Signaling Pathway In Osteosarcoma Cells Research Articles

CNOT1 cooperates with LMNA to aggravate osteosarcoma tumorigenesis through the Hedgehog signaling pathway.

While treatments for childhood osteosarcoma have improved, the overall survival for this common type of bone cancer has not changed for three decades, and thus, new targets for therapeutic development are needed. To identify tumor‐related proteins in osteosarcoma, we used isobaric tags in a relative and absolute quantitation proteomic approach to analyze the differentially expressed proteins between osteosarcoma cells and human osteoblastic cells. Through clinical screening and functional evaluation, CCR4–NOT transcription complex subunit 1 (CNOT1) correlated with the growth of osteosarcoma cells. To date, the mechanisms and regulatory roles of CNOT1 in tumors, including osteosarcoma, remain largely elusive. Here, we present evidence that knockdown of CNOT1 inhibits the growth of osteosarcoma in vitro and in vivo. Mechanistically, we observed that CNOT1 interacted with LMNA (lamin A) and functioned as a positive regulator of this intermediate filament protein. The RNA‐seq analysis revealed that CNOT1 depletion inhibited the Hedgehog signaling pathway in osteosarcoma cells. A rescue study showed that the decreased growth of osteosarcoma cells and inhibition of the Hedgehog signaling pathway by CNOT1 depletion were reversed by LMNA overexpression, indicating that the activity of CNOT1 was LMNA dependent. Notably, the CNOT1 expression was significantly associated with tumor recurrence, Enneking stage, and poor survival in patients with osteosarcoma. Examination of clinical samples confirmed that CNOT1 expression positively correlated with LMNA protein expression. Taken together, these results suggest that the CNOT1–LMNA–Hedgehog signaling pathway axis exerts an oncogenic role in osteosarcoma progression, which could be a potential target for gene therapy.

TRIM14 regulates cell proliferation and invasion in osteosarcoma via promotion of the AKT signaling pathway

Recent studies have shown that some members of the tripartite motif-containing protein (TRIM) family serve as important regulators of tumorigenesis. However, the biological role of TRIM14 in osteosarcoma remains to be established. In this study, we showed that TRIM14 is upregulated in human osteosarcoma specimens and cell lines, and correlated with osteosarcoma progression and shorter patient survival times. Functional studies demonstrated that overexpression of TRIM14 enhances osteosarcoma cell proliferation, clone formation, cell cycle procession, migration and invasion in vitro and promotes tumor growth in vivo, and conversely, its silencing has the opposite effects. Furthermore, TRIM14 overexpression induced activation of the AKT pathway. Inhibition of AKT expression reversed the TRIM14-mediated promotory effects on cell growth and mobility, in addition to TRIM14-induced epithelial-to-mesenchymal transition (EMT) and cyclin D1 upregulation. Our findings collectively suggest that TRIM14 functions as an oncogene by upregulating the AKT signaling pathway in osteosarcoma cells, supporting its potential utility as a therapeutic target for this disease.

RASSF4 Overexpression Inhibits the Proliferation, Invasion, EMT, and Wnt Signaling Pathway in Osteosarcoma Cells.

RASSF4, a member of the RASSF family, is broadly expressed in normal tissues but often inactivated in human cancers. Despite various studies on RASSF4, its role in osteosarcoma remains unclear. Therefore, in this study, we investigated the effects of RASSF4 expression on osteosarcoma cells and explored the underlying mechanism. The results of our study showed that RASSF4 was lowly expressed in osteosarcoma tissues and cells. RASSF4 overexpression significantly inhibited proliferation, migration, and invasion as well as the EMT process in osteosarcoma cells. Meanwhile, we found that RASSF4 overexpression markedly decreased the protein expression of β-catenin, cyclin D1, and c-Myc in osteosarcoma cells. In conclusion, our findings showed that RASSF4 overexpression inhibits proliferation, invasion, EMT, and Wnt signaling pathway in osteosarcoma cells. Thus, RASSF4 may be considered a novel target for osteosarcoma treatment.

Matrine-induced autophagy counteracts cell apoptosis via the ERK signaling pathway in osteosarcoma cells.

The aim of the present study was to observe whether autophagy was induced by matrine, and to investigate the role of autophagy in the antitumor effects of matrine on human osteosarcoma MG-63 cells and its underlying mechanism. MG-63 cells were cultured in vitro in matrine at a concentration of 0.6, 0.8, 1.0 and 1.2 g/l for 0, 24, 48 and 72 h. A MTT assay was used to evaluate the proliferation inhibition of MG-63 cells by matrine, and Annexin V-fluorescein isothiocyanate/propidum iodide (PI) staining flow cytometry was used to analyze the apoptotic rate. Alterations in cell morphology was assessed by PI and Hoechst 33258 cell staining. Matrine-induced autophagy in MG-63 cells was confirmed by green fluorescent protein-microtubule-associated protein 1-light chain 3 (LC3) b transfection and fluorescence microscopy, and cell viability was investigated by MTT assay following inhibition of autophagy by chloroquine (CQ) pretreatment. The expression level of apoptosis-associated proteins B-cell lymphoma-2 (Bcl-2) and Bcl-2-like protein 4 (Bax), autophagy-associated LC3II protein, and the activation of extracellular signal-regulated kinase (ERK) was detected by western blotting. Cell proliferation was clearly inhibited by matrine in a dose- and time-dependent manner. Flow cytometry and Hoechst 33258/PI staining verified that matrine induced apoptosis in a time-dependent manner when cells were exposed to 1.1 g/l matrine; fluorescence microscopy demonstrated that green fluorescence puncta were enhanced with prolonged time of matrine incubation. Western blotting confirmed that the expression of pro-apoptosis-associated proteins Bax and LC3II, and phosphorylated-ERK were upregulated, and anti-apoptosis protein Bcl-2 was downregulated in a time-dependent manner following treatment with matrine. The cell viability of the matrine + CQ group was increased compared with the matrine group alone, which revealed that matrine treatment alone induced protective autophagy in MG-63 cells. In addiiton, expression of LC3II/LC3I decreased and the expression of BAX/Bcl-2 increased in the matrine + U0126 group compared with the matrine alone group. The present study demonstrated, to the best of our knowledge, for the first time that matrine induced protective autophagy via ERK activation in MG-63 cells, and matrine combined treatment with CQ or U0126 led to an increase in apoptosis in osteosarcoma cells.

Hippo/YAP signaling pathway is involved in osteosarcoma chemoresistance.

BackgroundOsteosarcoma is the most common bone malignancy in children and adolescents, and 20%–30% of the patients suffer from poor prognosis because of individual chemoresistance. The Hippo/yes-associated protein (YAP) signaling pathway has been shown to play a role in tumor chemoresistance, but no previous report has focused on its involvement in osteosarcoma chemoresistance. This study aimed to investigate the role of the Hippo/YAP signaling pathway in osteosarcoma chemoresistance and to determine potential treatment targets.MethodsUsing the Cell Titer-Glo Luminescent cell viability assay and flow cytometry analysis, we determined the proliferation and chemosensitivity of YAP-overexpressing and YAP-knockdown osteosarcoma cells. In addition, using western blotting and the real-time polymerase chain reaction technique, we investigated the alteration of the Hippo/YAP signaling pathway in osteosarcoma cells treated with chemotherapeutic agents.ResultsMammalian sterile 20-like kinase 1 (MST1) degradation was increased, and large tumor suppressor kinase 1/2 (LATS1/2) total protein levels were decreased by methotrexate and doxorubicin, which increased activation and nuclear translocation of YAP. Moreover, YAP increased the proliferation and chemoresistance of MG63 cells.ConclusionsThe Hippo/YAP signaling pathway plays a role in osteosarcoma chemoresistance, and YAP is a potential target for reducing chemoresistance.