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Studying the Effects of Tumor-Secreted Paracrine Ligands on Macrophage Activation using Co-Culture with Permeable Membrane Supports
Published on: November 28, 2019
In vivo imaging reveals a tumor-associated macrophage-mediated resistance pathway in anti-PD-1 therapy
Sean P Arlauckas1,2,3, Christopher S Garris1,4, Rainer H Kohler1
1Center for Systems Biology, Massachusetts General Hospital, 185 Cambridge Street, CPZN 5206, Boston, MA 02114, USA.
Abstract:
Monoclonal antibodies (mAbs) targeting the immune checkpoint anti-programmed cell death protein 1 (aPD-1) have demonstrated impressive benefits for the treatment of some cancers; however, these drugs are not always effective, and we still have a limited understanding of the mechanisms that contribute to their efficacy or lack thereof. We used in vivo imaging to uncover the fate and activity of aPD-1 mAbs in real time and at subcellular resolution in mice. We show that aPD-1 mAbs effectively bind PD-1+ tumor-infiltrating CD8+ T cells at early time points after administration. However, this engagement is transient, and aPD-1 mAbs are captured within minutes from the T cell surface by PD-1- tumor-associated macrophages. We further show that macrophage accrual of aPD-1 mAbs depends both on the drug's Fc domain glycan and on Fcγ receptors (FcγRs) expressed by host myeloid cells and extend these findings to the human setting. Finally, we demonstrate that in vivo blockade of FcγRs before aPD-1 mAb administration substantially prolongs aPD-1 mAb binding to tumor-infiltrating CD8+ T cells and enhances immunotherapy-induced tumor regression in mice. These investigations yield insight into aPD-1 target engagement in vivo and identify specific Fc/FcγR interactions that can be modulated to improve checkpoint blockade therapy.
Insights
Anti-programmed cell death protein 1 (aPD-1) monoclonal antibodies (mAbs) can be quickly captured by macrophages, reducing their effectiveness. Blocking Fc gamma receptors (FcγRs) prolongs aPD-1 mAb binding to T cells, improving cancer immunotherapy outcomes.
Area of Science:
- Immunology
- Cancer Biology
- Pharmacology
Background:
- Monoclonal antibodies (mAbs) targeting anti-programmed cell death protein 1 (aPD-1) are vital cancer immunotherapies.
- Limited understanding exists regarding the in vivo mechanisms of aPD-1 mAb efficacy and limitations.
Purpose of the Study:
- To investigate the real-time fate and subcellular activity of aPD-1 mAbs in vivo.
- To identify mechanisms limiting aPD-1 mAb target engagement on T cells.
- To explore strategies for enhancing aPD-1 mAb therapy effectiveness.
Main Methods:
- In vivo imaging techniques were employed to track aPD-1 mAbs in mice.
- Analysis of mAb binding to tumor-infiltrating CD8+ T cells and tumor-associated macrophages.
- Investigation of the role of Fc domain glycan and Fc gamma receptors (FcγRs) in mAb uptake.
- Assessment of FcγR blockade effects on mAb engagement and tumor regression.
Main Results:
- aPD-1 mAbs initially bind to PD-1+ CD8+ T cells but are rapidly internalized by PD-1- macrophages.
- Macrophage uptake of aPD-1 mAbs is dependent on Fc domain glycosylation and FcγRs on myeloid cells.
- In vivo blockade of FcγRs significantly extends aPD-1 mAb retention on CD8+ T cells.
- FcγR blockade enhances aPD-1 mAb efficacy, leading to improved tumor regression in mice.
Conclusions:
- Macrophage-mediated clearance limits the duration of aPD-1 mAb engagement with target T cells.
- Fc/FcγR interactions are critical determinants of aPD-1 mAb pharmacokinetics and pharmacodynamics.
- Modulating FcγR activity presents a promising strategy to optimize checkpoint blockade immunotherapy.
