2518 Background: Cytokine induced killer cells (CIKs) are ex-vivo activated and expanded CD8+ natural killer T cells that have been shown to have cytotoxic activity against cancers in randomized clinical trials. This preclinical study demonstrates the enhanced effect of CIK killing in primary ovarian carcinoma using bispecific antibodies (BSAbs) and the potential of translating our findings to a clinical trial. Methods: Primary ovarian cancer cells and autologous CIKs were collected and cultured under IRB approval. Cytotoxicity enhancing BSAbs against CA125 (BSAbxCA125) and Her2/neu (BSAbxHer2) were designed using chemical conjugation methods. Tumor cell lysis of ovarian primary ovarian cancer cells was quantified using 51Cr release assays. Anti-NKG2D monoclonal antibodies were used in antibody blocking assays. Using a SCID mouse model of minimal residual disease, tumor progression was monitored using the bioluminescence imaging (BLI) system. Three-color immunofluorescence analysis was performed on pathologic specimens to localize CIK migration to tumor cells. Results: The mean percent lysis with an Effector:Target (E:T) ratio at 100:1 was 22.2% (±2.0) in primary cells in 4-hour killing assays. Redirection with BSAbxCA125 significantly enhanced cytolysis to 65.7% (±0.6). Adding BSAbxHer2 significantly enhanced cytolysis of cell lines to 89.4% (±1.3). Anti-NKG2D antibodies significantly attenuated the CIK activity by 54%. In vivo BLI studies in SCID mice showed that CIK treatment at a 10:1 E:T ratio was well-tolerated and effective in reducing tumor burden by 80% after 21 days post-treatment compared to untreated mice (p<0.0001). Immunofluorescence staining clearly depicted the in vivo infiltration of CIK (CD8+NKG2D+) cells into Her2-expressing tumor targets. Conclusions: Bispecific antibodies effectively enhanced the cytotoxicity of autologous CIK cells against fresh ovarian tumors. Our in vivo studies suggest that CIK cells may ultimately prove to be efficacious immunotheraputic modality in the treatment of resistant ovarian cancer. No significant financial relationships to disclose.
42. Resistance of Primary Ovarian Cancer Cells to Viral Oncolysis
