Prognostic microRNA expression signature from examination of colorectal primary and metastatic tumors.

While previous studies have described associations between specific microRNAs and colorectal cancer (CRC) metastasis, our understanding of microRNA regulation of metastatic spread remains largely unexplored. To identify microRNAs critical for disease progression, we measured microRNA expression in primary CRC tumors and synchronous liver metastases in 19 cases using quantitative polymerase chain reaction (qPCR) arrays. We identified 16 microRNAs significantly differentially expressed between primary tumors and liver metastases that distinguish primary tumors and liver metastases by hierarchical clustering. Combinations of microRNAs expressed in the primary tumor and in the metastatic tumor are associated with survival, but these signatures have no microRNAs in common. We found that increased expression of miR-210 and miR-133b in liver metastases compared to primary tumors is associated with lower survival. We propose that evaluating the change in expression between primary and metastatic tumors in each patient may lead to improved biomarker development. Copyright