MicroRNA Expression Profiling of Inflammatory Breast Cancer.

Abstract Background: IBC (Inflammatory Breast Cancer) is a rare but very aggressive form of breast cancer with a particular phenotype. The molecular mechanisms responsible for IBC remain largely unknown. In particular, gene alterations specific to IBC remain to be identified. Emerging data suggest that microRNAs, a small class of non-coding RNAs able to regulate gene expression, are dysregulated in certain types of cancer and may therefore serve as tool for diagnosis and prediction. We aimed to determine a miRNA expression profiling (microRNAome) in IBC.Methods: We measured the miRNA expression levels of 936 miRNAs by using real-time quantitative RT-PCR in a well-defined series of 12 IBCs (stage T4d according to UICC classification), by comparison with 31 non stage-matched non inflammatory breast cancers (stage I to non inflammatory IIIB) and 8 normal breast tissues.Results: 573 microRNAs were retained for analysis (Ct < 32). Among these 573 miRNAs, 31 were significantly up-regulated (p<0,05 and fold-change > 2,5) in IBC compared with both non IBC and normal breast tissues. Five of the 31 up-regulated miRNAs were also significantly up-regulated in non IBC versus normal tissues. Eleven of the 31 up-regulated miRNAs showed fold-changes greater than 4 times between IBC and non IBC: miR-1308, miR-503, miR-1234, miR-1247, miR-612, miR-671, miR-1825, miR-1306, miR-99, miR-7-1, and miR-937.The expression levels of the 31 up-regulated candidate miRNAs are currently being measured using real time QRT-PCR in a new larger independent prospective series of 66 IBC collected in our institution between jul-03 and dec-08. Sixty-six non stage-matched non inflammatory breast tumor tissues are used as controls.Conclusions: This study represents the first analysis of miRNA expression in IBC. It may serve as a basis for functional studies of the role of miRNAs in the etiology of IBC. Citation Information: Cancer Res 2009;69(24 Suppl):Abstract nr 6118.