Project description:Epigenetic mechanism contributes to immune landscapes in cancer. Here we identify the SETDB1-TRIM28 complex as a critical suppressor of antitumor immunity. An epigenetic CRISPR-Cas9 screen of 1,218 chromatin regulators identified TRIM28 as a novel suppressor of PD-L1 expression. We revealed that expression of the SETDB1-TRIM28 complex negatively correlates with infiltration of effector CD8+ T cells. Inhibition of SETDB1-TRIM28 simultaneously upregulates PD-L1 and activates the cGAS-STING innate immune response to increase infiltration of CD8+ T cells. Mechanistically, SETDB1-TRIM28 inhibition leads to micronuclei formation in cytoplasm, a known activator of the cGAS-STING pathway. Thus, SETDB1-TRIM28 inhibition bridges the innate and adaptive immunity. Indeed, SETDB1 knockout enhances the antitumor effects of immune checkpoint blockade anti-PD-L1 in an ovarian cancer mouse model in a cGAS dependent manner. Our findings establish SETDB1-TRIM28 complex as a regulator of antitumor immunity and its loss activates cGAS-STING innate immunity to boost antitumor effects of immune checkpoint blockades.
Project description:Epigenetic mechanism contributes to immune landscapes in cancer. Here we identify the SETDB1-TRIM28 complex as a critical suppressor of antitumor immunity. An epigenetic CRISPR-Cas9 screen of 1,218 chromatin regulators identified TRIM28 as a novel suppressor of PD-L1 expression. We revealed that expression of the SETDB1-TRIM28 complex negatively correlates with infiltration of effector CD8+ T cells. Inhibition of SETDB1-TRIM28 simultaneously upregulates PD-L1 and activates the cGAS-STING innate immune response to increase infiltration of CD8+ T cells. Mechanistically, SETDB1-TRIM28 inhibition leads to micronuclei formation in cytoplasm, a known activator of the cGAS-STING pathway. Thus, SETDB1-TRIM28 inhibition bridges the innate and adaptive immunity. Indeed, SETDB1 knockout enhances the antitumor effects of immune checkpoint blockade anti-PD-L1 in an ovarian cancer mouse model in a cGAS dependent manner. Our findings establish SETDB1-TRIM28 complex as a regulator of antitumor immunity and its loss activates cGAS-STING innate immunity to boost antitumor effects of immune checkpoint blockades.
Project description:LARP7 plays a pivotal role in regulating endothelial-to-mesenchymal transition(EndMT) and EndMT-associated heart valve formation. LARP7 directly interactes with TRIM28 and cooperatively represses SLUG transcription, which thereby suppresses EndMT of endothelial cells. More importantly, inducible knockout of LARP7 or TRIM28 in the endocardium promotes EndMT in vivo and leads to the valvular hyperplasia.
Project description:Griffin GK, Wu J, Iracheta-Vellve A, Patti JC, Hsu J, Davis T, Dele-Oni D, Du PP, Halawi A, Ishizuka JJ, Kim S, Klaeger S, Knudsen NH, Miller BC, Nguyen T, Olander K, Papanastasiou M, Rachimi S, Robitschek EJ, Schneider EM, Yeary M, Zimmer M, Jaffe JD, Carr SA, Doench JG, Haining WN, Yates KB, Manguso RT, Bernstein BE. 2020. Epigenetic dysregulation is a defining feature of tumorigenesis and has been implicated in immune escape, yet mechanisms that drive immune evasion are poorly understood. To systematically identify epigenetic factors that modulate the immune sensitivity of tumor cells, we performed in vivo CRISPR-Cas9 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 represses 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 co-stimulatory 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:TRIM28 is a bromodomain protein implicated in the regulation of tumor growth. TRIM28 regulates gene expression by recruiting epigenetic writers including HDACs, SETDB1 and HP1. To determine the role of TRIM28 in melanoma cells we knocked down TRIM28 using lentiviral shRNA constructs followed by gene expression analysis using HTA 2.0 GeneChip.
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:Only a small percentage of human transcription factors (e.g. those associated with a specific differentiation program) are expressed in a given cell type. Thus, cell fate is mainly determined by cell type-specific silencing of transcription factors that drive different cellular lineages. Several histone modifications have been associated with gene silencing, including H3K27me3 and H3K9me3. We have previously shown that the two largest classes of mammalian transcription factors are marked by distinct histone modifications; homeobox genes are marked by H3K27me3 and zinc finger genes are marked by H3K9me3. Several histone methyltransferases (e.g. G9a and SETDB1) may be involved in mediating the H3K9me3 silencing mark. We have used ChIP-chip and ChIP-seq (GSE24632) to demonstrate that SETDB1, but not G9a, is associated with regions of the genome enriched for H3K9me3. A current model is that SETDB1 is recruited to specific genomic locations via interaction with the corepressor TRIM28 (KAP1), which is in turn recruited to the genome via interaction with zinc finger transcription factors that contain a Kruppel-associated box (KRAB) domain. However, specific KRAB-ZNFs that recruit TRIM28 (KAP1) and SETDB1 to the genome have not been identified. We now show that ZNF274 (a KRAB-ZNF that contains 5 C2H2 zinc finger domains), can interact with KAP1 in vitro and, using ChIP-seq, we show that ZNF274 binding sites co-localize with SETDB1, KAP1, and H3K9me3 at the 3â ends of zinc finger genes. Knockdown of ZNF274 with siRNAs reduced the levels of KAP1 and SETDB1 recruitment to the binding sites. These studies provide the first identification of a KRAB domain-containing ZNFs that is involved in recruitment of the KAP1 and SETDB1 to the human genome. This study includes the 4 ChIP-chip arrays only.