Combination CTLA-4 Blockade and 4-1BB Activation Enhances Tumor Rejection by Increasing T-Cell Infiltration, Proliferation, and Cytokine Production

BACKGROUND: The co-inhibitory receptor Cytotoxic T-Lymphocyte Antigen 4 (CTLA-4) attenuates immune responses and prevent autoimmunity, however, tumors exploit this pathway to evade the host T-cell response. The T-cell co-stimulatory receptor 4-1BB is transiently upregulated on T-cells following activation and increases their proliferation and inflammatory cytokine production when engaged. Antibodies which block CTLA-4 or which activate 4-1BB can promote the rejection of some murine tumors, but fail to cure poorly immunogenic tumors like B16 melanoma as single agents.METHODOLOGY/PRINCIPAL FINDINGS: We find that combining ?CTLA-4 and ?4-1BB antibodies in the context of a Flt3-ligand, but not a GM-CSF, based B16 melanoma vaccine promoted synergistic levels of tumor rejection. 4-1BB activation elicited strong infiltration of CD8+ T-cells into the tumor and drove the proliferation of these cells, while CTLA-4 blockade did the same for CD4+ effector T-cells. Anti-4-1BB also depressed regulatory T-cell infiltration of tumors. 4-1BB activation strongly stimulated inflammatory cytokine production in the vaccine and tumor draining lymph nodes and in the tumor itself. The addition of CTLA-4 blockade further increased IFN-? production from CD4+ effector T-cells in the vaccine draining node and the tumor. Anti 4-1BB treatment, with or without CTLA-4 blockade, induced approximately 75% of CD8+ and 45% of CD4+ effector T-cells in the tumor to express the killer cell lectin-like receptor G1 (KLRG1). Tumors treated with combination antibody therapy showed 1.7-fold greater infiltration by these KLRG1+CD4+ effector T-cells than did those treated with ?4-1BB alone.CONCLUSIONS/SIGNIFICANCE: This study shows that combining T-cell co-inhibitory blockade with ?CTLA-4 and active co-stimulation with ?4-1BB promotes rejection of B16 melanoma in the context of a suitable vaccine. In addition, we identify KLRG1 as a useful marker for monitoring the anti-tumor immune response elicited by this therapy. These findings should aid in the design of future trials for the immunotherapy of melanoma

Novel Foxo1-dependent transcriptional programs control Treg cell function

Regulatory T (T(reg)) cells, characterized by expression of the transcription factor forkhead box P3 (Foxp3), maintain immune homeostasis by suppressing self-destructive immune responses. Foxp3 operates as a late-acting differentiation factor controlling T(reg) cell homeostasis and function, whereas the early T(reg)-cell-lineage commitment is regulated by the Akt kinase and the forkhead box O (Foxo) family of transcription factors. However, whether Foxo proteins act beyond the T(reg)-cell-commitment stage to control T(reg) cell homeostasis and function remains largely unexplored. Here we show that Foxo1 is a pivotal regulator of T(reg )cell function. T(reg) cells express high amounts of Foxo1 and display reduced T-cell-receptor-induced Akt activation, Foxo1 phosphorylation and Foxo1 nuclear exclusion. Mice with T(reg)-cell-specific deletion of Foxo1 develop a fatal inflammatory disorder similar in severity to that seen in Foxp3-deficient mice, but without the loss of T(reg) cells. Genome-wide analysis of Foxo1 binding sites reveals ~300 Foxo1-bound target genes, including the pro-inflammatory cytokine Ifng, that do not seem to be directly regulated by Foxp3. These findings show that the evolutionarily ancient Akt-Foxo1 signalling module controls a novel genetic program indispensable for T(reg) cell function

Murine in vivo CD8+ T Cell Killing Assay

Antigen-specific killing ability of effector CD8+ T cells is critical for protective immunity against infection. Here, we describe in vivo cytotoxic T cell assay to examine effector function of antigen-specific CD8+ T cells. Mice infected with Listeria monocytogenes (L. monocytogenes) expressing chicken ovalbumin as a model antigen mount ovalbumin-specific CD8+ T cell responses. Effector CD8+ T cell function in vivo is determined by mixed transfer of OVA peptide-pulsed target cells with control target cells into the previously immunized mice. Difference in CFSE expression levels clearly marks two distinct populations: Antigen-pulsed target cells-CFSElow vs. unpulsed target cells-CFSEhi. The frequencies between antigen-pulsed target cells and control target cells are used as readouts of antigen-specific killing

Murine in vitro Memory T Cell Differentiation

Upon pathogen encounter, naïve CD8+ T cells are primed and undergo massive clonal expansion. A fraction of effector CD8+ T cells remains during the contraction phase and differentiate into memory T cells critical for mounting robust recall responses in response to secondary infection. Low frequency of memory T cells in vivo is a major obstacle to investigate their functional aspects including migration capacity and genetic regulation. Here, we describe detailed protocol for memory T cell differentiation developed by von Andrian’s group to generate large number of CD44hiCD62Lhi antigen-specific memory T cells in vitro

Image_1_Extracellular self-RNA: A danger elicitor in pepper induces immunity against bacterial and viral pathogens in the field.TIF

Plants and animals serve as hosts for microbes. To protect themselves from microbe-induced damage, plants and animals need to differentiate self-molecules/signals from non-self, microbe-derived molecules. Damage-associated molecular patterns (DAMPs) are danger signals released from the damaged host tissue or present on the surface of stressed cells. Although a self-extracellular DNA has previously been shown to act as a DAMP in different plant species, the existence of a self-extracellular RNA (eRNA) as a danger signal in plants remains unknown. Here, we firstly evaluated the ability of a pepper self-eRNA to activate immunity against viral and bacterial pathogens under field conditions. Pepper leaves pre-infiltrated with self-eRNA exhibited reduced titer of the naturally occurring Tomato spotted wilt virus and diminished symptoms of Xanthomonas axonopodis pv. vesicatoria infection through eliciting defense priming of abscisic acid signaling. At the end of the growing season at 90 days after transplanting, pepper plants treated with self- and non-self-eRNAs showed no difference in fruit yield. Taken together, our discovery demonstrated that self-eRNA can successfully activate plant systemic immunity without any growth penalty, indicating its potential as a novel disease management agent against a broad range of pathogenic microbes.</p

The Transcription Factor Foxo1 Controls Central-Memory CD8+ T Cell Responses to Infection

SummaryMemory T cells protect hosts from pathogen reinfection, but how these cells emerge from a pool of antigen-experienced T cells is unclear. Here, we show that mice lacking the transcription factor Foxo1 in activated CD8+ T cells have defective secondary, but not primary, responses to Listeria monocytogenes infection. Compared to short-lived effector T cells, memory-precursor T cells expressed higher amounts of Foxo1, which promoted their generation and maintenance. Chromatin immunoprecipitation sequencing revealed the transcription factor Tcf7 and the chemokine receptor Ccr7 as Foxo1-bound target genes, which have critical functions in central-memory T cell differentiation and trafficking. These findings demonstrate that Foxo1 is selectively incorporated into the genetic program that regulates memory CD8+ T cell responses to infection

A Phase II Study to Compare the Safety and Efficacy of Direct Oral Anticoagulants versus Subcutaneous Dalteparin for Cancer-Associated Venous Thromboembolism in Patients with Advanced Upper Gastrointestinal, Hepatobiliary and Pancreatic Cancer: PRIORITY

Background: We evaluated the safety and efficacy of direct oral anticoagulants (DOACs) versus subcutaneous dalteparin for cancer-associated venous thromboembolism (CA-VTE) in patients with advanced upper gastrointestinal (GI) tract, hepatobiliary, or pancreatic cancer. Methods: This was a multicenter, randomized, open-label, phase II trial in five centers. Patients randomly received rivaroxaban (15 mg twice daily for 3 weeks, then 20 mg once daily)/apixaban (10 mg twice daily for the first 7 days, then 5 mg twice daily) or dalteparin (200 IU/kg once daily for the first month, then 150 IU/kg once daily). Randomization was stratified by the Eastern Cooperative Oncology Group Performance Status, primary cancer type, active chemotherapy, and participating centers. The primary endpoint was the rates of clinically relevant bleeding (CRB) in the full analysis set (FAS). Results: A total of 90 patients were randomly assigned to the DOAC (n = 44) and dalteparin groups (n = 46) in FAS. CRB and major bleeding (MB) rates were 34.1% and 13.0% (p = 0.018) and 18.2% and 4.3% (p = 0.047) for the DOAC and dalteparin groups, respectively. Time to CRB and MB was higher in the DOAC group than in the dalteparin group (hazard ratio [HR] 2.83; p = 0.031 and HR 4.32; p = 0.064). Cancer involvement at the GI mucosa was also a significant risk factor for CRB. Recurrent CA-VTE occurred in 2.3% and 2.2% of patients given DOAC and dalteparin, respectively (p = 1.000). Conclusion: DOAC therapy further increased the risk of bleeding compared with dalteparin in patients with active advanced upper GI tract, hepatobiliary, or pancreatic cancer, suggesting that extra caution should be taken when selecting anticoagulants for CA-VTE