No abstract

Autophagy is a conserved catabolic process by which cytoplasmic components are delivered into lysosomes for degradation. Pigment epithelium-derived factor (PEDF) has been reported to be associated with autophagy and can induce p53 expression; however, the mechanism relating PEDF with autophagy in endothelial cells remains poorly understood. The present study aimed to investigate the association between the PEDF-p53-sestrin pathway and autophagy in human umbilical vein endothelial cells (HUVECs). PEDF-induced autophagy was examined by fluorescence microscopy and western blot analysis. p53 small interfering (si)RNA and sestrin2 siRNA were constructed and transfected into HUVECs prior to PEDF treatment. The protein expression levels of microtubule-associated protein light chain 3 (LC3) I, LC3 II and p62 were evaluated by western blot analysis, and the mRNA expression levels of p53 and sestrin2 were determined using reverse transcription-quantitative polymerase chain reaction analysis. The regulation of mechanistic target of rapamycin (mTOR) was reflected by p70S6 kinase (p70S6K) and eukaryotic translation initiation factor 4E-binding protein 1 (4E-BP1) protein expression levels, as determined by western blot analysis. PEDF could induce HUVEC autophagy by sequentially inducing p53 and sestrin2 expression, as observed by fluorescence microscopy and western blot analysis. Conversely, the induction of sestrin2 by PEDF was eliminated by p53 siRNA. In addition, p53 siRNA and sestrin2 siRNA could attenuate PEDF-induced HUVEC autophagy. Inhibition of mTOR may be the mechanism responsible for PEDF-induced autophagy; as p70S6K and 4E-BP1 phosphorylation levels were significantly upregulated in p53 siRNA-treated and sestrin2 siRNA-treated groups. The findings of the present study indicated that PEDF may trigger autophagy in HUVECs by inducing p53 and sestrin2 expression, and inhibiting mTOR expression; these findings may contribute to the improved understanding of diseases, including cancer and atherosclerosis.

Osteosarcoma is a common primary bone malignancy, with a 5-year survival rate of only 20-30% in patients undergoing surgical treatment. Thus, it is important to identify novel methods for diagnosing and treating osteosarcoma, which was the aim of the present study. Vascular endothelial growth factor (VEGF) was used as the tumor-targeting protein to synthesize a multifunctional core-shell nanostructure, Au@SiO 2 -drug/VEGF, in which the drug can be indocyanine green (ICG; as an optical tracer) or doxorubicin (DOX; as a chemotherapeutic agent). With VEGF as the osteosarcoma-targeting protein, Au exhibited optimal photothermal transformation performance, while SiO 2 served as the carrier for the drug. Au@SiO 2 -ICG/VEGF nanoparticles (NPs) were evaluated for imaging and for the monitoring of drug accumulation in a tumor region in mice. Once the optimal drug accumulation was achieved, combined treatment of osteosarcoma (chemotherapy and photothermal therapy) was assessed. In the perioperative period associated with minimal invasive embolization of osteosarcoma, photothermal therapy and chemotherapy were applied for osteosarcoma diagnosis using Au@SiO 2 -DOX/VEGF NPs. Taken together, the results of the present study provide a promising strategy for tumor detection prior to surgical treatment to improve the survival outcome of patients with osteosarcoma.