Nanobody-based targeting of the macrophage mannose receptor for effective in vivo imaging of tumor-associated macrophages.

Abstract

Tumor-associated macrophages (TAM) are an important component of the tumor stroma and exert several tumor-promoting activities. Strongly pro-angiogenic TAMs that reside in hypoxic tumor areas highly express macrophage mannose receptor (MMR, CD206). In this study, we targeted MMR+ TAMs using nanobodies, which are single-domain antigen-binding fragments derived from Camelidae heavy-chain antibodies. MMR-specific nanobodies stained TAMs in lung and breast tumor single-cell suspensions in vitro, and intravenous injection of 99mTc-labeled anti-MMR nanobodies successfully targeted tumor in vivo. Retention of the nanobody was receptor-specific and absent in MMR-deficient mice. Importantly, co-injection of excess unlabeled, bivalent anti-MMR nanobodies reduced nanobody accumulation in extratumoral organs to background levels, without compromising tumor uptake. Within tumors, the 99mTc-labeled nanobodies specifically labeled MMR+ TAMs, as CCR2-deficient mice that contain fewer TAMs showed significantly reduced tumor uptake. Further, anti-MMR nanobodies accumulated in hypoxic regions, thus targeting pro-angiogenic MMR+ TAMs. Taken together, our findings provide preclinical proof of concept that anti-MMR nanobodies can be used to selectively target and image TAM subpopulations in vivo.

• Authors: Kiavash Movahedi, Steve Schoonooghe, Damya Laoui, Isabelle Houbracken, Wim Waelput, Karine Breckpot, Luc Bouwens, Tony Lahoutte, Patrick De Baetselier, Geert Raes, Nick Devoogdt, Jo A Van Ginderachter
• Journal: Cancer research (Cancer Res) Vol. 72 Issue 16 Pg. 4165-77 (Aug 15 2012) ISSN: 1538-7445 [Electronic] United States
• PMID: 22719068 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't)
• Copyright: ©2012 AACR.

Chemical References

• Lectins, C-Type
• Mannose Receptor
• Mannose-Binding Lectins
• Receptors, Cell Surface
• Single-Domain Antibodies
• Technetium

Topics

• Amino Acid Sequence
• Animals
• Carcinoma, Lewis Lung (diagnostic imaging, immunology, metabolism)
• Cell Hypoxia (physiology)
• Female
• Lectins, C-Type (chemistry, immunology)
• Macrophages (chemistry, diagnostic imaging, immunology)
• Mannose Receptor
• Mannose-Binding Lectins (chemistry, immunology)
• Mice
• Mice, Inbred BALB C
• Mice, Inbred C57BL
• Molecular Sequence Data
• Receptors, Cell Surface (chemistry, immunology)
• Single-Domain Antibodies (chemistry, immunology, metabolism)
• Technetium (chemistry)
• Tissue Distribution
• Tomography, Emission-Computed, Single-Photon (methods)