PVR and glioblastoma: MDA-MB-231 cells express many of these ligands (Extended Data Fig. 8a), and they were present in purified MDA-MB-231 (breast cancer), Gli36 (glioblastoma) and B16-F1 (melanoma) blebbisomes (Fig. 7d and Extended Data Fig. 8b,c), including PD-L1, PD-L2, B7-H3, VISTA, PVR and HLA-E.