HES1 and medulloblastoma: For instance, miR-199b-5p inhibits the proliferation and metastasis of tumor stem cells in medulloblastoma by negatively regulating Hes1; demethylating agents (such as 5-aza-deoxycytidine) can restore the expression of miR-199b-5p, thereby suppressing Hes1 and reducing the population of tumor stem cells (128).