Hinrich Abken - assoc. RG

The spectacular success of chimeric antigen receptor (CAR) T cells in treating hematologic malignancies opens new ways in cancer therapy; the impact of metabolic reprogramming within the tumor tissue on the T cell anti-tumor response remains unclear. We address how metabolic reprogramming alters T cell physiology, persistence and anti-tumor response and whether this can be used to improve the T cell response towards an enduring control of malignant diseases.

Introduction 

Adoptive cell therapy with the transfer of genetically redirected autologous T cells has shown spectacular success in the treatment of hematologic malignancies and some solid tumors. Genetic engineering with a chimeric antigen receptor (CAR) is commonly used for redirecting T cells towards defined target. As a recombinant, composite membrane receptor the CAR recognizes a surface antigen on the targeted cancer cell by an antibody-derived extracellular domain and activates by a T cell receptor (TCR) derived intracellular signalling domain. A major advantage of the CAR T cell therapy is the applicability to a wide range of patients, based on the antibody mediated, MHC-independent recognition of antigen, to a wide range of malignancies due to targeting various tumor-associated antigens, and the orchestrated T cell activation based on signalling through the combination of signalling moieties. Of note, the modular CAR design recapitulates many aspects of the natural T cell signalling machinery and redirects the T cell response in a defined fashion.

Antigen receptor-redirected T cells derived from hematopoietic precursor cells lack expression of the endogenous TCR/CD3 receptor and exhibit specific anti-tumor capacities.

Currently, adoptive T cell therapy is derived from autologous peripheral blood T cells; T cells derived from healthy allogeneic donors may have advantages, however, the expected occurrence of graft versus host disease as a consequence of the diverse allogeneic T cell receptor (TCR) repertoire expressed by these cells seriously compromises the approach. We generated T cells from cord blood hematopoietic progenitor cells that were transduced to express either a CAR or a TCR with or without built-in costimulatory sequence. Transgenic precursor cells were in vitro differentiated to CD5+ CD7+ positive T lineage precursors, to CD4+ CD8+ double positive cells and finally to mature AR+ T cells on an OP9-DL1 feeder layer. The receptor expressing T cells were largely of naive CD45RA+CD62L+ phenotype and lack CD3 indicating that rearrangements of the endogenous TCR locus were blocked. However, the cells were functional as they displayed specific cytotoxic activity and cytokine release. Data sustain the concept that cord blood derived, in vitro generated CD3- CAR T cells can be used to more effectively eliminate tumor leukemic cells while at the same time limiting the occurrence of graft versus host disease.
Van Caeneghem et al., OncoImmunol. (2017)

CD4+CD25- T cells, but not CD4+CD25+ Treg cells, are cytolytic when redirected by a CAR.

Evidences are accumulating that CD4+ T cells can physiologically mediate antigen specific target cell lysis. By circumventing MHC restriction through an engineered CAR CD4+ T cells lyse defined target cells as efficiently as do CD8+ T cells. For activation, Treg cells require a strong CD28 signal together with CD3ζ inducing a distinct cytokine pattern with high IL-10 and lack of IL-2 release. Despite strong and antigen-specific activation, CAR Treg cells produced only weak target cell lysis whereas CD4+CD25- CAR T cells were potent killers. Cytolysis did not correlate with the target cell sensitivity to Fas/FasL mediated killing; CD4+CD25- T cells upregulated perforin and granzyme B upon CAR activation whereas Treg cells did less. The analysis clearly indicates different cytolytic capacities of CAR redirected conventional CD4+ cells and Treg cells which warrants further evaluation.
Hombach et al., Cancers (2017)

Chimeric antigen receptor-redirected regulatory T cells suppress experimental allergic airway inflammation, a model of asthma.

We explored a regulatory T (Treg) cell-based therapy in the treatment of allergic inflammation using a model for asthma characterized by a chronic, Th2 cell dominated immune response to allergen. We redirected Tregs by a CAR towards lung epithelia in mice upon experimentally induced allergic asthma, closely mimicking the clinical situation. Adoptively transferred CAR Tregs accumulated in the lung and in regional lymph nodes, reduced hyper-reactivity and diminished inflammation, prevented excessive pulmonary mucus production and increase in IgE and Th2 cytokine serum levels. CAR Tregs were more efficient in controlling asthma than non-modified Tregs, paving the way for CAR Treg cell therapy of severe allergic asthma.
Skuljec et al., Frontiers Immunol. (2017)

IL-18 induces T-bet(high) FoxO1(low) T cells with a distinct signature for the CAR therapy of advanced solid tumors.

We explored to sustain acute inflammation while preventing exhaustion by modulating the metabolic and signaling signature of effector T cells. A systematic screen identified IL-18 as a pro-inflammatory response modifier converting CAR T cells towards T-bet(high) FoxO1(low) effector cells resisting exhaustion. CAR T cells with inducible IL-18 release showed a distinct cytokine and functional signature superior in the activity against large established tumors. IL-18 CAR T cell treatment was accompanied by an overall change in the tumor immune cell landscape. 

T cells engineered with a TCR and transgenic inducible IL-12 and IL-18, respectively, produced enhanced levels of IFN-γ. Adoptive transfer of T cells with a melanoma specific TCR and inducible IL-12 to melanoma-bearing mice resulted in severe, edema-like toxicity that was accompanied by enhanced inflammation and infiltration of macrophages into the tumor. In contrast, transfer of  IL-18 producing TCR T cells were safe and significantly reduced tumor burden, prolonged overall survival. Data imply “IL18 TRUCKs” for eradicating large solid tumor lesions in an advanced stage of the disease.
Chmielewski et al., Cell Reports (2017)
Kunert et al., OncoImmunol (2018)

T cells with CD28-ζ CAR resist TGF-β repression through IL-2 signaling.

We revealed that T cells with a CD28 CAR, but not with a 4-1BB CAR, resist TGF-β repression due to LCK activation and autocrine IL-2 receptor signaling. Deleting the LCK binding motif in the CD28 CAR abolished both IL-2 secretion and TGF-β resistance. Other γ-cytokines like IL-7 and IL-15 could replace IL-2 in this context resulting in resistant T cells engineered with IL-2 deficient CD28 CAR and a hybrid IL-7 receptor to provide IL-2R β-chain signaling upon IL-7 binding. Data draw the concept that an autocrine loop resulting in IL-2R signaling can make CAR T cells more potent in staying active against TGF-β+ solid tumors.
Golumba-Nagy et al., Mol. Ther. (2018)

Van Caeneghem et al., Antigen receptor-redirected T cells derived from hematopoietic precursor cells lack expression of the endogenous TCR/CD3 receptor and exhibit specific anti-tumor capacities. OncoImmunol., 19, 6(3):e1283460 (2017)

Hombach, A.A., Abken, H., Some do, but some do not: CD4+CD25- T cells, but not CD4+CD25+ Treg cells, are cytolytic when redirected by a chimeric antigen receptor (CAR). Cancers 9, 112 (2017)

Skuljec et al., Chimeric antigen receptor-redirected regulatory T cells suppress experimental allergic airway inflammation, a model of asthma. Frontiers Immunol. 8, 1125 (2017)

Skuljec et al., Chimeric antigen receptor-redirected regulatory T cells suppress experimental allergic airway inflammation, a model of asthma. Frontiers Immunol. 8, 1125 (2017) 

Chmielewski et al., CAR T cells releasing IL-18 convert to T-bethigh FoxO1low effectors which exhibit augmented activity against advanced solid tumors. Cell Reports 12, 3205 – 3219 (2017)

Kunert et al., Intra-tumoral production of IL18, but not IL12, by TCR-engineered T cells is non-toxic and counteracts immune evasion of solid tumors. Oncoimmunol. 7, e1378842 (2018)

Golumba-Nagy et al., T cells with CD28-ζ CAR resist TGF-β repression through IL-2 signaling which can be mimicked by an engineered IL-7/IL-2Rβ autocrine loop. Mol. Ther., in press