MicroRNA profiling of clear cell renal cell cancer identifies a robust signature to define renal malignancy

MicroRNAs are short single‐stranded RNAs that are associated with gene regulation at the transcriptional and translational level. Changes in their expression were found in a variety of human cancers. Only few data are available on microRNAs in clear cell renal cell carcinoma (ccRCC). We performed genome‐wide expression profiling of microRNAs using microarray analysis and quantification of specific microRNAs by TaqMan real‐time RT‐PCR. Matched malignant and non‐malignant tissue samples from two independent sets of 12 and 72 ccRCC were profiled. The microarray‐based experiments identified 13 over‐expressed and 20 down‐regulated microRNAs in malignant samples. Expression in ccRCC tissue samples compared with matched non‐malignant samples measured by RT‐PCR was increased on average by 2.7‐ to 23‐fold for the hsa‐miR‐16, −452*, −224, −155 and −210, but decreased by 4.8‐ to 138‐fold for hsa‐miR‐200b, −363, −429, −200c, −514 and −141. No significant associations between these differentially expressed microRNAs and the clinico‐pathological factors tumour stage, tumour grade and survival rate were found. Nevertheless, malignant and non‐malignant tissue could clearly be differentiated by their microRNA profile. A combination of miR‐141 and miR‐155 resulted in a 97% overall correct classification of samples. The presented differential microRNA pattern provides a solid basis for further validation, including functional studies.