In patients with metastatic melanoma, high blood levels of galectin-9 are correlated with worse overall survival and a bias towards a Th2 inflammatory state supportive of tumor growth. Although galectin-9 signaling through TIM3 on T cells has been described, less is known about the interaction of galectin-9 with macrophages. We aimed to determine whether galectin-9 is a binding partner of CD206 on macrophages and whether the result of this interaction is tumor-supportive. It was determined that incubation of CD68 macrophages with galectin-9 or anti-CD206 blocked target binding and that both CD206 and galectin-9 were detected by immunoprecipitation of cell lysates. CD206 and galectin-9 had a binding affinity of 2.8 × 10 m. Galectin-9 causes CD206 macrophages to make significantly more FGF2 and monocyte chemoattractant protein (MCP-1), but less macrophage-derived chemokine (MDC). Galectin-9 had no effect on classical monocyte subsets, but caused expansion of the non-classical populations. Lastly, there was a positive correlation between increasing numbers of CD206 macrophages and galectin-9 expression in tumors, and high levels of CD206 macrophages correlated negatively with melanoma survival. These results indicate that galectin-9 binds to CD206 on M2 macrophages, which appear to drive angiogenesis and the production of chemokines that support tumor growth and poor patient prognoses. Targeting this interaction systemically through circulating monocytes may therefore be a novel way to improve local anti-tumor effects by macrophages. Copyright © 2018 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.

We developed a nano-antibody targeted chemotherapy (nATC) delivery strategy in which tumor specific and clinically relevant antibodies (rituximab, anti-CD20) are non-covalently bound to the albumin scaffold of nab-paclitaxel (ABX). We define the nanoparticle formed when the 2 drugs are bound (AR160). The newly created nATC retains the cytotoxicity of ABX and CD20 affinity of rituximab in vitro. We describe the binding characteristics of the ABX and rituximab in AR160 using peptide mapping/Biacore approach. Flow-based methods, including ImageStream and nanoparticle tracking, were used to characterize the AR160 particles in vitro. A mouse model of human B-cell lymphoma was utilized to test in vivo efficacy of AR160 therapy, which suggested improved tumor targeting (biodistribution) as the most likely mechanism of AR160 therapeutic superiority over ABX or rituximab alone. These data suggest a novel platform for nATC delivery using a slight modification of existing cancer drugs with significantly improved treatment efficacy.

Antibody directed chemotherapy (ADC) takes advantage of the selectivity of the monoclonal antibody to increase the efficacy of the chemotherapeutic agent, while reducing toxicity. Previously we described three nab-paclitaxel (Abraxane) nanoparticles coated with commercial monoclonal antibodies. Identifying the binding sites responsible for these particles could allow reverse engineering of nab-paclitaxel binding antibodies, creating a modular platform for antibody directed chemotherapeutic nanoparticles. Herein, Biacore surface plasmon resonance is used to identify an antibody binding site, HSA Peptide 40, on human serum albumin with nanomolar affinity for all three monoclonal antibodies. This 18-mer peptide, which lies in Subdomain IIIA of human serum albumin, blocks binding of all three antibodies to nab-paclitaxel when added in excess. We furthermore show the complementary binding region on all three monoclonal antibodies to be the CDR H3 loop of the Fab region, and show that they all have nano to micromolar affinity for HSA Peptide 40 and nab-paclitaxel nanoparticles. The presented data identify the nature of the critical protein-protein interaction that enables antibody coating of nab-paclitaxel.