Abstract 4408: Prevention of post surgery tumor recurrence and metastasis of melanoma by a fully human CSPG4-specific antibody

Proceedings: AACR 101st Annual Meeting 2010‐‐ Apr 17‐21, 2010; Washington, DC Despite a high cure rate for those who are diagnosed early with melanoma, there are currently no effective treatments for those who have post surgery melanoma recurrence and metastasis. Therefore, we have directed our research focus on preventing tumor recurrence and metastasis following the surgical removal of primary tumor by targeted immunotherapy. The target selected is the cell surface chondrotin sulfate proteoglycan 4 (CSPG4), which plays an important role in signaling pathways regulating tumor cell - survival, -growth and - motility. To implement CSPG4-targeted immunotherapy of melanoma, we have utilized the CSPG4-specific fully human monoclonal antibody scFv-FcC21. The latter was generated by fusing to human IgG1 Fc (Fc) the single chain of variable regions of heavy and light chains (scFv) C21 isolated by panning a phage display human scFv library with live CSPG4+ melanoma cells. The specificity of scFv-Fc C21 was tested with a panel of CSPG4+ and CSPG4- cell lines by flow cytometry. The anti-tumor activity of scFv-Fc C21 was tested by assessing its ability to inhibit tumor cell migration and cell growth in vitro and human melanoma cell-derived lung metastasis in vivo. Moreover, scFv-Fc C21 was tested for its ability to prevent post-surgery human melanoma recurrence and metastasis in SCID mice. Flow cytometric analysis showed that scFv-Fc C21 stained specifically the cell surface of a panel of CSPG4+ human melanoma cell lines but did not stain CSPG4- melanoma cell lines. Additionally, scFv-Fc C21 inhibited significantly melanoma cell migration and growth in vitro. Importantly, scFv-Fc C21 suppressed by 87% in vivo human melanoma cell-derived established lung metastasis. Lastly, scFv-Fc C21 prevented tumor recurrence and lung metastasis following the surgical removal of primary tumor in 100 and 83% of the mice tested, respectively. In contrast, 100% mice treated with the isotype control scFv-Fc had both local tumor recurrence and lung metastasis. The mechanism(s) of action mediated by scFv-Fc C21 is likely due to its blockade role in CSPG4 signaling transduction in melanoma cells as i) scFv-FcC21 in vitro treated melanoma cells MV3 cells had a decreased level of Protein kinase C alpha (PKCα) and FAK. Moreover, scFv-Fc C21 in vitro treatment inhibited the activation of FAK, Erk1/2, PDK1 and Akt and ii) scFv-Fc C21 in vivo treated primary tumors had a marked reduction in the level of PKCα, FAK, Src and β-catenin and in the activation of FAK, Erk1/2, PDK1 and Akt signaling pathways compared to those from mice treated with the control scFv-Fc 119. Our results strongly indicate that the fully human antibody scFv-Fc C21 holds promise in targeting CSPG4 to prevent post-surgery melanoma recurrence and metastasis. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 4408.