Project description:De novo DNA methylation establishes T cell exhaustion and inhibits PD-1 blockade-mediated T-cell rejuvenation. Expression profiling of chronically stimulated WT and Dnmt3a cKO antigen-specific CD8 T cells.
Project description:Most bladder cancers are poorly responsive to immune checkpoint blockade (ICB) of PD-L1. Thus, there is a need to define mechanisms of de novo resistance including contributions from tumor infiltrating immune cells. In this study, we used single-cell transcriptional profiling to map and define infiltrating myeloid cells in 10 human bladder tumors. Human data sets were qualitatively compared with myeloid data sets from the carcinogen (BBN) induced mouse model of bladder cancer which we have demonstrated to be poorly responsive to PD-L1 blockade. We previously established a signature of acquired ICB resistance which we apply here to new human and murine tumor data sets that have not received prior ICB (or systemic treatment). In doing so, we reveal conservation in EMT-stromal core genes and TGF beta signaling between human and mouse myeloid cells consistent with signatures of de novo ICB resistance. Untreated BBN tumors were highly infiltrated with M0-M2 macrophages, low in T-NK infiltration and modeled a patient subpopulation with poor survival outcome. Concordantly, the combined targeting of TGFb + PD-L1 reverted immune cell exclusion and resulted in increased survival and delayed BBN mouse tumor progression. These data constitute the stromal and myeloid cell populations as providing a coordinate mechanism de novo resistance to PD-L1 blockade in a TGF-beta dependent manner.
Project description:Cellular senescence is a fundamental driver of ageing and age-related diseases, characterized by irreversible growth arrest and profound epigenetic alterations. While long non-coding RNAs (lncRNAs) have emerged as key regulators of senescence, their potential for senescent cell rejuvenation remains unexplored. Here, we identify the ageing-associated lncRNA PURPL as an epigenetic regulator that controls cellular rejuvenation through H3K9me3-mediated transcriptional silencing. CRISPRi-mediated PURPL depletion produces striking rejuvenation effects, resulting in restored youthful cell morphology, as well as suppression of senescence markers such as p21 and SA-β-gal. Conversely, PURPL overexpression accelerates cellular senescence, recapitulating the transcriptional and phenotypic hallmarks of ageing. Mechanistically, nuclear-localized PURPL regulates H3K9me3 deposition at 411 genomic loci including SERPINE1 (PAI-1) and EGR1, which are key senescence drivers. PURPL-mediated H3K9me3 loss at these loci derepresses their transcription, establishing a pro-senescence gene expression program. These findings reveal that PURPL is an epigenetic modulator of senescence and highlight its potential as a therapeutic target for age-related pathologies.
Project description:PD-1 signalling blockade is highly effective at restoring immune surveillance and treating melanoma. However, redundant immune homeostatic mechanisms driven by chronic IFNγ signalling can lead to ongoing immune evasion and acquired resistance. PARP14 mediates IFNγ-driven resistance, and prolongs responsiveness to PD-1 blockade in preclinical models. Here we present a single cell RNAseq of immune cells from α-PD-1 relapsing mouse tumours, following subsequent PARP14i treatments alone and in combination with α-PD-1. Our findings highlight a robust PARP14i gene signature associated with improved patient survival, suggesting its potential to enhance PD-1 blockade efficacy.
Project description:CD8+ T cells in chronic viral infections like HIV develop functional defects such as loss of IL-2 secretion and decreased proliferative potential that are collectively termed exhaustion1. Exhausted T cells express increased levels of multiple inhibitory receptors, such as Programmed Death 1 (PD-1). PD-1 inhibition contributes to impaired virus-specific T cell function in chronic infection because antibody-mediated blockade of its ligand, Programmed Death Ligand 1 (PD-L1) is sufficient to improve T cell function and reduce viral replication in animal models. Reversing PD-1 inhibition is therefore an attractive therapeutic target, but the cellular mechanisms by which PD-1 ligation results in T cell inhibition are not fully understood. PD-1 is thought to limit T cell activation by attenuating T cell receptor (TCR) signaling. It is not known whether PD-1 ligation also acts by upregulating genes in exhausted T cells that impair their function. Here, we analyzed gene-expression profiles from HIV-specific CD8+ T cells in patients with HIV and show that PD-1 coordinately upregulates a program of genes in exhausted CD8+ T cells from humans and mice. This program includes upregulation of basic leucine transcription factor, ATF-like (BATF), a transcription factor in the AP-1 family. Enforced expression of BATF was sufficient to impair T cell proliferation and cytokine secretion, while BATF knockdown reduced PD-1 inhibition. Silencing BATF in CD4+ and CD8+ T cells from chronic viremic patients rescued HIV-specific T cell function. Thus inhibitory receptors can cause T cell exhaustion by upregulating genes â such as BATF â that inhibit T cell function. PD-1 expressing Jurkat cells were cultured for 18 hours with beads coated with antibodies to CD3 and CD28, with our without an antibody to PD-1.