Figure 4.

Low dose cyclophosphamide potentiates daratumumab mediated macrophage anti-myeloma activity. (a) Schematic of experimental setup. CFSE-labeled multiple myeloma cells were co-cultured with THP-1 macrophages pre-conditioned in 0–20 µM CTX-TCS. Following 18 hr incubation, fluorescent cells were analyzed by fluorescent microscopy and flow cytometry. (b) Daratumumab-mediated antibody-dependent cellular phagocytosis (ADCP) of MM1.S cells by 0–20 µM CTX-TCS conditioned THP-1 macrophages. (c) Daratumumab-mediated ADCP of RPMI-8226 cells by 0–20 µM CTX-TCS conditioned THP-1 macrophages. (d) Daratumumab-mediated ADCP of MM1.S cells by 0–20 µM CTX-TCS conditioned THP-1 macrophages in the absence or presence a phagocytosis inhibitor, 1 μg/ml CytoD. (e-f) Relative TNF-α release (fold change relative to control) from MM1.S and RPMI-8226 cells in the presence of CTX-TCS. Data from at least three independent experiments (n ≥ 3) are presented here as scatter plots with bars (mean ± S.E.M). Independent t-tests and one-way ANOVA statistical analysis carried out, followed by Tukey’s post-hoc test. *p < 0.05. **p < 0.01. ***p < 0.001