Fig. 1

Higher level of Sr-exosomal PD-L1 in OS patients compared to healthy donors and patients with benign tumor. a Plan for analysis of patients with OS and benign tumor and healthy donors; b Electron microscopy showing vesicles of 30–100 nm diameter as exosomes; c Nanoparticle tracking system for evaluation of exosome concentration and size; d Western blot analysis for the representative biomarkers of exosomes; e, f Analysis of particle concentration of Sr-exosomes between OS patients and healthy donors by nanoparticle tracking system; G-H. Concentration of RNA and total protein in Sr-exosomes between OS patients and healthy donors; I Density gradient centrifugation confirming that PD-L1 existing in Sr-exosomes derived from OS patients; j A representative TEM image of Sr-exosomes immunogold-labelled with PD-L1 antibody derived from healthy donors and patients with osteosarcoma and benign tumor; k, l Western blot analysis showing Sr-exosomal PD-L1 expression of healthy donors and patients with OS and benign tumors; m Schematic of ELISA to measure PD-L1 concentration in serum exosomes derived from healthy donors and patients with osteosarcoma and benign tumor; n Levels of PD-L1 in serum exosomes derived from healthy donors and patients with osteosarcoma and benign tumors by ELISA; o ROC analysis indicating Sr-exosomal PD-L1 having an AUC of 0.695 to distinguish OS patients from healthy donors