Immunotherapy of Primary Ovarian Cancer Using Autologous Cytokine Induced Killer Cells Retargeted with Bispecific Antibodies: A Preclinical Study.

Cytokine induced killer (CIK) cells are ex-vivo activated and expanded CD8+ natural killer T cells that have been shown to have anti-tumor activity. This is the first study exploring cell killing of primary ovarian carcinoma with and without bispecific antibodies (BSAbs). Primary cancer cells and autologous CIK cells were collected from women with epithelial ovarian cancer. BSAbs against CA125 (BSAbxCA125) and Her2 (BSAbxHer2) were developed using chemical heteroconjugation. On FACS analysis, the expansion and stimulation of CIK cells resulted in a significant increase of CD3⁺CD8⁺ and CD3⁺CD56⁺ T cells. With enhancement by BSAbs, the mean percent lysis in a ⁵¹Cr release assay of fresh ovarian cancer cells exposed to autologous CIK cells increased from 22% (±0.3) to 89% (±2.1) at an effector to target ratio (E:T) of 100:1. Anti-NKG2D antibodies significantly attenuated the CIK activity by 57% on primary cells. In a xenograft SCID mouse model, real-time tumor regression and progression was visualized using a non-invasive in vivo bioluminescence imaging system. Four hours after CIK cell injection, we were able to visualize CD8⁺NKG2D⁺ CIK cells infiltrating Her2-expressing cancer cells on fluorescence microscopy. Mice that underwent adoptive transfer of CIK cells redirected with BSAbxCA125 (p=0.0002) and BSAbxHer2 (p=0.0002) had a significant reduction in tumor burden and improvement in survival versus those treated with CIK cells alone (p=0.03). BSAbs significantly enhanced the cytotoxicity of CIK cells in primary ovarian cancer cells and in our in vivo mouse model. The mechanism of cytolysis appears to be mediated in part by the NKG2D receptor.