Overexpressed genes/ESTs and characterization of distinct amplicons on 17q23 in breast cancer cells

17q23 is a frequent site of gene amplification in breast cancer. Several li nes of evidence suggest the presence of multiple amplicons on 17q23. To cha racterize distinct amplicons on 17q23 and localize putative oncogenes, we s creened genes and expressed sequence tags (ESTs) in existing physical and r adiation hybrid maps for amplification and overexpression in breast cancer cell lines by semiquantitative duplex PCR, semiquantitative duplex RT-PCR, Southern blot, and Northern blot analyses. We identified two distinct ampli cons on 17q23, one including TBX2 and another proximal region including RPS 6KB1 (PS6K) and MUL. In addition to these previously reported overexpressed genes, we also identified amplification and overexpression of additional u ncharacterized genes and ESTs, some of which suggest potential oncogenic ac tivity. In conclusion, we have further defined two distinct regions of gene amplification and overexpression on 17q23 with identification of new poten tial oncogene candidates. Based on the amplification and overexpression pat terns of known and as of yet unrecognized genes on 17q23, it is likely that some of these genes mapping to the discrete amplicons function as oncogene s and contribute to tumor progression in breast cancer cells.