clones

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Abstract
Microarray analysis using sets of known human genes provides a powerful platform for identifying candidate oncogenes involved in DNA amplification events but suffers from the disadvantage that information can be gained only on genes that have been preselected for inclusion on the array. To address this issue, we have performed comparative genome hybridization (CGH) and expression analyses on microarrays of clones, randomly selected from a cDNA library, prepared from a cancer containing the DNA amplicon under investigation. Application of this approach to the BT474 breast carcinoma cell line, which contains amplicons at 20q13, 17q11–21, and 17q22–23, identified 50 amplified and expressed genes, including genes from these regions previously proposed as candidate oncogenes. When considered together with data from microarray expression profiles and Northern analyses, we were able to propose five genes as new candidate oncogenes where amplification in breast cancer cell lines was consistently associated with higher levels of RNA expression. These included the HB01 histone acetyl transferase gene at 17q22–23 and the TRAP100 gene, which encodes a thyroid hormone receptor‐associated protein coactivator, at 17q11–21. The results demonstrate the utility of this microarray‐based CGH approach in hunting for candidate oncogenes within DNA amplicons.