The hypoxic environment of tumors dictates the phenotype of local myeloid-derived suppressor cells (MDSCs) via HIF-1a expression; hypoxia converts splenic MDSCs from specific into nonspecific suppressors.

Myeloid-derived suppressor cells (MDSC) are a major component of the immune suppressive network described in cancer and many other pathological conditions. Recent studies have demonstrated that one of the major mechanisms of MDSC-induced immune suppression is mediated by reactive oxygen species (ROS). However, the mechanism of this phenomenon remained unknown. In this study, we observed a substantial up-regulation of ROS by MDSC in all of seven different tumor models and in patients with head and neck cancer. The increased ROS production by MDSC is mediated by up-regulated activity of NADPH oxidase (NOX2). MDSC from tumor-bearing mice had significantly higher expression of NOX2 subunits, primarily p47phox and gp91phox, compared with immature myeloid cells from tumor-free mice. Expression of NOX2 subunits in MDSC was controlled by the STAT3 transcription factor. In the absence of NOX2 activity, MDSC lost the ability to suppress T cell responses and quickly differentiated into mature macrophages and dendritic cells. These findings expand our fundamental understanding of the biology of MDSC and may also open new opportunities for therapeutic regulation of these cells in cancer.

Purpose: Myeloid-derived suppressor cells (MDSC) are one of the major factors responsible for immune suppression in cancer. Therefore, it would be important to identify effective therapeutic means to modulate these cells.Experimental Design: We evaluated the effect of the synthetic triterpenoid C-28 methyl ester of 2-cyano-3,12-dioxooleana-1,9,-dien-28-oic acid (CDDO-Me; bardoxolone methyl) in MC38 colon carcinoma, Lewis lung carcinoma, and EL-4 thymoma mouse tumor models, as well as blood samples from patients with renal cell cancer and soft tissue sarcoma. Samples were also analyzed from patients with pancreatic cancer treated with CDDO-Me in combination with gemcitabine.Results: CDDO-Me at concentrations of 25 to 100 nmol/L completely abrogated immune suppressive activity of MDSC in vitro. CDDO-Me reduced reactive oxygen species in MDSCs but did not affect their viability or the levels of nitric oxide and arginase. Treatment of tumor-bearing mice with CDDO-Me did not affect the proportion of MDSCs in the spleens but eliminated their suppressive activity. This effect was independent of antitumor activity. CDDO-Me treatment decreased tumor growth in mice. Experiments with severe combined immunodeficient-beige mice indicated that this effect was largely mediated by the immune system. CDDO-Me substantially enhanced the antitumor effect of a cancer vaccines. Treatment of pancreatic cancer patients with CDDO-Me did not affect the number of MDSCs in peripheral blood but significantly improved the immune response.Conclusions: CDDO-Me abrogated the immune suppressive effect of MDSCs and improved immune responses in tumor-bearing mice and cancer patients. It may represent an attractive therapeutic option by enhancing the effect of cancer immunotherapy.

Helper-dependent adenovirus (HD-Ad

No abstract

Summary Dendritic cell (DC) differentiation is regulated by stroma via a network of soluble and cell-bound factors. Notch is one of the major elements of this network. Its role in DC differentiation, however, is controversial. Here, we demonstrate that activation of Notch signaling in hematopoietic progenitor cells (HPC) up-regulates differentiation of conventional DCs via activation of the canonical Wnt pathway. Inhibition of the Wnt pathway abrogated the effect of Notch on DC differentiation. Activation of the Wnt pathway in Notch-1-deficient embryonic stem cells restored DC differentiation, which indicates that Wnt signaling is downstream of the Notch pathway in regulating DC differentiation. Notch signaling activated the Wnt pathway in HPCs via up-regulated expression of multiple members of the Frizzled family of Wnt receptors. That expression was directly regulated by the CSL/RPB-Jκ transcription factor. Thus, these data suggest a new model of DC differentiation via cooperation between Wnt and Notch pathways.

Purpose The goal of this study was to determine the effect of combination of intratumoral administration of dendritic cells (DC) and fractionated external beam radiation (EBRT) on tumor-specific immune responses in patients with soft tissue sarcoma (STS). Methods and Material Seventeen patients with large (>5 cm) high grade STS were enrolled in the study. They were treated in the neoadjuvant setting with 5040 cGy of EBRT, split into 28 fractions and delivered 5 days a week, combined with intratumoral injection of 107 DCs followed by complete resection. DCs were injected on the second, third, and fourth Friday of the treatment cycle. Clinical evaluation and immunological assessments were performed. Results The treatment was well tolerated. No patient had tumor-specific immune responses before combined EBRT/DC therapy; nine patients (52.9%) developed tumor-specific immune responses, which lasted from 11 to 42 weeks. Twelve of 17 patients (70.6%) were progression free after one year. Treatment caused a dramatic accumulation of T cells in the tumor. The presence of CD4+ T cells in the tumor positively correlated with tumor-specific immune responses that developed following combined therapy. Accumulation of myeloid-derived suppressor cells but not regulatory T cells negatively correlated with the development of tumor-specific immune responses. Experiments with 111In labeled DCs demonstrated that these antigen presenting cells need at least 48 hr to start migrating from tumor site. Conclusions Combination of intratumoral DC administration with EBRT was safe and resulted in induction of antitumor immune responses. This suggests that this therapy is promising and need further testing in clinical trials design to assess clinical efficacy.

Inappropriate neutrophil activation has been implicated in the pathology of several clinically important inflammatory conditions. Although murine models are extensively used in the investigation of such pathological processes, a reliable method by which viable, quiescent neutrophils can be isolated from murine blood has not been developed. Here we describe a novel method based on negative immunomagnetic separation, which yields highly pure populations of murine neutrophils. Blood is incubated with a cocktail of antibodies against specific cell markers on unwanted cells, and then with secondary antibody-coated magnetic beads. After running the preparation through a column within a magnetic field, labeled cells are retained, and a neutrophil-rich effluent is collected. This method yields a >95% pure suspension of >97% viable neutrophils, recovering ϳ70% of neutrophils from whole blood. Flow cytometric analysis shows little difference in surface Lselectin and CD18 expression on isolated neutrophils compared with neutrophils in whole blood, indicating that neutrophils are minimally activated by the isolation process. Stimulation with phorbol 12-myristate 13-acetate (PMA) reduced L-selectin and increased CD18 expression. Isolated neutrophils migrate under agarose in response to fMLP, and fluorescently labeled neutrophils transfused into recipient mice interact with postcapillary venules in a manner comparable to endogenous leukocytes. These findings show that neutrophils isolated using this method can be used for inflammatory studies in vitro and in vivo.