Among the wide family of microRNAs, microRNA 23b (miR-23b) intriguingly assumes opposite roles on regulation of reactive oxygen species (ROS) and on the development of human cancers. In this review we describe novel findings concerning the molecular events involved in miR-23b gene activation or repression and in both ROS regulation and tumour development. In particular, we define the molecular targets of miR-23b that determine its function as either a tumour suppressor or oncomir in different cell types. Finally, we analyze the involvement of miR-23b in cancer cell metabolism, including autophagy, and in biomarker signatures of microRNAs allowing a prognostic and therapeutic evaluation in various human cancers.
