Abstract 5026: Tumor associated targeting with Manocept: HIV associated Kaposi's sarcoma as a model system

Proceedings: AACR 106th Annual Meeting 2015; April 18-22, 2015; Philadelphia, PA Introduction Inflammation appears to play a critical role in tumor development of HIV-associated Kaposi's sarcoma (KS). Specifically, emerging data show that KS tumor cells that co-express various macrophage (MO) antigens become resistant to current anti-viral therapies used to treat KS and AIDS. MOs also are a known source of KS tumor cell growth factors and substantial evidence suggests that tumor associated macrophages (TAMs) may represent a reservoir for HIV and its evolved retroviral variants. The MO pool driving these two pathological pathways share a common element rooted in the MOs, the CD206 human macrophage mannose receptor. Manocept, a molecular targeting agent, binds and enters MOs via pinocytosis of holo-CD206, providing a cell portal for the evaluation of Manocept as a MO and KS targeting agent. Methods Manocept was prepared as a synthetic molecule with a dextran backbone, and 12-20 mannose moieties. The reporter molecule (Cy3) was included as a fluorescent tracer for locating Manocept on and in MOs and KS tumor cells. Binding and localization Cy3-Manocept was assessed through intracellular visualization and flow cytometric quantitation of Cy3-Manocept binding and uptake using in vitro generation of monocyte-derived CD206+ MOs. The fresh HIV+ KS tumor tissue culture followed by immunofluorescence staining and confocal imaging was performed to confirm Cy3-Manocept uptake in KS tumor cells and TAMs. Results In vitro culture showed that Cy3-Manocept binds avidly to CD206 expressing MOs. Time course studies of increasing Cy3-Manocept concentrations confirmed continuous and ongoing uptake of Manocept into CD206+ MOs at 37°C. Fresh HIV+ KS tissue culture studies showed both Manocept uptake and CD206 staining of TAMs as well as KS tumor spindle cells (HHV8+ cells). Cy3-Manocept co-localized with CD206 in nearly all KS-associated cells expressing HHV8 and/or CD68 (Tissue MO marker), confirming that CD206 acts both as a target and Manocept concentrating receptor for TAMs and KS tumor cells. Conclusions Our results support the potential use of CD206 macrophage mannose receptor-targeted Manocept for imaging KS tumor cells, TAMs, and more importantly, for delivery of therapeutic/diagnostic agents capable of targeting all KS-associated cells including a potential MO reservoir for HIV. Citation Format: Rongzhen Zhang, Frederick O. Cope, Paige M. Bracci, Michael S. McGrath. Tumor associated targeting with Manocept: HIV associated Kaposi's sarcoma as a model system. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 5026. doi:10.1158/1538-7445.AM2015-5026