Abstract 3034: miR-224 is marker of poor prognosis in breast cancer
Authors: McGee Sharon F. , Mulrane Laoighse , Brennan Donal J. , McDonnell Susan , Jirstrom Karin , O'Connor Darran P. , Gallagher William M. 
Published: February 2011

Breast cancer is the most common cancer in women and, after lung cancer, the second leading cause of cancer-related deaths. Sixty-thousand women in the European Union, many in their reproductive and economically productive ages, succumb to this disease every year. MicroRNAs (miRNAs) are highly conserved 10 to 22 nucleotide non-coding RNA molecules that regulate gene expression by binding the 3’ untranslated (UTR) region of mRNA causing inhibition of translation or degradation of mRNA by argonaute proteins. miRNAs regulate a variety of target genes allowing them to induce changes in multiple pathways and processes. Here, we examine a tractable cell line model of breast cancer progression to identify miRNAs involved.

Total RNA from Hs578T breast cancer cells and an isogenic superinvasive variant Hs578T(I8)1 was isolated in triplicate using the mirVana miRNA isolation kit (Ambion) and miRNAs reverse transcribed using miRNA-specific primers (Applied Biosystems). miRNA profiling was performed using a TaqMan® MicroRNA Assays Human Panel Early Access Kit (Applied Biosystems), enabling the simultaneous relative quantification of the expression 180 human miRNAs. Differentially expressed miRNAs were identified by the ΔΔCT method using qBase data analysis software with 4 endogenous controls, determined by geNORM, used for data normalisation. Eight miRNAs were differentially expressed between breast cancer cells and its superinvasive variant Hs578T(I8) with a minimum fold change of 2 and a minimal cycle threshold of 32. Of these, miR-224 was most significantly up-regulated in Hs578T(I8) cells. Additionally, miR-224 expression was significantly up-regulated in aggressive invasive breast cancer cell lines (MDA-MB-231, Hs578T) compared to non-invasive cell lines (MCF7, T47D) (p&lt;0.05).

Subsequently, expression of miR-224 was evaluated in a cohort of breast cancer patients (n=98), by locked nucleic acid in situ hybridisation (LNA-ISH) on tissue microarrays, and quantified by automated image analysis. High miR-224 expression correlated with poor overall survival in the entire cohort (p=0.022) and, more specifically with poor overall survival in ER-positive (p=0.015) and Her2-negative (p=0.008) patients [HR 4.107 (p = 0.015, 95% CI 1.322-12.758)]. We believe that miR-224 represents a novel marker of poor prognosis in breast cancer that may regulate breast cancer invasiveness and disease progression.

1. Hughes L, O'Brien SL, Gallagher WM, McDonnell S. DNA microarray-based transcriptomic profiling of an isogenic cell culture model of breast tumour cell invasion. Anticancer Res. 2007 May-Jun;27(3A):1353-9.

Note: This abstract was not presented at the AACR 101st Annual Meeting 2010 because the presenter was unable to attend.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 3034.