Immunosuppressive CD14+HLA-DRlow/- monocytes in prostate cancer

Prostatectomy restores the maturation competence of blood dendritic cell precursors and reverses the abnormal expansion of regulatory T lymphocytes

OBJECTIVE

To verify the presence of deviated dendritic cell (DC) precursors and of suppressor lymphocytes (Treg) in tumor bearing prostate cancer (PCa) patients and to monitor the corrective effect of tumor ablation.

METHODS

Monocytes isolated from the blood of patients before and 1 month after prostatectomy were allowed to reach complete maturation (mDC) ex vivo in a clinical grade two-step process. T-regulatory cells were identified in the lymphocyte cell fraction by the CD4(+)CD25(high)FoxP3(+)/CD4(+)CD25(high)CD127(low/-) phenotype.

RESULTS

Despite loss of the monocytes marker CD14, cytokine-matured DCs of tumor bearing patients expressed lower levels of the costimulatory molecule CD80 and of the maturation markers CD83 and CCR7 compared to mDC of normal subjects (NS, P = 0.001, 0.001, and 0.008, respectively). Prostatectomy restored CD80, CD83, and CCR7 expression to values not different from those of NS (P = 0.15, 0.60, and 0.71) and significantly higher than those of the pre-surgery state (CD83, P = 0.0003 and CCR7, P = 0.002). The frequency of Tregs, identified as either CD4 + CD25(high)FoxP3(+) or CD4(+)CD25(high)CD127(low/-), was significantly higher in pre-surgery patients than in NS (P = 0.0001 and 0.0003) and significant recovery of the CD4(+)CD25(high)CD127(low/-) (P = 0.0005) was observed after surgery.

CONCLUSIONS

The presence of defective DC precursors and suppressor lymphocytes in the tumor-bearing, but not tumor-free stage, positions the latter as the ideal setting for clinical success of PCa vaccine therapy.

The consequence of immune suppressive cells in the use of therapeutic cancer vaccines and their importance in immune monitoring

Evaluating the number, phenotypic characteristics, and function of immunosuppressive cells in the tumor microenvironment and peripheral blood could elucidate the antitumor immune response and provide information to evaluate the efficacy of cancer vaccines. Further studies are needed to evaluate the correlation between changes in immunosuppressive cells and clinical outcomes of patients in cancer vaccine clinical trials. This paper focuses on the role of T-regulatory cells, myeloid-derived suppressor cells, and tumor-associated macrophages in cancer and cancer immunotherapy and their role in immune monitoring.

Dendritic cell therapy for oncology roundtable conference

2-3 September 2010, Brussels, Belgium

The Dendritic Cell Therapy for Oncology Roundtable Conference was organized by Reliable Cancer Therapies and moderated by Prof. Dr. Steven De Vleeschouwer. The organizer, Reliable Cancer Therapies, is a Swiss non-profit organization that provides information on evidence-based cancer treatments and funding for the development of a selection of promising cancer therapies. In order to be able to give valuable information about dendritic cell (DC) therapy to patients and physicians, the organizing committee felt it necessary to organize this conference to get an up-to-date status of the academic DC therapy field, collect ideas to guide patients towards clinical trials and to induce cross-fertilization for protocol optimization. In total, 31 experts participated to an in-depth discussion about the status and the future development path for dendritic cell vaccines. The conference started with general presentations about cancer immunotherapy, followed by comprehensive overview presentations about the progress in DC vaccine development achieved by each speaker. At the end of the meeting, a thorough general discussion focused on key questions about what is needed to improve DC vaccines. This report does not cover all presentations, but aims to highlight selected points of interest, particularly relating to possible limitations and potential approaches to improvement of DC therapies specifically, and also immunotherapeutic interventions in general terms.

Tumor vaccines and beyond

For the last two decades the immunotherapy of patients with solid and hematopoietic tumors has met with variable success. We have reviewed the field of tumor vaccines to examine what has worked and what has not, why this has been the case, how the anti-tumor responses were examined, and how we can make tumor immunity successful for the majority of individuals rather than for the exceptional patients who currently show successful immune responses against their tumors.

Myeloid-derived suppressor cells in human cancer

Myeloid-derived suppressor cells are one of the major factors responsible for immune suppression in cancer. They also contribute to limited efficacy of current vaccination strategies. Here, we give an overview of the myeloid-derived suppressor cells field focusing primarily on the studies in cancer patients and current and future therapeutic options targeting these cells.

A paradoxical role for myeloid-derived suppressor cells in sepsis and trauma

Myeloid-derived suppressor cells (MDSCs) are a heterogenous population of immature myeloid cells whose numbers dramatically increase in chronic and acute inflammatory diseases, including cancer, autoimmune disease, trauma, burns and sepsis. Studied originally in cancer, these cells are potently immunosuppressive, particularly in their ability to suppress antigen-specific CD8(+) and CD4(+) T-cell activation through multiple mechanisms, including depletion of extracellular arginine, nitrosylation of regulatory proteins, and secretion of interleukin 10, prostaglandins and other immunosuppressive mediators. However, additional properties of these cells, including increased reactive oxygen species and inflammatory cytokine production, as well as their universal expansion in nearly all inflammatory conditions, suggest that MDSCs may be more of a normal component of the inflammatory response ("emergency myelopoiesis") than simply a pathological response to a growing tumor. Recent evocative data even suggest that the expansion of MDSCs in acute inflammatory processes, such as burns and sepsis, plays a beneficial role in the host by increasing immune surveillance and innate immune responses. Although clinical efforts are currently underway to suppress MDSC numbers and function in cancer to improve antineoplastic responses, such approaches may not be desirable or beneficial in other clinical conditions in which immune surveillance and antimicrobial activities are required.

Immunosuppressive CD14+HLA-DR(low)/- monocytes in B-cell non-Hodgkin lymphoma

Immunosuppression is a known risk factor for B-cell non-Hodgkin lymphoma (NHL), yet mechanisms of tumor-associated immunosuppression remain to be fully characterized. We examined the immunophenotype of 40 NHL patients and 27 age-matched healthy volunteers to better understand systemic immune suppression. NHL peripheral blood mononuclear cells had significantly decreased interferon-γ production and proliferation. This suppression was not the result of regulatory T cells, interleukin-6 or interleukin-10, as these factors were not different between NHL and healthy volunteers (controls). We were able to restore T-cell proliferation by removing NHL monocytes, suggesting that these monocytes are suppressive. This suppression was mediated in part through arginine metabolism as exogenous arginine supplementation partially overcame monocytes' suppression of T-cell proliferation in vitro and NHL patients had elevated arginase I in their plasma. NHL monocytes had impaired STAT1 phosphorylation and interferon-α production to CpG stimulation and a dendritic cell differentiation deficiency. Further studies demonstrated that monocytes from NHL patients had decreased HLA-DR and Tumor necrosis factor-α receptor II (CD120b) expression compared with controls (CD14(+)HLA-DR(low/-)CD120b(low)). Patients with increased ratios of CD14(+)HLA-DR(low/-) monocytes had more aggressive disease and suppressed immune functions. In summary, we report that CD14(+)HLA-DR(low/-) monocytes are a major and multifactorial contributor to systemic immunosuppression in NHL.

Immuno-Fluorescence Scanning Electron Microscopy of Biological Cells

Scanning electron microscopy (SEM) can produce striking three-dimensional images of biological cells and tissues with submicron resolution of surface morphology. Such cell surfaces are often complex blends of folds, extrusions, and pockets that may be necessary in the positioning of specific molecules within interaction range of each other. Thus, surface changes can have a spatial control over some molecular functions, and identification of select molecules at distinct morphological locations becomes critical to our understanding of total cell function.