lncRNAPVT1 targets miR-152 to enhance chemoresistance of osteosarcoma to gemcitabine through activating c-MET/PI3K/AKT pathway.

BACKGROUND: LncRNA PVT1 has been reported to be involved in a variety of biological processes, including cell proliferation, cell differentiation and cancer progression. However, the mechanism by which LncRNA PVT1 contributes to chemoresistance of osteosarcoma cell, has not been fully elucidated. METHODS: We first generatedLncRNA PVT1-overexpressed MG63 cells and LncRNA PVT1 knockdown MG63/DOX cells. Then, we examined the effect of LncRNA PVT1 on cell viability and colony formation ability by MTT assay and soft agar assay, respectively. In addition, we performed flow cytometry analysis to detect apoptosis induced by GEM. Dual luciferase reporter assay and RIP were used to confirmed the interaction between LncRNA PVT1 and miR-152. Finally, we determined protein level of c-MET, p-PI3K, and p-AKT by westernblot. RESULTS: LncRNA PVT1 overexpression promoted cell proliferation and exhibited the anti-apoptotic property in LncRNA PVT1-overexpressing MG63 cells treated with gemcitabine. While, LncRNA PVT1-depleted MG63/DOX cells treated with gemcitabine exhibited significant lower survival rate and high percentage of apoptosis. Next, we found that LncRNA PVT1 could target and downregulated the level of miR-152. Interestingly, miR-152 greatly rescued the biological outcomes of LncRNA PVT1 not only in MG63 but also in MG63/DOX cells. We observed that LncRNA PVT1 markedly induced PI3K/AKT pathway activation, which was abolished by miR-152 mimics overexpression. Finally, c-MET inhibitor was used to confirm the essential role of c-MET in LncRNA PVT1 and miR-152-regulated PI3K/AKT signaling. CONCLUSION: We showed thatlncRNA PVT1 played a contributory role in chemoresistance of osteosarcoma cells through c-MET/PI3K/AKT pathway activation, which was largely dependent on miR-152. Our findings advance our understanding of how lncRNA PVT1 promotes chemoresistance of osteosarcoma cells and facilitate development of novel strategies for treating osteosarcoma.

Thrombospondin 1 Triggers Osteosarcoma Cell Metastasis and Tumor Angiogenesis.

Osteosarcomas, especially those with metastatic or unresectable disease, have limited treatment options. The antitumor effects of pharmacologic inhibitors of angiogenesis in osteosarcomas are hampered in patients by the rapid development of tumor resistance, notably through increased invasiveness and accelerated metastasis. Here we demonstrated that thrombospondin 1 (TSP-1) is a potent inhibitor of the growth and metastasis of the osteosarcoma cell line MG-63. Moreover, we demonstrate that upregulation of TSP-1 facilitated expression of vasculostatin in MG-63 cells. In angiogenesis assays, overexpression of TSP-1 inhibited MG-63 cells and induced tube formation of human umbilical vein endothelial cells (HUVECs) in a CD36-dependent fashion. Finally, in xenografted tumors, we observed that TSP-1 overexpression inhibited angiogenesis and tumor growth. These results provided strong evidence for an important role of the TSP-1/CD36/vasculostatin signaling axis in mediating the antiangiogenic activity of osteosarcoma.

Biomechanical researches on tissue engineering bone constructed by deproteinated bone.

OBJECTIVE: To study biomechanical changes of newly formed bones 24 weeks after repairing large defects of long bones of goats using heterogeneous deproteinated bone (DPB) prepared by modified methods as an engineering scaffold. METHODS: According to a fully randomized design, 18 goats were evenly divided into three groups: normal bone control group (Group A), autologous bone group (Group B) and experimental group (Group C). Each goat in Groups B and C were subjected to the periosteum and bone defect at middle-lower part of the right tibia (20% of the whole tibia in length), followed by autologous bone or DPB plus autologous MSCs + rhBMP2 implantation, respectively and semi-ring slot fixation; while goats in Group A did not perform osteotomy. At 24 weeks after surgery, biomechanical tests were carried out on the tibias. RESULTS: At 24 weeks after surgery, the results of anti-compression test on tibias in three groups were recorded by a functional recorder presented as linear pressure-deformation curve. The shapes of the curves and their change tendency were similar among three groups. The ultimate pressure values were 10.74 MPa+/-1.23 MPa, 10.11 MPa+/-1.35 MPa and 10.22 MPa+/-1.32 MPa and fracture compression rates were 26.82%+/-0.87%, 27.17%+/-0.75% and 28.22%+/-1.12% in Groups A, B and C, respectively. Comparisons of anti-compression ultimate pressures and fracture compression rates among three groups demonstrated no significant difference (P(AB) equal to 0.415, P(BC) equal to 0.494). Three-point anti-bend test on tibias was recorded as load-deformation curves, and the shapes of the curves and their change tendency were similar among three groups. The ultimate pressure values of the anti-bend test were 481.52 N+/-12.45 N, 478.34 N+/-14.68 N and 475.62 N+/-13.41 N and the fracture bend rates were 2.62 mm+/-0.12 mm, 2.61 mm+/-0.15 mm and 2.81 mm+/-0.13 mm in Groups A, B and C, respectively. There was no significant difference between groups (P(AB) equal to 0.7, P(BC) equal to 0.448). The ultimate anti-torsion torque values were 6.55 Nm+/-0.25 Nm, 6.34 Nm+/-0.18 Nm and 6.42 Nm+/-0.21 Nm and fracture torsion rates were 29.51 degree+/-1.64degree, 28.88 degree+/-1.46 degree and 28.81 degree+/-1.33 degree in Groups A, B and C, respectively. There was no significant difference between groups (P(AB) equal to 0.123, P(BC) equal to 0.346). CONCLUSIONS: The biomechanical characteristics of newly formed bones from heterogeneous DPB for repairing large segmental long bone defect are comparable to those of normal bones and autologous bones. DPB has the potential for clinical usage as bone graft material.

Properties of deproteinized bone for reparation of big segmental defect in long bone.

OBJECTIVE: To explore suitable scaffold material for big segmental long bone defect by studying the properties of the prepared deproteinized bone. METHODS: Cancellated bone were made as 30 mm x mm x 3 mm bone blocks from inferior extremity of pig femur along bone trabecula. The deproteinized bone was prepared with an improved method. Their morphological features, components, cell compatibility, mechanical and immunological properties were investigated respectively. RESULTS: Deproteinized bone maintained natural reticular pore system. The main organic material is collagen I and inorganic composition is hydroxyapatite. It has good mechanical properties, cell adhesion rate and histocompatibility. CONCLUSION: This deproteinized bone can be applicable as scaffold for reparation of big segmental defect in long bone.

Preparation and physicochemical properties of scaffold materials of heterogeneous deproteinized bone.

OBJECTIVE: To prepare and observe the physicochemical properties of scaffold materials of heterogeneous deproteinized tissue-engineered bone. METHODS: Deproteinized bone was made through a series of physicochemical treatments in pig ribs and analyzed with histological observation, scanning electron microscopy, infrared spectrum, X-ray diffraction and energy dispersive analysis, Kjeldahl determination and mechanics analysis. RESULTS: Interstitial collagen fiber was positive and mucin was negative in deproteinized bone, but, both were positive in fresh bone. Deproteinized bone maintained natural pore network. Its pore size was 472.51 micromolar+/-7.02 micromolar and the porosity was 78.15%+/-6.45%. The results of infrared spectrum showed that collagen was present in deproteinized bone. Both fresh and deproteinized bone had curve of hydroxyapatite. The Ca/P ratios were 1.71+/-0.95 and 1.68+/-0.76 (P larger than 0.05), and the protein contents were 26.6%+/-2.23% and 19.1%+/-2.14% (P less than 0.05) in fresh and deproteinized bone, respectively. There was no significant difference of destruction load under compression and maximal destruction load between fresh and deproteinized bone (P larger than 0.05). The elastic modulus was higher in deproteinized bone than that in fresh bone (P less than 0.05). CONCLUSIONS: Physicochemical properties and mechanic strength of deproteinized tissue-engineered bone meet the demands of ideal scaffold materials. But, its immunogenicity should be observed through further experiments for its clinical applications.