MicroRNA expression patterns in lobular neoplasia.

Abstract

10551 Background: Lobular carcinoma in situ (LCIS) is a marker of increased risk for subsequent development of invasive breast cancer. Molecular studies have identified a clonal relationship between LCIS and concurrent invasive lobular carcinoma (ILC), suggesting that LCIS may be a precursor lesion of ILC. We hypothesized that differences in miRNA expression patterns might exist in LCIS lesions with concurrent ILC compared with LCIS lesions found alone. Methods: RNA was collected from matched frozen and archival formalin fixed paraffin embedded (FFPE) breast tissue using TRIZOL extractions. MiRNA expression profiling was performed using the Illumina miRNA DASL assay, in duplicate experiments, allowing simultaneous profiling of 735 miRNAs. MiRNAs of interest were further validated and analyzed by quantitative RT-PCR (qrt-PCR) in triplicate. To verify our data by localizing specific miRNA sequences of interest, in situ hybridization was performed on FFPE sections using a one-day protocol with locked nucleic acid (LNA) detection probes for miR-375 and miR-182, the U6 small nuclear RNA probe as a positive control and a scrambled miRNA probe as a negative control. Results: qrt-PCR analysis of the miR-183/182/96 cluster and miR-375 was performed using normal breast tissue, LCIS alone, and matched synchronous LCIS and ILC. A trend of increasing miRNA expression correlating with a model of histological progression toward invasive disease was observed. Results of in-situ hybridization confirmed this trend, showing the weakest signal intensity for both miR-375 and miR-182 in normal breast tissue, a stronger signal in LCIS alone, and the strongest signal in LCIS associated with synchronous ILC. Localization of signal to the nucleus was observed in normal breast tissue and LCIS alone, while a more diffuse cytoplasmic localization pattern was observed in LCIS associated with ILC, possibly suggesting nucleocytoplasmic transport for further processing of these miRNAs during progression to a more invasive phenotype. Conclusions: Upregulation of miR-375 and the miR-183/182/96 cluster in LCIS may correlate with risk for progression to ILC. These novel biomarkers may also be potential targets for treatment.