Direct pe conjugate

For quantification of surface receptor expression, cells were trypsinized and brought to single-cell suspension in FACS buffer (1× PBS + 2% FBS). Primary antibody was added at 1 μg/million cells in 100 μL total solution (for mouse cells: rat anti-mouse α_v integrin (BD Pharmingen 551380) or rat IgG isotype control (Invitrogen); for human cells: mouse anti-α_vβ₃ integrin, direct PE conjugate (BioLegend 304406) or mouse IgG κ chain isotype control, direct PE conjugate (BioLegend 400112); for neuropilin-1 staining in all cells, rabbit anti-NRP-1 (Novus Biologicals NBP1-40666) or normal rabbit IgG isotype control (R&D)) and incubated for one hour on ice. For direct fluorophore-conjugated primary antibodies, cells were washed with PBS and resuspended in FACS buffer. Otherwise, after washing the cells 2× in PBS, cells were incubated with secondary fluorescently-tagged antibody (Invitrogen) for 45 minutes and washed 1× in PBS. Cells were analyzed on BD LSR-II or Fortessa HTS flow cytometers. Data were analyzed in FlowJo (TreeStar Software).