CORR Insights(®): Transcriptional Profiling Identifies the Signaling Axes of IGF and Transforming Growth Factor-β as Involved in the Pathogenesis of Osteosarcoma

Extracellular vesicles-mediated signaling in the osteosarcoma microenvironment: Roles and potential therapeutic targets

Osteosarcoma (OS) is the most common non-hematologic malignant tumor of bone in children. It is usually characterized by a high risk of developing lung metastasis and poor prognosis. Extracellular vesicles (EVs) are cell-derived nanoparticles with a small size of 50–200 nm in diameter. As a communicator, the contents of the EVs secreted via either fusing with lysosomes for degradation and recycling or fusing with the cell plasma membrane into the extracellular environment, which play an important role in regulating the tumor microenvironment of OS and mediating the Wnt/β-catenin and TGF-β signalings. Increasing evidences suggest that EVs have significant role in OS growth, progression, metastasis and drug resistance. In this study, the roles of EVs in the physiology and pathogenesis of OS and the potential attractive therapeutic target for the treatment of OS were reviewed.

Effects of SOST Gene Silencing on Proliferation, Apoptosis, Invasion, and Migration of Human Osteosarcoma Cells Through the Wnt/β-Catenin Signaling Pathway

Our study explored the effects of SOST gene silencing on the proliferation, apoptosis, invasion, and migration of human osteosarcoma cells through Wnt/β-catenin signaling pathway. Fresh tissues were obtained from 108 patients with osteosarcoma and 46 patients with osteochondroma. Human osteosarcoma cells (MG-63, U2-OS, HOS, and Saos-2) and normal osteoblast (hFoB1.19) were selected and cultured. Osteosarcoma cells were grouped randomly into the blank group, the scrambled control group, and the SOST-siRNA group. Cell proliferation was determined by MTT assay. Cell cycle and apoptosis were tested by flow cytometry. Transwell and scratch test were performed to determine cell invasion and migration. The qRT-PCR and Western blotting were used to detect mRNA and protein expression level of sclerostin, Wnt1, β-catenin, C-Myc, Cyclin D1, and MMP-7. The activity of caspase-3 was assessed by immunocytochemistry. Alkaline phosphatase (ALP) activity was measured using P-nitrophenylphosphate as a substrate. Low SOST mRNA and sclerostin protein expression levels were observed in osteosarcoma tissues and cells. Compared with the blank and scrambled control groups, sclerostin expression, apoptotic cells, ALP activity, and caspase-3 activity were down-regulated, while the proliferation, invasion, and migration abilities of osteosarcoma cells were evidently enhanced in the SOST-siRNA group. After SOST gene silencing, the mRNA and protein expression levels of Wnt1, β-catenin, C-Myc, Cyclin D1, and MMP-7 in osteosarcoma cells and β-catenin protein expression levels in the nucleus and cytoplasm were significantly elevated. SOST gene silencing promotes the proliferation, invasion, and migration, and inhibits apoptosis of osteosarcoma cells by activating Wnt/β-catenin signaling pathway.