Precision Targeting of Human M2 Macrophages by Magnetic Nanoparticles Functionalized with an in-House Antibody.

Introduction: Non-small cell lung cancer (NSCLC) remains the leading cause of cancer-related mortality, particularly due to resistance induced by tumor-associated macrophages (TAMs)-exhibiting a M2-like phenotype-within the tumor microenvironment. The specific targeting of pro-tumoral M2 TAMs constitutes thus a major challenge in anticancer therapies but current strategies lack specificity. We produced and patented a monoclonal antibody, called mAb6-25, that specifically targets M2-like macrophages (M2M) but not M1-like macrophages (M1M) or monocytes. Here, we investigated the conjugation of this antibody on magnetic nanoparticles (MNPs) as a potential nanoplatform for specific M2 TAM targeting. Methods: Magnetic iron oxide multicore nanoflowers (NF) were functionalized with a fluorophore allowing their detection and the mAb6-25 for M2 TAM targeting. The M2M targeting by MNP-mAb6-25 was determined, comparatively to M1M, in 2D and 3D in vitro co-culture models with cancer cells by flow cytometry and confocal microscopy analysis, while MNP-mAb6-25 uptake was evaluated by NMR relaxometry. The in vivo M2 TAM targeting was analyzed in a xenograft mouse model of NSCLC by IVIS optical imaging. Results: We demonstrated that the MNP-mAb6-25 nanoplatform preferentially binds M2M compared to M1M (13-fold higher uptake in M2M) or cancer cells in monoculture as well as in 2D and 3D co-culture models mixing M2M or M1M with A549 NSCLC cells. Moreover, MNP-mAb6-25 internalized and accumulated in the lysosomes of M2M. The efficacy of intravenously injected MNP-mAb6-25 to target NSCLC sub-cutaneous xenografted models containing M2M was subsequently demonstrated. Conclusion: This study highlights the potential of MNP-mAb6-25 as a nanoplatform for selective targeting TAM-containing NSCLC tumors. This nanotechnology tool may lead to the development of new applications: one involving the imaging-based detection of pro-tumoral M2 TAMs by MRI, and the other involving their potential depletion through the application of localized magnetic fields, paving the way for imaging-guided diagnosis and further therapeutic evaluation.