MicroRNAs in the tumour microenvironment: big role for small players

MicroRNAs (miRNAs) represent a class of small non-coding RNAs with an important regulatory role in various physiological processes as well as in several pathologies including cancers. It is noteworthy that recent evidence suggests that the regulatory role of miRNAs during carcinogenesis is not limited to the cancer cells but they are also implicated in the activation of tumour stroma and its transition into a cancer-associated state. Results from experimental studies involving cells cultured in vitro and mice bearing experimental tumours, corroborated by profiling of clinical cancers for miRNA expression, underline this role and identify miRNAs as a potent regulator of the crosstalk between cancer and stroma cells. Considering the fundamental role of the tumour microenvironment in determining both the clinical characteristics of the disease and the efficacy of anticancer therapy, miRNAs emerge as an attractive target bearing important prognostic and therapeutic significance during carcinogenesis. In this article, we will review the available results that underline the role of miRNAs in tumour stroma biology and emphasise their potential value as tools for the management of the disease.