Mathias Zech

CD8 T Cell Tolerance to a Tumor-Associated Self-Antigen Is Reversed by CD4 T Cells Engineered To Express the Same T Cell Receptor

Ag receptors used for cancer immunotherapy are often directed against tumor-associated Ags also expressed in normal tissues. Targeting of such Ags can result in unwanted autoimmune attack of normal tissues or induction of tolerance in therapeutic T cells. We used a murine model to study the phenotype and function of T cells redirected against the murine double minute protein 2 (MDM2), a tumor-associated Ag that shows low expression in many normal tissues. Transfer of MDM2-TCR–engineered T cells into bone marrow chimeric mice revealed that Ag recognition in hematopoietic tissues maintained T cell function, whereas presentation of MDM2 in nonhematopoietic tissues caused reduced effector function. TCR-engineered CD8+ T cells underwent rapid turnover, downmodulated CD8 expression, and lost cytotoxic function. We found that MDM2-TCR–engineered CD4+ T cells provided help and restored cytotoxic function of CD8+ T cells bearing the same TCR. Although the introduction of the CD8 coreceptor enhanced the ability of CD4+ T cells to recognize MDM2 in vitro, the improved self-antigen recognition abolished their ability to provide helper function in vivo. The data indicate that the same class I–restricted TCR responsible for Ag recognition and tolerance induction in CD8+ T cells can, in the absence of the CD8 coreceptor, elicit CD4 T cell help and partially reverse tolerance. Thus MHC class I–restricted CD4+ T cells may enhance the efficacy of therapeutic TCR-engineered CD8+ T cells and can be readily generated with the same TCR.

Genetic Regulation of Fate Decisions in Therapeutic T Cells to Enhance Tumor Protection and Memory Formation.

A key challenge in the field of T-cell immunotherapy for cancer is creating a suitable platform for promoting differentiation of effector cells while at the same time enabling self-renewal needed for long-term memory. Although transfer of less differentiated memory T cells increases efficacy through greater expansion and persistence in vivo, the capacity of such cells to sustain effector functions within immunosuppressive tumor microenvironments may still be limiting. We have therefore directly compared the impact of effector versus memory differentiation of therapeutic T cells in tumor-bearing mice by introducing molecular switches that regulate cell fate decisions via mTOR. Ectopic expression of RAS homolog enriched in brain (RHEB) increased mTORC1 signaling, promoted a switch to aerobic glycolysis, and increased expansion of effector T cells. By rapidly infiltrating tumors, RHEB-transduced T cells significantly reduced the emergence of immunoedited escape variants. In contrast, expression of proline-rich Akt substrate of 40 kDa (PRAS40) inhibited mTORC1, promoted quiescence, and blocked tumor infiltration. Fate mapping studies following transient expression of PRAS40 demonstrated that mTORC1(low) T cells made no contribution to initial tumor control but instead survived to become memory cells proficient in generating recall immunity. Our data support the design of translational strategies for generating heterogeneous T-cell immunity against cancer, with the appropriate balance between promoting effector differentiation and self-renewal. Unlike pharmacologic inhibitors, the genetic approach described here allows for upregulation as well as inhibition of the mTORC1 pathway and is highly selective for the therapeutic T cells without affecting systemic mTORC1 functions.

Redirection to the bone marrow improves T cell persistence and antitumor functions

A key predictor for the success of gene-modified T cell therapies for cancer is the persistence of transferred cells in the patient. The propensity of less differentiated memory T cells to expand and survive efficiently has therefore made them attractive candidates for clinical application. We hypothesized that redirecting T cells to specialized niches in the BM that support memory differentiation would confer increased therapeutic efficacy. We show that overexpression of chemokine receptor CXCR4 in CD8+ T cells (TCXCR4) enhanced their migration toward vascular-associated CXCL12+ cells in the BM and increased their local engraftment. Increased access of TCXCR4 to the BM microenvironment induced IL-15–dependent homeostatic expansion and promoted the differentiation of memory precursor–like cells with low expression of programmed death-1, resistance to apoptosis, and a heightened capacity to generate polyfunctional cytokine-producing effector cells. Following transfer to lymphoma-bearing mice, TCXCR4 showed a greater capacity for effector expansion and better tumor protection, the latter being independent of changes in trafficking to the tumor bed or local out-competition of regulatory T cells. Thus, redirected homing of T cells to the BM confers increased memory differentiation and antitumor immunity, suggesting an innovative solution to increase the persistence and functions of therapeutic T cells.

Targeting therapeutic T cells to the bone-marrow niche

Abstract Background Immunotherapy has demonstrated exciting curative potential in the treatment of lymphoid malignancies, but cancer cells have developed a variety of immune evasion mechanisms requiring targeted strategies. CXCR4 is a G-protein coupled receptor with crucial roles in homing, maintenance, and proliferation of a wide range of haematological cancers. We hypothesised that overexpression of CXCR4 in CD8 T cells (T-CXCR4) would improve homing to CXCL12-rich niches such as bone marrow, enhancing tumour killing. Methods We transduced murine CD8 T cells with a retroviral vector encoding either the Cxcr4 gene coupled to a GFP marker or a separate inducible vector encoding Cxcr4 and GFP under control of the Tet-On system. For allogeneic bone-marrow transplants, irradiated BALB/c recipient mice received intravenous B6 donor bone marrow and subcutaneous A20 lymphoma cells on day 0, and B6 T-CXCR4 or control T cells on day 2. For in-vivo imaging of T-cell accumulation, anaesthetised mice received luciferase-positive transduced T cells and luciferin. Transgenic OT-1 CD8 T cells expressing T-cell receptors specific for the SIINFEKL peptide were used in vaccination experiments. Findings In an allogeneic B-cell lymphoma model, T-CXCR4 were significantly better than control T cells at tumour control (p Interpretation Coupled with gene expression data, these results suggest that heightened antitumour efficacy is mediated by successful homing and competition for cell-extrinsic niche-related factors, in particular interleukin 15 presentation by CXCL12-abundant reticular cells. Preferential generation of enhanced early memory T cells with therapeutic superiority to effector-type cells currently used in investigational protocols has great relevance for the design of next-generation immunotherapies. Funding Bloodwise.

Expression of a dominant T cell receptor can reduce toxicity and enhance tumor protection of allogeneic T cell therapy

Due to the lack of specificity for tumor antigens, allogeneic T-cell therapy is associated with graft-versus-host disease. Enhancing the anti-tumor specificity while reducing the graft-versus-host disease risk of allogeneic T cells has remained a research focus. In this study, we demonstrate that the introduction of ‘dominant’ T-cell receptors into primary murine T cells can suppress the expression of endogenous T-cell receptors in a large proportion of the gene-modified T cells. Adoptive transfer of allogeneic T cells expressing a ‘dominant’ T-cell receptor significantly reduced the graft-versus-host toxicity in recipient mice. Using two bone marrow transplant models, enhanced anti-tumor activity was observed in the presence of reduced graft-versus-host disease. However, although transfer of T-cell receptor gene-modified allogeneic T cells resulted in the elimination of antigen-positive tumor cells and improved the survival of treated mice, it was associated with accumulation of T cells expressing endogenous T-cell receptors and the development of delayed graft-versus-host disease. The in vivo deletion of the engineered T cells, mediated by endogenous mouse mammary tumor virus MTV8 and MTV9, abolished graft-versus-host disease while retaining significant anti-tumor activity of adoptively transferred T cells. Together, this study shows that the in vitro selection of allogeneic T cells expressing high levels of a ‘dominant’ T-cell receptor can lower acute graft-versus-host disease and enhance anti-tumor activity of adoptive cell therapy, while the in vivo outgrowth of T cells expressing endogenous T-cell receptors remains a risk factor for the delayed onset of graft-versus-host disease.

T Cell Tuning for Tumour Therapy: Enhancing Effector Function and Memory Potential of Therapeutic T cells

The genetic engineering of T cells can lead to enhanced immune-mediated tumour destruction and harbors a great potential for the treatment of cancer. Recent efforts have centered on the design of receptors to re-direct the specificity of T cells towards tumour antigens by means of viral gene transfer. This strategy has shown great success in a number of phase one clinical trials. However, there are still challenges to overcome. On the one hand, T cell function can be further improved to optimize the therapeutic outcome. On the other hand, so called safety switches are required to deal with possible on and off target toxicities. In this review, we will give a brief summary of the success and risks of T cell gene therapy before discussing in detail current strategies to enhance effector function, persistence and safety of adoptively transferred T cells.