The MDM2 Inhibitor Navtemadlin Arrests Mouse Melanoma Growth In Vivo and Potentiates Radiotherapy.

The tumor suppressor protein p53 is mutated in close to 50% of human tumors and is dysregulated in many others, for instance by silencing or loss of p14ARF. Under steady-state conditions, the two E3 ligases MDM2/MDM4 interact with and inhibit the transcriptional activity of p53. Inhibition of p53-MDM2/4 interaction to reactivate p53 in tumors with wild-type (WT) p53 has therefore been considered a therapeutic strategy. Moreover, studies indicate that p53 reactivation may synergize with radiation and increase tumor immunogenicity. In vivo studies of most MDM2 inhibitors have utilized immunodeficient xenograft mouse models, preventing detailed studies of action of these molecules on the immune response. The mouse melanoma cell line B16-F10 carries functional, WT p53 but does not express the MDM2 regulator p19ARF. In this study, we tested a p53-MDM2 protein-protein interaction inhibitor, the small molecule Navtemadlin, which is currently being tested in phase II clinical trials. Using mass spectrometry-based proteomics and imaging flow cytometry, we identified specific protein expression patterns following Navtemadlin treatment of B16-F10 melanoma cells compared with their p53 CRISPR-inactivated control cells. In vitro, Navtemadlin induced a significant, p53-dependent, growth arrest but little apoptosis in B16-F10 cells. When combined with radiotherapy, Navtemadlin showed synergistic effects and increased apoptosis. In vivo, Navtemadlin treatment significantly reduced the growth of B16-F10 melanoma cells implanted in C57Bl/6 mice. Our data highlight the utility of a syngeneic B16-F10 p53+/+ mouse melanoma model for assessing existing and novel p53-MDM2/MDM4 inhibitors and in identifying new combination therapies that can efficiently eliminate tumors in vivo. Significance: The MDM2 inhibitor Navtemadlin arrests mouse tumor growth and potentiates radiotherapy. Our results support a threshold model for apoptosis induction that requires a high, prolonged p53 signaling for cancer cells to become apoptotic.

Constitutive activation of WASp leads to abnormal cytotoxic cells with increased granzyme B and degranulation response to target cells.

X-linked neutropenia (XLN) is caused by gain-of-function mutations in the actin regulator Wiskott-Aldrich Syndrome protein (WASp). XLN patients have reduced numbers of cytotoxic cells in peripheral blood; however, their capacity to kill tumor cells remains to be determined. Here, we examined NK and T cells from 2 patients with XLN harboring the activating WASpL270P mutation. XLN patient NK and T cells had increased granzyme B content and elevated degranulation and IFN-γ production when compared with healthy control cells. Murine WASpL272P NK and T cells formed stable synapses with YAC-1 tumor cells and anti-CD3/CD28-coated beads, respectively. WASpL272P mouse T cells had normal degranulation and cytokine response whereas WASpL272P NK cells showed an enhanced response. Imaging experiments revealed that while WASpL272P CD8+ T cells had increased accumulation of actin upon TCR activation, WASpL272P NK cells had normal actin accumulation at lytic synapses triggered through NKp46 signaling but had impaired response to lymphocyte function associated antigen-1 engagement. When compared with WT mice, WASpL272P mice showed reduced growth of B16 melanoma and increased capacity to reject MHC class I-deficient cells. Together, our data suggest that cytotoxic cells with constitutively active WASp have an increased capacity to respond to and kill tumor cells.

CD36 and LC3B initiated autophagy in B cells regulates the humoral immune response.

Scavenger receptors are pattern recognition receptors that recognize both foreign and self-ligands, and initiate different mechanisms of cellular activation, often as co-receptors. The function of scavenger receptor CD36 in the immune system has mostly been studied in macrophages but it is also highly expressed by innate type B cells where its function is less explored. Here we report that CD36 is involved in macro-autophagy/autophagy in B cells, and in its absence, the humoral immune response is impaired. We found that CD36-deficient B cells exhibit a significantly reduced plasma cell formation, proliferation, mitochondrial mobilization and oxidative phosphorylation. These changes were accompanied by impaired initiation of autophagy, and we found that CD36 regulated autophagy and colocalized with autophagosome membrane protein MAP1LC3/LC3 (microtubule-associated protein 1 light chain 3). When we investigated T-cell-dependent immune responses, we found that mice with CD36 deficiency, specifically in B cells, exhibited attenuated germinal center responses, class switching, and antibody production as well as autophagosome formation. These findings establish a critical role for CD36 in B cell responses and may also contribute to our understanding of CD36-mediated autophagy in other cells as well as in B cell lymphomas that have been shown to express the receptor.Abbreviations: AICDA/AID: activation-induced cytidine deaminase; ATG5: autophagy related 5; ATP: adenosine triphosphate; BCR: B-cell receptor; CPG: unmethylated cytosine-guanosine; CQ: chloroquine; DC: dendritic cells; FOB: follicular B cells; GC: germinal center; Ig: immunoglobulin; LPS: lipopolysaccharide; MAP1LC3/LC3: microtubule-associated protein 1 light chain 3; MFI: mean fluorescence intensity; MZB: marginal zone B cells; NP-CGG: 4-hydroxy-3-nitrophenylacetyl-chicken gamma globulin; OCR: oxygen consumption rate; oxLDL: oxidized low-density lipoprotein; PC: plasma cells; Rapa: rapamycin; SQSTM1/p62: sequestosome 1; SRBC: sheep red blood cells; Tfh: follicular helper T cells; TLR: toll-like receptor.

Combined proinflammatory cytokine and cognate activation of invariant natural killer T cells enhances anti-DNA antibody responses.

Invariant natural killer T (iNKT) cells serve as early rapid responders in the innate immune response to self-derived autoantigens and pathogen-derived danger signals and antigens. iNKT cells can serve both as helpers for effector B cells and negatively regulate autoreactive B cells. Specifically, iNKT cells drive B cell proliferation, class switch, and antibody production to induce primary antigen-specific immune responses. On the other hand, inflammasome-mediated activation drives accumulation of neutrophils, which license iNKT cells to negatively regulate autoreactive B cells via Fas ligand (FasL). This positions iNKT cells at an apex to support or inhibit B cell responses in inflammation. However, it is unknown which effector mechanism dominates in the face of cognate glycolipid activation during chronic inflammation, as might result from glycolipid vaccination or infection during chronic autoimmune disease. We stimulated iNKT cells by cognate glycolipid antigen α-galactosylceramide (αGalCer) and measured B cell activation during interleukin 18 (IL-18)-induced chronic inflammation. Moreover, glycolipid-activated iNKT cells increased the serum concentration of autoantibodies, frequency of germinal center (GC) B cells, and antigen-specific plasma cells induced during chronic IL-18-mediated inflammation, as compared with IL-18 alone. Further, activation of iNKT cells via cognate glycolipid during IL-18-mediated inflammation overrides the licensing function of neutrophils, instead inducing iNKT follicular helper (iNKTfh) cells that in turn promote autoimmunity. Thus, our data demonstrate that glycolipids which engage iNKT cells support antigen-specific B cell help during inflammasome-mediated inflammation.

Promotion or Suppression of Murine Intestinal Polyp Development by iNKT Cell Directed Immunotherapy.

The glycosphingolipid α-galactosylceramide (α-GalCer) is a well-described immune activator with strong anti-tumor properties in animal models. It is presented on CD1d and acts by stimulating the invariant, type I, natural killer T (iNKT) lymphocytes to rapidly secrete TH1 and TH2 associated cytokines. This in turn promotes activation of a diversity of immune cells including natural killer (NK) cells with anti-tumor functions. Prior to tumor development, iNKT cells can also perform tumor surveillance and naturally protect from emergence of cancer. In contrast, we have recently demonstrated that iNKT cells naturally promote polyps in the spontaneous murine adenomatous polyposis coli (Apc) ApcMin/+ model for colon cancer, associated with suppressed TH1 immunity and enhanced immunoregulation. Here we investigated whether iNKT cell directed immunotherapy could subvert the polyp promoting function of iNKT cells and reduce polyp growth in this model. We treated ApcMin/+ mice with α-GalCer, or synthetic derivatives of this ligand (C-glycoside and C20:2) that have enhanced immunoregulatory properties. Treatment with iNKT cell ligands led to increased iNKT cell division, but reduced iNKT cell frequencies, lower NK1.1 expression and elevation of PD-1. ApcMin/+ mice that had been treated either long-term (5-15 weeks of age), or short-term (12-15 weeks of age) with α-GalCer demonstrated a significant decrease in polyp burden. Surprisingly, long-term treatment with the TH1 biasing ligand C-glycoside did not have significant effects on polyps, while long-term treatment with the TH2 biasing ligand C20:2 enhanced polyp growth. In stark contrast, short-term treatment with C20:2 led to reduction in polyp numbers and size. Reduced polyp burden after long-term treatment was associated with increased expression of genes indicating a pro-inflammatory polyp microenvironment. Polyp-reducing short-term treatment led to CD8 T cell activation specifically in polyps, and decreased tumor infiltrating and splenic macrophages, and a switch toward a pro-inflammatory phenotype. Thus, iNKT cell directed therapy could subvert the natural polyp enhancing function of iNKT cells, overcome immunosuppression, and reduce polyps. However, different iNKT cell activating ligands had opposite effects, and the timing of treatment had a major influence on outcomes.

Innate and adaptive stimulation of murine diverse NKT cells result in distinct cellular responses.

Natural killer T (NKT) cells recognize glycolipids presented on CD1d. They share features of adaptive T lymphocytes and innate NK cells, and mediate immunoregulatory functions via rapid production of cytokines. Invariant (iNKT) and diverse (dNKT) NKT cell subsets are defined by their TCR. The immunological role of dNKT cells, that do not express the invariant TCRα-chain used by iNKT cells, is less well explored than that of iNKT cells. Here, we investigated signals driving Toll-like receptor (TLR) ligand activation of TCR-transgenic murine dNKT cells. IFN-γ production by dNKT cells required dendritic cells (DC), cell-to-cell contact and presence of TLR ligands. TLR-stimulated DC activated dNKT cells to secrete IFN-γ in a CD1d-, CD80/86- and type I IFN-independent manner. In contrast, a requirement for IL-12p40, and a TLR ligand-selective dependence on IL-18 or IL-15 was observed. TLR ligand/DC stimulation provoked early secretion of pro-inflammatory cytokines by both CD62L+ and CD62L- dNKT cells. However, proliferation was limited. In contrast, TCR/co-receptor-mediated activation resulted in proliferation and delayed production of a broader cytokine spectrum preferentially in CD62L- dNKT cells. Thus, innate (TLR ligand/DC) and adaptive (TCR/co-receptor) stimulation of dNKT cells resulted in distinct cellular responses that may contribute differently to the formation of immune memory.

Publisher Correction: A DHODH inhibitor increases p53 synthesis and enhances tumor cell killing by p53 degradation blockage.

The original PDF version of this Article listed the authors as "Marcus J.G.W. Ladds," where it should have read "Marcus J. G. W. Ladds, Ingeborg M. M. van Leeuwen, Catherine J. Drummond et al.#".Also in the PDF version, it was incorrectly stated that "Correspondence and requests for materials should be addressed to S. Lín.", instead of the correct "Correspondence and requests for materials should be addressed to S. Laín."This has been corrected in the PDF version of the Article. The HTML version was correct from the time of publication.

A DHODH inhibitor increases p53 synthesis and enhances tumor cell killing by p53 degradation blockage.

The development of non-genotoxic therapies that activate wild-type p53 in tumors is of great interest since the discovery of p53 as a tumor suppressor. Here we report the identification of over 100 small-molecules activating p53 in cells. We elucidate the mechanism of action of a chiral tetrahydroindazole (HZ00), and through target deconvolution, we deduce that its active enantiomer (R)-HZ00, inhibits dihydroorotate dehydrogenase (DHODH). The chiral specificity of HZ05, a more potent analog, is revealed by the crystal structure of the (R)-HZ05/DHODH complex. Twelve other DHODH inhibitor chemotypes are detailed among the p53 activators, which identifies DHODH as a frequent target for structurally diverse compounds. We observe that HZ compounds accumulate cancer cells in S-phase, increase p53 synthesis, and synergize with an inhibitor of p53 degradation to reduce tumor growth in vivo. We, therefore, propose a strategy to promote cancer cell killing by p53 instead of its reversible cell cycle arresting effect.

PPAR-γ promotes type 2 immune responses in allergy and nematode infection.

A hallmark of immunity to worm infections and many allergies is a strong type 2 immune response. This is characterized by the production of cytokines interleukin-5 (IL-5) and IL-13 by adaptive T helper 2 (TH2) cells and/or type 2 innate lymphoid cells. Peroxisome proliferator activated receptor-γ (PPAR-γ) is typically regarded as an anti-inflammatory factor. We report that TH2 cells express high levels of PPAR-γ in response to the allergen house dust mite and after infection with the parasite Heligmosomoides polygyrus Mice lacking PPAR-γ in T cells failed to effectively differentiate into IL-5- and IL-13-secreting cells and, hence, did not develop TH2 cell-associated pathologies, including goblet cell metaplasia and eosinophilia, in response to allergen challenge. Furthermore, these mice could not mount protective immune responses to nematode infection. In addition, mice lacking PPAR-γ in T cells had greatly reduced frequencies of TH2 cells in visceral adipose tissue. Mechanistically, PPAR-γ appeared to promote the expression of the IL-33 receptor on the surface of TH2 cells. These results pinpoint PPAR-γ as a factor that drives type 2 responses in allergy, worm infection, and visceral adipose tissue.

Regulation of Subunit-Specific Germinal Center B Cell Responses to the HIV-1 Envelope Glycoproteins by Antibody-Mediated Feedback.

The regulation of germinal center (GC) B cell responses to single epitopes is well investigated. How monoclonal B cells are regulated within the polyclonal B cell response to protein antigens is less so. Here, we investigate the primary GC B cell response after injection of mice with HIV-1 envelope glycoproteins. We demonstrate that single GCs are seeded by a diverse number of B cell clones shortly after a single immunization and that the presence of Env-specific antibodies can inhibit the development of early GC B cells. Importantly, the suppression was dependent on the GC B cells and the infused antibodies to target the same subunit of the injected HIV-1 envelope glycoproteins. An affinity-dependent antibody feedback has previously been shown to regulate GC B cell development. Here, we propose that this antibody-based feedback acts on GC B cells only if they target the same or overlapping epitopes. This study provides important basic information of GC B cell regulation, and for future vaccine designs with aim to elicit neutralizing antibodies against HIV-1.

Neutrophils license iNKT cells to regulate self-reactive mouse B cell responses.

The innate responsiveness of the immune system is important not only for quick responses to pathogens but also for the initiation and shaping of the subsequent adaptive immune response. Activation via the cytokine IL-18, a product of inflammasomes, gives rise to a rapid response that includes the production of self-reactive antibodies. As increased concentrations of this cytokine are found in inflammatory diseases, we investigated the origin of the B cell response and its regulation. We identified an accumulation of B cell-helper neutrophils in the spleen that interacted with innate-type invariant natural killer T cells (iNKT cells) to regulate B cell responses. We found that neutrophil-dependent expression of the death-receptor ligand FasL by iNKT cells was needed to restrict autoantibody production. Neutrophils can thus license iNKT cells to regulate potentially harmful autoreactive B cell responses during inflammasome-driven inflammation.

Selective Memory to Apoptotic Cell-Derived Self-Antigens with Implications for Systemic Lupus Erythematosus Development.

Autoimmune diseases are characterized by pathogenic immune responses to self-antigens. In systemic lupus erythematosus (SLE), many self-antigens are found in apoptotic cells (ACs), and defects in removal of ACs from the body are linked to a risk for developing SLE. This includes pathological memory that gives rise to disease flares. In this study, we investigated how memory to AC-derived self-antigens develops and the contribution of self-memory to the development of lupus-related pathology. Multiple injections of ACs without adjuvant into wild-type mice induce a transient primary autoimmune response without apparent anti-nuclear Ab reactivity or kidney pathology. Interestingly, as the transient Ab response reached baseline, a single boost injection fully recalled the immune response to ACs, and this memory response was furthermore transferable into naive mice. Additionally, the memory response contains elements of pathogenicity, accompanied by selective memory to selective Ags. Thus, we provide evidence for a selective self-memory that underlies progression of the response to self-antigens with implications for SLE development therapy.

IL-18 in inflammatory and autoimmune disease.

Inflammation serves as the first line of defense in response to tissue injury, guiding the immune system to ensure preservation of the host. The inflammatory response can be divided into a quick initial phase mediated mainly by innate immune cells including neutrophils and macrophages, followed by a late phase that is dominated by lymphocytes. Early in the new millennium, a key component of the inflammatory reaction was discovered with the identification of a number of cytosolic sensor proteins (Nod-like receptors) that assembled into a common structure, the 'inflammasome'. This structure includes an enzyme, caspase-1, which upon activation cleaves pro-forms of cytokines leading to subsequent release of active IL-1 and IL-18. This review focuses on the role of IL-18 in inflammatory responses with emphasis on autoimmune diseases.

CRYAB-650 C>G (rs2234702) affects susceptibility to Type 1 diabetes and IAA-positivity in Swedish population.

BACKGROUND: Single nucleotide polymorphisms (SNPs) in the promoter region of CRYAB gene have been associated with in multiple sclerosis. CRYAB gene, which encodes alpha B-crystallin (a member of small heat shock protein), was reported as a potential autoimmune target. In this study we investigated whether SNPs in the promoter region of CRYAB gene were also important in the etiology of Type 1 diabetes (T1D). METHODS: Genotyping of SNPs in the promoter region of CRYAB gene was performed in a Swedish cohort containing 444 T1D patients and 350 healthy controls. Three SNPs were included in this study: CRYAB-652 A>G (rs762550), -650 C>G (rs2234702) and -249 C > G (rs14133). Two SNPs (CRYAB-652 and -650) were not included in previous genome wide association studies. RESULTS: CRYAB-650 (rs2234702)*C allele was significantly more frequent in patients than in controls (OR = 1.48, Pc = 0.03). CRYAB-650*C allele was associated with IAA positivity (OR = 8.17, Pc < 0.0001) and IA-2A positivity (OR = 2.14, Pc = 0.005) in T1D patients. This association with IAA was amplified by high-risk HLA carrier state (OR = 10.6, P < 0.0001). No association was found between CRYAB-650 and other autoantibody positivity (GADA and ICA). CRYAB haplotypes were also associated with IAA and IA-2A positivity (highest OR = 2.07 and 2.11, respectively), these associations remain in high HLA-risk T1D patients. CONCLUSIONS: CRYAB-650 was associated with T1D in the Swedish cohort we studied. CRYAB-650*C allele might confers susceptibility to the development of T1D. CRYAB-650 was also associated with the development of IAA-positivity in T1D patients, especially in those carrying T1D high-risk HLA haplotypes.

Killer cell immunoglobulin-like receptor along with HLA-C ligand genes are associated with type 1 diabetes in Chinese Han population.

OBJECTIVE: Killer cell immunoglobulin-like receptor (KIR) genes and their putative ligands human leukocyte antigen (HLA)-C genes have been associated with type 1 diabetes (T1D). We hypothesize that KIR genes and their ligands HLA-C genes are important in T1D aetiology. RESEARCH DESIGN AND METHODS: KIR and HLA-C ligand genotyping was performed in 259 T1D patients and 262 healthy children. RESULTS: No significant difference was observed in the distribution of KIR genes between T1D patients and healthy controls. However, frequency of HLA-C1 gene and HLA-C2 gene (marginal association) was higher in patient group. The combinations 2DL2-/HLA-C1+; 2DL3+/HLA-C1+; 2DS2-/HLAC1+ were positively associated with T1D. The combinations 2DL1+/HLA-C2-; 2DL2-/HLA-C1-; 2DL3+/HLA-C1-; 2DS2-/HLAC1- were found to be negatively associated with T1D. Among the genes we tested, a combination of HLA-C1 and -C2 conferred the strongest association with T1D and the strength of this association was higher than that of HLA-C1 alone. The frequencies of KIR 2DL1, 2DL2 and 2DL3 and HLA-C1 were higher in T1D patients positive for GAD65 autoantibody; frequency of KIR 2DS4 is higher in T1D patients positive for IA-2 autoantibody. The association between KIR/HLA-C gene and autoantibody status was not statistically significant after applying Bonferroni correction. CONCLUSION: In our study of a Han population (East China), we found no direct association of KIR genes with T1D. However, a combination of HLA-C1 and -C2 showed a positive association with T1D. Different combinations of HLA-C and KIR showed positive and negative association with T1D.

[Killer cell immunoglobin-like receptor and its ligand gene polymorphisms in Hunan Han patients with type 1 diabetes].

OBJECTIVE: To investigate the association of Killer cell immunoglobin-like receptor (KIR) gene and KIRs'ligand (HLA-C) gene polymorphisms with type 1 diabetes (T1DM). METHODS: Using polymerase chain reaction-sequence specific primer (PCR-SSP) to detect KIR and HLA-C genotype in 180 T1DM patients and 199 healthy controls from Hunan Han population. RESULTS: (1) The frequencies of KIR 2DL1 (98.9% vs 92.0%, OR = 7.78, P = 0.002), 3DL1 (94.3% vs 86.4%, OR = 2.67, P = 0.009) and 2DS4 (83.9% vs 70.9%, OR = 2.14, P = 0.003) were significantly higher in T1DM patients than those in the controls. (2) There were no differences in the frequencies of HLA-C1 and HLA-C2 between the patients and the controls, but the frequency of HLAC1+/C2+ (3.9% vs 9.6%, OR = 0.38, P = 0.03) was significantly lower in the T1DM patients. (3) The combination KIR2DL1-/HLA-C2-(0.6% vs 6.0%, OR = 0.087, P = 0.003) and KIR 2DS1-/HLA-C2-(53.3% vs 64.8%, OR = 0.62, P = 0.023) was significantly lower in the T1DM patients. CONCLUSION: The KIR gene polymorphism and KIR/HLA-C gene compatibility are associated with T1DM.

Prevention of beta-cell destruction in autoimmune diabetes: current approaches and future prospects.

Type 1 diabetes (T1D) is an autoimmune disease resulting from the destruction of pancreatic beta-cells. The main aim of treatment should be to prevent beta-cell destruction and preserve existing beta-cells in individuals with progressive autoimmunity. This can be achieved in several ways and in this chapter the authors have reviewed recent approaches that are currently being tested in animal models and human T1D patients under the following categories: i) antigen based therapy, ii) antibody-based therapy iii) other forms of therapy and iv) failed therapies.

Alternative routes of insulin delivery.

Parenteral route of insulin administration has been the mode of treatment for all Type 1 diabetics and Type 2 diabetics with complications. Patient compliance has really been a major concern for this route of administration. Several alternative routes of administration are under consideration for effective glycemic control, including oral, inhaled, buccal, nasal, and patch routes. One of the approaches involving inhaled insulin has now reached the market. Several other candidates may reach the market in the near future, the promising one being oral insulin.

Diabetes--role of epigenetics, genetics, and physiological factors.

Cells of organ systems are endowed with a relatively similar genome while epigenome niches keep varying chronologically and defined explicitly in the respective tissues. The genome of an individual is always influenced by parental, embryonic, tissue-specific, and environmental epigenomes and the same must have been the possible reason for invariable inquiries relating to familial, environmental and life style patterns in the preliminary investigations of diabetic complications. Unprecedented methylation of lysine residues of histones and cytosines of CpG islands of promoter DNA impede the transcription of genes and homocysteine is the metabolic key player of methyl groups. Gck and COX7A1 are the 2 examples in the present review to elucidate the epigenetic influence on the onset of diabetes. miRNAs are additional promising cellular components influencing both at transcriptional and translational levels and promoting either in favour or against (i.e., feed back) TFs, signaling factors and proteins through their pliotropic effects and thus are reported to regulate cellular physiology. miR-124a and miR-9 are primarily endemic to nervous tissue and they are now being exploited in islets for their function in executing exocytosis of insulin, which of course is one of the fundamental canons of diabetes. miR-375 persuades beta cells for glucose-induced insulin gene expression. The current approach to evaluate the constellation of genes and their products involved in diabetes in huge number of samples through GWA studies may unravel intricacies involved in the management of diabetes and its associated consequences.