PLXNB2 and breast cancer: We then measured the PLXNB2 expression in human blood CTCs and white blood cells (WBCs) from patients with stage III-IV breast cancer using multiple complementary methods16,26: FDA-approved CellSearch® with blood collected into fixative-containing CellSave tubes (N = 15 patients) (Fig. 1e, and Supplementary Fig. S2b–i), live cell flow cytometry18,26 with blood drawn into EDTA tubes (N = 17 patients) (Supplementary Fig. S3a–b), immunoblotting (Supplementary Fig. S2d), and MS proteomic analysis (Supplementary Data 1-tabs 5).