In addition to primary natural killer (NK) cells, continuously growing cytotoxic cell lines such as NK-92 are being considered for adoptive cancer immunotherapy. High cytotoxicity of NK-92 has been shown against malignant cells of hematologic origin in preclinical studies, and general safety of infusion of NK-92 cells has been established in phase I clinical trials. To enhance their therapeutic utility, we genetically modified NK-92 cells to express chimeric antigen receptors (CAR) specific for different tumor-associated surface antigens including ErbB2 (HER2). Such CAR were composed of a tumor-specific scFv antibody fragment fused via hinge and transmembrane domains to intracellular signaling proteins such as CD3 zeta chain or a composite CD28-CD3 zeta fusion molecule.

Glioblastoma multiforme (GBM) is the most common and severe intracranial malignant tumor in humans. Despite aggressive therapy, recurrence of GBM is very frequent, and the median survival of GBM patients is only 12 to 15 months. Since enhanced ErbB2 expression was found in up to 80% of GBM cases, adoptive ErbB2-targeted immunotherapy may represent a more efficient alternative to standard therapy. For development towards clinical applications, here we generated a lentiviral second generation CAR construct (5.28.z) specific for the ErbB2 antigen, and established GMP-compliant protocols for transduction and expansion of NK-92 cells. An ErbB2-specific single cell clone (NK-92/5.28.z) was isolated, which showed high and selective cytotoxicity towards different established ErbB2-expressing glioblastoma cells and tumor cells of various other origins in vitro, as well as specific tumor homing in murine in vivo models. Treatment with NK-92/5.28.z cells also resulted in marked inhibition of the growth of subcutaneous glioblastoma xenografts in NOD/SCID γc KO mice. Ongoing work now focuses on evaluating the feasibility and efficacy of intracranial application of NK-92/5.28.z cells in orthotopic xenograft models of ErbB2-positive glioblastoma cells as a basis for further development of these cells as an adoptive immunotherapy for glioblastoma patients.

Citation Format: Concong Zhang, Kurt Schönfeld, Michael Burger, Sabrina Genßler, Christiane Sahm, Christian Brendel, Sonja Naundorf, Marcus Odendahl, Ulrike Köhl, Torsten Tonn, Manuel Grez, Joachim P. Steinbach, Winfried S. Wels. ErbB2/HER2-specific natural killer cells for adoptive immunotherapy of glioblastoma. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 3967. doi:10.1158/1538-7445.AM2013-3967