Cancer Immunotherapy: Macrophage-Mediated Phagocytosis

Tumor Associated Macrophages

Macrophages are important effector cells of innate immunity. Depending on the tissue microenvironment, tumor-associated macrophages (TAM) can differentiate into either cytotoxic (M1) or tumor-promoting (M2) states. While cytotoxic M1 macrophages are typically induced by IFN-γ alone or in concert with microbial products, tumor promoting M2 macrophages are induced by IL-4 or IL-13, IL-10, IL-21, TGFβ, immune complexes, and glucocorticoids.

Application Highlight: M1 Macrophage-Mediated Tumor Cell Killing

In a recent study the secreted glycoprotein thrombospondin 1 (TSP1) was shown to be a positive modulator of innate antitumor immunity by increasing M1 macrophage recruitment and stimulating reactive oxygen species (ROS)-mediated tumor cell killing. These conclusions were drawn, in part, by using xCELLigence RTCA impedance monitoring to evaluate the effect of TSP1 on macrophage/monocyte activity when co-cultured with MDA-MB-231 breast adenocarcinoma target cells. The % cytolysis data clearly indicate that the tumoricidal activity of both differentiated U937 human monocytes (left panel) and activated ANA-1 murine macrophages (right panel) are enhanced in the presence of TSP1.

Secreted glycoprotein TSP1 increases macrophage/monocyte-mediated tumoricidal activity

Secreted glycoprotein TSP1 increases macrophage/monocyte-mediated tumoricidal activity.  MDA-MB-231 breast adenocarcinoma target cells were seeded in ACEA’s electronic microtiter plates (E-Plates) and incubated for up to 24 hours. Differentiated U937 human monocytes (left panel) or activated ANA-1 murine macrophages (right panel) were then added in the presence or absence of soluble TSP1. Figure adapted from Cancer Res. 2008;68(17):7090-9.  Note that the RT-CES® described in this publication was ACEA’s first generation real-time cell analysis (RTCA) system, and has subsequently been rebranded as xCELLigence RTCA.

Key Benefits of Using xCELLigence To Study Bispecific Antibodies/BiTEs:
  1. Label-Free: Allowing for more physiological assay conditions; labeling or secondary assays aren’t required.
  2. Real-Time: Quantitative monitoring of both fast (hours) and slow (days) killing kinetics.
  3. Sensitive: Capable of evaluating low effector cell to target cell ratios that are physiologically relevant.
  4. Simple Workflow: Requires only the addition of effector cells to target cells (in the presence or absence of antibodies); homogeneous assay without additional sample handling.
  5. Automatic Data Plotting: RTCA software enables facile data display and objective analysis, precluding the subjective data vetting that is common to imaging-based assays.

Macrophage-mediated phagocytosis – Supporting Information:
  • Adherent target cells tested:
    MDA-MB-231, MDA-MB-435, MCF-7
  • Macrophage-Mediated Phagocytosis – Compatible xCELLigence Systems:
3×16 wells1×96 wells6×96 wellsUp to 4×384 wells
  • References:
  1. Thrombospondin 1 promotes tumor macrophage recruitment and enhances tumor cell cytotoxicity of differentiated U937 cells. Martin-Manso G, Galli S, Ridnour LA, Tsokos M, Wink DA, Roberts DD. Cancer Res. 2008 Sep 1;68(17):7090-9. (National Institutes of Health, USA)
  2. Hydroxychloroquine inhibits autophagy to potentiate antiestrogen responsiveness in ER+ breast cancer. Cook KL, Wärri A, Soto-Pantoja DR, Clarke PA, Cruz MI, Zwart A, Clarke R. Clin Cancer Res. 2014 Jun 15;20(12):3222-32. (Georgetown University Medical Center, USA)