Abstract 2305: Tumor MUC1 glycoprotein-highly specific CAR T cells control triple-negative breast cancer

Abstract

Abstract Antibody-derived Chimeric Antigen Receptor (CAR) T cells have great success in reduction of liquid form of tumor, but not solid tumor. Our novel antibody TAB004 can specifically recognize the tumor form of MUC1 (tMUC1) while sparing the normal MUC1 in several subtypes of breast cancers including >95% of triple negative breast cancer (TNBC). In vivo delivery of TAB004 specifically accumulates in the xenograft TNBC tumor only. Therefore, we hypothesize that TNBC can be specifically targeted with TAB004-derived tMUC1-specific CAR T cells. A panel of 45 human breast cancer cell lines were tested for tMUC1 level, and 11 out of 13 TNBC cell lines showed higher frequency of tMUC1 expression compared to that on normal cells. We engineered a 2nd generation human CAR using TAB004 that was coupled to the CD28-CD3zeta, named as MUC28z CAR. MUC28z was well expressed on activated human T cells. Compared to their mock control, MUC28z CAR T cells retained higher CD25 and CD11c, particularly on CD8 T cells. The susceptibility of TNBC cells to MUC28z CAR T cell cytolysis was dramatic while still corresponding to their tMUC1 level. Only the tMUC1-specific MUC28z CAR T cells expressed and released large amount of IFN-gamma after antigen recognition on TNBC cells. However, IFN-gamma was only involved in the tumor killing by MUC28z CAR T cells at lower E:T ratio. The in vivo treatment of TNBC tumor by MUC28z CAR T cells dramatically controlled HCC70 TNBC tumor growth in a xenograft model. Taken together, our TAB004-derived MUC28z CAR T cells are very potent at killing TNBC tumor cells both in vitro and in vivo, which is very promising to provide a safe, effective and tumor antigen-specific novel immunotherapeutic intervention. Citation Format: Ru Zhou, Mahboubeh Yazdanifar, Lopamudra Das Roy, John Maher, Pinku Mukherjee. Tumor MUC1 glycoprotein-highly specific CAR T cells control triple-negative breast cancer [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 2305.