MicroRNAs Reprogram Normal Fibroblasts into Cancer-Associated Fibroblasts in Ovarian Cancer

Cancer-associated fibroblasts (CAF) are a major constituent of the tumor stroma, but little is known about how cancer cells transform normal fi broblasts into CAFs. microRNAs (miRNA) are small noncoding RNA molecules that negatively regulate gene expression at a posttranscriptional level. Although it is clearly established that miRNAs are deregulated in human cancers, it is not known whether miRNA expression in resident fi broblasts is affected by their interaction with cancer cells. We found that in ovarian CAFs, miR-31 and miR-214 were downregulated, whereas miR-155 was upregulated when compared with normal or tumor-adjacent fi broblasts. Mimicking this deregulation by transfecting miRNAs and miRNA inhibitors induced a functional conversion of normal fi broblasts into CAFs, and the reverse experiment resulted in the reversion of CAFs into normal fi broblasts. The miRNA-reprogrammed normal fi broblasts and patient-derived CAFs shared a large number of upregulated genes highly enriched in chemokines, which are known to be important for CAF function. The most highly upregulated chemokine, CCL5, (C-C motif ligand 5) was found to be a direct target of miR-214. These results indicate that ovarian cancer cells reprogram fi broblasts to become CAFs through the action of miRNAs. Targeting these miRNAs in stromal cells could have therapeutic benefit. SIGNIFICANCE: The mechanism by which quiescent fi broblasts are converted into CAFs is unclear. The present study identifies a set of 3 miRNAs that reprogram normal fi broblasts to CAFs. These miRNAs may represent novel therapeutic targets in the tumor microenvironment. Cancer Discov; 2(12); 1100-8. (C) 2012 AACR.