Project description:RNA-binding proteins (RBPs) can recognize thousands of RNAs that help to maintain cell homeostasis, and RBP dysfunction is frequently observed in various cancers. However, whether specific RBPs are involved in tumor immune evasion by regulating programmed death ligand-1 (PD-L1) is unclear. We performed targeted RBP CRISPR/Cas9 screening and identified density regulated re-initiation and release factor (DENR) as a PD-L1 regulator. DENR-depleted cancer cells exhibited reduced PD-L1 expression in vitro and in vivo. DENR depletion significantly suppressed tumor growth and enhanced the tumor-killing activity of CD8+ T cells. Mechanistically, DENR antagonized the translational repression of three consecutive upstream open reading frames (uORFs) upstream of Janus kinase 2 (JAK2); thus, DENR deficiency impaired JAK2 translation and the IFNγ-JAK-STAT signaling pathway, resulting in reduced PD-L1 expression in tumors. Overall, we discovered that the RBP DENR is a novel regulator in PD-L1 expression and highlighted the potential of DENR as a therapeutic target for immunotherapy.
Project description:The activation of PD-1 (Programmed Death receptor-1) on T cells can cause T cell exhaustion and immune tolerance. Some tumors up-regulate the expression of the ligand of PD-1, namely PD-L1 (Programmed Death Receptor-Ligand 1), thus preventing anti-tumor immune response and promoting immune-escape. Previous studies have shown that JAK2 (Janus Kinase 2) signaling can promote PD-L1 expression in Hodgkin Lymphoma. In Myeloproliferative Neoplasms (MPN), JAK2 is frequently characterized by the the presence of the point-mutation V617F, which leads to its constitutive activation and to uncontrolled cell proliferation and survival. Accordingly, tumor cell lines expressing JAK2 V617F express higher levels of PD-L1 as compared to tumor cell lines negative for such mutations. In this experiment, we transfected BaF3 cells with a vector (plasmid for Murine Stem Cell Virus) containing the gene for JAK2 with the point-mutation V617F. As control, we used BaF3 cells transfected with the same vector, but without the gene for JAK2 V617F (empty vector). Both the cell lines (with/without JAK2 V617F) were co-cultured with primary murine T cells. When co-cultured with BaF3 cells expressing JAK2 V617F, T cells upregulated genes connected to senescence pathways, showed increased apoptosis, less cytokine production, and displayed other forms of dysfunction which can be associated with the activation of PD-1.
Project description:To identify the potential signaling pathway involved in DENR KO cells upon PD-L1 production, we harvested IFNγ-treated control and DENR KO cells for RNA-seq. Bioinformatic analysis of the RNA-seq data showed that 114 genes, including PD-L1, were significantly downregulated in DENR KO cells, and multiple classical signaling pathways, including JAK-STAT, and PD-L1, were enriched.
Project description:Genomic instability can trigger cancer-intrinsic innate immune responses that promote tumor rejection. However, 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 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. SMARCAL1 loss hinders the ability of tumor cells to induce PD-L1 in response to genomic instability, enhances anti-tumor immune responses and sensitizes tumors to immune checkpoint blockade in a mouse melanoma model. Collectively, these studies uncover SMARCAL1 as a promising target for cancer immunotherapy.
Project description:Genomic instability can trigger cancer-intrinsic innate immune responses that promote tumor rejection. However, 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 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. SMARCAL1 loss hinders the ability of tumor cells to induce PD-L1 in response to genomic instability, enhances anti-tumor immune responses and sensitizes tumors to immune checkpoint blockade in a mouse melanoma model. Collectively, these studies uncover SMARCAL1 as a promising target for cancer immunotherapy.
Project description:Genomic instability can trigger cancer-intrinsic innate immune responses that promote tumor rejection. However, 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 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. SMARCAL1 loss hinders the ability of tumor cells to induce PD-L1 in response to genomic instability, enhances anti-tumor immune responses and sensitizes tumors to immune checkpoint blockade in a mouse melanoma model. Collectively, these studies uncover SMARCAL1 as a promising target for cancer immunotherapy.
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.