Project description:Loss of MHC class I (MHC-I) antigen presentation in cancer cells can lead to immunotherapy resistance. Using a genome-wide CRISPR/Cas9 screen we identify a critical role for polycomb repressive complex 2 (PRC2) in the coordinated transcriptional silencing of the MHC-I antigen processing pathway (MHC-I APP). This evolutionarily conserved function of PRC2 promotes evasion of T-cell mediated immunity, enabling tumor transmission to non-histocompatible recipients in small cell lung cancer (SCLC) and Tasmanian Devil Facial Tumor. MHC-I APP gene promoters in MHC-I low cancers harbour bivalent activating H3K4me3 and repressive H3K27me3 histone modifications, silencing basal MHC-I expression and restricting cytokine induced MHC-I APP gene upregulation. Bivalent chromatin at MHC-I APP genes is a normal developmental process active in embryonic stem cells and maintained during neural progenitor differentiation. This physiological silencing of MHC-I expression highlights a conserved mechanism by which cancers arising from these primitive tissues coopt PRC2 activity to enable immune evasion.
Project description:Histone dimethyl transferase WHSC1 drives the transcription of MHC-I machinery in mouse and human colorectal cancer cells (CRCs); thus, WHSC1 downregulation potentiates CRCs to escape from cytotoxic CD8+ T cell responses. WHSC1 directly interacts with MHC-I transactivator, NLRC5 to selectively stimulate MHC-I gene expression. Thus, silencing Whsc1 diminished MHC-I level, impaired anti-tumor immunity and blunted immunotherapy efficacy.
Project description:Histone dimethyl transferase WHSC1 drives the transcription of MHC-I machinery in mouse and human colorectal cancer cells (CRCs); thus, WHSC1 downregulation potentiates CRCs to escape from cytotoxic CD8+ T cell responses. WHSC1 directly interacts with MHC-I transactivator, NLRC5 to selectively stimulate MHC-I gene expression. Thus, silencing Whsc1 diminished MHC-I level, impaired anti-tumor immunity and blunted immunotherapy efficacy.
Project description:There is increasing recognition of the prognostic significance of tumor cell major histocompatibility complex (MHC) class II expression in anti-cancer immunity. Relapse of acute myeloid leukemia (AML) following allogeneic stem cell transplantation (alloSCT) has recently been linked to MHC class II silencing in leukemic blasts; however, the regulation of MHC class II expression remains incompletely understood. Utilizing unbiased CRISPR-Cas9 screens, we identify that the C-terminal binding protein (CtBP) complex transcriptionally represses MHC class II pathway genes, while the E3 ubiquitin ligase complex component FBXO11 mediates degradation of CIITA, the principal transcription factor regulating MHC class II expression. Targeting these repressive mechanisms selectively induces MHC class II upregulation across a range of AML cell lines. Functionally, MHC class II+ leukemic blasts stimulate antigen-dependent CD4+ T cell activation and potent anti-tumor immune responses, providing fundamental insights into the graft-versus-leukemia effect. These findings establish the rationale for therapeutic strategies aimed at restoring tumor-specific MHC class II expression to salvage AML relapse post-alloSCT and also potentially to enhance immunotherapy outcomes in non-myeloid malignancies.
Project description:The switch from the faster α-MHC to the slower β-MHC isoform that occurs in cardiac hypertrophy is generally thought to reduce contractile performance and to contribute to functional maladaptation. This MHC switch is regulated by miRNAs and thyroid hormones in development and hypertrophy. Since exacerbated hypertrophy is observed in absence of β-MHC expression in PTP1B cKO mice, we speculated that PTP1B inactivation associated with pressure-overload hypertrophy could disrupt miRNAs homeostasis. In this dataset, expression status of 1908 mouse miRNAs was investigated and reveal that PTP1B contribute to gene silencing by mediating miRNA loading onto the RISC complex.