Cancer "stemness"- regulating microRNAs: role, mechanisms and therapeutic potential.

Failure of conventional as well as target-based therapy against the advanced metastatic cancers is a significant clinical problem. While some cancers, such as pancreatic cancer, respond poorly to any kind of therapies, tumor relapse is often observed in many other cancer types after initial therapeutic response. Hence, significant research is being conducted to understand the mechanisms underlying therapeutic refractoriness of cancer. During the past decade, cancer stem cell (CSC) hypothesis has gained significant experimental and clinical support, and CSCs have emerged as potentially useful pharmacologic targets. MicroRNAs (miRNAs) are a group of small (~18-25 nucleotides) non-protein encoding RNAs that are now established as important regulators of gene expression. They can function as tumor promoters (oncomirs) or suppressors (anti-oncomirs) and thus hold profound implications for cancer therapy. Recent studies have identified several miRNAs to be differentially expressed in CSCs and established their role in targeting genes and pathways supporting cancer stemness properties. Here, we discuss these findings and review recent advances in miRNA-based strategies to exploit therapeutic potential of miRNAs in cancer treatment.