Abstract 4708: A novel anti-MUC1 CAR T cell drives immunity to pancreatic cancer
Authors: Yazdanifar Mahboubeh , Zhou Ru , Wu Shu-ta , Grover Priyanka , Mukherjee Pinku 
Published: July 2017

Background: Pancreatic cancer is the 4th leading cause of cancer deaths in the US with very poor prognosis. Treatment options are limited to surgery and chemo/radiation that often times do not increase survival and are associated with high toxicity. Targeted immune-based therapies have shown some promise but needs further exploration. Mucin 1 (MUC1), a glycoprotein expressed on the apical surface of epithelial cells of most epithelial organs, undergoes hypoglycozylation in tumors. This tumor-form of MUC1 (tMUC1) is over-expressed in 80% of pancreatic ductal adenocarcinomas (PDAC). tMUC1 therefore remains a promising target for therapeutic intervention. We have developed a patented antibody (TAB004) which specifically detects tMUC1 and spares normal MUC1. Using a novel technology, functional fragments of TAB004 antibody (scFv) were incorporated into the chimeric antigen receptor (CAR) construct and used to genetically modify primary human T cells. ScFv domain which recognizes tMUC1 is linked to the co-stimulatory molecules of T cells (CD28 and CD3ζ). When the engineered T cells come in contact with tMUC1 expressing tumor cells, multiple T cell signaling pathways are initiated leading to fully activated cytotoxic T cells that lyse the tumor cells.

Methods: Retroviral based technique was used to deliver the CAR gene into human PBMC derived primary T cells. A fluorescent tag (mKate) was fused to the C-terminus of CAR molecules, in order to visualize CAR expression on T cell membrane by fluorescent microscopy and potentially for in vivo tracking. Cytotoxicity was evaluated using co-culture method with varying T cell to target cell ratios followed by MTT assay. Intracellular IFNγ was measured by flow cytometry.

Results: tMUC1-CAR-T cells show increased activation and proliferation compared to normal T cells. These cells bind strongly to tMUC1 expressing human pancreatic cancer cells forming immunologic synapse. Minimal binding of the tMUC1-CAR T cells was observed to normal or low MUC1 expressing tumors cells suggesting high specificity of these CAR T cells to tMUC1. CAR expression was distributed evenly on the cell surface of the T cells. Engineered tMUC1-CAR T cells exhibit robust cytotoxicity against a panel of PDA cell lines, associated with high IFNγ release. Fortunately, the same CAR T cells display minimum toxicity against normal epithelial cells. CAR T cell function will be evaluated in the preclinical mouse model of PDA, as single treatment and also in combination with checkpoint inhibitors and chemotherapy drugs.

Conclusion: Despite the remarkable successes reported using CAR T cells in clinic, particularly CD19 CAR T for leukemia; some adverse effects have been attributed to this treatment. This highlights the urgent need for developing tumor-specific CAR T cells. This study demonstrates the specificity and effectiveness of tMUC1-CAR T cells against pancreatic cancer cells. Thus, tMUC1 CAR T cells have the potential to be further developed for future clinical use.

Citation Format: Mahboubeh Yazdanifar, Ru Zhou, Shu-ta Wu, Priyanka Grover, Pinku Mukherjee. A novel anti-MUC1 CAR T cell drives immunity to pancreatic cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 4708. doi:10.1158/1538-7445.AM2017-4708