Disruption of TET2 promotes the therapeutic efficacy of CD19-targeted T cells

Abstract

Cancer immunotherapy based on genetically redirecting T cells has been used successfully to treat B cell malignancies. In this strategy, the T cell genome is modified by integration of viral vectors or transposons encoding chimaeric antigen receptors (CARs) that direct tumour cell killing. However, this approach is often limited by the extent of expansion and persistence of CAR T cells. Here we report mechanistic insights from studies of a patient with chronic lymphocytic leukaemia treated with CAR T cells targeting the CD19 protein. Following infusion of CAR T cells, anti-tumour activity was evident in the peripheral blood, lymph nodes and bone marrow; this activity was accompanied by complete remission. Unexpectedly, at the peak of the response, 94% of CAR T cells originated from a single clone in which lentiviral vector-mediated insertion of the CAR transgene disrupted the methylcytosine dioxygenase TET2 gene. Further analysis revealed a hypomorphic mutation in this patient's second TET2 allele. TET2-disrupted CAR T cells exhibited an epigenetic profile consistent with altered T cell differentiation and, at the peak of expansion, displayed a central memory phenotype. Experimental knockdown of TET2 recapitulated the potency-enhancing effect of TET2 dysfunction in this patient's CAR T cells. These findings suggest that the progeny of a single CAR T cell induced leukaemia remission and that TET2 modification may be useful for improving immunotherapies.

T-cells “à la CAR-T(e)” – Genetically engineering T-cell response against cancer

“…Indeed, these approaches were demonstrated to reliably knock down the expression of PD1 and other checkpoint inhibitors or key signaling molecules [280][281][282][283] and further optimization has been performed to delineate proper conditions for CRISPR editing in primary T cells [284] showing the successful silencing of several checkpoint targets. Unexpectedly, Fraietta et al recently showed that in the case of a CLL patient that achieved complete remission when treated with anti-CD19 CAR T-cells, the insertion of the CAR transgene caused a disruption in the methylcytosine dioxygenase TET2 gene [285]. Further investigation revealed that TET2 deficient cells from clonal origin constituted at the peak of the response, 94% of the CAR T cells in the patient and displayed a central memory phenotype.…”

Chimeric antigen receptor T cell persistence and memory cell formation

“…16,64 In particular, a recent study found that in one CLL patient in remission, CAR T cells had preferentially expanded from a single clone that harbored one allele with an inborn loss of tet2 function, while the second allele had been mutated by the transgene insertion. 64 The conclusion being that tet2 mutations not only conferred a cell division survival advantage, but also enabled potent anti-tumor activity. 64 T cell suppression by tet2 may be explained by a loss of DNA methylation at the PD-1 promotor region.…”

“…64 The conclusion being that tet2 mutations not only conferred a cell division survival advantage, but also enabled potent anti-tumor activity. 64 T cell suppression by tet2 may be explained by a loss of DNA methylation at the PD-1 promotor region. 15 In contrast to the key role of TET2 in demethylation, DNMT3a is a DNA methylase.…”

Evolution of chimeric antigen receptor (CAR) T cell therapy: current status and future perspectives

“…Alternatively, many patients could be treated with a CAR-T product produced in a single batch by significantly reducing the number of CAR-T cells required from its current clinical dose (10 6 -10 8 cells/kg). Interestingly, it has been recently reported that CAR-T cells derived from a single clone in which the CAR gene was accidentally inserted at the TET2 (tet methylcytosine dioxygenase) gene locus underwent rapid proliferation and induced complete remission in a CLL patient (Fraietta et al 2018b). Because TET2 encodes a known tumor-suppressor protein, the patient should be monitored for signs of insertional oncogenesis.…”