MicroRNAs: A complex regulatory network drives the acquisition of malignant cell phenotype

Several lines of evidence indicate that tumorigenesis is a complex multistep process, and that most, if not all, cancers acquire the same set of functional capabilities during development and progression, albeit through various mechanistic strategies. Increasing data show an important role of microRNAs (miRNAs or miRs) in regulating various aspects of cancer biology. This review describes the role of microRNAs during the multiple steps that drive the progressive transformation of normal cells into highly malignant derivatives, outlining the role of microRNAs in regulating the common hallmarks of tumorigenesis: self-sufficiency in growth signals, insensitivity to antigrowth signals, abnormal apoptosis, limitless replicative potential, induction and sustained angiogenesis, and tissue invasion and metastasis. Recent evidence suggests an important role of microRNAs in the regulation of the expression of most genes regulating and coordinating a wide variety of processes in endocrine glands. We will highlight microRNAs of potential relevance to endocrine tumors and hormone-dependent cancers. Through this overview of how microRNAs regulate multiple targets and entire pathways, we will provide insight into the potential to develop new molecular microRNA-targeted therapies for endocrine tumors.