This strategy was validated in two ways: First, prostate cancer cells injected intratibially were visualized after 24 hours in situ by immunofluorescent imaging for HLA-ABC (Figure S1G); second, specificity was confirmed by inoculating SCID mice with GFP (green)-labeled PCa cells and recovering the DTCs from the marrow using APC (red)-labeled anti-HLA-ABC antibodies. Here, APC is linked to prostate carcinoma.