miRNA expression profile between ER-beta- and ER-beta+ breast tumors

FFPE tissues samples were cut in 5-µm-thick sections on a microtome with a disposable blade. RNA was extracted either from three or eight sequential sections using miRNeasy FFPE Kit (QIAGEN), following the steps described in the manufacturers protocol. RNA extracted from same biological samples and different numbers of sections were pooled. Total RNA was fluorescently labelled, amplified in triplicate, to be then pooled, for hybridization. Each pool, were hybridized for 18 hours on Illumina v2 MicroRNA Expression BeadChips, and after scanning, the intensity files were analized.