MiR-107 suppresses cell proliferation and tube formation of Ewing sarcoma cells partly by targeting HIF-1ß.

MicroRNAs serve a crucial role in the regulation of malignant biological behavior of Ewing's sarcoma (ES). Abnormal expression of miR-107 has been reported in a cohort of cancers, while its exact function in ES remains unclear. Hence, we explored the expression of miR-107 in ES cells and detected its effects on the malignant phenotype of ES cells. Firstly, we perceived the under-expression of miR-107 in human ES cells contrast with the human mesenchymal stem cells. Over-expression of miR-107 restrained cell proliferation and tube formation, arrested cell cycle progression, and facilitated cell apoptosis in SK-ES-1 and RD-ES cell lines. Furthermore, hypoxia inducible factor-1ß (HIF-1ß) was assumed as a target gene of miR-107. We confirmed the target role of HIF-1ß in ES cells. Finally, restoring the expression of HIF-1ß could partly abolish miR-107-mediated tumor suppression in ES cells. In conclusion, our results advised that miR-107 suppressed the malignant biological ability of ES cells through targeting HIF-1ß.

MicroRNA-638 inhibits cell growth and tubule formation by suppressing VEGFA expression in human Ewing sarcoma cells.

Ewing sarcoma (EWS) is a kind of aggressive tumor of bone and soft tissues, which most occurring in children and adolescents. MicroRNAs (miRNAs) perform essential function in the progression and development of EWS, while the putative role of miR-638 in EWS remains uncertain. Accordingly, we detected the expression of miR-638 and explored its putative biological effects on the malignant phenotype of EWS cells. As expected, miR-638 was significantly down-regulated in EWS cells. Moreover, overexpression of miR-638 suppressed cell growth, induced cell apoptosis, and inhibited tubule formation of EWS cells in vitro Among the putative target genes of miR-638 predicted by the miRNA target prediction tools, vascular endothelial cell growth factor A (VEGFA) attracted out attention most. The luciferase reporter assays reaffirmed that VEGFA was a targeted gene of miR-638 in EWS cells. Furthermore, miR-638 suppressed the mRNA and protein level of VEGFA, and restored the expression of VEGFA reversed the suppressed effects of miR-638 in EWS cells. Taken together, the results suggested that miR-638 might perform tumor suppressive effects in EWS, which might be mediated, at least partially, through suppressing the activity of VEGFA.

miR­186 functions as a tumor suppressor in osteosarcoma cells by suppressing the malignant phenotype and aerobic glycolysis.

Osteosarcoma (OS) is the most common primary bone malignancy among children and adolescents. Deregulation of microRNAs has been well documented in OS, while the putative effects of miR­186 have not been identified yet. In the present study, we assessed the expression of miR­186 in a cohort of 40 OS tissues and explored its effects on OS cells. As expected, miR­186 was suppressed in OS tissues compared with relative normal tissues. Overexpression of miR­186 inhibited cell proliferation, arrested the cell cycle progression and suppressed the cell invasion of the HOS and U2 OS cell lines. These results indicated the tumor­suppressive role of miR­186 in OS. Among the target genes of miR­186, we found that pituitary tumor transforming gene 1 (PTTG1) may be a target gene of miR­186 in OS and that the overexpression of PTTG1 could partially abolish miR­186­mediated suppressive effects on OS cells. Aerobic glycolysis is the major way of energy supply and is one of the characteristic phenotypes of tumor cells. In addition, we found that overexpression of miR­186 significantly suppressed the expression of hypoxia­inducible factor 1 (HIF­1) and inhibited the glucose uptake and lactate production of OS cells. Collectively, our findings demonstrated that miR­186 functions as a tumor suppressor in OS cells partially by targeting PTTG1 and that HIF­1­mediated suppression of aerobic glycolysis may be also involved in its suppressive effects.

Overexpression of miR-140 Inhibits Proliferation of Osteosarcoma Cells via Suppression of Histone Deacetylase 4.

miRNAs play a pivotal role in the development and progression of osteosarcoma (OS). Previous studies indicated that miR-140 acts as a tumor suppressor in many cancers. However, its accurate expression and exact function in OS cells remain unknown. Herein, we demonstrated the lower expression of miR-140 in 40 paired OS tissues. Restoring miR-140 expression in OS cells had a marked effect on inhibiting cell proliferation and invasion, inducing cell apoptosis in vitro, and suppressing tumor growth in vivo. Moreover, a bioinformatics prediction indicated that the histone deacetylase 4 (HDAC4) is a target gene of miR-140 and is involved in miR-140-mediated suppressive effects. In conclusion, our findings show that miR-140 acts as a tumor suppressor in OS by targeting HDAC4.

Let-7a suppresses macrophage infiltrations and malignant phenotype of Ewing sarcoma via STAT3/NF-κB positive regulatory circuit.

The interaction between tumors cells, tumor-derived humoral factors and the bone marrow in the bone niches has been shown to be essential for bone tumor initiation and promotion. Among the tumor stromal cells, tumor-associated macrophages (TAMs) are usually the most abundant immune population. Previously, we reported that let-7a functions as a tumor suppressor in ES. Herein, we found that the suppressive effects are not only limited on the malignant phenotype of tumor cells but also on the regulation of macrophage infiltration. We observed that the let-7a expression is negatively related to macrophage infiltrations in ES. Moreover, overexpression of putative ts-miRNA let-7a significantly suppressed the recruitment of PBMCs in vitro and decreased the macrophage infiltrations in ES-xenografted tumors in vivo. Most importantly, a positive regulatory feedback loop consisting of let-7a, signal transducer and activator of transcription 3 (STAT3), and nuclear factor-kappa B (NF-κB) (let-7a/STAT3/NF-κB) was involved in let-7a-mediated suppressive effects. These data might provide evidence of a novel intracellular signaling network function in ES pathogenesis, and manipulating this novel feedback loop will have therapeutic potential for ES patients.