Engineering of CAR-T cells that overcome MYC-dependent immunosuppression in a genetically engineered mouse model of pancreatic cancer
Hematology, Oncology, Transfusion Medicine (205-14); Gastroenterology, Metabolism (205-15)
Amplification or increased expression of the MYC proto-oncogene or one of its paralogues, MYCN and MYCL, is a hallmark of the majority of all human tumors and many tumors depend on elevated MYC expression throughout their lifetime. Recent evidence argues that a major reason for this dependency is the ability of MYC to enable tumor cells to escape immune surveillance. MYC compromises the T cell response through several mechanisms including (1) direct induction of the expression of the immune checkpoint programmed deathligand 1 on tumor cells, (2) suppression of a broad range of cytokines and (3) reduction of exosomal secretion of intron-derived dsRNA from tumor cells.
Genetically modified T cells expressing a chimeric antigen receptor (CAR) directed against tumor surface antigens are a promising concept for the treatment of cancer. However, the therapeutic efficiency of CAR-T cells is often compromised in the tumor niche. In this project, we will dissect how MYC-dependent tumorintrinsic factors impair the functionality of ROR1-directed CAR-T cells and we will explore T cell engineering strategies to render the adoptively transferred lymphocytes at least temporarily unresponsive to inhibitory factors coming from the tumor (microenvironment). To this end, we will study a mouse model of pancreatic carcinoma (PDAC) driven by a mutated KRAS oncogene and a mutated p53 gene. This model (LSL-KrasG12D/+;LSL- Trp53R172H/+;Pdx-1- Cre (“KPC”)) is poorly immunogenic and faithfully mimics the human disease. We have used several strategies to inducibly deplete or delete the endogenous MYC gene. These strategies lead to a slow-down of proliferation in culture, and to an immune cell-mediated tumor regression and greatly extended survival in vivo. Engineering strategies will include (1) the protection of CAR T cells from known factors of MYC-driven immunosuppression (PD-L1, TGF-β), (2) the augmentation of T cell susceptibility to microvesicular dsRNA and (3) the exploration of further beneficial T cell modifications as evaluable in functional CRISPR/Cas9 screens to define relevant gene products in T cells to overcome MYC-driven immunosuppression.
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