Amplification and overexpresssion of IKBKE activates NF-kB pathway in breast cancers.

5261 Since the successful use of kinase inhibitors in the clinical setting (e.g., Gleevec and Iressa), kinases have become an area of intense focus in the search for oncogene candidates. Based on our array CGH (Comparative Genomic Hybridization) and SAGE (Serial Analysis of Gene Expression) data on breast tumors, we selected 22 kinases that were both amplified and overexpressed in breast tumors as candidate oncogenic kinases. Quantitative PCR (QPCR) was performed to verify amplification and overexpression of these kinases in 30 breast tumors using genomic DNA and cDNAs, respectively. The result was further confirmed using additional samples from 13 breast tumors which had not been analyzed by array CGH. This lead us to find 9 kinases that were amplified to different degrees in breast tumors and had concomitant overexpression when compared to normal breast tissues. Among these putative oncogenes we focused on IKBKE, which encode IkB kinase epsilon (IKKe), a kinase involved in NF-kB and interferon activation. Array CGH analysis and QPCR demonstrated that IKBKE was gained or amplified in at 10 of 30 breast tumors, which is accompanied by overexpression in at least 8 tumors. It is also amplified/gained and overexpressed in three breast cancer cell lines (ZR75-1, UACC812, and MCF-7). QPCR also detected overexpression of IKKe in non-amplified tumors and cell lines, suggesting other mechanisms are involved in IKKe upregulation. We demonstrated that overexpression of IKKe lead to transformation of kidney embryonic cells, while downregulation of IKKe by RNAi inhibited growth of ZR75-1 and MCF-7 breast cancer cells. Thus, IKBKE represents a promising oncogene candidate that function through activation of NF-kB in breast cancers and a promising therapeutic target.