Multiple Myeloma (MM) is characterized by the clonal expansion of malignant plasma cells in the bone marrow, and is the second most common hematological cancer. Cellular therapies including chimeric antigen T receptor cell (CAR-T) have emerged as a promising therapeutic strategy to combat this devastating disease. MM are derived from a rare population of cancer stem cells (CSC) that are responsible for initiation, progression, resistance to conventional therapy and recurrence. To date there have been no CAR-T therapies directed at CSC-specific antigens. In this report, we describe the effects of a novel CAR-T targeting the CSC marker DCLK1 on MM cells. Using mouse models, it has been demonstrated that DCLK1 marks the cell of origin of colon and pancreatic cancers. DCLK1 regulates epithelial to mesenchymal transition (EMT), and its upregulation is associated with poor overall survival in many cancer subtypes. Inhibition of DCLK1 activity following RNA silencing resulted in tumor xenograft growth arrest. These features lead us to explore the therapeutic potential of targeting DCLK1+ cells in MM. In order to create a novel DCLK1 CAR, we generated a new humanized DCLK1 monoclonal antibody, clone CBT-15 #8. This antibody recognizes a small extra cellular C-terminal epitope on human isoform 2 and 4 of DCLK1. Novel DCLK1 CAR-T cells containing the clone were generated and detected with anti-human FAB antibody by flow cytometry. Furthermore, we observed cell surface expression of DCLK1 on >93 percent of MM Cells (RPMI8226) by flow cytometry. The CAR-T cells had significantly higher cytotoxicity in MM (RPMI8226 and MM1S) cells than in leukemia K562 cells. The CAR-T cells secreted significantly higher levels of IFN-γ in vitro than T cells (p=0.0036). Further studies are underway to determine its efficacy in inhibiting tumor xenografts in vivo. This report is the first to link the TSC marker DCLK1 to MM and may represent a novel therapeutic strategy for MM and other hematologic malignancies.

Citation Format: Sripathi M. Sureban, Robert Berahovich, Hua Zhou, Shirley Xu, Lijun Wu, Vita Golubovskaya, Dongfeng Qu, Randal May, Edwin Bannerman-Menson, Courtney W. Houchen. DCLK1 monoclonal antibody-based CAR-T cells as novel treatment strategy against multiple myeloma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 1154.