Downregulation of neuropilin-1 on macrophages modulates antibody-mediated tumoricidal activity
Neuropilin-1 (NRP-1)-expressing macrophages are engaged in antitumor immune functions via various mechanisms. In this study, we investigated the role of NRP-1 on macrophages in antibody-mediated tumoricidal activity. Treatment of macrophages with NRP-1 knockdown or an anti-NRP-1-neutralizing antibody significantly suppressed antibody-dependent cellular cytotoxicity and modulated cytokine secretion from macrophages in vitro. Furthermore, in vivo studies using a humanized mouse model bearing human epidermal growth factor receptor-2 (HER2)-positive breast cancer xenografts showed that antibody-mediated antitumor activity and tumor infiltration of CD4+ T lymphocytes were significantly downregulated when peripheral blood mononuclear cells in which NRP-1 was knocked down were co-administered with an anti-HER2 antibody. These results revealed that NRP-1 expressed on macrophages plays an important role in antibody-mediated antitumor immunity. Taken together, the induction of NRP-1 on macrophages may be a therapeutic indicator for antibody treatments that exert antibody-dependent cellular cytotoxicity activity, although further studies are needed in order to support this hypothesis.
KeywordsNeuropilin-1 Breast cancer HER2 Humanized mouse Antibody-dependent cellular cytotoxicity
Antibody-dependent cellular cytotoxicity
Fetal bovine serum
Granulocyte colony-stimulating factor
Human epidermal growth factor receptor-2
Macrophage inflammatory protein-1α
Macrophage inflammatory protein-1β
Nod/Shi-scid, IL-2Rγ null
Peripheral blood mononuclear cells
Quantitative real-time PCR
Relative luminescence units
Standard error of the mean
Small interfering RNA
Tumor necrosis factor
Vascular endothelial growth factor
We thank the medical staff of the Department of Breast Surgery of Kyoto University Hospital for their help in the recruitment of participants and collection of samples. We also thank Dr. Hitoshi Niwa (RIKEN CDB, Kobe, Japan) for providing the pCAGIPuro vector.
Compliance with ethical standards
Conflict of interest
The authors declare no conflicts of interests.
All procedures performed in studies involving human participants were in accordance with the ethical standards of the institutional and/or national research committee and with the 1964 Helsinki declaration and its later amendments or comparable ethical standards. All applicable international, national, and/or institutional guidelines for the care and use of animals were followed. All procedures performed in studies involving animals were in accordance with the ethical standards of the institution or practice at which the studies were conducted.
This research was supported by a grant from the Japan Society for the Promotion of Science (KAKENHI Grant Number 12907996).
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