miR-146a Controls Immune Response in the Melanoma Microenvironment.

MicroRNAs (miR) are small noncoding RNAs that regulate gene expression, posttranscription, and manipulate immune responses in different types of cancers. In this study, we identify miR-146a as a negative regulator of immune activation, comparable to immune-checkpoint molecules. miR-146a levels were increased in melanoma microenvironmental tissue, and miR-146a-/- mice survived longer and developed less metastases in comparison with wild-type melanoma-bearing mice. T cells isolated from miR-146a-/- mice revealed higher expression levels of the miR-146a target gene Stat1 and the Stat1-regulated cytokine IFNγ. Neutralization of IFNγ in miR-146a-/- mice decreased survival and increased melanoma metastasis patterns to those of wild-type mice. In vitro, IFNγ reduced melanoma cell migration, cell-cycle activity, and basal metabolic rate. Conversely, IFNγ also increased PD-L1 levels on the melanoma cells, which may counterbalance some of the beneficial effects increasing immune escape in vivo. Combined treatment with a miR-146a antagomiR and anti-PD-1 resulted in improved survival over isotype control or anti-PD-1 treatment alone. In summary, these data show that miR-146a plays a central role within the STAT1/IFNγ axis in the melanoma microenvironment, affecting melanoma migration, proliferation, and mitochondrial fitness as well as PD-L1 levels. Additionally, combined inhibition of PD-1 and miR-146a could be a novel strategy to enhance antitumor immune response elicited by checkpoint therapy. SIGNIFICANCE: These findings identify a microRNA-based mechanism by which melanoma cells escape the immune system, providing a new therapeutic strategy to improve the current management of patients with melanoma.

Neutrophils provide cellular communication between ileum and mesenteric lymph nodes at graft-versus-host disease onset.

Conditioning-induced damage of the intestinal tract plays a critical role during the onset of acute graft-versus-host disease (GVHD). Therapeutic interference with these early events of GVHD is difficult, and currently used immunosuppressive drugs mainly target donor T cells. However, not donor T cells but neutrophils reach the sites of tissue injury first, and therefore could be a potential target for GVHD prevention. A detailed analysis of neutrophil fate during acute GVHD and the effect on T cells is difficult because of the short lifespan of this cell type. By using a novel photoconverter reporter system, we show that neutrophils that had been photoconverted in the ileum postconditioning later migrated to mesenteric lymph nodes (mLN). This neutrophil migration was dependent on the intestinal microflora. In the mLN, neutrophils colocalized with T cells and presented antigen on major histocompatibility complex (MHC)-II, thereby affecting T cell expansion. Pharmacological JAK1/JAK2 inhibition reduced neutrophil influx into the mLN and MHC-II expression, thereby interfering with an early event in acute GVHD pathogenesis. In agreement with this finding, neutrophil depletion reduced acute GVHD. We conclude that neutrophils are attracted to the ileum, where the intestinal barrier is disrupted, and then migrate to the mLN, where they participate in alloantigen presentation. JAK1/JAK2-inhibition can interfere with this process, which provides a potential therapeutic strategy to prevent early events of tissue damage-related innate immune cell activation and, ultimately, GVHD.

Biglycan expression in the melanoma microenvironment promotes invasiveness via increased tissue stiffness inducing integrin-ß1 expression.

Novel targeted and immunotherapeutic approaches have revolutionized the treatment of metastatic melanoma. A better understanding of the melanoma-microenvironment, in particular the interaction of cells with extracellular matrix molecules, may help to further improve these new therapeutic strategies.We observed that the extracellular matrix molecule biglycan (Bgn) was expressed in certain human melanoma cells and primary fibroblasts when evaluated by microarray-based gene expression analysis. Bgn expression in the melanoma tissues correlated with low overall-survival and low progression-free-survival in patients. To understand the functional role of Bgn we used gene-targeted mice lacking functional Bgn. Here we observed that melanoma growth, metastasis-formation and tumor-related death were reduced in Bgn-/- mice compared to Bgn+/+ mice. In vitro invasion of melanoma cells into organotypic-matrices derived from Bgn-/- fibroblasts was reduced compared to melanoma invasion into Bgn-proficient matrices. Tissue stiffness as determined by atomic-force-microscopy was reduced in Bgn-/- matrices. Isolation of melanoma cells and fibroblasts from the stiffer Bgn+/+ matrices revealed an increase in integrin-ß1 expression compared to the Bgn-/- fibroblast matrices. Overexpression of integrin-ß1 in B16-melanoma cells abolished the survival benefit seen in Bgn-/- mice. Consistent with the studies performed in mice, the abundance of Bgn-expression in human melanoma samples positively correlated with the expression of integrin-ß1, which is in agreement with results from the organotypic invasion-assay and the in vivo mouse studies.This study describes a novel role for Bgn-related tissue stiffness in the melanoma-microenvironment via regulation of integrin-ß1 expression by melanoma cells in both mice and humans.

A Novel Function for P2Y2 in Myeloid Recipient-Derived Cells during Graft-versus-Host Disease.

Acute graft-versus-host disease (GvHD) is a life-threatening complication of allogeneic hematopoietic cell transplantation. During the initiation phase of acute GvHD, endogenous danger signals such as ATP are released and inform the innate immune system via activation of the purinergic receptor P2X7 that a noninfectious damage has occurred. A second ATP-activated purinergic receptor involved in inflammatory diseases is P2Y2. In this study, we used P2y2(-/-) mice to test the role of this receptor in GvHD. P2y2(-/-) recipients experienced reduced GvHD-related mortality, IL-6 levels, enterocyte apoptosis, and histopathology scores. Chimeric mice with P2y2 deficiency restricted to hematopoietic tissues survived longer after GvHD induction than did wild-type mice. P2y2 deficiency of the recipient was connected to lower levels of myeloperoxidase in the intestinal tract of mice developing GvHD and a reduced myeloid cell signature. Selective deficiency of P2Y2 in inflammatory monocytes decreased GvHD severity. Mechanistically, P2y2(-/-) inflammatory monocytes displayed defective ERK activation and reactive oxygen species production. Compatible with a role of P2Y2 in human GvHD, the frequency of P2Y2(+) cells in inflamed GvHD lesions correlated with histopathological GvHD severity. Our findings indicate a novel function for P2Y2 in ATP-activated recipient myeloid cells during GvHD, which could be exploited when targeting danger signals to prevent GvHD.

The IL-33/ST2 axis augments effector T-cell responses during acute GVHD.

Interleukin (IL)-33 binding to the receptor suppression of tumorigenicity 2 (ST2) produces pro-inflammatory and anti-inflammatory effects. Increased levels of soluble ST2 (sST2) are a biomarker for steroid-refractory graft-versus-host disease (GVHD) and mortality. However, whether sST2 has a role as an immune modulator or only as a biomarker during GVHD was unclear. We show increased IL-33 production by nonhematopoietic cells in the gastrointestinal (GI) tract in mice post-conditioning and patients during GVHD. Exogenous IL-33 administration during the peak inflammatory response worsened GVHD. Conversely, GVHD lethality and tumor necrosis factor-α production was significantly reduced in il33(-/-) recipients. ST2 was upregulated on murine and human alloreactive T cells and sST2 increased as experimental GVHD progressed. Concordantly, st2(-/-) vs wild-type (WT) donor T cells had a marked reduction in GVHD lethality and GI histopathology. Alloantigen-induced IL-18 receptor upregulation was lower in st2(-/-) T cells, and linked to reduced interferon-γ production by st2(-/-) vs WT T cells during GVHD. Blockade of IL-33/ST2 interactions during allogeneic-hematopoietic cell transplantation by exogenous ST2-Fc infusions had a marked reduction in GVHD lethality, indicating a role of ST2 as a decoy receptor modulating GVHD. Together, these studies point to the IL-33/ST2 axis as a novel and potent target for GVHD therapy.

Therapeutic activity of multiple common γ-chain cytokine inhibition in acute and chronic GVHD.

The common γ chain (CD132) is a subunit of the interleukin (IL) receptors for IL-2, IL-4, IL-7, IL-9, IL-15, and IL-21. Because levels of several of these cytokines were shown to be increased in the serum of patients developing acute and chronic graft-versus-host disease (GVHD), we reasoned that inhibition of CD132 could have a profound effect on GVHD. We observed that anti-CD132 monoclonal antibody (mAb) reduced acute GVHD potently with respect to survival, production of tumor necrosis factor, interferon-γ, and IL-6, and GVHD histopathology. Anti-CD132 mAb afforded protection from GVHD partly via inhibition of granzyme B production in CD8 T cells, whereas exposure of CD8 T cells to IL-2, IL-7, IL-15, and IL-21 increased granzyme B production. Also, T cells exposed to anti-CD132 mAb displayed a more naive phenotype in microarray-based analyses and showed reduced Janus kinase 3 (JAK3) phosphorylation upon activation. Consistent with a role of JAK3 in GVHD, Jak3(-/-) T cells caused less severe GVHD. Additionally, anti-CD132 mAb treatment of established chronic GVHD reversed liver and lung fibrosis, and pulmonary dysfunction characteristic of bronchiolitis obliterans. We conclude that acute GVHD and chronic GVHD, caused by T cells activated by common γ-chain cytokines, each represent therapeutic targets for anti-CD132 mAb immunomodulation.

Metadherin exon 11 skipping variant enhances metastatic spread of ovarian cancer.

Metastatic ovarian cancer has a dismal prognosis and current chemotherapeutic approaches have very limited success. Metadherin (MTDH) is expressed in human ovarian cancer tissue and its expression inversely correlates with patients overall survival. Consistent with these studies, we observed MTDH expression in tissue specimens of FIGO Stage III ovarian carcinomas (72/83 cases). However, we also observed this in normal human ovarian epithelial (OE) cells, which raised the question of whether MTDH-variants with functional differences exist. We identified a novel MTDH exon 11 skipping variant (MTDHdel) which was seen at higher levels in ovarian cancer compared to benign OE cells. We analyzed MTDH-binding partner interactions and found that 12 members of the small ribosomal subunit and several mRNA binding proteins bound stronger to MTDHdel than to wildtype MTDH which indicates differential effects on gene translation. Knockdown of MTDH in ovarian cancer cells reduced the amount of distant metastases and improved the survival of ovarian cancer-bearing mice. Selective overexpression of the MTDHdel enhanced murine and human ovarian cancer progression and caused a malignant phenotype in originally benign human OE cells. MTDHdel was detectable in microdissected ovarian cancer cells of some human tissue specimens of ovarian carcinomas. In summary, we have identified a novel MTDH exon 11 skipping variant that shows enhanced binding to small ribosomal subunit members and that caused reduced overall survival of ovarian cancer bearing mice. Based on the findings in the murine system and in human tissues, MTDHdel must be considered a major promalignant factor for ovarian cancer.

Inflammatory neovascularization during graft-versus-host disease is regulated by αv integrin and miR-100.

Acute graft-versus-host disease (GvHD) is a complex process involving endothelial damage and neovascularization. Better understanding of the pathophysiology of neovascularization during GvHD could help to target this process while leaving T-cell function intact. Under ischemic conditions, neovascularization is regulated by different micro RNAs (miRs), which potentially play a role in inflamed hypoxic GvHD target organs. We observed strong neovascularization in the murine inflamed intestinal tract (IT) during GvHD. Positron emission tomography imaging demonstrated abundant αvß3 integrin expression within intestinal neovascularization areas. To interfere with neovascularization, we targeted αv integrin-expressing endothelial cells, which blocked their accumulation in the IT and reduced GvHD severity independent of immune reconstitution and graft-versus-tumor effects. Additionally, enhanced neovascularization and αv integrin expression correlated with GvHD severity in humans. Expression analysis of miRs in the inflamed IT of mice developing GvHD identified miR-100 as significantly downregulated. Inactivation of miR-100 enhanced GvHD indicating a protective role for miR-100 via blocking inflammatory neovascularization. Our data from the mouse model and patients indicate that inflammatory neovascularization is a central event during intestinal GvHD that can be inhibited by targeting αv integrin. We identify negative regulation of GvHD-related neovascularization by miR-100, which indicates common pathomechanistic features of GvHD and ischemia.

Phase I trial of a novel intradermal idiotype vaccine in patients with advanced B-cell lymphoma: specific immune responses despite profound immunosuppression.

The immunoglobulin receptor of B-cell lymphomas constitutes a specific tumor antigen (idiotype) and a target for active immunotherapy. Encouraging results have been reported in phase II trials after s.c. vaccination of follicular lymphoma patients during clinical remission with idiotype produced from eukaryotic cell lines and coupled to an immunogenic carrier macromolecule. We have developed a good manufacturing protocol for rapid expression of idiotype vaccines as recombinant Fab fragments in Escherichia coli. The objectives of this trial were to show safety and feasibility of intradermal immunization with this vaccine and to investigate whether immune responses were induced by this immunization route. Patients (n = 18) with advanced B-cell malignancies received repetitive intradermal vaccinations with 0.5 to 1.65 mg recombinant idiotype Fab fragment mixed with lipid-based adjuvant in combination with 150 mug granulocyte macrophage colony-stimulating factor s.c. at the same location. The patients' immune status was assessed by flow cytometry of peripheral blood lymphocytes and concomitant hepatitis B vaccination. Cellular and humoral immune responses to the vaccine were assessed by enzyme-linked immunospot and ELISA. Side effects of a total of 65 vaccinations were mild and did not affect the immunization schedule. No patient developed hepatitis B surface antibodies (anti-HBs) after two hepatitis B immunizations. Of 17 evaluable patients, five developed specific anti-vaccine antibodies, and eight developed anti-Fab T-cell responses. T-cell reactivity was independent of the cellular immune status and was idiotype specific as shown by statistical regression analysis (P = 0.0024) and epitope mapping studies. Intradermal administration of uncoupled recombinant idiotype with appropriate adjuvants may overcome profound clinical immunosuppression and induce specific immune responses.

Murine dendritic cells generated under serum-free conditions have a mature phenotype and efficiently induce primary immune responses.

Vaccination with in vitro-generated dendritic cells (DC) that present tumor-associated antigens is a promising approach for immunotherapy of malignant tumors. For optimization of DC-based vaccination protocols, preclinical tumor models that mimic the clinical situation closely are highly desirable. Strong non-specific T cell activation was observed in experimental immunization of mice with syngeneic DC generated in standard FCS-supplemented culture medium. To avoid deviation of the immune response to FCS-derived antigens, a serum-free culture protocol for in vitro generation of murine DC from bone marrow progenitor cells was developed. In comparison to DC differentiated with FCS supplementation, DC generated under serum-free conditions (sfDC) have a more homogeneous phenotype with higher expression of IL-12 and the differentiation and activation markers CD11c, CD40, CD80, CD83, CD86, DEC-205, and MHC class II. Demonstration of strong uptake of protein and carbohydrate antigens and analysis of the in vivo migration behaviour of sfDC also indicated excellent APC function. Vaccination of mice with peptide-pulsed sfDC efficiently induced an antigen-specific T cell response as assessed by MHC tetramer staining, IFN-gamma ELISPOT and in vivo cytotoxicity assay. sfDC may therefore represent a valuable tool to improve active tumor immunotherapy in animal models.