Jarosław Baran

Tumour-derived microvesicles carry several surface determinants and mRNA of tumour cells and transfer some of these determinants to monocytes

This study was designed to determine the characteristics of tumour cell-derived microvesicles (TMV) and their interactions with human monocytes. TMV were shed spontaneously by three different human cancer cell lines but their release was significantly increased upon activation of the cells with phorbol 12-myristate 13-acetate (PMA). TMV showed the presence of several surface determinants of tumour cells, e.g. HLA class I, CD29, CD44v7/8, CD51, chemokine receptors (CCR6, CX3CR1), extracellular matrix metalloproteinase inducer (EMMPRIN), epithelial cell adhesion molecule (EpCAM), but their level of expression differed from that on cells they originated from. TMV also carried mRNA for growth factors: vascular endothelial growth factor (VEGF), hepatocyte growth factor (HGF), interleukin-8 (IL-8) and surface determinants (CD44H). TMV were localized at the monocytes surface following their short exposure to TMV, while at later times intracellularly. TMV transferred CCR6 and CD44v7/8 to monocytes, exerted antiapoptotic effect on monocytes and activated AKT kinase (Protein Kinase B). Thus, TMV interact with monocytes, alter their immunophenotype and biological activity. This implicates the novel mechanism by which tumour infiltrating macrophages may be affected by tumour cells not only by a direct cell to cell contact, soluble factors but also by TMV.

Expansion and differentiation of CD14+CD16− and CD14++CD16+ human monocyte subsets from cord blood CD34+ hematopoietic progenitors

To determine whether monocytes can be generated from CD34+ hematopoietic progenitors in large numbers, cord blood CD34+ cells were first expanded for 3–10 days in X‐VIVO 10 medium supplemented with FCS, stem cell factor (SCF), thrombopoietin (TPO), and Flt‐3 Ligand (Flt‐3L), and then differentiated in IMDM medium supplemented with FCS, SCF, Flt‐3L, IL‐3 and M‐CSF for 7–14 days. These two step cultures resulted in up to a 600‐fold mean increase of total CD14+ cells. Using this approach, two subpopulations of monocytes were obtained: CD14+CD16− and CD14++CD16+ occurring at 2:1 ratio. 1.25(OH)2 Vitamin D3 added to the differentiation medium altered this ratio by decreasing proportion of CD14++CD16+ monocytes. In comparison to CD14+CD16−, the CD14++CD16+ cells showed different morphology and an enhanced expression of CD11b, CD33, CD40, CD64, CD86, CD163, HLA‐DR, and CCR5. Both subpopulations secreted TNF and IL‐12p40 but little or no IL‐10. CD14++CD16+ monocytes released significantly more IL‐12p40, were better stimulators of MLR but showed less S. aureus phagocytosis. These subpopulations are clearly different from those present in the blood and may be novel monocyte subsets that represent different stages in monocyte differentiation with distinct biological function.

Intracellular cytokine production by Th1/Th2 lymphocytes and monocytes of children with symptomatic transient hypogammaglobulinaemia of infancy (THI) and selective IgA deficiency (SIgAD)

Intracellular expression of several cytokines was assessed in lymphocytes and monocytes of children with transient hypogammaglobulinaemia of infancy (THI) and selective IgA deficiency (SIgAD). THI was characterized by an increased frequency of CD3+/CD4+ lymphocytes expressing tumour necrosis factor α (TNF‐α), TNF‐β and interleukin 10 (IL‐10), while in SIgAD elevated numbers of these cells containing TNF‐α and interferon γ (IFN‐γ) were observed. No changes in the number of CD4+ T cells expressing IL‐4 in both diseases were noted. The proportion of CD33+ monocytes containing TNF‐α both in THI and SIgAD was unchanged. The secretion of IL‐12 by peripheral blood mononuclear cells (PBMCs) of patients with THI and SIgAD was significantly elevated and associated with an increased frequency of IL‐12 expressing monocytes in THI but not in SIgAD. IL‐18 secretion was slightly, but not significantly, elevated in both diseases. Intracellular Th1 and Th2 type cytokines within CD3+/CD4+ lymphocytes were also determined in the normal blood donors that showed high or low production of IgG and IgA in vitro. In low producers of IgG an increased proportion of CD3+/CD4+ cells expressing TNF‐α and IFN‐γ was found, while in low IgA responders only elevated TNF‐α positive CD3+/CD4+ cells were observed. These results suggest that THI and SIgAD may represent diseases with an excessive Th1 type response that is associated with an up‐regulation of IL‐12 secretion and, at least in THI, elevated numbers of monocytes expressing intracellular IL‐12. Up‐regulation of IL‐12 may be the essential factor in the patomechanism(s) of these diseases as already described in common variable immunodeficiency (CVID).

Fenofibrate enhances barrier function of endothelial continuum within the metastatic niche of prostate cancer cells

Objective: Extravasation of circulating cancer cells is an important step of the metastatic cascade and a potential target for anti-cancer strategies based on vasoprotective drugs. Reports on anti-cancer effects of fenofibrate (FF) prompted us to analyze its influence on the endothelial barrier function during prostate cancer cell diapedesis. Research design and methods: In vitro co-cultures of endothelial cells with cancer cells imitate the ‘metastatic niche’ in vivo. We qualitatively and quantitatively estimated the effect of 25 μM FF on the events which accompany prostate carcinoma cell diapedesis, with the special emphasis on endothelial cell mobilization. Results: Fenofibrate attenuated cancer cell diapedesis via augmenting endothelial cell adhesion to the substratum rather than through the effect on intercellular communication networks within the metastatic niche. The inhibition of endothelial cell motility was accompanied by the activation of PPARα-dependent and PPARα-independent reactive oxygen species signaling, Akt and focal adhesion kinase (FAK) phosphorylation, in the absence of cytotoxic effects in endothelial cells. Conclusions: Fenofibrate reduces endothelial cell susceptibility to the paracrine signals received from prostate carcinoma cells, thus inhibiting endothelial cell mobilization and reducing paracellular permeability of endothelium in the metastatic niche. Our data provide a mechanistic rationale for extending the clinical use of FF and for the combination of this well tolerated vasoactive drug with the existing multidrug regimens used in prostate cancer therapy.

DEMONSTRATION OF INOS-MRNA AND INOS IN HUMAN MONOCYTES STIMULATED WITH CANCER CELLS IN VITRO

Synthesis and localization of inducible nitric oxide synthase mRNA (iNOS‐mRNA) and iNOS protein in the cultures of human monocytes (Mφ) and colon carcinoma cell line (DeTa) that resulted in nitric oxide (NO) synthesis has been studied. The iNOS‐mRNA was observed around the sixth hour of culture and peaked at the twelfth hour. The iNOS‐mRNA, as determined by the in situ hybridization and iNOS protein, as detected by staining with specific anti‐iNOS monoclonal antibodies, were observed preferentially in the cytoplasm of some Mφ, but not in cancer cells. Mφ cultured alone did not show detectable iNOS‐mRNA expression and iNOS protein. Mφ sorted out from tumor cells after 8hof co‐culture expressed iNOS protein and iNOS‐mRNA, which were not detected in Mφ without previous contact with cancer cells. Prevention of NO synthesis by (L‐N 5‐1‐iminoethyl)‐ornithine (L‐NIO) partly inhibited Mφ cytotoxic activity against DeTa (NO‐inducing cancer cell line) but not against the human pancreatic cancer (HPC‐4) cell line that does not induce NO production in Mφ. This suggests that Mφ cytotoxic activity, at least in some cases, may be NO dependent. These observations provide further evidence that Mφ can be directly stimulated by cancer cells for de novo production of NO and suggest that iNOS occurring in the tumor‐infiltrating macrophages may arise as a result of their interactions with tumor cells. However, because only some tumor cells are able to induce NO production in a small proportion of Mφ, its role in the anti‐tumor response of the host is probably limited. J. Leukoc. Biol. 65: 597–604; 1999.

Modulation of monocyte–tumour cell interactions by Mycobacterium vaccae

Immunotherapy with Mycobacterium vaccae as an adjuvant to chemotherapy has recently been applied to treatment of patients with cancer. One of the mechanisms of antitumour activity of Mycobacterium bovis bacillus Calmette-Guérin (BCG), the prototype immunomodulator, is associated with activation of monocytes/macrophages. These studies were undertaken to determine how M. vaccae affects monocyte–tumour cell interactions and, in particular, whether it can prevent or reverse deactivation of monocytes that occurrs following their contact with tumour cells during coculture in vitro. Deactivation is characterised by the impaired ability of monocytes to produce tumour necrosis factor α (TNF-α), interleukin 12 (IL-12), and enhanced IL-10 secretion following their restimulation with tumour cells. To see whether deactivation of monocytes can be either prevented or reversed, three different strains of M. vaccae—B 3805, MB 3683, and SN 920—and BCG were used to stimulate monocytes before or after exposure to tumour cells. Pretreatment of monocytes with M. vaccae MB 3683, SN 920 and BCG before coculture resulted in increased TNF-α and decreased IL-10 production. All strains of M. vaccae and BCG used for treatment of deactivated monocytes enhanced depressed TNF-α secretion. Strain SN 920 and BCG increased IL-12 release but only BCG treatment inhibited an enhanced IL-10 production by deactivated monocytes. Thus, although some strains of M. vaccae may either prevent or reverse tumour-induced monocyte deactivation, none of them appears to be more effective than BCG.

Elimination of monocytes from cultures activated with recall antigens

Recent data provide evidence that antigen-specific CD4+ T-cell clones or antigen-activated T-cell lines can kill antigen-presenting cells (APC). We focused our studies on monocytes acting as APC in cultures of T cells freshly isolated from peripheral blood. The presence of monocytes in culture was monitored by their ability to emit light during phagocytosis of latex particles (latex-induced chemiluminescence). Using this approach as well as flow cytometry, evidence is presented that monocytes are eliminated from cultures with T cells activated with recall antigens (PPD or TT). The mechanism of monocyte elimination involved apoptosis as judged from in situ detection of DNA strand breaks by the terminal deoxynucleotidyl transferase assay. The antigen- but not lectin-dependent monocyte elimination was MHC-restricted and mediated by CD4+ T lymphocytes. This finding supports the hypothesis that elimination of APC is a general phenomenon during T-cell activation and may represent an important immunoregulatory mechanism.

Interactions of monocyte subpopulations generated from cord blood CD34+ hematopoietic progenitors with tumor cells: Assessment of antitumor potential

Monocytes and their subsets (CD14(++)CD16(+) and CD14(+)CD16(-)) generated from cord blood CD34(+) progenitor cells were used for determination of their capacity to interact with tumor cells in vitro and in vivo. The studies in vitro included adhesion to human umbilical vein endothelial cells, cytotoxicity, production of toxic mediators: reactive oxygen and nitrogen intermediates (ROI and RNI, respectively), and finally their effect on transplantable human tumor growth in nonobese diabetic severe combined immunodeficient mice. The CD14(++)CD16(+) subset exhibited an increased adherence to human umbilical vein endothelial cells and cytotoxicity toward tumor cells in vitro. CD14(+)CD16(-) monocytes showed a higher production of reactive oxygen and nitrogen intermediates after stimulation with tumor cells, and more pronounced inhibition of tumor growth in vivo. The results revealed significant differences in the behavior of CD14(++)CD16(+) and CD14(+)CD16(-) monocyte subsets toward tumor cells, thus providing further evidence that CD34(+) cell-derived monocytes differ in this respect from blood monocytes. The protocol for generation of monocytes with antitumor reactivity described here may be useful to obtain monocytes from CD34(+) progenitor cells of cancer patients. This might offer a basis for a novel approach for various forms of cellular immunotherapy of cancer.

Lectin-Activated CD4+CD45RA+ T-Lymphocytes have no Ability to Kill Monocytes

Monocytes are eliminated from cell culture by antigen or mitogen activated cytotoxic CD4+ T-lymphocytes. In this report we asked the question whether CD4+CD45RA+ and CD4+CD45RO+ subpopulations differ in the ability to kill monocytes in pokeweed mitogen (PWM)-activated cultures. Data are presented that although CD4+CD45RA+ vigorously proliferate in the presence of PWM, they do not kill monocytes or secrete IFN gamma.

Interactions among myeloid regulatory cells in cancer

Mounting evidence has accumulated on the critical role of the different myeloid cells in the regulation of the cancerous process, and in particular in the modulation of the immune reaction to cancer. Myeloid cells are a major component of host cells infiltrating tumors, interacting with each other, with tumor cells and other stromal cells, and demonstrating a prominent plasticity. We describe here various myeloid regulatory cells (MRCs) in mice and human as well as their relevant therapeutic targets. We first address the role of the monocytes and macrophages that can contribute to angiogenesis, immunosuppression and metastatic dissemination. Next, we discuss the differential role of neutrophil subsets in tumor development, enhancing the dual and sometimes contradicting role of these cells. A heterogeneous population of immature myeloid cells, MDSCs, was shown to be generated and accumulated during tumor progression as well as to be an important player in cancer-related immune suppression. Lastly, we discuss the role of myeloid DCs, which can either contribute to effective anti-tumor responses or play a more regulatory role. We believe that MRCs play a critical role in cancer-related immune regulation and suggest that future anti-cancer therapies will focus on these abundant cells.