Targeting RAGE expression in ovarian cancer for in-vivo imaging

230 Objectives Early diagnosis for ovarian cancer is inadequate and patients frequently present with advanced disease. Certain tumor lines including ovarian cancer express RAGE (Receptor for Advanced Glycated Endproducts). RAGE is also expressed by multiple cell types in the tumor environment including vascular cells and inflammatory cells. These observations from tumor biology suggest that targeting RAGE for imaging ovarian cancer would potentially be a good approach. We developed an anti-RAGE antibody against a unique peptide sequence on the V-domain of RAGE and have shown uptake of Tc-99m labeled murine antibody in vascular disease. We are currently developing a human anti-RAGE antibody. Methods Female nude mice (n=14) at 6 weeks of age were injected with 3x106 luciferase expressing human ovarian cancer cells into the right flank or peritoneal space. Six -7 weeks later, animals were injected with D-luciferin and imaged on optical imager. For nuclear probe imaging, mice were injected with 111In-anti-RAGE F(ab’)2 (n=7) or 111In-nonimmune IgG F(ab’)2 and 48 h later, were imaged on micro-SPECT/CT (Bioscan/Mediso). After in-vivo imaging, the tumors were explanted, ex-vivo images acquired, radioactivity counted, and sectioned for histological and immunohistochemical examination. Results There was good co-localization of the luciferase expressing tumor on the optical scan or tumor location at necropsy with the focal uptake of the 111In anti-RAGE F(ab’)2. Quantitative tracer uptake in the tumor from scan showed that uptake of 111In-anti-RAGE F(ab’)2 as %ID was 2.4 x higher than 111In-nonimmune IgG F(ab’)2 (P = 0.008) confirmed by gamma well counting. Dual immunofluorescent staining for RAGE and PAX8 (Ovarian specific antigen) in tumors showed high expression of RAGE and co-localization with PAX8 positive stained cells. Conclusions The results of this study in mice using a tracer that could go into humans supports further preclinical studies as development of this imaging probe for ovarian cancer.