Project description:Cytotoxic T-lymphocyte associated antigen-4 (CTLA-4) and Programmed death-1 (PD-1) are immunoregulatory receptors expressed on T cells that play important roles in suppressing immune responses to cancer. Although monoclonal antibodies that target CTLA-4 or PD-1 stimulate therapeutic anti-tumour T cell responses, the tumour antigens recognized by checkpoint blockade immunotherapy remain undefined. Herein, we use genomics and bioinformatics approaches to identify tumour-specific mutant proteins as a major class of T cell rejection antigens following αPD-1 and/or αCTLA-4 treatment of mice bearing progressively growing sarcomas. We validate this conclusion by showing that (a) the predicted mutant epitopes associate with MHC class I molecules of the tumour; (b) T cells specific for these mutant epitopes infiltrate tumours; and (c) therapeutic vaccines incorporating these mutant epitopes induce tumour rejection comparably to checkpoint blockade immunotherapy. Whereas, T cells with the same antigen specificity are present in progressively growing tumours in control mice, tumour-specific T cells in αPD-1- and/or αCTLA-4-treated mice express some overlapping but mostly treatment-specific transcriptional profiles that render them capable of tumour rejection. Thus, tumour-specific mutant antigens are not only important targets of checkpoint blockade therapy but also can be used to identify tumour antigen-specific T cells that function as biomarkers of successful anti-tumour responses.
Project description:Upstream open reading frames (uORFs) represent translational control elements within eukaryotic transcript leader sequences. Recent data showed that uORFs can encode for biologically active proteins and human leucocyte antigen (HLA)-presented peptides and suggest their potential role in cancer cell development and survival. However, it is so far unclear if uORF-encoded peptides could serve as tumor-associated antigen targets and thus also play a role in cancer immune surveillance. Combining mass spectrometry-based immunopeptidome analysis in primary tumor and healthy tissues and evaluation of proto-oncogene-associated uORF-mediated translational control we here identified a panel of HLA-presented tumor-associated uORF-derived antigens. These uORF-derived tumor antigens were further shown to induce multifunctional antigen-specific T cells, validating their suitability as antigen targets for T cell-based cancer immunotherapy. Our data further unravel the role of uORF-encoded peptides in malignant disease, suggesting uORF-derived tumor-associated antigens as targets for anti-cancer immune surveillance and immunotherapy development.
Project description:Checkpoint blockade immunotherapy is a promising strategy in cancer treatment, depending on a favorable preexisting tumor immune microenvironment. However, prostate cancer is usually considered as an immune “cold” tumor with the poor immunogenic response and low density of tumor-infiltrating immune cells. This research uses samples from prostate cancer patients showing that docetaxel-based chemohormonal therapy reprograms the immune microenvironment and increases tumor-infiltrating T cells. Mechanistically, docetaxel treatment activates the cGAS/STING pathway and induces the type I interferon signaling, which may boost T cell-mediated immune response. In a murine prostate cancer model, chemohormonal therapy sensitizes tumor-bearing mice to PD1-blockade therapy. These findings demonstrate that docetaxel-based chemohormonal therapy activates prostate cancer immunogenicity and acts cooperatively with anti-PD-1 checkpoint blockade, providing a combination immunotherapy strategy that would lead to better therapeutic benefit for prostate cancer.
Project description:Epigenetic dysregulation is a defining feature of tumorigenesis and has been implicated in immune escape. However, the epigenetic mechanisms that drive immune evasion in cancer are poorly understood. To systematically identify epigenetic factors that modulate the immune sensitivity of tumor cells, we performed in vivo loss of function screens targeting 936 chromatin regulators in mouse tumor models treated with immune checkpoint blockade. We identified the H3K9-methyltransferase SETDB1 and other members of the HUSH and KAP1 complexes as cell-intrinsic mediators of immune escape in tumor cells. We also found that amplification of SETDB1 (1q21) in human tumors is associated with reduced cytotoxic T-cell infiltration and resistance to immune checkpoint blockade. Mechanistically, we demonstrate that SETDB1 targets broad domains, hundreds of kilobases in size, many of which reside within the open genome compartment. These SETDB1 domains are enriched for transposable elements (TEs) and immune gene clusters associated with segmental duplication events, a central mechanism of mammalian genome evolution. SETDB1 loss derepresses latent TE-encoded regulatory elements and proximal immune genes within these repetitive regions, including canonical NKG2D ligands, and induces hundreds of putative TE-encoded viral antigens. Our study establishes SETDB1 as an epigenetic checkpoint that suppresses intrinsic immunogenicity in cancer cells, and thus represents a candidate target for immunotherapy.
Project description:Enhancer RNA (eRNA) is critical element with highly specific pattern in regulatory network across infiltrated immune cells. Herein we developed eRNA immunotherapy signature (eRIS) based on these eRNAs which significantly connected with anti-tumor immune cells. The eRIS was highly correlated with objective response rate (ORR) to immune checkpoint blockade (ICB) treatment, and was significantly increased in these patients who benefit from ICB treatment. By integrating with pharmacogenomics datasets, we screened hundreds of eRIS associated anti-cancer drugs, which showed potential in improving immunotherapy with cancer type or subtype-specific specific manner. We further characterized one drug, the HDAC inhibitor vorinostat, in isocitrate dehydrogenase mutant gliomas, and found Combining vorinostat with anti-PD-1 could decrease tumor size and increase survival time in vivo by enhancing abundance of anti-tumor immune cells. We further provided eRIS markers which showed strong capacity of eRIS in predicting immunotherapy response in clinical samples or animal models. Our study revealed the potential utility of eRIS to improve immunotherapy response by identifying combinational drugs, that provide novel insights to benefit patients in certain cancer or subtypes.
Project description:drugs targeting mitosis might affect the tumor microenvironment and sensitize cancer cells to immunotherapy. BAL101553 monotherapy increased survival in immune checkpoint blockade–resistant SB28 glioblastoma tumors and synergized with anti-CD40 antibody
Project description:Although genomic instability can trigger cancer-intrinsic innate immune responses that promote tumor rejection, cancer cells often evade these responses by overexpressing immune checkpoint regulators, such as PD-L1. Here, we identify the SNF2-family DNA translocase SMARCAL1 as a factor that favors tumor immune evasion by a dual mechanism involving both the suppression of innate immune signaling and the induction of PD-L1-mediated immune checkpoint responses. Mechanistically, SMARCAL1 relieves endogenous DNA damage and suppresses cGAS-STING-dependent immune signaling during cancer cell growth. Simultaneously, it cooperates with the AP-1 family member JUN to maintain chromatin accessibility at a transcriptional regulatory element in the PD-L1 gene, thereby promoting PD-L1 expression in cancer cells. Loss of SMARCAL1 enhances anti-tumor immune responses and sensitizes tumors to immune checkpoint blockade in a mouse melanoma model. Collectively, these studies uncover SMARCAL1 as a valuable target for cancer immunotherapy.
Project description:Although mutations in DNA are the best-studied source of neoantigens that determine response to immune checkpoint blockade, alterations in RNA splicing within cancer cells could similarly result in neoepitope production. However, the endogenous antigenicity and clinical potential of such splicing-derived epitopes have not been tested. Here, we demonstrate that pharmacologic modulation of splicing via specific drug classes generates bona fide neoantigens and elicits anti-tumor immunity, augmenting checkpoint immunotherapy. Splicing modulation inhibited tumor growth and enhanced checkpoint blockade in a manner dependent on host T cells and peptides presented on tumor MHC class I. Splicing modulation induced stereotyped splicing changes across tumor types, altering the MHC I-bound immunopeptidome to yield splicing-derived neoepitopes that trigger an anti-tumor T cell response in vivo. These data definitively identify splicing modulation as an untapped source of immunogenic peptides and provide a means to enhance response to checkpoint blockade that is readily translatable to the clinic.
Project description:CD8+ T cells activated by cancer immunotherapy execute tumor clearance mainly by inducing cell death through perforin-granzyme- and Fas/Fas ligand-pathways. Ferroptosis is a form of cell death that differs from apoptosis and results from iron-dependent lipid peroxide accumulation. Although it was mechanistically illuminated in vitro, emerging evidence has shown that ferroptosis may be implicated in a variety of pathological scenarios. However, the involvement of ferroptosis in T cell immunity and cancer immunotherapy is unknown. Here, we find that immunotherapy-activated CD8+ T cells enhance ferroptosis-specific lipid peroxidation in tumor cells, and in turn, increased ferroptosis contributes to the anti-tumor efficacy of immunotherapy. Mechanistically, IFNg released from CD8+ T cells downregulates expression of SLC3A2 and SLC7A11, two subunits of glutamate-cystine antiporter system xc-, restrains tumor cell cystine uptake, and as a consequence, promotes tumor cell lipid peroxidation and ferroptosis. In preclinical models, depletion of cyst(e)ine by cyst(e)inase in combination with checkpoint blockade synergistically enhances T cell-mediated anti-tumor immunity and induces tumor cell ferroptosis. Thus, T cell-promoted tumor ferroptosis is a novel anti-tumor mechanism. Targeting tumor ferroptosis pathway constitutes a therapeutic approach in combination with checkpoint blockade.
Project description:CD8 T cells drive the anti-cancer immune response through the recognition of MHC I-associated peptides. In order to identify relevant targets for cancer immunotherapy in breast cancer, we characterized the immunopeptidome of 26 primary breast cancer samples from two different subtypes, hormone-receptor positive (n=14) and triple negative (n=12). We were able to identify tumor-specific and tumor associated antigens in both subtypes of breast cancer, which can be used for the development of anti-cancer vaccines or as targets for engineered T-cells.