Abstract B50: Tissue factor-targeting CAR-NK cells for immunotherapy of triple-negative breast cancer

The objective of the study is to develop tissue factor (TF)-targeted chimeric antigen receptor-natural killer (TF-CAR-NK) cell immunotherapy for the treatment of triple-negative breast cancer (TNBC). TNBC represents nearly 15% of globally diagnosed breast cancer, which is also the most frequently diagnosed cancer in women in the United States. Due to the lack of validated therapeutic target molecules, TNBC is one of the most difficult-to-treat malignancies, and, in most cases, is considered an incurable malignancy. CAR-expressing NK and T-cell therapy represents a novel cancer immunotherapy approach. To address the unmet issue, we first identified that TF is a novel, common, yet selective membrane-bound surface protein receptor and oncotarget for TNBC on the TNBC cancer cells, tumor neovascular endothelial cells and cancer stem cells. It is worth noting that under physiologic conditions, TF is not expressed on normal peripheral lymphocytes such as NK, B, T cells and monocytes, nor on the cells (quiescent vascular endothelial cells) forming the inner layer of normal vasculature, but is solely restricted on some cells (such as pericytes and smooth muscle cells) that are located outside the blood circulation and inner layer of blood vessel walls. Then we developed and tested a novel TF-targeting CAR-NK cell line (NK92MI, a human NK line derived from NK92 after being transfected for endogenous production of interleukin-2) expressing factor VII light chain, natural ligand for TF, as TF-targeting domain followed by CD28-4-1BB-CD3zeta with or without a hinge region of human IgG1 as TF-CAR1 dimer or monomer for CAR-NK immunotherapy of TNBC. Our preclinical results demonstrate that both the TF-CAR1 dimer and monomer-NK cells can kill TNBC cells in vitro and are effective and safe for the treatment of TNBC in mouse models of TNBC cell line-derived and patient’s tumor-derived xenografts (CDX and PDX). Thus, this study established the proof of concept of targeting TF for CAR-NK immunotherapy of TNBC and may warrant further investigation for TNBC patients. Accumulating evidence suggested that TF is selectively expressed in pathologic angiogenesis-dependent as well as macrophage-associated human diseases. Pathologic angiogenesis, the formation of neovasculature, is involved in many clinically significant human diseases, notably cancer (including solid cancer, acute leukemia and sarcoma), age-related macular degeneration, endometriosis and rheumatoid arthritis, whereas macrophage is involved in the progression of a variety of human diseases, such as atherosclerosis and viral infections (HIV and Ebola). If successful, TF-CAR immunotherapy may have potential to treat a broad range of angiogenesis-dependent or macrophage-associated human diseases. Acknowledgments: This work was supported by the Dr. Ralph and Marian Falk Medical Research Trust Awards Programs and partly by an NCI grant (R21CA216697). Z.H. is the inventor of PCT/U.S. Pending Patents on “Tissue Factor-Targeting CAR-NK and CAR-T Cell Therapy.” Citation Format: Zhiwei Hu. Tissue factor-targeting CAR-NK cells for immunotherapy of triple-negative breast cancer [abstract]. In: Proceedings of the AACR Special Conference on Tumor Immunology and Immunotherapy; 2018 Nov 27-30; Miami Beach, FL. Philadelphia (PA): AACR; Cancer Immunol Res 2020;8(4 Suppl):Abstract nr B50.