Safety levels of systemic IL-12 induced by cDNA expression as a cancer therapeutic.

Aim: The aim of this work is to utilize a gene expression procedure to safely express systemic IL-12 and evaluate its effects in mouse tumor models. Materials & methods: Secondary lymphoid organs and tumors from EL4 and B16 tumor-bearing mice were analyzed by supervised and unsupervised methods. Results: IL-12 cDNA induced systemic IL-12 protein levels lower than the tolerated dose in patients. Control of tumor growth was observed in subcutaneous B16 and EL4 tumors. Systemic IL-12 expression induced a higher frequency of both total tumor-infiltrated CD45+ cells and proliferative IFN-γ+CD8+ T cells along with a lower frequency of CD4+FOXP3+ and CD11b+Gr-1+ cells. Conclusion: This approach characterizes the systemic effects of IL-12, helping to improve treatment of metastases or solid tumors.

Lay abstract IL-12 has emerged as a potent cytokine in mediating antitumor activity in preclinical models of cancer. However, this antitumor response has not yet been translated into the clinic because of toxic side effects. The aim of our work is to analyze the effects of IL-12 in mouse tumor models. We demonstrate that one injection of IL-12 cDNA can induce systemic IL-12 levels in serum even lower than the tolerated dose in patients. At this dose, an efficient control of tumor growth can be observed. We found a higher frequency of both total tumor-infiltrated leukocytes and IFN-γ-producing CD8⁺ T cells along with a lower frequency of regulatory CD4⁺FOXP3⁺ and CD11b⁺Gr1⁺ cells. Our work demonstrates that IL-12 cDNA can safely be used to treat cancer.

IFN-gamma AU-rich element removal promotes chronic IFN-gamma expression and autoimmunity in mice.

We generated a mouse model with a 162 nt AU-rich element (ARE) region deletion in the 3' untranslated region (3'UTR) of the interferon-gamma (IFN-γ) gene that results in chronic circulating serum IFN-γ levels. Mice homozygous for the ARE deletion (ARE-Del) (-/-) present both serologic and cellular abnormalities typical of patients with systemic lupus erythematosus (SLE). ARE-Del(-/-) mice display increased numbers of pDCs in bone marrow and spleen. Addition of IFN-γ to Flt3-ligand (Flt3L) treated in vitro bone marrow cultures results in a 2-fold increase in pDCs with concurrent increases in IRF8 expression. Marginal zone B (MZB) cells and marginal zone macrophages (MZMs) are absent in ARE-Del(-/-) mice. ARE-Del(+/-) mice retain both MZB cells and MZMs and develop no or mild autoimmunity. However, low dose clodronate treatment in ARE-Del(+/-) mice specifically eliminates MZMs and promotes anti-DNA antibody development and glomerulonephritis. Our findings demonstrate the consequences of a chronic IFN-γ milieu on B220(+) cell types and in particular the impact of MZB cell loss on MZM function in autoimmunity. Furthermore, similarities between disease states in ARE-Del(-/-) mice and SLE patients suggest that IFN-γ may not only be a product of SLE but may be critical for disease onset and progression.

Abrogation of TNFα production during cancer immunotherapy is crucial for suppressing side effects due to the systemic expression of IL-12.

For more than a decade, the cytokine interleukin-12 (IL-12) has been utilized, either alone or in combination with other drugs, as a treatment for cancer. The numerous anti-tumor properties of IL-12 still generate interest in the clinical use of this cytokine, even though it has demonstrated toxicity when administrated systemically. As an approach to overcome this toxicity, numerous laboratories have attempted to induce IL-12 expression at the site of the tumor. However for tumors that are difficult to remove surgically or for the treatment of disseminated metastases, systemic expression of this cytokine still remains as the most efficient method of administration. Nevertheless, finding alternative approaches for the use of IL-12 in the treatment of cancer and unraveling the basis of IL-12-side effects remain a challenge. In the present work we demonstrate that systemic expression of IL-12 through hydrodynamic injection of IL-12 cDNA is able to induce different types of liver lesions associated with a toxic pathology. However we report here that hepatic toxicity is diminished and survival of mice enhanced in the absence of tumor necrosis factor alpha (TNFα). This observation is in contrast to several murine models and clinical trials that postulate interferon gamma (IFNγ) as the main cytokine responsible for IL-12 toxicity. Moreover, our work demonstrates that when IL-12 cDNA is co-injected with IL-18 cDNA or when mice are pre-treated with a low dose of IL-12 cDNA prior to receiving a high dose of IL-12 cDNA, systemic levels of TNFα are almost completely abrogated, resulting in improved survival and less hepatic damage. Importantly, abrogation of TNFα signaling does not affect the strong anti-tumor activity of IL-12. Thus, neutralizing TNFα with antagonists already approved for human use offers a promising approach to abrogate IL-12 side effects during the use of this cytokine for the treatment of cancer.

Progression of chronic liver inflammation and fibrosis driven by activation of c-JUN signaling in Sirt6 mutant mice.

The human body has a remarkable ability to regulate inflammation, a biophysical response triggered by virus infection and tissue damage. Sirt6 is critical for metabolism and lifespan; however, its role in inflammation is unknown. Here we show that Sirt6-null (Sirt6(-/-)) mice developed chronic liver inflammation starting at ∼2 months of age, and all animals were affected by 7-8 months of age. Deletion of Sirt6 in T cells or myeloid-derived cells was sufficient to induce liver inflammation and fibrosis, albeit to a lesser degree than that in the global Sirt6(-/-) mice, suggesting that Sirt6 deficiency in the immune cells is the cause. Consistently, macrophages derived from the bone marrow of Sirt6(-/-) mice showed increased MCP-1, IL-6, and TNFα expression levels and were hypersensitive to LPS stimulation. Mechanistically, SIRT6 interacts with c-JUN and deacetylates histone H3 lysine 9 (H3K9) at the promoter of proinflammatory genes whose expression involves the c-JUN signaling pathway. Sirt6-deficient macrophages displayed hyperacetylation of H3K9 and increased occupancy of c-JUN in the promoter of these genes, leading to their elevated expression. These data suggest that Sirt6 plays an anti-inflammatory role in mice by inhibiting c-JUN-dependent expression of proinflammatory genes.

MCP-1/CCR2 interactions direct migration of peripheral B and T lymphocytes to the thymus during acute infectious/inflammatory processes.

Mature lymphocyte immigration into the thymus has been documented in mouse, rat, and pig models, and highly increases when cells acquire an activated phenotype. Entrance of peripheral B and T cells into the thymus has been described in healthy and pathological situations. However, it has not been proposed that leukocyte recirculation to the thymus could be a common feature occurring during the early phase of a Th1 inflammatory/infectious process when a large number of peripheral cells acquire an activated phenotype and the cellularity of the thymus is seriously compromised. The data we present here demonstrate that in well-established Th1 models triggered by different types of immunogens, for example, LPS treatment (a bacterial product), Candida albicans infection (a fungus), and after Trypanosoma cruzi infection (a parasite), a large number of mature peripheral B and T cells enter the thymus. This effect is dependent on, but not exclusive of, the available space in the thymus. Our data also demonstrate that MCP-1/CCR2 (where MCP-1 is monocyte chemoattractant protein-1) interaction is responsible for the infiltration of peripheral cells to the thymus in these Th1-inflammatory/infectious situations. Finally, systemic expression of IL-12 and IL-18 produced during the inflammatory process is ultimately responsible for these migratory events.

A novel role for IL-22R1 as a driver of inflammation.

The interleukin (IL)-22R1 chain of the heterodimeric IL-22 receptor is not expressed on normal leukocytes, but this receptor is expressed on T cells from anaplastic lymphoma kinase-positive (ALK(+)) anaplastic large cell lymphoma (ALCL) patients. To investigate the consequences of aberrant expression of this receptor on lymphocytes, we generated transgenic mice that express IL-22R1 on lymphocytes. The health of these animals progressively deteriorated at 8 to 12 weeks of age, as they displayed respiratory distress, rough coat and sluggish movement, and subsequent lethality due to multiorgan inflammation. The IL-22R1 transgenic animals developed neutrophilia that correlated with increased levels of circulating IL-17 and granulocyte colony-stimulating factor. In addition, these mice had increased serum IL-22 levels, suggesting that T cells expressing IL-22R1 generate IL-22 in a positive autoregulatory loop. As a result of the mouse model findings, we analyzed circulating cytokine levels in ALK(+)ALCL patients and detected elevated levels of IL-22, IL-17, and IL-8 in untreated patient samples. Importantly, IL-22 and IL-17 were undetectable in all patients who were in complete remission after chemotherapy. This study documents a previously unknown role of IL-22R1 in inflammation and identifies the involvement of IL-22R1/IL-22 in ALK(+)ALCL.

Coexpression of IL-18 strongly attenuates IL-12-induced systemic toxicity through a rapid induction of IL-10 without affecting its antitumor capacity.

IL-12 is an excellent candidate for the treatment of cancer due to its ability to drive strong antitumor responses. Recombinant IL-12 protein is currently used in cancer patients; however, systemic expression of rIL-12 presents disadvantages including cost and dose limitation due to its toxicity. In this study, we used hydrodynamic shear of cDNA as a tool to achieve systemic expression of IL-12. We found that sustained but toxic levels of serum IL-12 could be generated in 6- to 7-wk-old B6 mice after a single injection of the cDNA. Unexpectedly, we observed that when IL-12 cDNA is coinjected with IL-18 cDNA, IL-12 antitumor activity was maintained, but there was a significant attenuation of IL-12 toxicity, as evidenced by a greater survival index and a diminution of liver enzymes (ALT and AST). Interestingly, after IL-12 plus IL-18 cDNA administration, more rapid and higher IL-10 levels were observed than after IL-12 cDNA treatment alone. To understand the mechanism of protection, we coinjected IL-12 plus IL-10 cDNAs and observed an increase in survival that correlated with diminished serum levels of the inflammatory cytokines TNF-alpha and IFN-gamma. Confirming the protective role of early IL-10 expression, we observed a significant decrease in survival in IL-10 knockout mice or IL-10R-blocked B6 mice after IL-12 plus IL-18 treatment. Thus, our data demonstrate that the high and early IL-10 expression induced after IL-12 plus IL-18 cDNA treatment is critical to rapidly attenuate IL-12 toxicity without affecting its antitumor capacity. These data could highly contribute to the design of more efficient/less toxic protocols for the treatment of cancer.

The proinflammatory cytokine interleukin-18 alters multiple signaling pathways to inhibit natural killer cell death.

The proinflammatory cytokine, interleukin-18 (IL-18), is a natural killer (NK) cell activator that induces NK cell cytotoxicity and interferon-gamma (IFN-gamma) expression. In this report, we define a novel role for IL-18 as an NK cell protective agent. Specifically, IL-18 prevents NK cell death initiated by different and distinct stress mechanisms. IL-18 reduces NK cell self-destruction during NK-targeted cell killing, and in the presence of staurosporin, a potent apoptotic inducer, IL-18 reduces caspase-3 activity. The critical regulatory step in this process is downstream of the mitochondrion and involves reduced cleavage and activation of caspase-9 and caspase-3. The ability of IL-18 to regulate cell survival is not limited to a caspase death pathway in that IL-18 augments tumor necrosis factor (TNF) signaling, resulting in increased and prolonged mRNA expression of c-apoptosis inhibitor 2 (cIAP2), a prosurvival factor and caspase-3 inhibitor, and TNF receptor-associated factor 1 (TRAF1), a prosurvival protein. The cumulative effects of IL-18 define a novel role for this cytokine as a molecular survival switch that functions to both decrease cell death through inhibition of the mitochondrial apoptotic pathway and enhance TNF induction of prosurvival factors.

The scaffold protein Cybr is required for cytokine-modulated trafficking of leukocytes in vivo.

Trafficking and cell adhesion are key properties of cells of the immune system. However, the molecular pathways that control these cellular behaviors are still poorly understood. Cybr is a scaffold protein highly expressed in the hematopoietic/immune system whose physiological role is still unknown. In vitro studies have shown it regulates LFA-1, a crucial molecule in lymphocyte attachment and migration. Cybr also binds cytohesin-1, a guanine nucleotide exchange factor for the ARF GTPases, which affects actin cytoskeleton remodeling during cell migration. Here we show that expression of Cybr in vivo is differentially modulated by type 1 cytokines during lymphocyte maturation. In mice, Cybr deficiency negatively affects leukocytes circulating in blood and lymphocytes present in the lymph nodes. Moreover, in a Th1-polarized mouse model, lymphocyte trafficking is impaired by loss of Cybr, and Cybr-deficient mice with aseptic peritonitis have fewer cells than controls present in the peritoneal cavity, as well as fewer leukocytes leaving the bloodstream. Mutant mice injected with Moloney murine sarcoma/leukemia virus develop significantly larger tumors than wild-type mice and have reduced lymph node enlargement, suggesting reduced cytotoxic T-lymphocyte migration. Taken together, these data support a role for Cybr in leukocyte trafficking, especially in response to proinflammatory cytokines in stress conditions.

Synthesis and biological study of a flavone acetic acid analogue containing an azido reporting group designed as a multifunctional binding site probe.

Flavone-8-acetic acid (FAA) is a potent immunomodulatory small molecule that is uniquely characterized as being active on mouse but not human cells. Although FAA is a potent inducer of murine cytokine, chemokine and interferon gene expression, its mode of action remains unknown. In this report, we describe the synthesis of a new flavone acetic acid (FAA) analogue, (2-[2-(4-azidophenyl)-4-oxochromen-8-yl-]acetic acid (compound 2). We demonstrate that compound 2 is equally active as the parent FAA in inducing chemokine gene expression and that the azide functional group is capable of reacting with a reporter molecule, such as the FLAG peptide-phosphine, under mild conditions. This reaction will be useful for detecting the drug-bound protein active complex utilizing an anti-FLAG antibody.

Peroxisome proliferator-activated receptor-gamma and its ligands attenuate biologic functions of human natural killer cells.

Interferon-gamma (IFN-gamma) production and cytolytic activity are 2 major biologic functions of natural killer (NK) cells that are important for innate immunity. We demonstrate here that these functions are compromised in human NK cells treated with peroxisome proliferator-activated-gamma (PPAR-gamma) ligands via both PPAR-gamma-dependent and -independent pathways due to variation in PPAR-gamma expression. In PPAR-gamma-null NK cells, 15-deoxy-Delta(12,14) prostaglandin J(2) (15d-PGJ(2)), a natural PPAR-gamma ligand, reduces IFN-gamma production that can be reversed by MG132 and/or chloroquine, and it inhibits cytolytic activity of NK cells through reduction of both conjugate formation and CD69 expression. In PPARgamma-positive NK cells, PPAR-gamma activation by 15d-PGJ(2) and ciglitazone (a synthetic ligand) leads to reduction in both mRNA and protein levels of IFN-gamma. Overexpression of PPAR-gamma in PPAR-gamma-null NK cells reduces IFN-gamma gene expression. However, PPAR-gamma expression and activation has no effect on NK cell cytolytic activity. In addition, 15d-PGJ(2) but not ciglitazone reduces expression of CD69 in human NK cells, whereas CD44 expression is not affected. These results reveal novel pathways regulating NK cell biologic functions and provide a basis for the design of therapeutic agents that can regulate the function of NK cells within the innate immune response.

Characterization of an interleukin-7-dependent thymic cell line derived from a p53(-/-) mouse.

In order to study the response of T cells to IL-7, we aimed to generate an IL-7-dependent thymocyte line. CD4(-)CD8(-) thymocytes from a p53(-)/(-) mouse were continuously propagated in interleukin-7 (IL-7), and after 2 months there developed an immortal line termed "D1." The D1 line has retained a stable dependency on IL-7. Withdrawal of IL-7 from D1 cells induced arrest in G1 phase of the cell cycle, followed by apoptosis. In addition to IL-7, several other cytokines that employ gamma(c) as part of their receptor were also capable of stimulating D1 cell survival and proliferation. Gene induction by IL-7 was analyzed in D1 cells using RNase protection and array analysis and revealed a number of transcripts potentially involved in cell cycle, apoptosis and signaling.

IL-2 and IL-12 alter NK cell responsiveness to IFN-gamma-inducible protein 10 by down-regulating CXCR3 expression.

Cytokine treatment of NK cells results in alterations in multiple cellular responses that include cytotoxicity, cytokine production, proliferation, and chemotaxis. To understand the molecular mechanisms underlying these responses, microarray analysis was performed and the resulting gene expression patterns were compared between unstimulated, IL-2, IL-2 plus IL-12, and IL-2 plus IL-18-stimulated NK92 cells. RNase protection assays and RT-PCR confirmed microarray predictions for changes in mRNA expression for nine genes involved in cell cycle progression, signal transduction, transcriptional activation, and chemotaxis. Multiprobe RNase protection assay also detected changes in the expression of CCR2 mRNA, a gene that was not imprinted on the microarray. We subsequently expanded our search for other chemokine receptor genes absent from the microarray and found an IL-2- and IL-12-dependent decrease in CXCR3 receptor mRNA expression in NK92 cells. A detailed analysis of CXCR3 expression in primary NK cells revealed that an IL-2 and an IL-12 together significantly decreased the CXCR3 receptor mRNA and receptor surface expression by 6 and 24 h of treatment, respectively. This decrease in receptor expression was associated with a significant reduction in chemotaxis in the presence of IFN-gamma-inducible protein-10. The decline in CXCR3 mRNA was due to transcriptional and posttranscriptional mechanisms as the addition of actinomycin D to IL-2- and IL-12-treated NK92 slightly altered the half-life of the CXCR3 mRNA. Collectively, these data suggest that IL-2 and IL-12 directly affect NK cell migratory ability by rapid and direct down-regulation of chemokine receptor mRNA expression.

IL-7 withdrawal induces a stress pathway activating p38 and Jun N-terminal kinases.

IL-7 delivers survival signals to cells at an early stage in lymphoid development. In the absence of IL-7, pro-T cells undergo programmed cell death, which has previously been associated with a decline in Bcl-2 and translocation of Bax from cytosol to mitochondria. A new, earlier feature of IL-7 withdrawal was identified using an IL-7-dependent thymocyte line. We observed that withdrawal of IL-7 induced increased expression of jun and fos family member genes including c-jun, junB, junD, c-fos and fra2. This transient response peaked 3-4 h after IL-7 was withdrawn and resulted in increased DNA-binding activity of AP-1 and in a change in the composition of the Jun/Fos family dimers shown by electrophoretic mobility shift and supershift assays. Induction of jun and fos genes and the increased DNA-binding activity of AP-1 were attributable to the phosphorylation-induced activation of the stress kinases p38 and JNK and were blocked by the chemical kinase inhibitors SB203580 and SB202190. The stress response contributed to cell death following IL-7 withdrawal as shown by blocking the activity of the stress (MAP) kinases or by blocking the production of c-Jun and c-Fos using antisense oligonucleotides.