MicroRNA expression profiling on formalin-fixed paraffin-embedded (FFPE) tissue blocks of human adrenal pheochromocytomas. Homo sapiens

MicroRNAs are involved in the pathogenesis of several tumors, however, there have been no data on microRNA expression in pheochromocytomas to date. In this study we have performed microRNA expression profiling in sporadic benign, hereditary benign (multiplex endocrine neoplasia type 2-related and von Hippel-Lindau syndrome-related pheochromocytomas), and sporadic recurring adrenomedullary tumors. Due to the rarity of these neoplasms, the retrieval of sufficient quantities of fresh or immediately snap frozen tumor samples is difficult, therefore the applicability of formalin-fixed paraffin-embedded tissue samples for the analysis of microRNA expression in pheochromocytomas was examined. Overall design: In this study microRNA expression pattern of sporadic benign, sporadic recurring, MEN2-related and VHL-related hereditary adrenal pheochromocytomas has been reported. For microRNA expression profiling, total RNA was extracted from formalin-fixed paraffin-embedded (FFPE) tissue blocks. Biological replicates: 6 sporadic benign, 5 sporadic recurring, 5 MEN2-related and 5 VHL-related pheochromocytoma FFPE tissues has been investigated (n=21). To prove the applicability of FFPE blocks for microRNA microarray analysis, the microRNA expression data of three matched frozen and FFPE pheochromocytoma samples derived from the same patients were compared. MicroRNA expression analysis of 21 FFPE and 3 frozen samples was performed on Agilent Human miRNA Microarray Rel12.0 (v3.0) (8x15k) containing probes corresponding to 866 human and 89 human viral miRs.