Tumor cell-induced deactivation of human monocytes

Plants against cancer: the immune-boosting herbal microbiome: not of the plant, but in the plant. Basic concepts, introduction, and future resource for vaccine adjuvant discovery

The presence of microorganism communities (MOCs) comprised of bacteria, fungi, archaea, algae, protozoa, viruses, and the like, are ubiquitous in all living tissue, including plant and animal. MOCs play a significant role in establishing innate and acquired immunity, thereby influencing susceptibility and resistance to disease. This understanding has fostered substantial advancements in several fields such as agriculture, food science/safety, and the development of vaccines/adjuvants, which rely on administering inactivated-attenuated MOC pathogens. Historical evidence dating back to the 1800s, including reports by Drs Busch, Coley, and Fehleisen, suggested that acute febrile infection in response to "specific microbes" could trigger spontaneous tumor remission in humans. This discovery led to the purposeful administration of the same attenuated strains, known as "Coley's toxin," marking the onset of the first microbial (pathogen) associated molecular pattern (MAMPs or PAMPs)-based tumor immunotherapy, used clinically for over four decades. Today, these same MAMPS are consumed orally by billions of consumers around the globe, through "specific" mediums (immune boosting "herbal supplements") as carriers of highly concentrated MOCs accrued in roots, barks, hulls, sea algae, and seeds. The American Herbal Products Association (AHPA) mandates microbial reduction in botanical product processing but does not necessitate the removal of dead MAMP laden microbial debris, which we ingest. Moreover, while existing research has focused on the immune-modulating role of plant phytochemicals, the actual immune-boosting properties might instead reside solely in the plant's MOC MAMP laden biomass. This assertion is logical, considering that antigenic immune-provoking epitopes, not phytochemicals, are known to stimulate immune response. This review explores a neglected area of research regarding the immune-boosting effects of the herbal microbiome - a presence which is indirectly corroborated by various peripheral fields of study and poses a fundamental question: Given that food safety focuses on the elimination of harmful pathogens and crop science acknowledges the existence of plant microbiomes, what precisely are the immune effects of ingesting MAMPs of diverse structural composition and concentration, and where are these distributed in our botanicals? We will discuss the topic of concentrated edible MAMPs as acid and thermally stable motifs found in specific herbs and how these would activate cognate pattern recognition receptors (PPRs) in the upper gut-associated lymphoid tissue (GALT), including Peyer's patches and the lamina propria, to boost antibody titers, CD8+ and CD4+ T cells, NK activity, hematopoiesis, and facilitating M2 to M1 macrophage phenotype transition in a similar manner as vaccines. This new knowledge could pave the way for developing bioreactor-grown/heat-inactivated MOC therapies to boost human immunity against infections and improve tumor surveillance.

Mapping and Validation of scRNA-Seq-Derived Cell-Cell Communication Networks in the Tumor Microenvironment

Recent advances in single-cell technologies, particularly single-cell RNA-sequencing (scRNA-seq), have permitted high throughput transcriptional profiling of a wide variety of biological systems. As scRNA-seq supports inference of cell-cell communication, this technology has and continues to anchor groundbreaking studies into the efficacy and mechanism of novel immunotherapies for cancer treatment. In this review, we will highlight methods developed to infer inter- and intracellular signaling from scRNA-seq and discuss how they have contributed to studies of immunotherapeutic intervention in the tumor microenvironment (TME). However, a central challenge remains in validating the hypothesized cell-cell interactions. Therefore, this review will also cover strategies for integration of these scRNA-seq-derived interaction networks with existing experimental and computational approaches. Integration of these networks with imaging, protein secretion measurements, and network analysis and mathematical modeling tools addresses challenges that remain with scRNA-seq to enhance studies of immunosuppressive and immunotherapy-altered signaling in the TME.

The Role of miRNA in Regulating the Fate of Monocytes in Health and Cancer

Monocytes represent a heterogeneous population of blood cells that provide a link between innate and adaptive immunity. The unique potential of monocytes as both precursors (e.g., of macrophages) and effector cells (as phagocytes or cytotoxic cells) makes them an interesting research and therapeutic target. At the site of a tumor, monocytes/macrophages constitute a major population of infiltrating leukocytes and, depending on the type of tumor, may play a dual role as either a bad or good indicator for cancer recovery. The functional activity of monocytes and macrophages derived from them is tightly regulated at the transcriptional and post-transcriptional level. This review summarizes the current understanding of the role of small regulatory miRNA in monocyte formation, maturation and function in health and cancer development. Additionally, signatures of miRNA-based monocyte subsets and the influence of exogenous miRNA generated in the tumor environment on the function of monocytes are discussed.

Perturbation of miR-146b and relevant inflammatory elements in esophageal carcinoma patients supports an immune downregulatory mechanism

BACKGROUND

Esophageal Cancer is known as one of the deadliest cancers worldwide with the squamous cell carcinoma (ESCC) being the predominant subtype. There is a growing body of evidence linking the dysregulated microRNA (miRNA) pathway of immune cells to the progression of several tumors. In a previous study, we investigated molecular alterations pertaining to miR-146a and some components of NF-kB signaling pathway and proposed a possible immune downregulatory mechanism in peripheral blood mononuclear cells (PBMCs) of ESCC patients. Here, we further scrutinized other components of this pathway by evaluating PBMC levels of miR-146b, TLR4, IL10, and TNFA.

METHODS

Gene expressions were quantified using RT-qPCR assays. To prevent the vulnerability of results to the expression instability of reference genes, nine additional transcripts were quantified, and stable reference genes for normalizing qPCR data were identified using the NormFinder and the geNorm algorithms. The efficiency-corrected normalized relative quantity values were used to compare gene expressions among study groups.

RESULTS

The PBMC expression of miR-146b and TNFA was downregulated in ESCC patients as compared to healthy subjects. While the level of TLR4 was not different among the study groups, the PBMC level of IL10 was upregulated in ESCC patients. Logistic regression analyses coupled with the ROC curve and cross-validation analysis suggested that PBMC expression may serve as potential candidate biomarker for discriminating ESCC patients from healthy subjects.

CONCLUSION

The present findings, in line with our previous report, propose a particular gene expression pattern in PBMCs of ESCC patients, providing evidence in support of an immune downregulatory mechanism.

Nanomedicine-based cancer immunotherapies developed by reprogramming tumor-associated macrophages

Tumor microenvironment is a complex ecosystem composed of tumor extracellular matrix, fibroblasts, blood vessels, and immune cells, promoting tumor development by secreting various growth factors, hydrolase, and inflammatory factors. Tumor-associated macrophages (TAMs) constitute the largest number of immune cells in the TME, and they have a "double-edged sword" effect on tumor growth, invasion, metastasis, angiogenesis, and immunosuppression. Under the regulation of different cytokines in the TME, the bidirectional TAMs can switch their phenotypes between tumoricidal M1-like and pro-tumorigenic M2-like macrophages. TAM polarization suggests that scientists can use this property to design drugs targeting this regulation as a promising immunotherapy strategy to enhance tumor therapy efficiency. In this review, we summarize a brief introduction of TAMs and their implications for tumorigenesis. Next, we review recent advances in designing various functionalized nanomedicines and their applications in nanomedicine-based cancer therapies that target TAMs by killing them, inhibiting macrophage recruitment, and repolarizing them from pro-tumorigenic M2-like to tumoricidal M1-like macrophages. Simultaneously, the regulation of nanomedicines on the signaling pathways accounting for these effects is also summarized. This review will not only provide background scientific information for the understanding of TAMs and their roles in cancer treatment but also help scientists design nanomedicines based on tumor TAMs, which can help achieve better clinical treatment outcomes for tumors.

Hyaluronan preconditioning of monocytes/macrophages affects their angiogenic behavior and regulation of TSG-6 expression in a tumor type-specific manner

Hyaluronan is a glycosaminoglycan normally present in the extracellular matrix in most tissues. Hyaluronan is a crucial player in many processes associated with cancer, such as angiogenesis, invasion, and metastasis. However, little has been reported regarding the action of hyaluronan on monocytes/macrophages (Mo/MØ) in tumor angiogenesis and its consequences on tumor development. In the present study, we investigated the effects of hyaluronan of different sizes on human Mo/MØ angiogenic behavior in colorectal and breast carcinoma. In vitro, the treatment of Mo/MØ with lysates and conditioned media from a breast but not from colorectal carcinoma cell line plus high-molecular weight hyaluronan induced: (a) an increased expression of angiogenic factors VEGF, IL-8, FGF-2, and MMP-2, (b) an increased endothelial cell migration, and (c) a differential expression of hyaluronan-binding protein TSG-6. Similar results were observed in Mo/MØ derived from breast cancer patients treated with tumor lysates. Besides, macrophages primed with high-molecular weight hyaluronan and inoculated in human breast cancer xenograft tumor increased blood vessel formation and diminished TSG-6 levels. In contrast, the effects triggered by high-molecular weight hyaluronan on Mo/MØ in breast cancer context were not observed in the context of colorectal carcinoma. Taken together, these results indicate that the effect of high-molecular weight hyaluronan as an inductor of the angiogenic behavior of macrophages in breast tumor context is in part consequence of the presence of TSG-6.

Prognostic significance and population dynamics of peripheral monocytes in patients with oropharyngeal squamous cell carcinoma

BACKGROUND

Several inflammatory biomarkers are considered potential prognostic factors in various cancers. This study aimed to investigate the prognostic significance and population dynamics of pretreatment inflammatory biomarker levels in patients with oropharyngeal squamous cell carcinoma (OPSCC).

METHODS

The influence of neutrophil counts, lymphocyte counts, monocyte counts, platelet counts, lymphocyte-to-monocyte ratio (LMR), neutrophil-to-lymphocyte ratio, and platelet-to-lymphocyte ratio on progression-free survival (PFS), and overall survival (OS) was analyzed. We also analyzed the peripheral blood mononuclear cells collected from patients and healthy donors (HDs).

RESULTS

Elevated monocyte count was an independent prognostic factor for PFS. Low LMR was an independent prognostic factor for OS. The proportion of intermediate monocytes was lower, and that of classical monocytes was higher in patients than in HDs. Furthermore, PD-L1 expression on monocytes was higher in patients than in HDs.

CONCLUSIONS

We showed the prognostic significance and population dynamics of peripheral monocytes in patients with OPSCC.

Adoptive cell transfer: new perspective treatment in veterinary oncology

Cancer immunotherapy is recently considered the most promising treatment for human patients with advanced tumors and could be effectively combined with conventional therapies such as chemotherapy or radiotherapy. Patients with hematological malignancies and melanoma have benefited greatly from immunotherapies such as, adoptive cell transfer therapy, experiencing durable remissions and prolonged survival. In the face of increasing enthusiasm for immunotherapy, particularly for the administration of tumor-specific T lymphocytes, the question arises whether this method could be employed to improve treatment outcomes for canine patients. It is warranted to determine whether veterinary clinical trials could support comparative oncology research and thus facilitate the development of new cell-based therapies for humans. Herein, we discuss adoptive transfer of T lymphocytes and lymphokine-activated cells for application in veterinary oncology, in the context of human medicine achievements. Furthermore, we discuss potential benefits of using domestic dog as a model for immunotherapy and its advantages for translational medicine. We also focus on an emerging genome-editing technology as a useful tool to improve a T cells’ phenotype.

Inflammation and Epithelial-Mesenchymal Transition in Pancreatic Ductal Adenocarcinoma: Fighting Against Multiple Opponents

Pancreatic ductal adenocarcinoma (PDAC) is the most common type of pancreatic cancer and one of the most lethal human cancers. Inflammation is a critical component in PDAC initiation and progression. Inflammation also contributes to the aggressiveness of PDAC indirectly via induction of epithelial-mesenchymal transition (EMT), altogether leading to enhanced resistance to chemotherapy and poor survival rates. This review gives an overview of the key pro-inflammatory signaling pathways involved in PDAC pathogenesis and discusses the role of inflammation in induction of EMT and development of chemoresistance in patients with PDAC.

Soluble CD83 Inhibits T Cell Activation by Binding to the TLR4/MD-2 Complex on CD14+ Monocytes

The transmembrane protein CD83, expressed on APCs, B cells, and T cells, can be expressed as a soluble form generated by alternative splice variants and/or by shedding. Soluble CD83 (sCD83) was shown to be involved in negatively regulating the immune response. sCD83 inhibits T cell proliferation in vitro, supports allograft survival in vivo, prevents corneal transplant rejection, and attenuates the progression and severity of autoimmune diseases and experimental colitis. Although sCD83 binds to human PBMCs, the specific molecules that bind sCD83 have not been identified. In this article, we identify myeloid differentiation factor-2 (MD-2), the coreceptor within the TLR4/MD-2 receptor complex, as the high-affinity sCD83 binding partner. TLR4/MD-2 mediates proinflammatory signal delivery following recognition of bacterial LPSs. However, altering TLR4 signaling can attenuate the proinflammatory cascade, leading to LPS tolerance. Our data show that binding of sCD83 to MD-2 alters this signaling cascade by rapidly degrading IL-1R-associated kinase-1, leading to induction of the anti-inflammatory mediators IDO, IL-10, and PGE2 in a COX-2-dependent manner. sCD83 inhibited T cell proliferation, blocked IL-2 secretion, and rendered T cells unresponsive to further downstream differentiation signals mediated by IL-2. Therefore, we propose the tolerogenic mechanism of action of sCD83 to be dependent on initial interaction with APCs, altering early cytokine signal pathways and leading to T cell unresponsiveness.

A novel role of breast cancer-derived hyaluronan on inducement of M2-like tumor-associated macrophages formation

Microenvironmental signals determine the differentiation types and distinct functions of macrophages. Tumor-associated macrophages (TAM) constitute major infiltrates around solid tumor cells and accelerate tumor progression due to their immunosuppressive functions. However, the mechanisms through which tumor microenvironment modulates macrophages transition are not completely elucidated. Hyaluronan (HA), a prominent component in tumor microenvironment, is a notable immunoregulator and its high level is often related to poor prognosis. Herein, we found that the number of M2 macrophages was highly correlated with HA expression in tumor tissues from breast cancer patients. Experimental data showed that breast cancer-derived HA stimulated M2-like TAM formation in a mouse model and had multiple effects on macrophages transformation in vitro, including upregulating CD204, CD206, IL-10 and TGF-β, activating STAT3 signal, and suppressing killing capacity. These data indicate that HA derived from breast cancer activates macrophages in an alternative manner. Further mechanism study revealed that HA-CD44-ERK1/2-STAT3 pathway served as an important regulator in M2-like TAM formation. Therefore, targeting TAM by abrogating HA-CD44 interaction may be a potential strategy for breast cancer immunotherapy.

Colorectal cancer-derived microvesicles modulate differentiation of human monocytes to macrophages

BACKGROUND

Tumour-derived microvesicles (TMVs) are important players in tumour progression, modulating biological activity of immune cells e.g. lymphocytes, monocytes and macrophages. This phenomenon is particularly interesting in the progression of colon cancer, as macrophages in this type of tumour are relevant for the recovery processes. In the present study, the role of colon cancer cell-derived microvesicles in monocyte differentiation and activity profile (polarization) was investigated.

METHODS

Monocyte-derived macrophages (MDM) were differentiated in vitro in the presence of TMVs obtained from colon cancer: Caco-2, SW620, LoVo or SW480 cell lines and analysed according to their morphology and biological functions, as defined by cytokine secretion, reactive oxygen intermediate (ROI) production and cytotoxic activity against respective colon cancer cells.

RESULTS

Monocytes differentiated with TMVs exhibited morphological and phenotypical characteristics of macrophages. An early contact (beginning with the first day of the in vitro culture) of monocytes with TMVs resulted in increased IL-10 secretion and only slightly elevated TNF release. Early, or prolonged contact resulted in low ROI production and low cytotoxicity against tumour cells. On the other hand, late contact of MDM with TMVs, stimulated MDM to significant TNF and IL-12 secretion, ROI production and enhanced cytotoxicity against tumour cells in vitro. In addition, differences in MDM response to TMVs from different cell lines were observed (according to cytokine secretion, ROI production and cytotoxicity against tumour cells in vitro). Biological activity, STATs phosphorylation and microRNA profiling of MDMs indicated differences in their polarization/activation status which may suggest mixed polarization type M1/M2 with the predominance of proinflammatory cells after late contact with TMVs.

CONCLUSIONS

Macrophage activity (polarization status) may be regulated by contact with not only tumour cells but also with TMVs. Their final polarization status depends on the contact time, and probably on the vesicle "cargo", as signified by the distinct impact of TMVs which enabled the switching of MDM maturation to regulatory macrophages.

Hyaluronan carried by tumor-derived microvesicles induces IL-10 production in classical (CD14++CD16-) monocytes via PI3K/Akt/mTOR-dependent signalling pathway

Tumor-derived microvesicles (TMV) can mimic effects of tumor cells leading to an increased anti-inflammatory cytokine production, such as interleukin 10 (IL-10), by tumor-infiltrating monocytes and macrophages. Yet, the mechanism of IL-10 induction by TMV in monocytes remains unclear. The co-incubation of TMV derived from the human pancreas carcinoma cell line (HPC-4) with human monocytes resulted in a nearly 30-fold increase in IL-10 protein production. This effect operates at the level of transcription since monocytes transduced with an adenovirus containing IL-10-promoter luciferase reporter gene showed a 5-fold induction of luciferase activity after treatment with TMV. Since tumor cells can express hyaluronan (HA), which participates in tumor invasion and metastases, we have tested its effect on IL-10 expression. We showed that HA at the concentration of 100μg/ml induces IL-10 protein expression and the IL-10 promoter activation in monocytes. Moreover, hyaluronidase treatment of TMV reduced IL-10 protein production by 50% and promoter activity by 40%. Inhibitors of the PI3K/Akt/mTOR pathway reduced both, TMV-induced IL-10 promoter activity and protein production, and the same was observed in monocytes when stimulated by HPC-4 cells or HA. Inhibition of PI3K activity down-regulated phosphorylation of the Akt and (to a lesser extent) mTOR proteins in monocytes following TMV or HA stimulation. When comparing monocyte subsets, TMV induced IL-10 protein and mRNA synthesis only in classical CD14⁺⁺CD16^- but not in CD16-positive monocytes. Our data show that TMV induce IL-10 synthesis in human classical monocytes via HA, which, in turn, activates the PI3K/Akt/mTOR pathway.

High and low molecular weight hyaluronic acid differentially influence macrophage activation

Macrophages exhibit phenotypic diversity permitting wide-ranging roles in maintaining physiologic homeostasis. Hyaluronic acid, a major glycosaminoglycan of the extracellular matrix, has been shown to have differential signaling based on its molecular weight. With this in mind, the main objective of this study was to elucidate the role of hyaluronic acid molecular weight on macrophage activation and reprogramming. Changes in macrophage activation were assessed by activation state selective marker measurement, specifically quantitative real time polymerase chain reaction, and cytokine enzyme-linked immunoassays, after macrophage treatment with differing molecular weights of hyaluronic acid under four conditions: the resting state, concurrent with classical activation, and following inflammation involving either classically or alternatively activated macrophages. Regardless of initial polarization state, low molecular weight hyaluronic acid induced a classically activated-like state, confirmed by up-regulation of pro-inflammatory genes, including nos2, tnf, il12b, and cd80, and enhanced secretion of nitric oxide and TNF-α. High molecular weight hyaluronic acid promoted an alternatively activated-like state, confirmed by up regulation of pro-resolving gene transcription, including arg1, il10, and mrc1, and enhanced arginase activity. Overall, our observations suggest that macrophages undergo phenotypic changes dependent on molecular weight of hyaluronan that correspond to either (1) pro-inflammatory response for low molecular weight HA or (2) pro-resolving response for high molecular weight HA. These observations bring significant further understanding of the influence of extracellular matrix polymers, hyaluronic acid in particular, on regulating the inflammatory response of macrophages. This knowledge can be used to guide the design of HA-containing biomaterials to better utilize the natural response to HAs.

Drug Carriers: Not an Innocent Delivery Man

Biomaterials used as drug carriers are often considered inactive and assumed to have no other roles than modifying pharmacokinetics and biodistribution of a drug. On the other hand, there are several examples in which the carrier materials show bioactivities in the body, which may have been underestimated or inadvertently ignored. This review highlights several examples where biomaterials used as drug carriers bring biological effects, known or newly discovered, and discusses their implications in development of new drug delivery systems.

Lactic acid delays the inflammatory response of human monocytes

Lactic acid (LA) accumulates under inflammatory conditions, e.g. in wounds or tumors, and influences local immune cell functions. We previously noted inhibitory effects of LA on glycolysis and TNF secretion of human LPS-stimulated monocytes. Here, we globally analyze the influence of LA on gene expression during monocyte activation. To separate LA-specific from lactate- or pH-effects, monocytes were treated for one or four hours with LPS in the presence of physiological concentrations of LA, sodium lactate (NaL) or acidic pH. Analyses of global gene expression profiles revealed striking effects of LA during the early stimulation phase. Up-regulation of most LPS-induced genes was significantly delayed in the presence of LA, while this inhibitory effect was attenuated in acidified samples and not detected after incubation with NaL. LA targets included genes encoding for important monocyte effector proteins like cytokines (e.g. TNF and IL-23) or chemokines (e.g. CCL2 and CCL7). LA effects were validated for several targets by quantitative RT-PCR and/or ELISA. Further analysis of LPS-signaling pathways revealed that LA delayed the phosphorylation of protein kinase B (AKT) as well as the degradation of IκBα. Consistently, the LPS-induced nuclear accumulation of NFκB was also diminished in response to LA. These results indicate that the broad effect of LA on gene expression and function of human monocytes is at least partially caused by its interference with immediate signal transduction events after activation. This mechanism might contribute to monocyte suppression in the tumor environment.

Intraperitoneal delivery of platinum with in-situ crosslinkable hyaluronic acid gel for local therapy of ovarian cancer

Intraperitoneal (IP) chemotherapy is a promising post-surgical therapy of solid carcinomas confined within the peritoneal cavity, with potential benefits in locoregional and systemic management of residual tumors. In this study, we intended to increase local retention of platinum in the peritoneal cavity over a prolonged period of time using a nanoparticle form of platinum and an in-situ crosslinkable hyaluronic acid gel. Hyaluronic acid was chosen as a carrier due to the biocompatibility and biodegradability. We confirmed a sustained release of platinum from the nanoparticles (PtNPs) and nanoparticle/gel hybrid (PtNP/gel), receptor-mediated endocytosis of PtNPs, and retention of the gel in the peritoneal cavity over 4 weeks: conditions desirable for a prolonged local delivery of platinum. However, PtNPs and PtNP/gel did not show a greater anti-tumor efficacy than CDDP solution administered at the same dose but rather caused a slight increase in tumor burdens at later time points, which suggests a potential involvement of empty carriers and degradation products in the growth of residual tumors. This study alerts that although several materials considered biocompatible and safe are used as drug carriers, they may have unwanted biological effects on the residual targets once the drug is exhausted; therefore, more attention should be paid to the selection of drug carriers.

Tumor cell lysate induces the immunosuppression and apoptosis of mouse immunocytes

Although tumor cell lysate (TCL) is a type of immunocyte stimulator, its immunosuppressive function must not be ignored. The present study reported that TCL prepared from a Lewis lung cancer cell was able to induce the development of immunosuppressive macrophages (MΦ) and tolerogenic dendritic cells. In addition, TCL upregulated the expression of CD69 in mouse splenocytes, and cell apoptosis and the percentage of regulatory T cells in mouse splenocytes simultaneously increased. Furthermore, the present study found that the immunosuppressive factor, hyaluronan, and the apoptosis inducers, Fas ligand and transforming growth factor-β, are present in TCL. These components may be associated with the emergence of immunosuppressive cells or splenocyte apoptosis. Thus, the present study has enriched our understanding of the composition of TCL and its negative regulatory effect on immunocytes.

Pancreatic ductal adenocarcinoma: a review of immunologic aspects

With the continued failures of both early diagnosis and treatment options for pancreatic cancer, it is now time to comprehensively evaluate the role of the immune system on the development and progression of pancreatic cancer. It is important to develop strategies that harness the molecules and cells of the immune system to treat this disease. This review will focus primarily on the role of immune cells in the development and progression of pancreatic ductal adenocarcinoma and to evaluate what is known about the interaction of immune cells with the tumor microenvironment and their role in tumor growth and metastasis. We will conclude with a brief discussion of therapy for pancreatic cancer and the potential role for immunotherapy. We hypothesize that the role of the immune system in tumor development and progression is tissue specific. Our hope is that better understanding of this process will lead to better treatments for this devastating disease.

Deregulation of hyaluronan synthesis, degradation and binding promotes breast cancer

Clinical and experimental data indicate that hyaluronan accumulates in breast cancer compared with normal breast epithelium, which correlates to poor prognosis. In this review, we discuss the expression of genes encoding enzymes that synthesize or degrade hyaluronan, i.e. hyaluronan synthases and hyaluronidases or bind hyaluronan, i.e. CD44 and receptor for hyaluronan-mediated motility (RHAMM, also designated as HMMR or CD168), in relation to breast cancer progression. Hyaluronan and hyaluronan receptors have multi-faceted roles in signalling events in breast cancer. A better understanding of the molecular mechanisms underlying these signalling pathways is highly warranted and may lead to improvement of cancer treatment.

Can exercise-related improvements in immunity influence cancer prevention and prognosis in the elderly?

Cancer incidence increases with advancing age. Over 60% of new cancers and 70% of cancer deaths occur in individuals aged 65 years or older. One factor that may contribute to this is immunosenescence - a canopy term that is used to describe age-related declines in the normal functioning of the immune system. There are multiple age-related deficits in both the innate and adaptive systems that may play a role in the increased incidence of cancer. These include decreased NK-cell function, impaired antigen uptake and presentation by monocytes and dendritic cells, an increase in 'inflammaging', a decline in the number of naïve T-cells able to respond to evolving tumor cells, and an increase in functionally exhausted senescent cells. There is consensus that habitual physical exercise can offer protection against certain types of cancer; however the evidence linking immunological mechanisms, exercise, and reduced cancer risk remain tentative. Multiple studies published over the last two decades suggest that exercise can mitigate the deleterious effects of age on immune function, thus increasing anti-cancer immunity. The potential ameliorative effect of exercise on these mechanisms include evidence that physical activity is able to stimulate greater NK-cell activity, enhance antigen-presentation, reduce inflammation, and prevent senescent cell accumulation in the elderly. Here we discuss the role played by the immune system in preventing and controlling cancer and how aging may retard these anti-cancer mechanisms. We also propose a pathway by which exercise-induced alterations in immunosenescence may decrease the incidence of cancer and help improve prognosis in cancer patients.

Characterization of blood monocyte phenotype in patients with endometrial cancer

BACKGROUND

Endometrial tumors induce various tumor escape mechanisms that result in immunosuppression in patients and, ultimately, tumor progression. Blood monocytes are able to exhibit potent cytotoxic action against tumor cells where novel immunotherapeutics targeting antigen-presenting cells including dendritic cells, and blood monocytes are being used as a means of delivering immunogens to stimulate an antitumor and, ultimately, therapeutic response. This study shows that peripheral blood monocytes from patients with endometrial cancer show functional deficiencies, and these deficiencies can be characterized by phenotypic changes as well as altered cytokine secretion.

METHODS

This study assessed the phenotypic changes of peripheral blood monocytes by flow cytometry as well as the functional status via cytokine production measured by enzyme-linked immunosorbent assay in patients with endometrial cancer versus controls.

RESULTS

Altered blood monocyte phenotype incorporating a decrease in costimulatory and adhesion factor expression and increased expression of vascular endothelial growth factor receptor 1 in patients with endometrial cancer versus controls. Increased interleukin 12 and decreased interleukin 10 secretion by blood monocytes in patients with endometrial cancer were also observed.

CONCLUSIONS

These findings showed that peripheral blood monocytes from patients with endometrial cancer show an altered phenotype and cytokine secretion when compared with controls. Limitations to this study include the small sample size, the need to investigate the effect of phenotype and cytokine changes in functional assays, as well as future studies investigating the effect on tumor-associated macrophages from endometrial tissue from cancer versus control patients. Nevertheless, these findings suggest that peripheral blood monocyte induced immunosuppression in endometrial cancer and implications in the design of future immunotargeting therapies remain to be elucidated.

The importance of the macrophage within the human endometrium

The human endometrium is exposed to cyclical fluctuations of ovarian-derived sex steroids resulting in proliferation, differentiation (decidualization), and menstruation. An influx of leukocytes (up to 15% macrophages) occurs during the latter stages of the menstrual cycle, including menses. We believe the endometrial macrophage is likely to play an important role during the menstrual cycle, especially in the context of tissue degradation (menstruation), which requires regulated repair, regeneration, and phagocytic clearance of endometrial tissue debris to re-establish tissue integrity in preparation for fertility. The phenotype and regulation of the macrophage within the endometrium during the menstrual cycle and interactions with other cell types that constitute the endometrium are currently unknown and are important areas of study. Understanding the many roles of the endometrial macrophage is crucial to our body of knowledge concerning functionality of the endometrium as well as to our understanding of disorders of the menstrual cycle, which have major impacts on the health and well-being of women.

Interactions of human monocytes with TMVs (tumour-derived microvesicles)

The tumour microenvironment represents a dynamic complex milieu, which includes tumour cells, cells of the immune system and other (cellular and non-cellular) components. The role of these particular ‘puzzle pieces’ may change substantially due to their mutual interactions. The present review concerns different opinions on interactions that occur between monocytes, tumour cells and TMVs (tumour-derived microvesicles).

Pre-clinical assessment of autologous DC-based therapy in ovarian cancer patients with progressive disease

Dendritic cell-based vaccines offer promise for therapy of ovarian cancer. Previous studies have demonstrated that oxidation of several antigens, including ovarian cancer cells, using hypochlorous acid strongly enhances their immunogenicity and their uptake and presentation by dendritic cells. The response of T cells and dendritic cells to autologous tumour from patients with active disease has not previously been investigated. Monocyte-derived dendritic cells were generated from patients with active disease and activated by co-culture with oxidised tumour cells and the TLR agonist poly I:C. The dendritic cells showed an activated phenotype, but secreted high levels of TGFβ. Co-culture of the antigen-loaded dendritic cells with autologous T cells generated a population of effector T cells that showed a low level of specific lytic activity against autologous tumour, as compared to autologous mesothelium. The addition of neutralising antibody to TGFβ in DC/T cell co-cultures increased the levels of subsequent tumour killing in three samples tested. Co-culture of monocytes from healthy volunteers with the ovarian cell line SKOV-3 prior to differentiation into dendritic cells reduced the ability of dendritic cells to stimulate cytotoxic effector cells. The study suggests that co-culture of dendritic cells with oxidised tumour cells can generate effector cells able to kill autologous tumour, but that the high tumour burden in patients with active disease may compromise dendritic cell and/or T cell function.

Impaired antigen presentation and potent phagocytic activity identifying tumor-tolerant human monocytes

Monocyte exposure to tumor cells induces a transient state in which these cells are refractory to further exposure to cancer. This phenomenon, termed "tumor tolerance", is characterized by a decreased production of proinflammatory cytokines in response to tumors. In the past, we found that this effect comprises IRAK-M up regulation and TLR4 and CD44 activation. Herein we have established a human model of tumor tolerance and have observed a marked down-regulation of MHCII molecules as well as the MHCII master regulator, CIITA, in monocytes/macrophages. These cells combine an impaired capability for antigen presentation with potent phagocytic activity and exhibit an M2-like phenotype. In addition circulating monocytes isolated from Chronic Lymphocytic Leukemia patients exhibited the same profile as tumor tolerant cells after tumor ex vivo exposition.

Pancreatic ductal adenocarcinoma: a review of immunologic aspects

With the continued failures of both early diagnosis and treatment options for pancreatic cancer, it is now time to comprehensively evaluate the role of the immune system on the development and progression of pancreatic cancer. It is important to develop strategies that harness the molecules and cells of the immune system to treat this disease. This review will focus primarily on the role of immune cells in the development and progression of pancreatic ductal adenocarcinoma and to evaluate what is known about the interaction of immune cells with the tumor microenvironment and their role in tumor growth and metastasis. We will conclude with a brief discussion of therapy for pancreatic cancer and the potential role for immunotherapy. We hypothesize that the role of the immune system in tumor development and progression is tissue specific. Our hope is that better understanding of this process will lead to better treatments for this devastating disease.

Neutrophils promote motility of cancer cells via a hyaluronan-mediated TLR4/PI3K activation loop

Inflammation is a component of tumour progression mechanisms. Neutrophils are a common inflammatory infiltrate in many tumours, but their regulation and functions in neoplasia are not understood. We recently demonstrated that pro-inflammatory IL-17-producing cells recruited blood neutrophils into the peritumoural stroma of hepatocellular carcinoma by epithelium-derived CXC chemokines. Here we show that a substantial population of neutrophils accumulates in the peritumoural stroma of hepatocellular, cervical, colorectal, and gastric carcinomas, and that this correlates with metastases in hepatocellular and gastric carcinomas. Exposure of neutrophils to culture supernatants from several types of solid tumour cells (TSN) resulted in sustained survival and pro-tumourigenic effects of cells. Kinetic experiments reveal that, shortly after exposure to TSN, neutrophils began to provoke activation and then produced significant inflammatory cytokines and expressed more anti-apoptotic Mcl-1 but less pro-apoptotic Bax. These long-lived neutrophils effectively enhanced the cancer cell motility via a contact-dependent mechanism; this effect, together with early activation and subsequent longevity of TSN-exposed neutrophils, could be reversed by blocking the activation of PI3K/Akt signalling in neutrophils. Moreover, we found that hyaluronan (HA) fragments constitute a common factor produced by various tumours that mimics the effect of TSN to induce long-lived neutrophils and subsequent malignant cell migration. The effects of TSN were inhibited by function blocking interactions between HA and its receptor TLR4 on neutrophils, suggesting that this is a key signalling pathway involved. These results indicate that HA derived from malignant cells educates neutrophils to adopt an activated phenotype, and in that way stimulates the metastasis of malignant cells, which represents a positive regulatory loop between tumours and their stroma during neoplastic progression.

TGF-β-induced IRAK-M expression in tumor-associated macrophages regulates lung tumor growth

Tumor associated macrophages (TAMs) constitute a major component of the immune cell infiltrate observed in the tumor microenvironment (TME). Factors present in the TME including TGF-β, allow tumors to circumvent host mediated immune responses to promote tumor progression. However, the molecular mechanism(s) involved are not clear. Toll-like receptors (TLRs) are important mediators of innate immune responses by immune cells, whose activation triggers the production of molecules required for anti-tumoral responses. Interleukin receptor associated kinase (IRAK)-M is an inactive serine/threonine kinase, predominantly expressed in macrophages and is a potent negative regulator of TLR signaling. Here we show that TAMs express significantly higher levels of IRAK-M compared to peritoneal macrophages (PEMs) in a syngeneic mouse model of lung cancer. Subcutaneous implantation of LLC cells in IRAK-M^−/− mice resulted in a five-fold reduction in tumor growth, as compared to tumors in wild type animals. Furthermore, compared to WT TAMs, TAMs isolated from IRAK-M^−/− mice displayed features of a classically activated (M1) rather than alternatively activated (M2) phenotype, as manifest by greater expression of IL-12, IFN-γ, and iNOS. Human lung cancer cells induced IRAK-M expression in human PBMCs when co-cultured together. Tumor cell-induced expression of IRAK-M was dependent on the activation of TGF-β pathway. Similarly, treatment of human PBMCs or mouse macrophage cell line, RAW 264.4, with TGF-β, induced IRAK-M expression. Interestingly, IRAK-M gene expression in 439 human lung adenocarcinoma tumors correlated with poor survival in patients with lung cancer. Together, our data demonstrates that TGF-β-dependent induction of IRAK-M expression is an important, clinically relevant mechanism by which tumors may circumvent anti-tumor responses of macrophages.

Tumor macrophages protective and pathogenic roles in cancer development

Macrophage infiltration often occurs in cancer and has stimulated new efforts to define macrophage function within solid tumors. The macrophage, a myelophagocytic cell of the immune system, is at the front line of pathogen defense, wound healing, and maintaining homeostasis within the body. However, increased macrophage numbers during cancer generally correlates with poor prognosis. This chapter will focus on the function of myelophagocytic cells within solid tumors, their potential roles in tumor progression, and the possibilities of their manipulation as a component of cancer therapy.

Squamous carcinoma cells influence monocyte phenotype and suppress lipopolysaccharide-induced TNF-alpha in monocytes

Bacteria and chronic inflammation are present in squamous cell carcinoma of the head and neck (HNSCC), but their roles in the pathogenesis of HNSCC are unclear. Our studies described here revealed that human monocytes co-cultured short term with HNSCC cells were more likely to express CD16, and CD16(+) small mononuclear cells were common in HNSCC specimens. In addition, we identified monocytes as the primary source of LPS-induced IL-6 and TNF-alpha in the monocyte-HNSCC co-cultures. Remarkably, relative to LPS-stimulated monocytes cultured alone, HNSCC cells profoundly suppressed LPS-induced TNF-alpha in monocytes, without compromising IL-6 production. High levels of cytoprotective factors like IL-6 and low levels of TNF-alpha are important for the tumor microenvironment that enables tumor cell survival, affects monocyte differentiation and may contribute to tumor colonization by bacteria. This study provides novel observations that HNSCC cells affect monocyte phenotype and function, which are relevant to the regulation of the HNSCC microenvironment.

Reduced interleukin-12 release from stimulated monocytes in patients with sepsis after major cancer surgery

BACKGROUND

Major cancer surgery is a high-risk situation for sepsis in the post-operative period. The aim of this study was to assess the relation between the monocyte production of IL-12 and the development of post-operative sepsis in patients undergoing major cancer surgery.

METHODS

In 19 patients undergoing major cancer surgery, the production of cytokines by basal and lipolysaccharide (LPS)-stimulated monocytes was measured before and after (from day 1 to day 3 and day 7) surgery. Seven of them developed a post-operative sepsis. Ten healthy volunteers were used as controls for the assessment of pre-operative values.

RESULTS

Before surgery, the production of interleukin (IL)-12 p40 by LPS-stimulated monocytes was similar in the patients and the healthy volunteers. The production of IL-12 p40 by unstimulated monocytes was higher in the patients than in the healthy volunteers. IL-12 production did not differ between the septic and the non-septic patients. After surgery, the production of IL-12 p40 was dramatically reduced in the LPS-stimulated monocytes of the septic patients from day 1 to day 3, as compared with that of the non-septic patients. Before surgery, the production of IL-6, IL-10, and IL-1 receptor antagonist (IL-1ra) in the patients was significantly higher than that of the healthy volunteers for both stimulated and unstimulated monocytes. After surgery, the production of these cytokines by both stimulated and unstimulated monocytes of the septic patients was similar to that of the non-septic patients. Intragroup analysis showed significant changes for IL-6, IL-10, and IL-1ra under all conditions, with the exception of changes in unstimulated monocytes of septic patients that were not significant for IL-10 release.

CONCLUSION

After surgery, the septic patients showed drastic failure to up-regulate monocyte LPS-stimulated production of IL-12 p40.

CL097, a TLR7/8 ligand, inhibits TLR-4--dependent activation of IRAK-M and BCL-3 expression

Prolonged or repeated stimulation of Toll-like receptor (TLR) 4 leads to hyporesponsiveness of monocyte-derived macrophages, which seems to be a hallmark of immunosuppression related to sepsis and cancer. Two negative regulators of TLR-4 signaling are IL-1 receptor-associated kinase M and B-cell leukemia 3. Here, we demonstrate that the expression of both proteins is inhibited when the TLR-7/TLR-8 agonist CL097 is added to monocyte cultures despite costimulation with the TLR-4 agonist LPS or hyaluronic acid. Reduction of IL-1 receptor-associated kinase M and B-cell leukemia 3 was paralleled by a significant increased cytokine induction of TNF-alpha, IL-10, and IL-12 observed after intracellular and extracellular TLR stimulation. In ex vivo stimulated whole blood of patients who have prolonged sepsis or metastatic cancer, TLR-7/TLR-8 agonists retained their ability of increased stimulation of TNF-alpha. These data might add to the understanding of sepsis and cancer-associated immune suppression in men.

Lactic acid and acidification inhibit TNF secretion and glycolysis of human monocytes

High concentrations of lactic acid (LA) are found under various pathophysiological conditions and are accompanied by an acidification of the environment. To study the impact of LA on TNF secretion, human LPS-stimulated monocytes were cultured with or without LA or the corresponding pH control. TNF secretion was significantly suppressed by low concentrations of LA (< or = 10 mM), whereas only strong acidification had a similar effect. This result was confirmed in a coculture model of human monocytes with multicellular tumor spheroids. Blocking synthesis of tumor-derived lactate by oxamic acid, an inhibitor of lactate dehydrogenase, reversed the suppression of TNF secretion in this coculture model. We then investigated possible mechanisms underlying the suppression. Uptake of [3-(13)C]lactate by monocytes was shown by hyphenated mass spectrometry. As lactate might interfere with glycolysis, the glycolytic flux of monocytes was determined. We added [1,2-(13)C(2)]glucose to the culture medium and measured glucose uptake and conversion into [2,3-(13)C(2)]lactate. Activation of monocytes increased the glycolytic flux and the secretion of lactate, whereas oxygen consumption was decreased. Addition of unlabeled LA resulted in a highly significant decrease in [2,3-(13)C(2)]lactate secretion, whereas a mere corresponding decrease in pH exerted a less pronounced effect. Both treatments increased intracellular [2,3-(13)C(2)]lactate levels. Blocking of glycolysis by 2-deoxyglucose strongly inhibited TNF secretion, whereas suppression of oxidative phosphorylation by rotenone had little effect. These results support the hypothesis that TNF secretion by human monocytes depends on glycolysis and suggest that LA and acidification may be involved in the suppression of TNF secretion in the tumor environment.

Mononuclear phagocytes in head and neck squamous cell carcinoma

The head and neck squamous cell carcinoma microenvironments contain many immune cells and their secretory products. Many of these cells belong to the mononuclear phagocyte system. The aim of this review is to study the interactions between mononuclear phagocytes and head and neck squamous cell carcinoma tissue. The role of inflammation in tumours and the cytokine interleukin-6 will be highlighted. Future therapy strategies in the treatment of head and neck cancer might be directed towards mononuclear phagocytes and their cytokine production.

Blood monocytes stimulate migration of human pancreatic carcinoma cells in vitro: the role of tumour necrosis factor - alpha

In some types of cancers, tumour-infiltrating monocytes/macrophages (TIM) may be responsible for the formation of an invasive microenvironment in a manner dependent on the secretion of soluble mediators such as tumour necrosis factor-alpha (TNF). Human pancreatic carcinoma (HPC-4) cells are able to induce TNF production by monocytes. Here, the effect of human peripheral blood monocytes, precursors of TIM, on the motility of co-cultured HPC-4 cells, was directly analysed in vitro. A phenotypic transition, i.e., the appearance of rear-front polarised HPC-4 cells paralleled by their increased motility, and increased motility of monocytes, were observed. This effect was attenuated when HPC-4 cells and monocytes were co-cultured in the presence of inhibitors of TNF production and anti-TNF monoclonal antibodies, indicating the specific role of this cytokine in determining paracrine loops between monocytes and cancer cells. Moreover, exogenous TNF induced HPC-4 cell motility concomitantly to the appearance of cellular features characteristic for epithelial-mesenchymal transition (EMT) such as rear-front polarisation, rearrangements of the actin cytoskeleton characteristic for motile cells and the induction of Snail-1 expression. Since cell movement is crucial for cancer invasion and the formation of metastases, these findings demonstrate an EMT-dependent mechanism of cancer progression which acts through the phenotypic transition of pancreatic cancer cells dependent on monocyte-derived TNF.

Immunomodulation in endometrial cancer

Endometrial cancer is the most frequent gynecological cancer and the fourth most common cancer in women in the developed world. Over the last decade, immunotherapy has been the focus of intense investigation as a form of cancer treatment whereby the treatment initiates a host immune response ultimately eradicating the tumor. It has been suggested that in endometrial cancer and many other forms of cancer, immunosuppression poses a significant obstacle at inducing antitumor immunity by immunotherapy. This review will look at the different studies that have identified immunomodulation of T cells, cytokines and macrophages, and regulation of apoptotic and angiogenic factors in endometrial cancer patients that may contribute to the inefficiency of immunotherapy.

The interleukin-1 receptor-associated kinase M selectively inhibits the alternative, instead of the classical NFkappaB pathway

The innate immunity signaling process is controlled by numerous positive and negative regulators. The interleukin-1 receptor-associated kinase M (IRAK-M) is one of the negative regulators that contribute to the attenuation of NFkappaB activation. The molecular mechanism involved, however, is poorly defined. In this report, we observed that IRAK-M selectively suppresses the NIK-IKKalpha-mediated alternative NFkappaB pathway. Deletion of IRAK-M led to NIK stabilization, favored the formation of the IKKalpha/IKKalpha homodimer instead of the IKKalpha/IKKbeta heterodimer, and enhanced RelB nuclear distribution. In contrast, p65 nuclear localization and phosphorylation was not affected by IRAK-M deficiency. IRAK-M-deficient cells exhibited increased expression of selected cytokines such as IL-6 and GM-CSF, as well as quickened resynthesis of IkappaBalpha. The increased expression of IL-6 and GM-CSF was ablated when RelB expression was knocked down using specific siRNA. We also demonstrated that the observed inhibitory effect of IRAK-M was primarily limited to the TLR2 ligand, instead of TLR4. Taken together, our findings suggest that IRAK-M negatively regulates the alternative NFkappaB pathway in a ligand-specific manner.

Hyaluronan in human tumors: pathobiological and prognostic messages from cell-associated and stromal hyaluronan

Cancers are supported by a distinct type of connective tissue stroma, crucial for tumor survival and advancement. Hyaluronan is a major matrix molecule in the stroma of many common tumors, and involved in their growth and spreading. Here we focus in recent data on stromal hyaluronan in human tumors, and that on the surface of the malignant cells. Hyaluronan accumulation is most conspicuous in malignancies that develop in cells and tissues normally devoid of hyaluronan, such as single layered epithelia and their hyaluronan-poor connective tissue stroma. The magnitude of the hyaluronan accumulation in the malignant epithelium itself (e.g. colon and gastric cancers) or tumor stroma (breast, ovarian, prostate cancers) strongly correlates with an unfavorable prognosis of the patient, i.e. advancement of the malignancy. A completely different pattern arises from stratified epithelia that normally produce hyaluronan and are surrounded by a hyaluronan-rich stroma. The cell surface of the latter group of tumors (e.g. squamous cell carcinomas of skin, mouth, larynx and esophagus, and skin melanoma) show abundant hyaluronan which tends to get reduced and patchy in the most advanced stages of the tumors, suggesting enhanced turnover. While the assays of human tumors represent snapshots of currently unknown processes and kinetics of hyaluronan metabolism, it is obvious that hyaluronan accumulation at some stage is an inherent feature in most of the common epithelial malignant tumors. The possible contributions of inflammatory cells, stem cells, mutated stromal cells, or otherwise deranged growth factor exchange between stromal and cancer cells are discussed as possible explanations to hyaluronan abundance in the tumors. The importance of hyaluronan in human tumor progression will be further clarified when drugs become available to modify hyaluronan metabolism.

The involvement of the interleukin-1 receptor-associated kinases (IRAKs) in cellular signaling networks controlling inflammation

Innate immunity and inflammation plays a key role in host defense and wound healing. However, Excessive or altered inflammatory processes can contribute to severe and diverse human diseases including cardiovascular disease, diabetes and cancer. The interleukin-1 receptor-associated kinases (IRAKs) are critically involved in the regulation of intracellular signaling networks controlling inflammation. Collective studies indicate that IRAKs are present in many cell types, and can mediate signals from various cell receptors including toll-like-receptors (TLRs). Consequently, diverse downstream signaling processes can be elicited following the activation of various IRAKs. Given the critical and complex roles IRAK proteins play, it is not surprising that genetic variations in human IRAK genes have been found to be linked with various human inflammatory diseases. This review intends to summarize the recent advances regarding the regulations of various IRAK proteins and their cellular functions in mediating inflammatory signaling processes.

Tumour-derived microvesicles modulate biological activity of human monocytes

Tumour cells are shedding membrane fragments (tumour-derived microvesicles, TMV) that may interact with cells of immune system. Our previous observations indicated that TMV carry several surface determinants and mRNA of tumour cells and transfer some of them to monocytes. This study determined the effect of TMV on biological activity of human monocytes as the precursors of tumour infiltrating macrophages (TIM). It was found that TMV activated monocytes as shown by an increased HLA-DR expression, induced production of ROI (reactive oxygen intermediates) and of tumour necrosis factor (TNF), interleukin (IL)-10, IL-12p40 accumulation of mRNA and their secretion. Induction of TNF synthesis was CD44 dependent as blocking of CD44 on monocytes abolished its secretion. TMV-treated monocytes showed an increased antitumour activity as judged by enhanced cytotoxicity/cytostasis against tumour cells in vitro. Taken together, these results indicate that TMV significantly modulate biological activity of monocytes and thus mimic the effect of tumour cells on them. This may suggest that tumour cells interact with TIM not only via direct contact, soluble factors, but also 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.

Tumor-derived hyaluronan induces formation of immunosuppressive macrophages through transient early activation of monocytes

Macrophages (Mvarphi) in most solid tumors exhibit a distinct immunosuppressive phenotype, but the mechanisms that allow tumor microenvironments to "educate" Mvarphi are incompletely understood. Here, we report that culture supernatants (TSNs) from several types of tumor cell lines can drive monocytes to become immunosuppressive Mvarphi. Kinetic experiments revealed that soon after exposure to these TSNs, monocytes began to provoke transient proinflammatory responses and then became refractory to subsequent stimulation. Other TSNs that failed to cause such temporary preactivation did not alter Mvarphi polarization. Consistent with these results, we observed that the monocytes/Mvarphi in different areas of human tumor samples exhibited distinct activation patterns. Moreover, we found that hyaluronan fragments constitute a common factor produced by various tumors to induce the formation of immunosuppressive Mvarphi, and also that upregulation of hyaluronan synthase-2 in tumor cells is correlated with the ability of the cells to cause Mvarphi dysfunction. These results indicate that soluble factors derived from tumor cells, including hyaluronan fragments, co-opt the normal development of Mvarphi to dynamically educate the recruited blood monocytes in different niches of a tumor. The malignant cells can thereby avoid initiation of potentially dangerous Mvarphi functions and create favorable conditions for tumor progression.

Synergism between GM-CSF and IFNgamma: enhanced immunotherapy in mice with glioma

Glioblastoma multiforme is the most common malignant primary brain tumor and also one of the most therapy-resistant tumors. Because of the dismal prognosis, various therapies modulating the immune system have been developed in experimental models. Previously, we have shown a 37-70% cure in a rat glioma model where rats were peripherally immunized with tumor cells producing IFNgamma. On the basis of these results, we wanted to investigate whether a combination of GM-CSF and IFNgamma could improve the therapeutic effect in a mouse glioma model, GL261 (GL-wt). Three biweekly intraperitoneal (i.p.) immunizations with irradiated GM-CSF-transduced GL261 cells (GL-GM) induced a 44% survival in mice with intracranial glioma. While treatment of GL-wt and GL-GM with IFNgamma in vitro induced upregulation of MHC I and MHC II on the tumor cells, it could not enhance survival after immunization. However, immunizations with GL-GM combined with recombinant IFNgamma at the immunization site synergistically enhanced survival with a cure rate of 88%. Tumors from mice receiving only 1 immunization on Day 10 after tumor inoculation were sectioned on Day 20 for analysis of leukocyte infiltration. Tumor volume was reduced and the infiltration of macrophages was denser in mice immunized with GL-GM combined with IFNgamma compared with that of both wildtype and nonimmunized mice. To our knowledge, this is the first study to demonstrate a synergy between GM-CSF and IFNgamma in experimental immunotherapy of tumors, by substantially increasing survival as well as inducing a potent anti-tumor response after only 1 postponed immunization.

Tumour-associated macrophages and melanoma tumourigenesis: integrating the complexity

When the body discovers a tumour cell (foreign antigen), several kinds of mechanisms and cells operate in what is called an immune response. The latter has evolved into two mechanisms: non-specific immunity and specific immunity, which are closely linked to and influence each other. The former represents the first line of defence against neoplastic cells. The adaptive (specific) immunity is orchestrated by antigen-specific T and B lymphocytes. The effector cells of innate immunity include granulocytes, macrophages and natural killer cells. Among these cells, macrophages represent the most important part of innate immunity against tumours. Tumour-associated macrophages (TAMs) are important antigen-presenting cells and as such an understanding of their interactions with tumour cells gives insights into novel therapeutic strategies. In tumours, the effect of TAMs is the outcome of their two concomitantly competing interactions: tumour growth reduction and tumour growth promotion. The macrophage (TAMs) content of melanoma ranges from 0 to 30% and their density increases with increasing tumour thickness. The melanoma cells and TAMs seem to interact with each other through the release of soluble factors that either prevent or enhance tumour growth. For instance, syngeneic macrophages from tumour-bearing mice can inhibit melanoma growth in the nude mice more than the control macrophages. Alternatively, metastatic B16 melanoma cells can produce some macrophage cytotoxic substances that help tumour cells not only escape the host immunosurveillance system but also prevent distant metastasis. Together, these observations suggest opposing effects for these soluble factors in melanoma. To date, little is available in the literature about the interactions between TAMs and melanoma cells. This viewpoint not only tries to examine these interactions but also provides relevant speculations.