A Novel Dual NK Cell CAR Targeting CTLA-4 to Induce Regulatory T Cell Depletion in Head and Neck Cancer Microenvironment

Abstract

Head and neck cancer (HNC) is one of the most common cancers in the US affecting 66,470 people in 2022. Despite advances in chemotherapy, radiation therapy, and surgery, about 50% of patients still develop recurrent/metastatic disease (R/M) with a median survival of 12 months. The immune system plays a key role in the development of HNC. Epidermal growth factor receptor (EGFR) is overexpressed in approximately 80-90% of HNC cells. Subsequently, many studies use cetuximab, a known anti-EGFR antibody, to target HNC, but success has been limited. One of the major mechanisms of immune escape in solid tumors including HNC is via cytotoxic T lymphocyte-associated protein 4 (CTLA-4). Evidence has shown that intratumoral CD4+CD25+Foxp3+ regulatory T cells (Tregs) expressing CTLA-4 suppress NK cell cytotoxicity and contribute to the progression of HNC. With recent advances, immunotherapy has become a promising and potentially less toxic treatment option for HNC and other cancers. However, no studies have successfully eliminated the immunosuppressive Tregs associated with HNC. To address this major hurdle, my project aims to deplete Tregs in the HNC tumor microenvironment (TME) with a novel dual NK cell CAR against EGFR as the primary chimeric antigen receptor and secondary arming with single chain variable fragment (scFv) against CTLA-4. Our EGFR-targeting CAR was successfully expressed on both NK-92 and primary CIML NK cells and led to enhanced target cell killing in vitro. We also successfully transduced Jurkat cells with our designed CTLA-4-targeting CAR. Future efforts will focus on testing the cytotoxicity of CTLA-4-targeting CAR NK cells. We will then concentrate on constructing dual NK cell CAR and testing the functions of our dual CAR in pre-clinical models.