Extraction of miRNAs from Formalin-Fixed Paraffin-Embedded (FFPE) Tissues.

miRNAs are small non-coding RNAs that regulate gene expression and are involved in numerous diseases ranging from osteoporosis, cardiovascular disease, and numerous cancer indications. Most of the clinical material that is accessible for study is archival FFPE blocks. Due to the harsh nature of fixation and embedding procedures involved in preserving clinical material, these samples are heavily fragmented and chemically cross-linked by formalin. miRNAs, due to their small size and increased stability, are easier to retrieve and study in these precious tissues. Therefore, miRNAs have become useful tools in the diagnosis, prognosis, and prediction of diseases. Due to their increased importance, isolation of miRNAs from FFPE material is extremely clinically relevant. Here, we describe the best method for miRNA extraction from FFPE tissue blocks and determine the Qiagen miRNeasy FFPE kit to be the best kit for this task.