Abstract
MicroRNA-21 (miR-21) functions have been linked to cancer progression and chemo- or radiotherapy resistance. While an increasing number of studies have reported a potential role of miR-21 expression in promoting growth of a small population of stem/progenitor cells, knowledge on its role as a regulator of stemness in cancers remains limited. In a previous issue of Stem Cell Research & Therapy, Chung and colleagues provide evidence that miR-21 is highly expressed in stem/progenitor populations of ovarian teratocarcinoma cells and has the potential to mediate growth and self-renewal in cancer stem/progenitor cells. Here we summarize current knowledge on miR-21 functions in human cancers and discuss how this finding provides insight into the role of miR-21 as an oncogenic regulator in stem/progenitor cell populations of human cancers.