No abstract

Osteosarcoma is a malignant tumor abundant in vascular tissue, and its rich blood supply may have a significant impact on its metabolic characteristics. PDGFRβ is a membrane receptor highly expressed in osteosarcoma cells and vascular wall cells, and its effect on osteosarcoma metabolism needs to be further studied. In this study, we discussed the effect and mechanism of action of PDGFRβ on glucose metabolism in human osteosarcoma (HOS) cells. GSEA, Pearson’s correlation test, and PPI correlation analysis indicated positive regulation of PDGFRβ on aerobic glycolysis in osteosarcoma. The results of qPCR and western blot further confirmed the prediction of bioinformatics. Glucose metabolism experiments proved that PDGF/PDGFRβ could effectively promote aerobic glycolysis in osteosarcoma cells. In addition, the mitochondrial membrane potential (ΔΨm) experiment proved that the metabolic change triggered by PDGFRβ was not caused by mitochondrial damage. The PI3K pathway inhibitor LY294002, MEK pathway inhibitor U0126, or Warburg effect inhibitor DCA was used to perform western blot and glucose metabolism experiments, and the results showed that PDGFBB/PDGFRβ mainly activated the PI3K/AKT/mTOR/c-Myc pathway to promote aerobic glycolysis in osteosarcoma HOS cells. The newly elucidated role of PDGFRβ provides a novel metabolic therapeutic target for osteosarcoma.

Wilms' tumor (WT) is the most common pediatric renal malignancy. PDGFRβ belongs to the type III receptor tyrosine kinase family and is known to be involved in tumor metastasis and angiogenesis. Here, we studied the effect and underlying mechanism of PDGFRβ on WT G401 cells. Transwell assay and wound-healing assay were used to detect the effect of PDGFRβ on G401 cells invasion and migration. Western blot and immunofluorescence were used to detect the expression of EMT-related genes. The expression of PI3K/AKT/mTOR pathway proteins was detected by Western blot.The relationship between PDGFRβ and aerobic glycolysis was studied by assessing the expression of glycolysis-related enzymes detected by qRT-PCR and Western blot.The activity of HK, PK, and LDH was detected by corresponding enzyme activity kits.The concentration of lactic acid and glucose was detected by Lactic Acid Assay Kit and Glucose Assay Kit-glucose oxidase method separately. To investigate the mechanism of PDGFRβ in the development of WT, the changes of glucose and lactic acid were analyzed after blocking PI3K pathway, aerobic glycolysis, or PDGFRβ. The key enzyme was screened by Western blot and glucose metabolism experiment after HK2, PKM2, and PDK1 were inhibited. The results showed that PDGFRβ promoted the EMT process by modulating aerobic glycolysis through PI3K/AKT/mTOR pathway in which PKM2 plays a key role. Therefore, our study of the mechanism of PDGFRβ in G401 cells provides a new target for the treatment of WT.

Platelet‐derived growth factor receptor beta belongs to the tyrosine kinase family. Platelet‐derived growth factor receptor beta binds to its specific ligand and induces autophosphorylation to activate the downstream phosphatidylinositol 3‐kinase/AKT/mammalian target of rapamycin pathway. The activated pathway molecules then influence the epithelial–mesenchymal transition process by regulating the expression of epithelial–mesenchymal transition‐related proteins, and ultimately regulating tumor metastasis.

Background: Sepsis induces GAS5 expression in the vascular endothelium, but the molecular mechanism is unclear, as is the role of GAS5 in sepsis. Methods and results: We observed that GAS5 expression in the endothelium was significantly upregulated in a sepsis mouse model. ChIP-PCR and EMSA confirmed that the oxidative stress (OS)-activated MiT–TFE transcription factor (MITF, TFE3, and TFEB)-mediated GAS5 transcription. In vitro, GAS5 overexpression attenuated OS and inflammation in endothelial cells (ECs) while maintaining the structural and functional integrity of mitochondria. In vivo, GAS5 reduced tissue ROS levels, maintained vascular barrier function to reduce leakage, and ultimately attenuated sepsis-induced lung injury. Luciferase reporter assays revealed that GAS5 protected MITF from degradation by sponging miR-23, thereby forming a positive feedback loop consisting of MITF, GAS5, and miR-23. Despite the fact that the OS-activated MITF–GAS5–miR-23 loop boosted MITF-mediated p62 transcription, ECs do not need to increase mitophagy to exert mitochondrial quality control since MITF-mediated Nrf2 transcription exists. Compared to mitophagy, MITF-transcribed p62 prefers to facilitate the autophagic degradation of Keap1 through a direct interaction, thereby relieving the inhibition of Nrf2 by Keap1, indicating that MITF can upregulate Nrf2 at both the transcriptional and posttranscriptional levels. Following this, ChIP-PCR demonstrated that Nrf2 can also transcribe MITF, revealing that there is a reciprocal positive regulatory association between MITF and Nrf2. Conclusion: In sepsis, the ROS-activated MITF–GAS5–miR-23 loop integrated the antioxidant and autophagy systems through MITF-mediated transcription of Nrf2 and p62, which dynamically regulate the level and type of autophagy, as well as exert antioxidant and anti-inflammatory effects.