A study of T cell tolerance to the tumor-associated antigen MDM2: cytokines can restore antigen responsiveness, but not high avidity T cell function

Targeting MDM2 in malignancies is a promising strategy for overcoming resistance to anticancer immunotherapy

MDM2 has been established as a biomarker indicating poor prognosis for individuals undergoing immune checkpoint inhibitor (ICI) treatment for different malignancies by various pancancer studies. Specifically, patients who have MDM2 amplification are vulnerable to the development of hyperprogressive disease (HPD) following anticancer immunotherapy, resulting in marked deleterious effects on survival rates. The mechanism of MDM2 involves its role as an oncogene during the development of malignancy, and MDM2 can promote both metastasis and tumor cell proliferation, which indirectly leads to disease progression. Moreover, MDM2 is vitally involved in modifying the tumor immune microenvironment (TIME) as well as in influencing immune cells, eventually facilitating immune evasion and tolerance. Encouragingly, various MDM2 inhibitors have exhibited efficacy in relieving the TIME suppression caused by MDM2. These results demonstrate the prospects for breakthroughs in combination therapy using MDM2 inhibitors and anticancer immunotherapy.

Gemcitabine alters the proteasome composition and immunopeptidome of tumour cells

The antigenic makeup of tumour cells can have a profound effect on the progression of cancer and success of immunotherapies. Therefore, one strategy to improve the efficacy of cancer treatments is to augment the antigens displayed by tumours. The present study explores how the recognition of tumour cells may be altered by non-cytotoxic concentrations of gemcitabine (GEM). Testing a panel of chemotherapeutics in human cancer cell lines in vitro, it was found that GEM increased surface expression of HLA-A,B,C and that underlying this were specific increases in β-2-microglobulin and immunoproteasome subunit proteins. Furthermore, the peptide antigen repertoire displayed on HLA class I was altered, revealing a number of novel antigens, many of which that were derived from proteins involved in the DNA-damage response. Changes in the nature of the peptide antigens eluted from HLA-A,B,C after GEM treatment consisted of amino acid anchor-residue modifications and changes in peptide length which rendered peptides likely to favour alternative HLA-alleles and increased their predicted immunogenicity. Signalling through the MAPK/ERK and NFκB/RelB pathways was associated with these changes. These data may explain observations made in previous in vivo studies, advise as to which antigens should be used in future vaccination protocols and reinforce the idea that chemotherapy and immunotherapy could be used in combination.

T-cell receptor gene therapy: critical parameters for clinical success

T-cell receptor (TCR) gene therapy aims to induce immune reactivity against tumors by introducing genes encoding a tumor-reactive TCR into patient T cells. This approach has been extensively tested in preclinical mouse models, and initial clinical trials have demonstrated the feasibility and potential of TCR gene therapy as a cancer treatment. However, data obtained from preclinical and clinical studies suggest that both the therapeutic efficacy and the safety of TCR gene therapy can be and needs to be further enhanced. This review highlights those strategies that can be followed to develop TCR gene therapy into a clinically relevant treatment option for cancer patients.

Generation and characterization of transgenic mice expressing a T-cell receptor specific for the tumour-associated antigen MDM2

T-cell-based antigen-specific immunotherapy targeting tumour-associated antigens offers the potential for cancer immunotherapy. However, the majority of identified tumour-associated antigens are also expressed at low levels in normal tissues and mechanisms of tolerance induction are likely to affect the quality of T-cell responses to such antigens. In this study a T-cell receptor transgenic model was developed to determine the magnitude of T-cell tolerance to the tumour-associated antigen murine double minute-2 (MDM2), a widely expressed protein that is found at elevated levels in many tumours. The analysis of transgenic mice showed that thymic deletion was responsible for purging large numbers of MDM2-specific T cells from the repertoire. However, some T cells with specificity for MDM2 were able to escape thymic deletion and persisted in the peripheral T-cell pool. Functional analysis revealed that these T cells displayed defects in antigen-driven expansion. This functional impairment of the MDM2-specific T cells was maintained following adoptive transfer of the T cells into hosts that were unable to present the T-cell-receptor-recognized antigen. This study demonstrates that thymic deletion and the functional impairment of T cells present in the periphery both operate to establish T-cell tolerance to the tumour-associated antigen MDM2. Furthermore, the tolerant phenotype was stable and did not require continuous MDM2 peptide presentation in normal tissues.