Triple-negative breast cancer (TNBC), representing ~15% of globally diagnosed breast cancer, is typically an incurable malignancy due to the lack of targetable surface targets for development of effective therapy. To address the unmet need for TNBC treatment, we recently determined that tissue factor (TF) is a useful surface target in 50-85% of patients with TNBC and developed a secondgeneration TF-targeting antibody-like immunoconjugate (called L-ICON) for preclinical treatment of TNBC. Using the chimeric antigen receptor (CAR) approach, here we develop and test TF-targeting CARengineered natural killer (TF-CAR-NK) cells that co-express CD16, the Fc receptor (FcγIII) to mediate antibody-dependent cellular toxicity (ADCC), for a preclinical assessment of immunotherapy of TNBC using TF-CAR-NK cell as single agent therapy and in combination with L-ICON. Our preclinical results demonstrate that TF-CAR-NK cells alone could kill TNBC cells and its efficacy was enhanced with L-ICON ADCC in vitro. Moreover, TF-CAR-NK cells were effective in vivo for the treatment of tnBc in cell lineand patient's tumor-derived xenograft mouse models. Thus, this study established the proof of concept of targeting TF as a new target in CAR-NK immunotherapy for effective treatment of TNBC and may warrant further preclinical study and potentially future investigation in TNBC patients.The adoptive transfer of chimeric antigen receptor (CAR)-expressing T and natural killer (NK) cells represents a novel cancer immunotherapy approach. The concept of the CAR is based upon the idea of expressing novel receptors on the T or NK cell surface that would enable the T and NK cell to identify corresponding antigens on the surface of a target cell. The basic CAR construct consists of an extracellular antigen-recognition domain, usually single-chain antibody variable fragments (scFv), attached to an extracellular spacer domain, a transmembrane domain of CD28 and a signaling cytoplasmic domain such as 4-1BB (CD137), OX40 (CD134), DAP10, ICOS and CD3zeta chain (CD3ζ). The most advanced application is the use of CAR-T cells targeting CD19, a surface antigen on B cell malignancies, which has demonstrated antitumor efficacy in patients with these cancers 1 . However, early-phase clinical trials of CAR T therapy also showed that this treatment is frequently associated with side effects 1 , some even causing life-threatening toxicity 2 , partly due to the fact that current CAR targets are expressed by both the malignant cells and normal cells, such as CD19, which is also expressed by normal B cells throughout the B cell lineage 1 . Also, one of the major challenges in CAR therapy is the heterogeneity of tumor antigens, for instance, antigen loss or low antigen density on the cancer cells 3 . To overcome these challenges, it would be ideal to develop CAR T or CAR NK cells that could target a surface molecule that is commonly yet selectively expressed by several major tumor compartments, including but not limited to, the cancer cell, cancer stem cell (CSC) and tum...