MicroRNA regulation of cancer stem cells

Abstract

Cancer stem cells (CSC), or cancer cells with stem cell properties, have been reported in many human tumors and are thought to be responsible for tumor initiation, therapy resistance, progression, relapse, and metastasis. Despite their potential clinical importance, how CSCs are regulated at the molecular level is not well understood. MicroRNAs (miRNA), small noncoding RNAs that play critical roles in normal stem cell functions during development, have emerged as important regulators of CSCs as well. In this review, we summarize the current major findings of miRNA regulation of various CSCs and discuss our recent findings that miR-34a suppresses prostate CSCs and metastasis by directly repressing CD44. This recent progress has important implications for understanding how CSCs are intricately regulated by networks of miRNAs and for developing novel mechanism-based miRNA therapeutics that specifically target CSCs.

Figure 1. miRNAs distinctively and concertedly regulating key properties of CSCs

(A) let-7, miR-30, and miR-200 family miRNAs, via targeting critical downstream signaling molecules, regulate several fundamental properties of BCSCs including cell-cycle exit and differentiation, self-renewal, EMT, migration and invasion, and cell survival (represented by 4 shaded circles that overlap with each other). (B) miR-451, miR-128, and miR-34a distinctively and concertedly regulate the key biological properties of CSCs in GBM. Depicted in both (A) and (B) are representative miRNAs that are under-expressed in tumorigenic subpopulations.