Extended Data Fig. 2: Melanoma cells secrete exosomal PD-L1 into the circulation.
From: Exosomal PD-L1 contributes to immunosuppression and is associated with anti-PD-1 response
a, The monoclonal antibodies against the extracellular domain of human PD-L1 specifically detect human exosomal PD-L1, but not mouse exosomal PD-L1 (n = 3 biologically independent experiments). b, Levels of human PD-L1 in exosomes from the plasma of control nude mice (n = 10) and human WM9 melanoma xenograft-bearing nude mice (n = 10) per mg of total circulating exosomal proteins. c, Characterization of circulating exosomes purified from the plasma of a patient with Stage IV melanoma using NanoSight nanoparticle tracking analysis. d, Characterization of circulating microvesicles purified from the plasma sample of a patient with Stage IV melanoma using NanoSight nanoparticle tracking analysis. e, Immunoblots for PD-L1 in the microvesicles purified from the plasma samples of 8 patients with Stage IV melanoma (denoted as P1–P8). f, Immunoblots for PD-L1 in the exosomes purified from the plasma samples of 5 healthy donors and 5 patients with stage IV melanoma (left panel). Quantification of the levels of exosomal PD-L1 by western blot analysis (right panel). Results are expressed as the percentage of the mean value of healthy donors. g, Standard density gradient centrifugation analysis showing that circulating PD-L1 co-fractionated with exosome markers Hrs and TSG101 and melanoma-specific marker TYRP-2. Three (c, d) or two (e, g) experiments were repeated independently with similar results. Data represent mean ± s.d. (a, b, f). Statistical analyses were performed using two-sided unpaired t-test (b, f). For gel source data (e–g), see Supplementary Fig. 1.
