CD19-CD28: An affinity-optimized CD28 agonist for combination with glofitamab (CD20-TCB) as off-the-shelf immunotherapy

Effective T cell responses not only require the engagement of T cell receptors (TCRs, "signal 1"), but also the availability of costimulatory signals ("signal 2"). T cell bispecific antibodies (TCBs) deliver a robust signal 1 by engaging the TCR signaling component CD3ε, while simultaneously binding to tumor antigens. The CD20-TCB glofitamab redirects T cells to CD20-expressing malignant B cells. While glofitamab exhibits strong single agent efficacy, adding costimulatory signaling may enhance the depth and durability of T cell-mediated tumor cell killing. We developed a bispecific CD19-targeted CD28 agonist (RG6333, CD19-CD28) to enhance the efficacy of glofitamab and similar TCBs by delivering signal 2 to tumor-infiltrating T cells. CD19-CD28 distinguishes itself from the superagonistic antibody TGN1412, as its activity requires the simultaneous presence of a TCR signal and CD19 target binding. This is achieved through its engineered format incorporating a mutated Fc region with abolished FcγR and C1q binding, CD28 monovalency, and a moderate CD28 binding affinity. In combination with glofitamab, CD19-CD28 strongly increased T cell effector functions in ex vivo assays using lymphoma patient-derived PBMC and spleen samples, and enhanced glofitamab-mediated regression of aggressive lymphomas in humanized mice. Notably, the triple combination of glofitamab with CD19-CD28 with the costimulatory 4-1BB agonist CD19-4-1BBL, offered substantially improved long-term tumor control over glofitamab monotherapy and respective duplet combinations. Our findings highlight CD19-CD28 as a safe and highly efficacious off-the-shelf combination partner for glofitamab, similar TCBs, and other costimulatory agonists. CD19-CD28 is currently in a Phase 1 clinical trial in combination with glofitamab.

Macrophage IL-1β contributes to tumorigenesis through paracrine AIM2 inflammasome activation in the tumor microenvironment

Intracellular recognition of self and non-self -nucleic acids can result in the initiation of effective pro-inflammatory and anti-tumorigenic responses. We hypothesized that macrophages can be activated by tumor-derived nucleic acids to induce inflammasome activation in the tumor microenvironment. We show that tumor conditioned media (CM) can induce IL-1β production, indicative of inflammasome activation in primed macrophages. This could be partially dependent on caspase 1/11, AIM2 and NLRP3. IL-1β enhances tumor cell proliferation, migration and invasion while coculture of tumor cells with macrophages enhances the proliferation of tumor cells, which is AIM2 and caspase 1/11 dependent. Furthermore, we have identified that DNA-RNA hybrids could be the nucleic acid form which activates AIM2 inflammasome at a higher sensitivity as compared to dsDNA. Taken together, the tumor-secretome stimulates an innate immune pathway in macrophages which promotes paracrine cancer growth and may be a key tumorigenic pathway in cancer. Broader understanding on the mechanisms of nucleic acid recognition and interaction with innate immune signaling pathway will help us to better appreciate its potential application in diagnostic and therapeutic benefit in cancer.

The FRESH Study: Treatment of Intracranial Aneurysms with the New FRED X Flow Diverter with Antithrombotic Surface Treatment Technology-First Multicenter Experience in 161 Patients

BACKGROUND AND PURPOSE

Flow diverters with antithrombotic coatings are increasingly used to improve the safety of flow diverter treatments of intracranial aneurysms. This study aimed to investigate the safety and short-term efficacy of the new FRED X flow diverter.

MATERIALS AND METHODS

Medical charts and procedural and imaging data of a consecutive series of patients with intracranial aneurysms who were treated with the FRED X at 9 international neurovascular centers were retrospectively analyzed.

RESULTS

One hundred sixty-one patients (77.6% women; mean age, 55 years) with 184 aneurysms (11.2% acutely ruptured) were included in this study. Most aneurysms were located in the anterior circulation (77.0%), most frequently at the ICA (72.7%). The FRED X was successfully implanted in all procedures. Additional coiling was performed in 29.8%. In-stent balloon angioplasty was necessary in 2.5%. The rate of major adverse events was 3.1%. Thrombotic events occurred in 7 patients (4.3%) with 4 intra- and 4 postprocedural in-stent thromboses, respectively (1 patient had both peri- and postprocedural thrombosis). Of these thrombotic events, only 2 (1.2%) led to major adverse events (ischemic strokes). Postinterventional neurologic morbidity and mortality were observed in 1.9% and 1.2%, respectively. The rate of complete aneurysm occlusion after a mean follow-up of 7.0 months was 66.0%.

CONCLUSIONS

The new FRED X is a safe and feasible device for aneurysm treatment. In this retrospective multicenter study, the rate of thrombotic complications was low, and the short-term occlusion rates are satisfactory.

Combinations of Toll-like receptor 8 agonist TL8-506 activate human tumor-derived dendritic cells

BACKGROUND

Dendritic cells (DCs) are professional antigen presenting cells that initiate immune defense to pathogens and tumor cells. Human tumors contain only few DCs that mostly display a non-activated phenotype. Hence, activation of tumor-associated DCs may improve efficacy of cancer immunotherapies. Toll-like receptor (TLR) agonists and interferons are known to promote DC maturation. However, it is unclear if DCs in human tumors respond to activation signals and which stimuli induce the optimal activation of human tumor DCs.

METHODS

We first screened combinations of TLR agonists, a STING agonist and interferons (IFNs) for their ability to activate human conventional DCs (cDCs). Two combinations: TL8-506 (a TLR8 agonist)+IFN-γ and TL8-506+Poly(I:C) (a TLR3 agonist) were studied in more detail. cDC1s and cDC2s derived from cord blood stem cells, blood or patient tumor samples were stimulated with either TL8-506+IFN-γ or TL8-506+Poly(I:C). Different activation markers were analyzed by ELISA, flow cytometry, NanoString nCounter Technology or single-cell RNA-sequencing. T cell activation and migration assays were performed to assess functional consequences of cDC activation.

RESULTS

We show that TL8-506 synergized with IFN-γ or Poly(I:C) to induce high expression of different chemokines and cytokines including interleukin (IL)-12p70 in human cord blood and blood cDC subsets in a combination-specific manner. Importantly, both combinations induced the activation of cDC subsets in patient tumor samples ex vivo. The expression of immunostimulatory genes important for anticancer responses including CD40, IFNB1, IFNL1, IL12A and IL12B were upregulated on stimulation. Furthermore, chemokines associated with CD8⁺ T cell recruitment were induced in tumor-derived cDCs in response to TL8-506 combinations. In vitro activation and migration assays confirmed that stimulated cDCs induce T cell activation and migration.

CONCLUSIONS

Our data suggest that cord blood-derived and blood-derived cDCs are a good surrogate to study treatment responses in human tumor cDCs. While most cDCs in human tumors display a non-activated phenotype, TL8-506 combinations drive human tumor cDCs towards an immunostimulatory phenotype associated with Th1 responses on stimulation. Hence, TL8-506-based combinations may be promising candidates to initiate or boost antitumor responses in patients with cancer.

Regulation of adipogenic differentiation and adipose tissue inflammation by interferon regulatory factor 3

Dysfunction of adipocytes and adipose tissue is a primary defect in obesity and obesity-associated metabolic diseases. Interferon regulatory factor 3 (IRF3) has been implicated in adipogenesis. However, the role of IRF3 in obesity and obesity-associated disorders remains unclear. Here, we show that IRF3 expression in human adipose tissues is positively associated with insulin sensitivity and negatively associated with type 2 diabetes. In mouse pre-adipocytes, deficiency of IRF3 results in increased expression of PPARγ and PPARγ-mediated adipogenic genes, leading to increased adipogenesis and altered adipocyte functionality. The IRF3 knockout (KO) mice develop obesity, insulin resistance, glucose intolerance, and eventually type 2 diabetes with aging, which is associated with the development of white adipose tissue (WAT) inflammation. Increased macrophage accumulation with M1 phenotype which is due to the loss of IFNβ-mediated IL-10 expression is observed in WAT of the KO mice compared to that in wild-type mice. Bone-marrow reconstitution experiments demonstrate that the nonhematopoietic cells are the primary contributors to the development of obesity and both hematopoietic and nonhematopoietic cells contribute to the development of obesity-related complications in IRF3 KO mice. This study demonstrates that IRF3 regulates the biology of multiple cell types including adipocytes and macrophages to prevent the development of obesity and obesity-related complications and hence, could be a potential target for therapeutic interventions for the prevention and treatment of obesity-associated metabolic disorders.

cGAS-STING cytosolic DNA sensing pathway is suppressed by JAK2-STAT3 in tumor cells

Deficiencies in DNA repair and DNA degrading nucleases lead to accumulation of cytosolic DNA. cGAS is a critical DNA sensor for the detection of cytosolic DNA and subsequent activation of the STING signaling pathway. Here, we show that the cGAS-STING pathway was unresponsive to STING agonists and failed to induce type I interferon (IFN) expression in many tested human tumor cells including DU145 prostate cancer cells. Inhibition of IL-6 or the downstream JAK2/STAT3 signaling restored responsiveness to STING agonists in DU145 cells. STING activity in murine TRAMP-C2 prostate cancer cells was critical for tumor rejection and immune cell infiltration. Endogenous STING agonists including double-stranded DNA and RNA:DNA hybrids present in TRAMP-C2 cells contribute to tumor rejection, but tumor growth was further suppressed by administration of cGAMP. Intratumoral co-injections of IL-6 significantly reduced the anti-tumor effects of cGAMP. In summary, STING in tumor cells contributes to tumor rejection in prostate cancer cells, but its functions are frequently suppressed in tumor cells in part via JAK2 and STAT3 pathways.

Impact of progesterone on skin and hair in menopause - a comprehensive review

In clinical practice, micronized progesterone (MP) is frequently recommended to treat signs and symptoms of skin and hair aging in menopausal women. The aim of this comprehensive review was to evaluate whether topically or systemically applied MP may effectively prevent or slow down signs of skin and hair aging. Three out of six identified studies reported an impact of MP on skin aging markers in menopausal women. Of these, two studies reported a benefit: one for topically applied MP, another for systemically applied combined menopausal hormone therapy (MHT) comprising MP as progestogen for endometrial protection. Tolerability and safety of MP were good. However, there was no study investigating the impact of MP on menopausal scalp hair. In conclusion, delay of skin aging comprises lifestyle adjustment, antioxidants, and several esthetic procedures. In menopausal women, MHT displays beneficial effects on skin aging. There is poor quality but promising scientific evidence for MP displaying anti-aging skin effects in menopausal women. However, good quality studies are needed.

Advances in identification and selection of personalized neoantigen/T-cell pairs for autologous adoptive T cell therapies

Based on the success of tumor-infiltrating lymphocytes (TIL)-based therapies, personalized adoptive cell therapies (ACT) targeting neoantigens have the potential to become a disruptive technology and lead to highly effective treatments for cancer patients for whom no other options exist. ACT of TIL, peripheral blood or gene-engineered peripheral blood lymphocytes (PBLs) targeting neoantigens is a highly personalized intervention that requires three discrete steps: i) Identification of suitable personal targets (neoantigens), ii) selection of T cells or their T cell receptors (TCRs) that are specific for the identified neoantigens and iii) expansion of the selected T cell population or generation of sufficient number of TCR modified T cells. In this review, we provide an introduction into challenges and approaches to identify neoantigens and to select the Adoptive Cell Therapy, ACT, Neoantigen, T cell, Cancer respective neoantigen-reactive T cells for use in ACT.

Abstract B189: Tumoral STING is required for effective anticancer immunity

Cyclic GMP-AMP (cGAMP) synthase (cGAS) is a cytosolic DNA sensor that catalyses the synthesis of cGAMP, which serves as a ligand for stimulator of interferon (IFN) genes (STING). Activation of STING results in production of type I IFNs through phosphorylation of TANK-binding kinase 1 (TBK1) and IFN regulatory factor 3 (IRF3). Type I IFNs are critical participants in the innate and adaptive immune recognition of cancer cells. Deficiencies in the cGAS-STING signalling pathway have been reported in many tumors. This mitigates expression of type I IFNs and may thus contribute to non-inflamed tumor microenvironment. In particular, a non-T-cell-inflamed tumor microenvironment correlates with poor patient survival. STING agonists may contribute to antitumor activity by upregulating proinflammatory cytokines and type I IFNs and various STING agonists are now being tested in clinical trials. The role of STING in immune cells is relatively well understood; however, its role in tumor cells has not yet been described in detail. Here we show that cGAS is able to bind to DNA present in the cytosol of tumor cells and subsequently induces STING signaling leading to expression of type I IFNs. Knockout of STING in mouse prostate TRAMP-C2 tumor cells resulted in higher tumor burden and reduced infiltration of immune cells such as dendritic and CD8+ T-cells into the tumor microenvironment. Consistently, treatment with the STING agonist cGAMP elevated type I IFNs levels in TRAMP-C2 cells and led to a reduced tumor volume compared to untreated control. This suggests a pivotal role of tumoral STING in antitumor immunity. However, despite intact STING expression, most tested human cancer cell lines were not responsive to various STING agonists and consequently failed to upregulate expression of type I IFNs. In contrast, all tested tumor cell lines responded to Poly(I:C)-induced TLR3 signaling, suggesting that failure to respond to cGAMP was due to a defect upstream of TBK1. Downregulation of cGAS did not render cells responsive to cGAMP, indicating that inability to respond to cGAMP is due to deficiencies of STING to activate TBK1. In the human and mouse prostate cancer cell lines DU145 and TRAMP-C2, respectively, autocrine IL-6 rendered cells unresponsive to STING agonists. While treatment with anti-IL-6 antibodies restored cGAMP responsiveness in DU145 cells, addition of recombinant IL-6 suppressed cGAMP-mediated upregulation of type I IFNs. In summary, our data suggest that cytosolic DNA activates the cGAS-STING signaling pathway. A functional STING is pivotal for eliciting an effective anticancer immune response. In most human cancer cell lines, however, STING signalling is inhibited. Since STING agonists are being evaluated in clinical trials, it is crucial to understand mechanisms that mediate STING unresponsiveness. We show that in tested prostate cancer cells, IL-6 signals contribute to unresponsiveness of STING and blocking of IL-6 can restore responsiveness towards STING agonists.

Citation Format: Manuel Adrian Suter, Wendy Ya Ling Zhang, Muznah Bte Nazar Khan Khatoo, Nikki Ya Ling Tan, Chien Tei Too, Shubhita Tripathi, Paul A. MacAry, Veronique Angeli, Stephan Gasser. Tumoral STING is required for effective anticancer immunity [abstract]. In: Proceedings of the Fourth CRI-CIMT-EATI-AACR International Cancer Immunotherapy Conference: Translating Science into Survival; Sept 30-Oct 3, 2018; New York, NY. Philadelphia (PA): AACR; Cancer Immunol Res 2019;7(2 Suppl):Abstract nr B189.

The role of the tumour microenvironment in immunotherapy

Recent success in immunomodulating strategies in lung cancer and melanoma has prompted much enthusiasm in their potential to treat other advanced solid malignancies. However, their applications have shown variable success and are even ineffective against some tumours. The efficiency of immunotherapies relies on an immunogenic tumour microenvironment. The current field of cancer immunology has focused on understanding the interaction of cancer and host immune cells to break the state of immune tolerance and explain how molecular patterns of cytokines and chemokines affect tumour progression. Here, we review our current knowledge of how inherent properties of tumours and their different tumour microenvironments affect therapeutic outcome. We also discuss insights into recent multimodal therapeutic approaches that target tumour immune evasion and suppression to restore anti-tumour immunity.

Transplantation and Damage-Associated Molecular Patterns (DAMPs)

Upon solid organ transplantation and during cancer immunotherapy, cellular stress responses result in the release of damage-associated molecular patterns (DAMPs). The various cellular stresses have been characterized in detail over the last decades, but a unifying classification based on clinically important aspects is lacking. Here, we provide an in-depth review of the most recent literature along with a unifying concept of the danger/injury model, suggest a classification of DAMPs, and review the recently elaborated mechanisms that result in the emission of such factors. We further point out the differences in DAMP responses including the release following a heat shock pattern, endoplasmic reticulum stress, DNA damage-mediated DAMP release, and discuss the diverse pathways of regulated necrosis in this respect. The understanding of various forms of DAMPs and the consequences of their different release patterns are prerequisite to associate serum markers of cellular stresses with clinical outcomes.

DAMP-Induced Allograft and Tumor Rejection: The Circle Is Closing

The pathophysiological importance of the immunogenicity of damage-associated molecular patterns (DAMPs) has been pinpointed by their identification as triggers of allograft rejection following release from dying cells, such as after ischemia-reperfusion injury. In cancers, however, this strong trigger of a specific immune response gives rise to the success of cancer immunotherapy. Here, we review the recently literature on the pathophysiological importance of DAMP release and discuss the implications of these processes for allograft rejection and cancer immunotherapy, revealing a striking mechanistic overlap. We conclude that these two fields share a common mechanistic basis of regulated necrosis and inflammation, the molecular characterization of which may be helpful for both oncologists and the transplant community.

Sensing of dangerous DNA

The presence of damaged and microbial DNA can pose a threat to the survival of organisms. Cells express various sensors that recognize specific aspects of such potentially dangerous DNA. Recognition of damaged or microbial DNA by sensors induces cellular processes that are important for DNA repair and inflammation. Here, we review recent evidence that the cellular response to DNA damage and microbial DNA are tightly intertwined. We also discuss insights into the parameters that enable DNA sensors to distinguish damaged and microbial DNA from DNA present in healthy cells.

The DNA Structure-Specific Endonuclease MUS81 Mediates DNA Sensor STING-Dependent Host Rejection of Prostate Cancer Cells

Self-DNA is present in the cytosol of many cancer cells and can promote effective immune rejection of tumor cells, but the mechanisms leading to the presence of cytosolic DNA are unknown. Here, we report that the cleavage of genomic DNA by DNA structure-specific endonuclease MUS81 and PARP-dependent DNA repair pathways leads to the accumulation of cytosolic DNA in prostate cancer cells. The number of nuclear MUS81 foci and the amount of cytosolic dsDNA increased in tandem from hyperplasia to clinical stage II prostate cancers and decreased at stage III. Cytosolic DNA generated by MUS81 stimulated DNA sensor STING-dependent type I interferon (IFN) expression and promoted phagocytic and T cell responses, resulting in type I and II IFN-mediated rejection of prostate tumor cells via mechanisms that partly depended on macrophages. Our results demonstrate that the tumor suppressor MUS81 alerts the immune system to the presence of transformed host cells.

Generating Primary Fibroblast Cultures from Mouse Ear and Tail Tissues

Primary cells are derived directly from tissue and are thought to be more representative of the physiological state of cells in vivo than established cell lines. However, primary cell cultures usually have a finite life span and need to be frequently re-established. Fibroblasts are an easily accessible source of primary cells. Here, we discuss a simple and quick experimental procedure to establish primary fibroblast cultures from ears and tails of mice. The protocol can be used to establish primary fibroblast cultures from ears stored at RT for up to 10 days. When the protocol is carefully followed, contaminations are unlikely to occur despite the use of non-sterile tissue stored for extended time in some cases. Fibroblasts proliferate rapidly in culture and can be expanded to substantial numbers before undergoing replicative senescence.

Genome-derived cytosolic DNA contributes to type I interferon expression and immunogenicity of B-cell lymphoma cells

We recently provided evidence that genome-derived DNA is present in the cytosol of many tumor cells. Genomic loci that give rise to cytosolic DNA can potentially form non-B DNA structures including triple-stranded RNA:DNA structures (R-loops). The RNA:DNA-specific endonuclease RNaseh1 reduced the levels of cytosolic DNA and type I interferon-dependent rejection of B-cell lymphoma suggesting that cytosolic DNA may contribute to immune surveillance of B-cell lymphoma.

Genome-derived cytosolic DNA mediates type I interferon-dependent rejection of B cell lymphoma cells

The DNA damage response (DDR) induces the expression of type I interferons (IFNs), but the underlying mechanisms are poorly understood. Here, we show the presence of cytosolic DNA in different mouse and human tumor cells. Treatment of cells with genotoxic agents increased the levels of cytosolic DNA in a DDR-dependent manner. Cloning of cytosolic DNA molecules from mouse lymphoma cells suggests that cytosolic DNA is derived from unique genomic loci and has the potential to form non-B DNA structures, including R-loops. Overexpression of Rnaseh1, which resolves R-loops, reduced the levels of cytosolic DNA, type I Ifn transcripts, and type I IFN-dependent rejection of lymphoma cells. Live-cell imaging showed a dynamic contact of cytosolic DNA with mitochondria, an important organelle for innate immune recognition of cytosolic nucleotides. In summary, we found that cytosolic DNA is present in many tumor cells and contributes to the immunogenicity of tumor cells.

RNA polymerase III regulates cytosolic RNA:DNA hybrids and intracellular microRNA expression

RNA:DNA hybrids form in the nuclei and mitochondria of cells as transcription-induced R-loops or G-quadruplexes, but exist only in the cytosol of virus-infected cells. Little is known about the existence of RNA:DNA hybrids in the cytosol of virus-free cells, in particular cancer or transformed cells. Here, we show that cytosolic RNA:DNA hybrids are present in various human cell lines, including transformed cells. Inhibition of RNA polymerase III (Pol III), but not DNA polymerase, abrogated cytosolic RNA:DNA hybrids. Cytosolic RNA:DNA hybrids bind to several components of the microRNA (miRNA) machinery-related proteins, including AGO2 and DDX17. Furthermore, we identified miRNAs that are specifically regulated by Pol III, providing a potential link between RNA:DNA hybrids and the miRNA machinery. One of the target genes, exportin-1, is shown to regulate cytosolic RNA:DNA hybrids. Taken together, we reveal previously unknown mechanism by which Pol III regulates the presence of cytosolic RNA:DNA hybrids and miRNA biogenesis in various human cells.

NKG2D ligands link oncogenic RAS to innate immunity

RAS is constitutively active in multiple types of tumor cells. We have recently demonstrated that H-RASV12 enhances the translation of ligands for the activating immune receptor NKG2D, hence rendering cells more susceptible to natural killer (NK) cell-mediated lysis. This effect depends on MAPK and PI3K signaling, but not on the DNA damage response.

Abstract 3654: The role of structure-specific endonuclease MUS81 in the induction of cytosolic DNA in tumor cells

Genomic DNA is constantly damaged by endogenous and exogenous agents. The DNA damage response (DDR) is vital for recognizing DNA damage and instigating DNA repair reactions to ensure genome stability. MUS81 is a structure-specific endonuclease that is required for resolving stalled replication forks at sites of DNA damage to initiate Homologous Recombination repair. Our preliminary data suggests that the potentially detrimental DNA structures cleaved by MUS81 accumulate in the cytosol of many tumor cells. Furthermore, we found that DNA cleaved by MUS81 induces type I interferon expression in a STING-dependent manner, and initiates an innate immune response in vivo. Cytosolic DNA in tumor cells was also abrogated upon inhibition of DNA damage sensors, ATM/ATR and PARP1. In addition, genetic inhibition of Mus81 in different tumor cells lines impaired expression of cytosolic DNA and type I interferon. In summary, our data suggest that the structure-specific endonuclease MUS81 cleaves damaged nuclear DNA leading to accumulation of genomic DNA in the cytosol of tumor cells, activating immunosurveillance mechanisms.

Citation Format: Samantha Ho, Stephan Gasser. The role of structure-specific endonuclease MUS81 in the induction of cytosolic DNA in tumor cells. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 3654. doi:10.1158/1538-7445.AM2014-3654

STING-dependent cytosolic DNA sensor pathways regulate NKG2D ligand expression

The DNA damage response (DDR) upregulates the expression of NKG2D ligands (NKG2DLs).^1,2 We have recently reported that the DDR also induces the presence of cytosolic DNA in B-cell lymphoma cells, which leads to the activation of STING-dependent cytosolic DNA sensor pathways and the expression of RAE-1 ligands for NKG2D.^3.

Synergistic anticancer effects of Pam3CSK4 and Ara-C on B-cell lymphoma cells

PURPOSE

The low immunogenicity of many cancer cells and the immunosuppression by various cancers and anticancer therapies have been an obstacle in the development of efficacious immunotherapies. Our goal was to test whether Toll-like receptor (TLR) agonists and anticancer chemotherapeutic agents synergize in rendering tumor cells more immunogenic.

EXPERIMENTAL DESIGN

We treated B-cell lymphoma cells with the TLR1/2 agonist Pam3CSK4 and the genotoxic anticancer agent 1-β-D-arabinofuranosylcytosine (Ara-C). The effects on the immunogenicity of tumor cells were measured in transfer experiments and in vitro studies.

RESULTS

The treatment of B-cell lymphoma cells with the TLR1/2 agonist Pam3CSK4 enhanced the anticancer effects of the genotoxic agent Ara-C. Mice injected with cotreated tumor cells survived longer than mice challenged with Pam3CSK4 or Ara-C-treated cells. Administration of Pam3CSK4 or Ara-C reduced the tumor load of mice injected with tumor cells. Cotreatment had no effect on the rate of apoptosis or proliferation of Ara-C-treated cells, but upregulated the expression of several immunomodulatory molecules. Consistent with an increased immunogenicity of Pam3CSK4 and Ara-C-treated B-cell lymphoma cells, rejection of cotreated tumor cells required natural killer cells and T cells. We demonstrate that the upregulation of immunomodulatory molecules in response to Pam3CSK4 and Ara-C depended in part on NF-κB.

CONCLUSION

TLR agonists can increase the efficacy of conventional cancer therapies by altering the immunogenicity of B-cell lymphoma cells.

Induction of the DNA damage response by IAP inhibition triggers natural immunity via upregulation of NKG2D ligands in Hodgkin lymphoma in vitro

Evasion of apoptosis is a hallmark of cancer cells. Inhibitor of apoptosis proteins (IAPs) act as endogenous inhibitors of programmed cell death and are overexpressed in several tumors including Hodgkin lymphoma (HL). Preclinical studies indicate antitumor activity of IAP antagonists and clinical studies in hematological malignancies are underway. Here, we investigate the impact of the small molecule IAP antagonist LCL161 on HL cell lines. Although the antagonist caused rapid degradation of cIAP1 leading to TNFα secretion, LCL161 did not promote apoptosis significantly. However, LCL161 induced expression of MICA and MICB, ligands for the activating immune receptor NKG2D, and enhanced the susceptibility of HL cells to NKG2D-dependent lysis by NK cells. MICA/B upregulation was dependent on activation of the DNA damage response upon LCL161 treatment. Taken together, we demonstrate a novel link between IAP inhibition, DNA damage and immune recognition.

RAE1 ligands for the NKG2D receptor are regulated by STING-dependent DNA sensor pathways in lymphoma

The immunoreceptor NKG2D originally identified in natural killer (NK) cells recognizes ligands that are upregulated on tumor cells. Expression of NKG2D ligands (NKG2DL) is induced by the DNA damage response (DDR), which is often activated constitutively in cancer cells, revealing them to NK cells as a mechanism of immunosurveillance. Here, we report that the induction of retinoic acid early transcript 1 (RAE1) ligands for NKG2D by the DDR relies on a STING-dependent DNA sensor pathway involving the effector molecules TBK1 and IRF3. Cytosolic DNA was detected in lymphoma cell lines that express RAE1 and its occurrence required activation of the DDR. Transfection of DNA into ligand-negative cells was sufficient to induce RAE1 expression. Irf3(+/-);Eμ-Myc mice expressed lower levels of RAE1 on tumor cells and showed a reduced survival rate compared with Irf3(+/+);Eμ-Myc mice. Taken together, our results suggest that genomic damage in tumor cells leads to activation of STING-dependent DNA sensor pathways, thereby activating RAE1 and enabling tumor immunosurveillance.

The DNA damage response induces antigen presenting cell-like functions in fibroblasts

The DNA damage response (DDR) alerts the immune system to the danger posed by DNA damage through the induction of damage-associated molecular pattern molecules, chemokines, and ligands for activating immune receptors such as lymphocyte function-associated antigen 1 (LFA-1), NKG2D, and DNAX accessory molecule 1 (DNAM-1). Here we provide evidence that OVA(257-264) -pulsed fibroblasts gain the ability to activate naïve OT-I CD8(+) T cells in response to DNA damage. The ability of fibroblasts to activate OT-I CD8(+) T cells depended on the upregulation of ICAM-1 on fibroblasts and DNAM-1 expression of CD8(+) T cells. OVA(257-264) -pulsed fibroblasts were able to induce a protective T-cell response against B16-OVA cells in a DDR-dependent manner. Hence, the DDR may alert the immune system to the presence of potentially dangerous cells by upregulating the expression of ligands that can induce the activation of innate and adaptive immune cells.

Advances in NKG2D ligand recognition and responses by NK cells

The natural killer (NK) group 2 member D (NKG2D) is an activating immune receptor expressed on NK cells, cytotoxic T cells and a subset of other T cells. It has an important role in the recognition and lysis of a variety of infected and tumor cells. Despite significant gains in our understanding of NKG2D, the relevance of NKG2D and its ligands in human diseases has only recently started to emerge. Here, we present an overview of the recent advances in NKG2D biology, discuss the expression of NKG2D ligands in cancer patients and evaluate the diagnostic and prognostic potential of NKG2D ligands.

Annexin-A1 regulates TLR-mediated IFN-β production through an interaction with TANK-binding kinase 1

TLRs play a pivotal role in the recognition of bacteria and viruses. Members of the family recognize specific pathogen sequences to trigger both MyD88 and TRIF-dependent pathways to stimulate a plethora of cells. Aberrant activation of these pathways is known to play a critical role in the development of autoimmunity and cancer. However, how these pathways are entirely regulated is not fully understood. In these studies, we have identified Annexin-A1 (ANXA1) as a novel regulator of TLR-induced IFN-β and CXCL10 production. We demonstrate that in the absence of ANXA1, mice produce significantly less IFN-β and CXCL10, and macrophages and plasmacytoid dendritic cells have a deficiency in activation following polyinosinic:polycytidylic acid administration in vivo. Furthermore, a deficiency in activation is observed in macrophages after LPS and polyinosinic:polycytidylic acid in vitro. In keeping with these findings, overexpression of ANXA1 resulted in enhanced IFN-β and IFN-stimulated responsive element promoter activity, whereas silencing of ANXA1 impaired TLR3- and TLR4-induced IFN-β and IFN-stimulated responsive element activation. In addition, we show that the C terminus of ANXA1 directly associates with TANK-binding kinase 1 to regulate IFN regulatory factor 3 translocation and phosphorylation. Our findings demonstrate that ANXA1 plays an important role in TLR activation, leading to an augmentation in the type 1 IFN antiviral cytokine response.

Regulation of self-ligands for activating natural killer cell receptors

Natural killer (NK) cells are able to lyse infected and tumor cells while sparing healthy cells. Recognition of diseased cells by NK cells is governed by several activating and inhibitory receptors. We review numerous pathways that have been implicated in the regulation of self-ligands for activating receptors, including NKG2D, DNAM-1, LFA-1, NKp30, NKp44, NKp46, NKp65, and NKp80 found on NK cells and some T cells. Understanding how the regulation of self-encoded ligand expression is regulated may provide novel avenues for future therapeutic approaches to infections and cancer.

ATM activation mediates anticancer immunosurveillance by natural killer and T cells

The DNA damage response (DDR), which is frequently activated in cancer cells, has been proposed to operate as an early barrier against oncogenesis. We have recently shown that ATM mediates the spontaneous regression of Eμ-myc-driven murine B-cell leukemia in a natural killer and T cell-dependent manner. The DDR partially enhanced immune recognition by stimulating the expression of the DNAM-1 ligand CD155.

Toll-like receptor ligands induce expression of the costimulatory molecule CD155 on antigen-presenting cells

Genotoxic stress and RAS induce the expression of CD155, a ligand for the immune receptors DNAM-1, CD96 and TIGIT. Here we show that antigen-presenting cells upregulate CD155 expression in response to Toll-like receptor activation. Induction of CD155 by Toll-like receptors depended on MYD88, TRIF and NF-κB. In addition, IRF3, but not IRF7, modulated CD155 upregulation in response to TLR3 signals. Immunization of CD155-deficient mice with OVA and the TLR9 agonist CpG resulted in increased OVA-specific IgG2a/c titers when compared to wild type mice. Splenocytes of immunized CD155-deficient mice secreted lower levels of IL-4 and fewer IL-4 and GATA-3 expressing CD4⁺ T cells were present in the spleen of Cd155^−/− mice. Our data suggest that CD155 regulates T_h2 differentiation. Targeting of CD155 in immunization protocols using peptides may represent a promising new approach to boost protective humoral immunity in viral vaccines.

Regulation of ligands for the NKG2D activating receptor

NKG2D is an activating receptor expressed by all NK cells and subsets of T cells. It serves as a major recognition receptor for detection and elimination of transformed and infected cells and participates in the genesis of several inflammatory diseases. The ligands for NKG2D are self-proteins that are induced by pathways that are active in certain pathophysiological states. NKG2D ligands are regulated transcriptionally, at the level of mRNA and protein stability, and by cleavage from the cell surface. In some cases, ligand induction can be attributed to pathways that are activated specifically in cancer cells or infected cells. We review the numerous pathways that have been implicated in the regulation of NKG2D ligands, discuss the pathologic states in which those pathways are likely to act, and attempt to synthesize the findings into general schemes of NKG2D ligand regulation in NK cell responses to cancer and infection.

NK cells regulate CD8+ T cell priming and dendritic cell migration during influenza A infection by IFN-γ and perforin-dependent mechanisms

An effective immune response against influenza A infection depends on the generation of virus-specific T cells. NK cells are one of the first-line defenses against influenza A infection. We set out to delineate the role of NK cells in T cell immunity using a murine model of influenza A infection with A/PR/8/34. We show that early T cell recruitment mainly occurs in the posterior mediastinal lymph node (pMLN). Depletion of NK cells significantly impaired both dendritic cell (DC) and T cell recruitment into the pMLN. A similar reduction of T cell recruitment was observed when migration was blocked by pertussis toxin, suggesting that migration of pulmonary NK cells and DCs regulates cell recruitment to the pMLN. T cell recruitment was dependent on IFN-γ, and transfer of IFN-γ-competent naive NK cells into IFN-γ-/- mice restored T cell recruitment, whereas IFN-γ-deficient NK cells failed to do so. In addition, NK cell depletion reduced the uptake and transport of influenza A virus by DCs, and significantly impaired the virus-specific T cell response. Both IFN-γ-/- and perforin-/- mice showed reduced viral Ag transport by DCs, suggesting that the ability of NK cells to influence virus transport depends on IFN-γ and perforin. In summary, our data suggest that NK cells play a critical role in the initiation and shaping of the T cell response after influenza A infection.

CD137 ligand activated microglia induces oligodendrocyte apoptosis via reactive oxygen species

CD137 (4-1BB, TNFRSF9), a member of the tumor necrosis factor (TNF) receptor family, is a potent T cell co-stimulatory molecule. CD137 ligand (CD137L) is expressed by antigen presenting cells (APC) as a transmembrane protein and transmits activating signals into APC. In this study we investigated the effects of CD137L signaling in microglia, the resident APC in the central nervous system. In vitro, the murine microglia cell lines BV-2 and N9, as well as primary murine microglia responded with activation as evidenced by adherence and secretion of proinflammatory cytokines, MMP-9, and soluble intercellular adhesion molecule (ICAM). CD137L signaling is also important for microglia activation in vivo, since CD137L-deficient mice exhibited profoundly less microglia activation during experimental autoimmune encephalomyelitis (EAE) which is a well-established murine model for neuroinflammation and human multiple sclerosis (MS). Also CD137 is expressed in the CNS of mice during EAE. Activated microglia has been reported to mediate the destruction of axonal myelin sheaths and cause the death of oligodendrocytes, the main pathogenic mechanisms in EAE and MS. Corresponding to the lower microglia activation there were also fewer apoptotic oligodendrocytes in the CNS of CD137L-deficient mice. In vitro co-culture confirmed that CD137L-activated microglia induces apoptosis in oligodendrocytes, and identified reactive oxygen species as the mechanism of apoptosis induction. These data demonstrate activating effects of CD137L signaling to microglia, and show for the first time that the CD137 receptor/ligand system may be a mediator of neuroinflammatory and neurodegenerative disease, by activating microglia which in turn kill oligodendrocytes.

Ras activation induces expression of Raet1 family NK receptor ligands

NK cells play a crucial role in innate immunity against tumors. In many human tumors, Ras is chronically active, and tumor cells frequently express ligands for the activating NK cell receptor NKG2D. In this study, we report that Ras activation upregulates the expression of Raet1 protein family members Rae1α and Rae1β in mouse and ULBP1-3 in human cells. In addition, Ras also induced MHC class I chain-related protein expression in some human cell lines. Overexpression of the constitutively active H-RasV12 mutant was sufficient to induce NKG2D ligand expression. H-RasV12-induced NKG2D ligand upregulation depended on Raf, MAPK/MEK, and PI3K, but not ATM or ATR, two PI3K-like kinases previously shown to induce NKG2D ligand expression. Analysis of the 5' untranslated regions of Raet1 family members suggested the presence of features known to impair translation initiation. Overexpression of the rate-limiting translation initiation factor eIF4E induced Rae1 and ULBP1 expression in a Ras- and PI3K-dependent manner. Upregulation of NKG2D ligands by H-RasV12 increased sensitivity of cells to NK cell-mediated cytotoxicity. In summary, our data suggest that chronic Ras activation is linked to innate immune responses, which may contribute to immune surveillance of H-Ras transformed cells.