MicroRNA128-1 (miR128-1), as a brain-specific miRNA, is downregulated in glioblastoma multiforme (GBM) and closely associated with the progression of GBM. However, the underlying molecular mechanism of the downregulation and its role in the regulation of tumorigenesis and anticancer drug resistance in GBM remains largely unknown. In the current study,we found that miR128-1 was downregulated in GBM and glioma stem-like cells (GSCs). Intriguingly, treatment with the DNA methylation inhibitors 5-Aza-CdR (Aza) and 4-phenylbutyric acid (PBA) resulted in miR128-1 upregulation in both GBM cells and GSCs. Either forced expression of miR128-1 or Aza/PBA treatment inhibited tumor cell proliferation, migration and invasion in vitro. Moreover, overexpression of miR128-1 inhibited the growth of transplant tumor in vivo. BMI1 and E2F3 were found to be direct targets of miR128-1 and downregulated by miR128-1 in vitro and in vivo. Our results revealed a mechanism of methylation that controls miR128-1 expression in GBM cells and GSCs and indicate miR128-1 could function as a tumor suppressor in GBM by negatively regulating tumor cell proliferation, invasion and self-renewal through direct targeting BMI1 and E2F3. Our findings suggest that DNA methylation inhibitors are potential agents for GBM treatment by upregulating miR-128-1.

Abstract. An increasing number of studies have indicated that the deregulation of microRNAs (miRNAs) contributes to tumorigenesis and metastasis. In the present study, significant upregulation of miR-362-5p was identified in the breast cancer MDA-MB-231 and MCF7 cell lines compared with the control CCD-1095Sk cell line. The inhibition of miR-362-5p was demonstrated to significantly inhibit the cell proliferation, migration and invasion of human breast cancer MCF7 cells. In addition, the knockdown of miR-362-5p induced G1 arrest and promoted apoptosis in the breast cancer cells. Mechanistic investigations confirmed that the tumor suppressor gene CYLD is a direct target of miR-362-5p. The ectopic expression of miR-362-5p represses CYLD expression, whereas miR-362-5p inhibitor treatment induces CYLD protein expression and decreases NF-κB expression in the downstream signaling pathway. Thus, these findings may provide novel insights into the molecular mechanisms through which miR-362-5p regulates breast cancer cell proliferation, migration and invasion. This study also suggests that miR-362-5p may act as a novel potential therapeutic target for the treatment of breast cancer.

The function of miR16 in multiforme glioblastoma multiforme (GBM) and its stem cells (GSCs) remains elusive. To this end, we investigated the patterns of miR16 expression in these cells and their correlation with malignant behaviors and clinical outcomes. The levels of miR16 and its targeted genes in tumor tissue of GBM and GBM SGH44, U87, U251 cells as well as their stem cell counterparts were measured by qRT–PCR or western blot or immunohistochemistry. Luciferase reporter assay was used to confirm the binding of miR16 to 3′-UTR of its target genes. The effects of miR16 on malignant behaviors were investigated, including tumor cell viability, soft-agar colony formation, GSCs Matrigel colony forming and migration and invasion as well as nude mice xenograft model. Differentially expression patterns of miR16 in glioblastoma cells and GSCs cells were found in this study. Changes of miR16 targeted genes, Bcl2 (B cell lymphoma 2), CDK6 (Cyclin-dependent kinase 6), CCND1 (cyclin D1), CCNE1 (cyclin E1) and SOX5 were confirmed in glioblastoma cell lines and tissue specimens. In vitro and in vivo studies showed that tumor cell proliferation was inhibited by miR16 mimic, but enhanced by miR16 inhibitor. The expression level of miR16 positively correlates with GSCs differentiation, but negatively with the abilities of migration, motility, invasion and colony formation in glioblastoma cells. The inhibitory effects of miR16 on its target genes were also found in nude mice xenograft model. Our findings revealed that the miR16 functions as a tumor suppressor in GSCs and its association with prognosis in GBM.