Circular RNAs (circRNAs) are recently emerged to be promising therapeutic targets of tumors. Osteosarcoma is the most prevalent primary bone tumor and the third most prevalent cancer in children and adolescents. This study firstly analyzed circRNA microarray of osteosarcoma and selected circ-0001785 as the study object. We aimed to comprehensively investigate the expression pattern and biological function of circ-0001785 in the progression of osteosarcoma. Relative levels of circ-0001785 and miR-1200 in the normal human osteoblast cell line and osteosarcoma cell lines were determined. Bioinformatics analyses predicted the binding relationship between miR-1200 to HOXB2 and circ-0001785, while dual-luciferase reporter gene assay further verified this relationship. Flow cytometry and EdU assay were used for evaluating the regulatory effects of circ-0001785/miR-1200/HOXB2 axis on osteosarcoma cells. Consistent with the microarray analysis, circ-0001785 was highly expressed in osteosarcoma cell lines. Knockdown of circ-0001785 attenuated proliferative ability, but induced the apoptosis of osteosarcoma cells. Furthermore, we confirmed that circ-0001785 competitively bound to miR-1200, thus up-regulating its target gene HOXB2. Western blot analyses revealed that circ-0001785 regulated the PI3K/Akt signaling and Bcl-2 family pathway in osteosarcoma. In conclusion, circ-0001785 regulates the pathogenesis of osteosarcoma by sponging miR-1200 to up-regulate HOXB2 expression.

Osteosarcoma is an aggressive malignant neoplasm and cancerous bone tumor. Quercetin is a well-known flavonoid abundant in vegetables, fruits, grains, leaves, and red onions. In the present study, we evaluated the effects of quercetin-induced inhibition of parathyroid hormone receptor 1 (PTHR1) on proliferation, migration, and invasion in U2OS and Saos^-2 cells. Following incubation with quercetin (20, 40, 60, 80, or 100 μM) for 48 h, the cell viability of U2OS and Saos^-2 cells were significantly reduced in a dose-dependent manner. Additionally, there were significant decreases in cell adhesion, invasion, and migration as well as reduced cell viability at higher concentrations of quercetin. Furthermore, the mRNA expression levels of matrix metalloproteinases (MMP)-2 and -9 were attenuated, whereas the mRNA expression levels of tissue inhibitors of metalloproteinases (TIMP)-1 and -2 were elevated. Quercetin treatment also significantly reduced the mRNA expression levels of PTHR1 by 0.27-, and 0.55-fold at 80, and 100 μM, respectively, whereas 0.19 and 0.41 folds in Saos^-2 cells. PTHR1 protein expression in U2OS cells was reduced by 0.19-, and 0.43-fold at 80, and 100 μM of quercetin, respectively (P < 0.05), whereas 0.17 and 0.35 folds in Saos-2 cells. Immunofluorescence analyses revealed reduced expression of PTHR1 following treatment with quercetin. PTHR1 expression in U2OS cells was reduced by 0.18-, and 0.41-fold at 80, and 100 μM, respectively, whereas 0.15 and 0.38 folds in Saos^-2 cells. The knockdown of PTHR1enhanced quercetin-inhibited proliferation and invasion. Taken together, the present findings indicate that quercetin reduced human metastatic osteosarcoma cell invasion, adhesion, proliferation, and migration by inhibiting PTHR1.

Under the microenvironment, tumour progression is substantially affected by cell‐cell communication. In spite of the mediating effect of extracellular nanovesicles (EVs) on cell‐cell communication by packaging into circRNAs, the effect of EVs circRNA hsa_circ_0000190 (circ‐0000190) in osteosarcoma is still not clear. Circ‐0000190 expressions in tissues and EVs from plasma were compared between osteosarcoma patients and controls. Thereafter, receiver operating characteristic (ROC) curve was drawn and area under the curve was calculated to examine whether the diagnostic results were accurate, and the effect of EVs circ‐0000190 was dug out via the determination of cell phenotypes and animal assays. Results showed circ‐0000190 exhibited an obvious reduction in EVs and tissues of osteosarcoma patients (P < .05). It was also discovered that EVs encapsulated the majority of circ‐0000190, and EVs‐encapsulated circ‐0000190 could be applied to make a distinction between osteosarcoma patients and controls. Besides, EVs circ‐0000190 in osteosarcoma cells transported from normal cells weakened the capacities of osteosarcoma cells to migrate, proliferate and invade, so as to block their biological malignant behaviours (P < .05). In addition, under the action of EVs circ‐0000190, tumour growth was impeded and the expression of TET1 was inhibited via the competitive binding to miR‐767‐5p. In all, EVs circ‐0000190 has a good prospect as it can be regarded as a new biomarker for detecting osteosarcoma. EVs circ‐0000190 transported from normal cells to osteosarcoma cells impeded the in vitro and in vivo development of osteosarcoma, implying that EVs circ‐0000190 exerts an effect on communication between normal cells and osteosarcoma cells in the carcinogenesis process of osteosarcoma.

The hypothalamus, which is the initial part of the hypothalamic-pituitary-adrenal (HPA) axis, plays a critical role in regulating stress in the central nervous system. The present study aimed to determine whether endoplasmic reticulum stress in hypothalamic neurons is differentially stimulated by varying durations of stress exposure, which ultimately leads to pathological changes in neurons by affecting HPA axis function. There is a need for better morphological evidence of the mechanisms involved in stress-induced neuron injury. A stress model was established in rats by restraining for 8 h and forced ice-water swimming for 5 min each day. The stress-inducing process lasted for 1 day, 3 days, 7 days, 14 days, and 21 days. Enzyme-linked immunosorbent assay (ELISA) was used to assay serum glucocorticoid levels. Thionine staining was used to observe morphological changes in hypothalamic neurons. Immunohistochemistry and microscopy-based multicolor tissue cytometry (MMTC) was used to detect changes in expression of endoplasmic reticulum stress protein GRP78, ATF4, and CHOP. Serum glucocorticoid levels significantly increased after 3 days of stress exposure and the levels peaked by 7 days. By 21 days, however, the levels were significantly decreased. Thionine staining revealed that prolonged stress exposure resulted in hypothalamic neurons with edema, a lack of Nissl bodies, and pyknotic neurons. Immunohistochemistry and MMTC showed that increasing stress periods significantly decreased GRP78 expression, although ATF4 and CHOP protein expression significantly increased. Stress resulted in pathological changes and significant dynamic changes because of endoplasmic reticulum stress in rat hypothalamic neurons. These results suggested that the endoplasmic reticulum stress PERK-ATF4-CHOP pathway may be associated with hypothalamic neuronal injury.

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