Clone 12g5

Cells were dissociated into single cells with 0.05% trypsin (0.1% EDTA) wherever suitable or rinsed off from culture, and resuspended in a FACS washing buffer (PBS with 5% fetal calf serum (FCS) and 2.5 mM EDTA). The cell suspension was then stained with the desired antibodies. The antibodies used in this study were: CD56 (1:50, clone CMSSB; eBioscience), PE-conjugated CD309 (FLK1, 1:50, clone 7D4–6; Biolegend), PE-conjugated CD13(1:50, clone WM15; BD), FITC-conjugated CD31 (1:50, clone WM59; BD), APC-conjugated CD34 (1:50, clone 581; BD), FITC-conjugated CD43 (1:50, clone MEM-59; Biolegend), PE-conjugated CD43 (1:20, clone eBio84-3C1; eBioscience), FITC-conjugated CD45(1:50, clone 5B1; Miltenyi Biotec), FITC-conjugated CD14 (1:50, clone HCD14; Biolegend), PE-conjugated CD68 (1:50, clone Y1/82A; Biolegend), APC-conjugated CD11b (1:50, clone ICRF44; Biolegend), PE-conjugated CD163 (1:50, clone RM3/1; Biolegend), PE-conjugated CD73 (1:50, clone AD2; Biolegend) and APC/Cy7-conjugated CD163 (1:50, clone 12G5; Biolegend). FITC-conjugated mouse IgG2a (1:20, 130-098-846; Miltenyi Biotec), APC-conjugated mouse IgG1 (1:20, 130-098-877; Miltenyi Biotec) and PE-conjugated mouse IgG1κ (1:20, clone P3.6.2.8.1; eBioscience) were used as isotype-matched negative controls. Data were collected with a FACS Calibur flow cytometer (BD) and analyzed using FlowJo software, version 10.0.7.

Peripheral blood samples (8 mL EDTA tubes) were collected at baseline, and at C1D15. After RBC lysis, blood cells were incubated with nuclear dye (#H3570, Hoechst 33342, Life Technologies, DC, USA), viability dye (#L34966, LIVE/DEAD Fixable Aqua, Life Technologies) and antibodies including PE-conjugated anti-human epithelial cell adhesion molecule (EpCAM) Ab (#130-091-253, clone HEA-125, Miltenyi Biotec, CA, USA). The anti-PE magnetic beads (#130-048-801, Miltenyi Biotec) were then used to enrich EpCAM-positive cells. Cell quantification was calculated by multiparameter flow cytometry^{77 (link)–79 (link)}. Viable, nucleated, EpCAM-positive, CD45 (#304014, clone HI30, BioLegend, CA, USA) negative cells were finally considered CTCs and further characterized for CD117 (#313212, clone 104D2, BioLegend), CXCR4 (#306516, clone 12G5, BioLegend), PDL1 (#329708, clone 29E.2A3, BioLegend) and MUC-1 (#559774, clone HMPV, BD Biosciences, CA, USA) expression. Antibody dilution details are provided in Supplementary Table 4.

Isolated neutrophils (50,000 cells) were stained in fluorescent activated cell sorting (FACS) buffer containing 2% heat-inactivated fetal bovine serum (FBS) (Life Technologies, Dun Laoghaire, Ireland) and 1 mM EDTA (Life Technologies) in phosphate buffer saline (PBS) without calcium and magnesium (Corning, Corning, NY, USA). Cells were stained with antibodies for 30 min at 4 °C in FACS buffer containing (BV421) anti-CD10 (1:200 dilution; clone HI10a; BioLegend, San Diego, CA, USA) and (BV786) anti-CXCR4 (1:100 dilution; clone12G5; BioLegend) and (AF647) anti-CD64 (1:100 dilution; clone 10.1; BioLegend) or (BV786) anti-CD63 (1:100 dilution; clone H5C6; BioLegend) and (APC) anti-CD66b (1:800 dilution; clone G10F5; BioLegend), or (BV421) anti-CD62L (1:200 dilution; clone DREG-56; BioLegend), and (PE/Dazzle) anti-CD32 (1:200 dilution; clone FUN-2; BioLegend). Data were acquired on a BD FACSCelesta (BD Biosciences, San Jose, CA, USA) with a BVR laser configuration (488 nm, 405 nm, 640 nm). Before recording data, gates were prepared so that 10,000 neutrophil events could be collected. FCS files were exported from BD FACSDiva Software (BD Biosciences) in a 3.0 format. FCS files were analyzed using FlowJo v.10 software (BD Biosciences).