Macrophage colony-stimulating factor augments Tie2-expressing monocyte differentiation, angiogenic function, and recruitment in a mouse model of breast cancer

ICAM-1-decorated extracellular vesicles loaded with miR-146a and Glut1 drive immunomodulation and hinder tumor progression in a murine model of breast cancer

Tumor-associated immune cells play a crucial role in cancer progression. Myeloid-derived suppressor cells (MDSCs), for example, are immature innate immune cells that infiltrate the tumor to exert immunosuppressive activity and protect cancer cells from the host's immune system and/or cancer-specific immunotherapies. While tumor-associated immune cells have emerged as a promising therapeutic target, efforts to counter immunosuppression within the tumor niche have been hampered by the lack of approaches that selectively target the immune cell compartment of the tumor, to effectively eliminate "tumor-protecting" immune cells and/or drive an "anti-tumor" phenotype. Here we report on a novel nanotechnology-based approach to target tumor-associated immune cells and promote "anti-tumor" responses in a murine model of breast cancer. Engineered extracellular vesicles (EVs) decorated with ICAM-1 ligands and loaded with miR-146a and Glut1, were biosynthesized (in vitro or in vivo) and administered to tumor-bearing mice once a week for up to 5 weeks. The impact of this treatment modality on the immune cell compartment and tumor progression was evaluated via RT-qPCR, flow cytometry, and histology. Our results indicate that weekly administration of the engineered EVs (i.e., ICAM-1-decorated and loaded with miR-146a and Glut1) hampered tumor progression compared to ICAM-1-decorated EVs with no cargo. Flow cytometry analyses of the tumors indicated a shift in the phenotype of the immune cell population toward a more pro-inflammatory state, which appeared to have facilitated the infiltration of tumor-targeting T cells, and was associated with a reduction in tumor size and decreased metastatic burden. Altogether, our results indicate that ICAM-1-decorated EVs could be a powerful platform nanotechnology for the deployment of immune cell-targeting therapies to solid tumors.

Mechanism of paracrine communications between hepatic progenitor cells and endothelial cells

Hepatic progenitor cells (HPCs) are facultative tissue-specific stem cells lining reactive ductules, which are ubiquitously observed in chronic liver diseases and cancer. Although previous research mainly focused on their contribution to liver regeneration, it turned out that in vivo differentiation of HPCs into hepatocytes only occurs after extreme injury. While recent correlative evidence implies the association of HPCs with disease progression, their exact role in pathogenesis remains largely unknown. Our previous research demonstrated that HPCs expressing angiogenic paracrine factors accumulate in the peritumoral area and are positively correlated with the extent of intratumoral cell proliferation and angiogenesis in the livers of patients with liver cancer. Given the crucial roles of angiogenesis in liver disease progression and carcinogenesis, we aimed to test the hypothesis that HPCs secrete paracrine factors to communicate with endothelial cells, to determine molecular mechanisms mediating HPCs-endothelial interactions, and to understand how the paracrine function of HPCs is regulated. HPCs promoted viability and tubulogenesis of human umbilical vein endothelial cells (HUVECs) and upregulated genes known to be involved in angiogenesis, endothelial cell function, and disease progression in a paracrine manner. The paracrine function of HPCs as well as expression of colony stimulating factor 1 (CSF1) were inhibited upon differentiation of HPCs toward hepatocytes. Inhibition of CSF1 receptor partly suppressed the paracrine effects of HPCs on HUVECs. Taken together, our study indicates that inhibition of the paracrine function of HPCs through modulation of their differentiation status and inhibition of CSF1 signaling is a promising strategy for inhibition of angiogenesis during pathological progression.

Neuregulin-1 signaling regulates cytokines and chemokines expression and secretion in granulosa cell

BACKGROUND

Granulosa cells (GCs) are multilayered somatic cells within the follicle that provide physical support and microenvironment for the developing oocyte. In recent years, the role of Neuregulin-1 (NRG1), a member of the EGF-like factor family, has received considerable attention due to its neurodevelopmental and cardiac function. However, the exact physiological role of NRG1 in GC is mainly unknown. In order to confirm that NRG1 plays a regulatory role in rat GC functions, endogenous NRG1-knockdown studies were carried out in GCs using RNA interference methodology.

RESULTS

Knockdown of NRG1 in GCs resulted in the enhanced expression and secretion of the cytokines and chemokines. In addition, the phosphorylation of PI3K/Akt/ERK1/2 was significantly low in GCs under these experimental conditions. Moreover, in vitro experimental studies suggest that tumor necrosis factor-α (TNFα) treatment causes the physical destruction of GCs by activating caspase-3/7 activity. In contrast, exogenous NRG1 co-treatment of GCs delayed the onset of TNFα-induced apoptosis and inhibited the activation of caspase-3/7 activity. Furthermore, current experimental studies suggest that gonadotropins promote differential expression of NRG1 and ErbB3 receptors in GCs of the antral follicle. Interestingly, NRG1 and ErbB3 were intensely co-localized in the mural and cumulus GCs and cumulus-oocyte complex of pre-ovulatory follicles in the estrus stage.

CONCLUSIONS

The present studies suggest that gonadotropins-dependent NRG1-signaling in GCs may require the balance of the cytokines and chemokines expression and secretion, ultimately which may be supporting the follicular maturation and oocyte competence for ovulation and preventing follicular atresia.

Sanguinarine Regulates Tumor-Associated Macrophages to Prevent Lung Cancer Angiogenesis Through the WNT/β-Catenin Pathway

Tumor-associated macrophage (TAM)-mediated angiogenesis in the tumor microenvironment is a prerequisite for lung cancer growth and metastasis. Therefore, targeting TAMs, which block angiogenesis, is expected to be a breakthrough in controlling the growth and metastasis of lung cancer. In this study, we found that Sanguinarine (Sang) inhibits tumor growth and tumor angiogenesis of subcutaneously transplanted tumors in Lewis lung cancer mice. Furthermore, Sanguinarine inhibited the proliferation, migration, and lumen formation of HUVECs and the expression of CD31 and VEGF by regulating the polarization of M2 macrophages in vitro. However, the inhibitory effect of Sanguinarine on angiogenesis remained in vivo despite the clearance of macrophages using small molecule drugs. Further high-throughput sequencing suggested that WNT/β-Catenin signaling might represent the underlying mechanism of the beneficial effects of Sanguinarine. Finally, the β-Catenin activator SKL2001 antagonized the effect of Sanguinarine, indicating that Sanguinarine can regulate M2-mediated angiogenesis through the WNT/β-Catenin pathway. In conclusion, this study presents the first findings that Sanguinarine can function as a novel regulator of the WNT/β-Catenin pathway to modulate the M2 macrophage polarization and inhibit angiogenesis, which has potential application value in immunotherapy and antiangiogenic therapy for lung cancer.

Decrease of Pro-Angiogenic Monocytes Predicts Clinical Response to Anti-Angiogenic Treatment in Patients with Metastatic Renal Cell Carcinoma

The modulation of subpopulations of pro-angiogenic monocytes (VEGFR-1+CD14 and Tie2+CD14) was analyzed in an ancillary study from the prospective PazopanIb versus Sunitinib patient preferenCE Study (PISCES) (NCT01064310), where metastatic renal cell carcinoma (mRCC) patients were treated with two anti-angiogenic drugs, either sunitinib or pazopanib. Blood samples from 86 patients were collected prospectively at baseline (T1), and at 10 weeks (T2) and 20 weeks (T3) after starting anti-angiogenic therapy. Various subpopulations of myeloid cells (monocytes, VEGFR-1+CD14 and Tie2+CD14 cells) decreased during treatment. When patients were divided into two subgroups with a decrease (defined as a >20% reduction from baseline value) (group 1) or not (group 2) at T3 for VEGFR-1+CD14 cells, group 1 patients presented a median PFS and OS of 24 months and 37 months, respectively, compared with a median PFS of 9 months (p = 0.032) and a median OS of 16 months (p = 0.033) in group 2 patients. The reduction in Tie2+CD14 at T3 predicted a benefit in OS at 18 months after therapy (p = 0.04). In conclusion, in this prospective clinical trial, a significant decrease in subpopulations of pro-angiogenic monocytes was associated with clinical response to anti-angiogenic drugs in patients with mRCC.

Targeting Tumor-Associated Macrophages in Cancer Immunotherapy

Tumor-associated macrophages (TAMs) represent the most abundant leukocyte population in most solid tumors and are greatly influenced by the tumor microenvironment. More importantly, these macrophages can promote tumor growth and metastasis through interactions with other cell populations within the tumor milieu and have been associated with poor outcomes in multiple tumors. In this review, we examine how the tumor microenvironment facilitates the polarization of TAMs. Additionally, we evaluate the mechanisms by which TAMs promote tumor angiogenesis, induce tumor invasion and metastasis, enhance chemotherapeutic resistance, and foster immune evasion. Lastly, we focus on therapeutic strategies that target TAMs in the treatments of cancer, including reducing monocyte recruitment, depleting or reprogramming TAMs, and targeting inhibitory molecules to increase TAM-mediated phagocytosis.

Targeting Tumor-Associated Macrophages in Cancer Immunotherapy

Tumor-associated macrophages (TAMs) represent the most abundant leukocyte population in most solid tumors and are greatly influenced by the tumor microenvironment. More importantly, these macrophages can promote tumor growth and metastasis through interactions with other cell populations within the tumor milieu and have been associated with poor outcomes in multiple tumors. In this review, we examine how the tumor microenvironment facilitates the polarization of TAMs. Additionally, we evaluate the mechanisms by which TAMs promote tumor angiogenesis, induce tumor invasion and metastasis, enhance chemotherapeutic resistance, and foster immune evasion. Lastly, we focus on therapeutic strategies that target TAMs in the treatments of cancer, including reducing monocyte recruitment, depleting or reprogramming TAMs, and targeting inhibitory molecules to increase TAM-mediated phagocytosis.

Tumor-Associated Neutrophils and Macrophages-Heterogenous but Not Chaotic

Tumor-associated macrophages (TAMs) and tumor-associated neutrophils (TANs) have been extensively studied. Their pleotropic roles were observed in multiple steps of tumor progression and metastasis, and sometimes appeared to be inconsistent across different studies. In this review, we collectively discussed many lines of evidence supporting the mutual influence between cancer cells and TAMs/TANs. We focused on how direct interactions among these cells dictate co-evolution involving not only clonal competition of cancer cells, but also landscape shift of the entire tumor microenvironment (TME). This co-evolution may take distinct paths and contribute to the heterogeneity of cancer cells and immune cells across different tumors. A more in-depth understanding of the cancer-TAM/TAN co-evolution will shed light on the development of TME that mediates metastasis and therapeutic resistance.

Targeting Tumor-Associated Macrophages to Increase the Efficacy of Immune Checkpoint Inhibitors: A Glimpse into Novel Therapeutic Approaches for Metastatic Melanoma

Immune checkpoint inhibitors (ICIs) represent a promising therapeutic intervention for a variety of advanced/metastatic solid tumors, including melanoma, but in a large number of cases, patients fail to establish a sustained anti-tumor immunity and to achieve a long-lasting clinical benefit. Cells of the tumor micro-environment such as tumor-associated M2 macrophages (M2-TAMs) have been reported to limit the efficacy of immunotherapy, promoting tumor immune evasion and progression. Thus, strategies targeting M2-TAMs have been suggested to synergize with immune checkpoint blockade. This review recapitulates the molecular mechanisms by which M2-TAMs promote cancer immune evasion, with focus on the potential cross-talk between pharmacological interventions targeting M2-TAMs and ICIs for melanoma treatment.

Myeloid Cells as Clinical Biomarkers for Immune Checkpoint Blockade

Immune checkpoint inhibitors are becoming standard treatments in several cancer types, profoundly changing the prognosis of a fraction of patients. Currently, many efforts are being made to predict responders and to understand how to overcome resistance in non-responders. Given the crucial role of myeloid cells as modulators of T effector cell function in tumors, it is essential to understand their impact on the clinical outcome of immune checkpoint blockade and on the mechanisms of immune evasion. In this review we focus on the existing clinical evidence of the relation between the presence of myeloid cell subsets and the response to anti-PD(L)1 and anti-CTLA-4 treatment. We highlight how circulating and tumor-infiltrating myeloid populations can be used as predictive biomarkers for immune checkpoint inhibitors in different human cancers, both at baseline and on treatment. Moreover, we propose to follow the dynamics of myeloid cells during immunotherapy as pharmacodynamic biomarkers. Finally, we provide an overview of the current strategies tested in the clinic that use myeloid cell targeting together with immune checkpoint blockade with the aim of uncovering the most promising approaches for effective combinations.

The role of the tumor microenvironment in tumor cell intravasation and dissemination

Metastasis, a process that requires tumor cell dissemination followed by tumor growth, is the primary cause of death in cancer patients. An essential step of tumor cell dissemination is intravasation, a process by which tumor cells cross the blood vessel endothelium and disseminate to distant sites. Studying this process is of utmost importance given that intravasation in the primary tumor, as well as the secondary and tertiary metastases, is the key step in the systemic spread of tumor cells, and that this process continues even after removal of the primary tumor. High-resolution intravital imaging of the tumor microenvironment of breast carcinoma has revealed that tumor cell intravasation exclusively occurs at doorways, termed "Tumor MicroEnvironment of Metastasis" (TMEM), composed of three different cell types: a Tie2^high/VEGF^high perivascular macrophage, a Mena overexpressing tumor cell, and an endothelial cell, all in direct contact. In this review article, we discuss the interactions between these cell types, the subsequent signaling events which lead to tumor cell intravasation, and the role of invadopodia in supporting tumor cell invasion and dissemination. We end our review by discussing how the knowledge acquired from the use of intravital imaging is now leading to new clinical trials targeting tumor cell dissemination and preventing metastatic progression.

Controlling chronic low-grade inflammation to improve follicle development and survival

Chronic low-grade inflammation is one cause of follicle development disturbance. Chronic inflammation exists in pathological conditions such as premature ovarian failure, physiological aging of the ovaries, and polycystic ovary syndrome. Inflammation of the whole body can affect oocytes via the follicle microenvironment, oxidative stress, and GM-CSF. Many substances without toxic side-effects extracted from natural organisms have gradually gained researchers' attention. Recently, chitosan oligosaccharide, resveratrol, anthocyanin, and melatonin have been found to contribute to an improvement in inflammation. This review discusses the interrelationships between chronic low-grade inflammation and follicle development, the underlying mechanisms, and methods that may improve follicle development by controlling the level of chronic low-grade inflammation.

Neuropilin1 Expression Acts as a Prognostic Marker in Stomach Adenocarcinoma by Predicting the Infiltration of Treg Cells and M2 Macrophages

Neuropilin1 (NRP1) plays a critical role in tumor progression and immune responses. Although the roles of NRP1 in various tumors have been investigated, the clinical relevance of NRP1 expression in stomach adenocarcinoma (STAD) has not been studied. To investigate the use of NRP1 as a prognostic biomarker of STAD, we analyzed NRP1 mRNA expression and its correlation with patient survival and immune cell infiltration using various databases. NRP1 mRNA expression was significantly higher in STAD than normal tissues, and Kaplan-Meier survival analysis showed that NRP1 expression was significantly associated with poor prognosis in patients with STAD. To elucidate the related mechanism, we analyzed the correlation between NRP1 expression and immune cell infiltration level. In particular, the infiltration of immune-suppressive cells, such as regulatory T (Treg) cells and M2 macrophage, was significantly increased by NRP1 expression. In addition, the expression of interleukin (IL)-35, IL-10, and TGF-β1 was also positively correlated with NRP1 expression, resulting in the immune suppression. Collectively in this study, our integrated analysis using various clinical databases shows that the significant correlation between NRP1 expression and the infiltration of Treg cells and M2 macrophage explains poor prognosis mechanism in STAD, suggesting the clinical relevance of NRP1 expression as a prognostic biomarker for STAD patients.

Growth and elongation of axons through mechanical tension mediated by fluorescent-magnetic bifunctional Fe3O4·Rhodamine 6G@PDA superparticles

Background

The primary strategy to repair peripheral nerve injuries is to bridge the lesions by promoting axon regeneration. Thus, the ability to direct and manipulate neuronal cell axon regeneration has been one of the top priorities in the field of neuroscience. A recent innovative approach for remotely guiding neuronal regeneration is to incorporate magnetic nanoparticles (MNPs) into cells and transfer the resulting MNP-loaded cells into a magnetically sensitive environment to respond to an external magnetic field. To realize this intention, the synthesis and preparation of ideal MNPs is an important challenge to overcome.

Results

In this study, we designed and prepared novel fluorescent-magnetic bifunctional Fe₃O₄·Rhodamine 6G@polydopamine superparticles (FMSPs) as neural regeneration therapeutics. With the help of their excellent biocompatibility and ability to interact with neural cells, our in-house fabricated FMSPs can be endocytosed into cells, transported along the axons, and then aggregated in the growth cones. As a result, the mechanical forces generated by FMSPs can promote the growth and elongation of axons and stimulate gene expression associated with neuron growth under external magnetic fields.

Conclusions

Our work demonstrates that FMSPs can be used as a novel stimulator to promote noninvasive neural regeneration through cell magnetic actuation.

The Immunosuppressive Niche of Soft-Tissue Sarcomas is Sustained by Tumor-Associated Macrophages and Characterized by Intratumoral Tertiary Lymphoid Structures

PURPOSE

Clinical trials with immune checkpoint inhibition in sarcomas have demonstrated minimal response. Here, we interrogated the tumor microenvironment (TME) of two contrasting soft-tissue sarcomas (STS), rhabdomyosarcomas and undifferentiated pleomorphic sarcomas (UPS), with differing genetic underpinnings and responses to immune checkpoint inhibition to understand the mechanisms that lead to response.

EXPERIMENTAL DESIGN

Utilizing fresh and formalin-fixed, paraffin-embedded tissue from patients diagnosed with UPS and rhabdomyosarcomas, we dissected the TME by using IHC, flow cytometry, and comparative transcriptomic studies.

RESULTS

Our results demonstrated both STS subtypes to be dominated by tumor-associated macrophages and infiltrated with immune cells that localized near the tumor vasculature. Both subtypes had similar T-cell densities, however, their in situ distribution diverged. UPS specimens demonstrated diffuse intratumoral infiltration of T cells, while rhabdomyosarcomas samples revealed intratumoral T cells that clustered with B cells near perivascular beds, forming tertiary lymphoid structures (TLS). T cells in UPS specimens were comprised of abundant CD8⁺ T cells exhibiting high PD-1 expression, which might represent the tumor reactive repertoire. In rhabdomyosarcomas, T cells were limited to TLS, but expressed immune checkpoints and immunomodulatory molecules which, if appropriately targeted, could help unleash T cells into the rest of the tumor tissue.

CONCLUSIONS

Our work in STS revealed an immunosuppressive TME dominated by myeloid cells, which may be overcome with activation of T cells that traffic into the tumor. In rhabdomyosarcomas, targeting T cells found within TLS may be key to achieve antitumor response.

The role of tumor-associated macrophages in gastric cancer development and their potential as a therapeutic target

Gastric cancer (GC) represents the fifth cause of cancer-related death worldwide. Molecular biology has become a central area of research in GC and there are currently at least three major classifications available to elucidate the mechanisms that drive GC oncogenesis. Further, tumor microenvironment seems to play a crucial role, and tumor-associated macrophages (TAMs) are emerging as key players in GC development. TAMs are cells derived from circulating chemokine- receptor-type 2 (CCR2) inflammatory monocytes in blood and can be divided into two main types, M1 and M2 TAMs. M2 TAMs play an important role in tumor progression, promoting a pro-angiogenic and immunosuppressive signal in the tumor. The diffuse GC subtype, in particular, seems to be strongly characterized by an immuno-suppressive and pro-angiogenic phenotype. No molecular targets in this subgroup have yet been identified. There is an urgent need to understand the molecular pathways and tumor microenvironment features in the GC molecular subtypes. The role of anti-angiogenics and checkpoint inhibitors has recently been clinically validated in GC. Both ramucirumab, a fully humanized IgG1 monoclonal anti-vascular endothelial growth factor receptor 2 (VEGFR2) antibody, and checkpoint inhibitors in Epstein Bar Virus (EBV) and Microsatellite Instable (MSI) subtypes, have proved beneficial in advanced GC. Nevertheless, there is a need to identify predictive markers of response to anti-angiogenics and immunotherapy in clinical practice for a personalized treatment approach. The importance of M2 TAMs in development of solid tumors is currently gaining increasing interest. In this literature review we analyze immune microenvironment composition and signaling related to M1 and M2 TAMs in GC as well as its potential role as a therapeutic target.

Monocytes and Macrophages in Cancer: Unsuspected Roles

The behavior of cancer is undoubtedly affected by stroma. Macrophages belong to this microenvironment and their presence correlates with reduced survival in most cancers. After a tumor-induced "immunoediting", these monocytes/macrophages, originally the first line of defense against tumor cells, undergo a phenotypic switch and become tumor-supportive and immunosuppressive.The influence of these tumor-associated macrophages (TAMs) on cancer is present in all traits of carcinogenesis. These cells participate in tumor initiation and growth, migration, vascularization, invasion and metastasis. Although metastasis is extremely clinically relevant, this step is always reliant on the angiogenic ability of tumors. Therefore, the formation of new blood vessels in tumors assumes particular importance as a limiting step for disease progression.Herein, the once unsuspected roles of macrophages in cancer will be discussed and their importance as a promising strategy to treat this group of diseases will be reminded.

Compromised Bone Healing in Aged Rats Is Associated With Impaired M2 Macrophage Function

Fracture repair is initiated by a multitude of immune cells and induction of an inflammatory cascade. Alterations in the early healing response due to an aged adaptive immune system leads to impaired bone repair, delayed healing or even formation of non-union. However, immuno-senescence is not limited to the adaptive immunity, but is also described for macrophages, main effector cells from the innate immune system. Beside regulation of pro- and anti-inflammatory signaling, macrophages contribute to angiogenesis and granulation tissue maturation. Thus, it seems likely that an altered macrophage function due to aging may affect bone repair at various stages and contribute to age related deficiencies in bone regeneration. To prove this hypothesis, we analyzed the expression of macrophage markers and angiogenic factors in the early bone hematoma derived from young and aged osteotomized Spraque Dawley rats. We detected an overall reduced expression of the monocyte/pan-macrophage markers CD14 and CD68 in aged rats. Furthermore, the analysis revealed an impaired expression of anti-inflammatory M2 macrophage markers in hematoma from aged animals that was connected to a diminished revascularization of the bone callus. To verify that the age related disturbed bone regeneration was due to a compromised macrophage function, CD14+ macrophage precursors were transplanted locally into the osteotomy gap of aged rats. Transplantation rescued bone regeneration partially after 6 weeks, demonstrated by a significantly induced deposition of new bone tissue, reduced fibrosis and significantly improved callus vascularization.

T cell-induced CSF1 promotes melanoma resistance to PD1 blockade

Colony-stimulating factor 1 (CSF1) is a key regulator of monocyte/macrophage differentiation that sustains the protumorigenic functions of tumor-associated macrophages (TAMs). We show that CSF1 is expressed in human melanoma, and patients with metastatic melanoma have increased CSF1 in blood compared to healthy subjects. In tumors, CSF1 expression correlated with the abundance of CD8⁺ T cells and CD163⁺ TAMs. Human melanoma cell lines consistently produced CSF1 after exposure to melanoma-specific CD8⁺ T cells or T cell-derived cytokines in vitro, reflecting a broadly conserved mechanism of CSF1 induction by activated CD8⁺ T cells. Mining of publicly available transcriptomic data sets suggested co-enrichment of CD8⁺ T cells with CSF1 or various TAM-specific markers in human melanoma, which was associated with nonresponsiveness to programmed cell death protein 1 (PD1) checkpoint blockade in a smaller patient cohort. Combination of anti-PD1 and anti-CSF1 receptor (CSF1R) antibodies induced the regression of BRAF^V600E -driven, transplant mouse melanomas, a result that was dependent on the effective elimination of TAMs. Collectively, these data implicate CSF1 induction as a CD8⁺ T cell-dependent adaptive resistance mechanism and show that simultaneous CSF1R targeting may be beneficial in melanomas refractory to immune checkpoint blockade and, possibly, other T cell-based therapies.

Perivascular macrophages in health and disease

Macrophages are a heterogeneous group of cells that are capable of carrying out distinct functions in different tissues, as well as in different locations within a given tissue. Some of these tissue macrophages lie on, or close to, the outer (abluminal) surface of blood vessels and perform several crucial activities at this interface between the tissue and the blood. In steady-state tissues, these perivascular macrophages maintain tight junctions between endothelial cells and limit vessel permeability, phagocytose potential pathogens before they enter tissues from the blood and restrict inappropriate inflammation. They also have a multifaceted role in diseases such as cancer, Alzheimer disease, multiple sclerosis and type 1 diabetes. Here, we examine the important functions of perivascular macrophages in various adult tissues and describe how these functions are perturbed in a broad array of pathological conditions.

The role of caveolin-1 in tumors of the brain - functional and clinical implications

BACKGROUND

Caveolin-1 (cav-1) is the major structural protein of caveolae, the flask-shaped invaginations of the plasma membrane mainly involved in cell signaling. Today, cav-1 is believed to play a role in a variety of disease processes including cancer, owing to the variations of its expression in association with tumor progression, invasive behavior, metastasis and therapy resistance. Since first detected in the brain, a number of studies has particularly focused on the role of cav-1 in the various steps of brain tumorigenesis. In this review, we discuss the different roles of cav-1 and its contributions to the molecular mechanisms underlying the pathobiology and natural behavior of brain tumors including glial, non-glial and metastatic subtypes. These contributions could be attributed to its co-localization with important players in tumorigenesis within the lipid-enriched domains of the plasma membrane. In that regard, the ability of cav-1 to interact with various cell signaling molecules as well as the impact of caveolae depletion on important pathways acting in brain tumor pathogenesis are noteworthy. We also discuss conversant causes hampering the treatment of malignant glial tumors such as limited transport of chemotherapeutics across the blood tumor barrier and resistance to chemoradiotherapy, by focusing on the molecular fundamentals involving cav-1 participation.

CONCLUSIONS

Cav-1 has the potential to pivot the molecular basis underlying the pathobiology of brain tumors, particularly the malignant glial subtype. In addition, the regulatory effect of cav-1-dependent and caveola-mediated transcellular transport on the permeability of the blood tumor barrier could be of benefit to overcome the restricted transport across brain barriers when applying chemotherapeutics. The association of cav-1 with tumors of the brain other than malignant gliomas deserves to be underlined, as well given the evidence suggesting its potential in predicting tumor grade and recurrence rates together with determining patient prognosis in oligodendrogliomas, ependymomas, meningiomas, vestibular schwannomas and brain metastases.

Regulation of Blood and Lymphatic Vessels by Immune Cells in Tumors and Metastasis

Research over the last decades has provided strong evidence for the pivotal role of the tumor-associated blood and lymphatic vasculature in supporting immunoevasion and in subverting T cell-mediated immunosurveillance. Conversely, tumor blood and lymphatic vessel growth is in part regulated by the immune system, with infiltrating innate as well as adaptive immune cells providing both immunosuppressive and various angiogenic signals. Thus, tumor angiogenesis and escape of immunosurveillance are two cancer hallmarks that are tightly linked and interregulated by cell constituents from compartments secreting both chemokines and cytokines. In this review, we discuss the implication and regulation of innate and adaptive immune cells in regulating blood and lymphatic angiogenesis in tumor progression and metastases. Moreover, we also highlight novel therapeutic approaches that target the tumor vasculature as well as the immune compartment to sustain and improve therapeutic efficacy in cancer.

IFN regulatory factor-8 expression in macrophages governs an antimetastatic program

High macrophage infiltration in cancer is associated with reduced survival in animal models and in patients. This reflects a shift in the macrophage response from a tumor-suppressive to tumor-supportive program governed by transcriptional events regulated by the inflammatory milieu. Although several transcription factors are known to drive a prometastatic program, those that govern an antimetastatic program are less understood. IFN regulatory factor-8 (IRF8) is integral for macrophage responses against infections. Using a genetic loss-of-function approach, we tested the hypothesis that IRF8 expression in macrophages governs their capacity to inhibit metastasis. We found that: (a) metastasis was significantly increased in mice with IRF8-deficient macrophages; (b) IRF8-deficient macrophages displayed a program enriched for genes associated with metastasis; and (c) lower IRF8 expression correlated with reduced survival in human breast and lung cancer, as well as melanoma, with high or low macrophage infiltration. Thus, a macrophagehiIRF8hi signature was more favorable than a macrophagehiIRF8lo signature. The same held true for a macrophageloIRF8hi vs. a macrophageloIRF8lo signature. These data suggest that incorporating IRF8 expression levels within a broader macrophage signature or profile strengthens prognostic merit. Overall, to our knowledge, our findings reveal a previously unrecognized role for IRF8 in macrophage biology to control metastasis or predict outcome.

The emerging roles of macrophages in cancer metastasis and response to chemotherapy

Macrophages represent a heterogeneous group of cells, capable of carrying out distinct functions in a variety of organs and tissues. Even within individual tissues, their functions can vary with location. Tumor-associated macrophages (TAMs) specialize into three major subtypes that carry out multiple tasks simultaneously. This is especially true in the context of metastasis, where TAMs establish most of the cellular and molecular prerequisites for successful cancer cell dissemination and seeding to the secondary site. Perivascular TAMs operate in the perivascular niche, where they promote tumor angiogenesis and aid in the assembly of intravasation sites called tumor microenvironment of metastasis (TMEM). Streaming TAMs co-migrate with tumor cells (irrespective of the perivascular niche) and promote matrix remodeling, tumor cell invasiveness, and an immunosuppressive local microenvironment. Premetastatic TAMs are recruited to the premetastatic niche, where they can assist in tumor cell extravasation, seeding, and metastatic colonization. The dynamic interplay between TAMs and tumor cells can also modify the ability of the latter to resist cytotoxic chemotherapy (a phenotype known as environment-mediated drug resistance) and induce chemotherapy-mediated pro-metastatic microenvironmental changes. These observations suggest that future therapeutics should be designed to target TAMs with the aim of suppressing the metastatic potential of tumors and rendering chemotherapy more efficient.

Macrophages and Fibroblasts, Key Players in Cancer Chemoresistance

Chemotherapy is routinely used in cancer treatment to eliminate primary and metastatic tumor cells. However, tumors often display or develop resistance to chemotherapy. Mechanisms of chemoresistance can be either tumor cell autonomous or mediated by the tumor surrounding non-malignant cells, also known as stromal cells, which include fibroblasts, immune cells, and cells from the vasculature. Therapies targeting cancer cells have shown limited effectiveness in tumors characterized by a rich tumor stroma. Tumor-associated macrophages (TAMs) and cancer-associated fibroblasts (CAFs) are the most abundant non-cancerous cells in the tumor stroma and have emerged as key players in cancer progression, metastasis and resistance to therapies. This review describes the recent advances in our understanding of how CAFs and TAMs confer chemoresistance to tumor cells and discusses the therapeutic opportunities of combining anti-tumor with anti-stromal therapies. The continued elucidation of the mechanisms by which TAMs and CAFs mediate resistance to therapies will allow the development of improved combination treatments for cancer patients.

CSF-1 and Ang-2 serum levels - prognostic and diagnostic partners in non-small cell lung cancer

Background

Lung cancer is the most incident and lethal form of cancer, with late diagnosis as a major determinant of its bad prognosis. Immunotherapies targeting immune checkpoints improve survival, but positive results encompass only 30%–40% of the patients, possibly due to alternative pathways to immunosuppression, including tumour-associated macrophages (TAM). Colony stimulating factor-1 (CSF-1) is implicated in TAM differentiation and recruitment to tumours and in tumour angiogenesis, through a special setting of Tie-2-expressing macrophages, which respond to angiopoietin-2 (Ang-2). We evaluated the role of serum levels of CSF-1 in non-small cell lung cancer (NSCLC) prognosis and whether these could serve as biomarkers for NSCLC detection, along with Ang-2.

Participants and methods

We prospectively studied an unselected cohort of 145 patients with NSCLC and a group of 30 control individuals. Serum levels of Ang-2 and CSF-1 were measured by ELISA prior to treatment.

Results

Serum levels of CSF-1 and Ang-2 are positively correlated (p<0.000001). Individuals with high serum levels of CSF-1 have a 17-fold risk for NSCLC presence and patients with combined High Ang-2/CSF-1 serum levels present a 5-fold increased risk of having NSCLC. High Ang-2/CSF-1 phenotype is also associated with worst prognosis in NSCLC.

Conclusions

Combined expression of CSF-1 and Ang-2 seems to contribute to worst prognosis in NSCLC and it is worthy to understand the basis of this unexplored partnership. Moreover, we think CSF-1 could be included as a biomarker in NSCLC screening protocols that can improve the positive predictive value of the current screening modalities, increase overall cost effectiveness and potentially improve lung cancer survival.

Angiogenic miRNAs, the angiopoietin axis and related TIE2-expressing monocytes affect outcomes in cholangiocarcinoma

Background

Tumour angiogenesis is modulated on both an epigenetic and protein level and has potential implications for immune cell responses. However, the importance of related angiogenic biomarkers in cholangiocarcinoma (CCA) is unknown. This study assessed human CCA samples for the expression of angiogenesis-associated microRNAs, angiopoietins (Angs) and monocytes expressing the Ang-receptor, TIE2, with regards to prognostic significance after liver resection.

Methods

Angiogenic miRNAs were analysed in frozen samples of intrahepatic CCA (iCC; n = 43) and hilar CCA (HC; n = 45). Ang-1 and Ang-2, as well as TIE2-expressing monocytes (TEMs), were detected in paraffin-embedded iCC sections (n = 88). MiRNA expression and the abundance of TEMs and Angs were correlated with clinicopathological characteristics and survival.

Results

MiR-126 was downregulated in 76.7% of all CCA samples, with high relative expression associated with smaller tumours and reduced lymph node metastasis. High Ang-1 expression was associated with less lymphangiosis carcinomatosa and better histological grading (all p < 0.05). The absence of TEMs in iCC correlated with elevated CA19-9 levels. High relative miR-126 and low miR-128 levels were associated with improved survival in iCC and HC, respectively (all p < 0.05). High miR-126, low miR-128 and TEMs were independent prognostic factors for recurrence-free and overall survival (all p < 0.05).

Conclusions

These results suggest that angiogenic miRNAs, Angs and TEMs are of prognostic value in CCA. In addition to the possible functional links between angiogenic miRNA expression profiles, Angs and immune-cell responses by TEMs, these data have clinical implications as novel diagnostic tools.

Mathematical modeling of tumor-associated macrophage interactions with the cancer microenvironment

Background

Immuno-oncotherapy has emerged as a promising means to target cancer. In particular, therapeutic manipulation of tumor-associated macrophages holds promise due to their various and sometimes opposing roles in tumor progression. It is established that M1-type macrophages suppress tumor progression while M2-types support it. Recently, Tie2-expressing macrophages (TEM) have been identified as a distinct sub-population influencing tumor angiogenesis and vascular remodeling as well as monocyte differentiation.

Methods

This study develops a modeling framework to evaluate macrophage interactions with the tumor microenvironment, enabling assessment of how these interactions may affect tumor progression. M1, M2, and Tie2 expressing variants are integrated into a model of tumor growth representing a metastatic lesion in a highly vascularized organ, such as the liver. Behaviors simulated include M1 release of nitric oxide (NO), M2 release of growth-promoting factors, and TEM facilitation of angiogenesis via Angiopoietin-2 and promotion of monocyte differentiation into M2 via IL-10.

Results

The results show that M2 presence leads to larger tumor growth regardless of TEM effects, implying that immunotherapeutic strategies that lead to TEM ablation may fail to restrain growth when the M2 represents a sizeable population. As TEM pro-tumor effects are less pronounced and on a longer time scale than M1-driven tumor inhibition, a more nuanced approach to influence monocyte differentiation taking into account the tumor state (e.g., under chemotherapy) may be desirable.

Conclusions

The results highlight the dynamic interaction of macrophages within a growing tumor, and, further, establish the initial feasibility of a mathematical framework that could longer term help to optimize cancer immunotherapy.

Targeting tumor-associated macrophages to combat pancreatic cancer

The tumor microenvironment is replete with cells that evolve with and provide support to tumor cells during the transition to malignancy. The hijacking of the immune system in the pancreatic tumor microenvironment is suggested to contribute to the failure to date to produce significant improvements in pancreatic cancer survival by various chemotherapeutics. Regulatory T cells, myeloid derived suppressor cells, and fibroblasts, all of which constitute a complex ecology microenvironment, can suppress CD8+ T cells and NK cells, thus inhibiting effector immune responses. Tumor-associated macrophages (TAM) are versatile immune cells that can express different functional programs in response to stimuli in tumor microenvironment at different stages of pancreatic cancer development. TAM have been implicated in suppression of anti-tumorigenic immune responses, promotion of cancer cell proliferation, stimulation of tumor angiogenesis and extracellular matrix breakdown, and subsequent enhancement of tumor invasion and metastasis. Many emerging agents that have demonstrated efficacy in combating other types of tumors via modulation of macrophages in tumor microenvironments are, however, only marginally studied for pancreatic cancer prevention and treatment. A better understanding of the paradoxical roles of TAM in pancreatic cancer may pave the way to novel preventive and therapeutic approaches. Here we give an overview of the recruitment and differentiation of macrophages, TAM and pancreatic cancer progression and prognosis, as well as the potential preventive and therapeutic targets that interact with TAM for pancreatic cancer prevention and treatment.

Immune-Mediated and Hypoxia-Regulated Programs: Accomplices in Resistance to Anti-angiogenic Therapies

In contrast to mechanisms taking place during resistance to chemotherapies or other targeted therapies, compensatory adaptation to angiogenesis blockade does not imply a mutational alteration of genes encoding drug targets or multidrug resistance mechanisms but instead involves intrinsic or acquired activation of compensatory angiogenic pathways. In this article we highlight hypoxia-regulated and immune-mediated mechanisms that converge in endothelial cell programs and preserve angiogenesis in settings of vascular endothelial growth factor (VEGF) blockade. These mechanisms involve mobilization of myeloid cell populations and activation of cytokine- and chemokine-driven circuits operating during intrinsic and acquired resistance to anti-angiogenic therapies. Particularly, we focus on findings underscoring a role for galectins and glycosylated ligands in promoting resistance to anti-VEGF therapies and discuss possible strategies to overcome or attenuate this compensatory pathway. Finally, we highlight emerging evidence demonstrating the interplay between immunosuppressive and pro-angiogenic programs in the tumor microenvironment (TME) and discuss emerging combinatorial anticancer strategies aimed at simultaneously potentiating antitumor immune responses and counteracting aberrant angiogenesis.

The association of depressed angiogenic factors with reduced capillary density in the Rhesus monkey model of myocardial ischemia

Depressed capillary density is associated with myocardial ischemic infarction, in which hypoxia-inducible factor 1α (HIF-1α) is increased. The present study was undertaken to examine changes in the angiogenic factors whose expression is regulated by HIF-1 and their relation to the depressed capillary density in the Rhesus monkey model of myocardial ischemic infarction. Male Rhesus monkeys 2-3 years old were subjected to myocardial ischemia by permanent ligation of left anterior descending (LAD) artery leading to the development of myocardial infarction. Eight weeks after LAD ligation, copper concentrations, myocardial histological changes and capillary density were examined, along with Western blot and immunohistochemical analysis of angiogenic factors and detection of HIF-1 activity. Capillary density was significantly decreased but the concentrations of HIF-1α and HIF-1β were significantly increased in the infarct area. However, the levels of mRNA and protein for VEGF and VEGFR1 were significantly decreased. Other HIF-1 regulated angiogenic factors, including Tie-2, Ang-1 and FGF-1, were also significantly depressed, but vascular destabilizing factor Ang-2 was significantly increased. Copper concentrations were depressed in the infarct area. Copper-independent HIF-1 activity was increased shown by the elevated mRNA level of IGF-2, a HIF-1 target gene. Removal of copper by a copper chelator, tetraethylenepentamine, from primary cultures of neonatal rat cardiomyocytes also suppressed the expression of HIF-1 regulated VEGF and BNIP3, but not IGF-2. The data suggest that under ischemic conditions, copper loss suppressed the expression of critical angiogenic genes regulated by HIF-1, but did not affect copper-independent HIF-1 activation of gene expression. This copper-dependent dysregulation of angiogenic gene expression would contribute to the pathogenesis of myocardial ischemic infarction.

One microenvironment does not fit all: heterogeneity beyond cancer cells

Human cancers exhibit formidable molecular heterogeneity, to a large extent accounting for the incomplete and transitory efficacy of current anti-cancer therapies. However, neoplastic cells alone do not manifest the disease, but conscript a battery of non-tumor cells to enable and sustain hallmark capabilities of cancer. Escaping immunosurveillance is one of such capabilities. Tumors evolve immunosuppressive microenvironment to subvert anti-tumor immunity. In this review, we will focus on tumor-associated myeloid cells, which constitute an essential part of the immune microenvironment and reciprocally interact with cancer cells to establish malignancy toward metastasis. The diversity and plasticity of these cells constitute another layer of heterogeneity, beyond the heterogeneity of cancer cells themselves. We envision that immune microenvironment co-evolves with the genetic heterogeneity of tumor. Addressing the question of how genetically distinct tumors shape and are shaped by unique immune microenvironment will provide an attractive rationale to develop novel immunotherapeutic modalities. Here, we discuss the complex nature of tumor microenvironment, with an emphasis on the cellular and functional heterogeneity among tumor-associated myeloid cells as well as immune environment heterogeneity in the context of a full spectrum of human breast cancers.

Innate immune cells for immunotherapy of autoimmune and cancer disorders

Modulation of the immune system has been widely targeted for the treatment of several immune-related diseases, such as autoimmune disorders and cancer, due to its crucial role in these pathologies. Current available therapies focus mainly on symptomatic treatment and are often associated with undesirable secondary effects. For several years, remission of disease and subsequently recovery of immune homeostasis has been a major goal for immunotherapy. Most current immunotherapeutic strategies are aimed to inhibit or potentiate directly the adaptive immune response by modulating antibody production and B cell memory, as well as the effector potential and memory of T cells. Although these immunomodulatory approaches have shown some success in the clinic with promising therapeutic potential, they have some limitations related to their effectiveness in disease models and clinical trials, as well as elevated costs. In the recent years, a renewed interest has emerged on targeting innate immune cells for immunotherapy, due to their high plasticity and ability to exert a potent and extremely rapid response, which can influence the outcome of the adaptive immune response. In this review, we discuss the immunomodulatory potential of several innate immune cells, as well as they use for immunotherapy, especially in autoimmunity and cancer.

Kaposi's sarcoma-associated herpesvirus infection promotes differentiation and polarization of monocytes into tumor-associated macrophages

Tumor associated macrophages (TAMs) promote angiogenesis, tumor invasion and metastasis, and suppression of anti-tumor immunity. These myeloid cells originate from monocytes, which differentiate into TAMs upon exposure to the local tumor microenvironment. We previously reported that Kaposi's sarcoma-associated herpes virus (KSHV) infection of endothelial cells induces the cytokine angiopoietin-2 (Ang-2) to promote migration of monocytes into tumors. Here we report that KSHV infection of endothelial cells induces additional cytokines including interleukin-6 (IL-6), interleukin-10 (IL-10), and interleukin-13 (IL-13) that drive monocytes to differentiate and polarize into TAMs. The KSHV-induced TAMs not only express TAM-specific markers such as CD-163 and legumain (LGMN) but also display a gene expression profile with characteristic features of viral infection. More importantly, KSHV-induced TAMs enhance tumor growth in nude mice. These results are consistent with the strong presence of TAMs in Kaposi's sarcoma (KS) tumors. Therefore, KSHV infection of endothelial cells generates a local microenvironment that not only promotes the recruitment of monocytes but also induces their differentiation and polarization into TAMs. These findings reveal a new mechanism of KSHV contribution to KS tumor development.

Tumor-associated macrophages: implications in cancer immunotherapy

Tumor-associated macrophages (TAMs), representing most of the leukocyte population in solid tumors, demonstrate great phenotypic heterogeneity and diverse functional capabilities under the influence of the local tumor microenvironment. These anti-inflammatory and protumorigenic macrophages modulate the local microenvironment to facilitate tumor growth and metastasis. In this review, we examine the origin of TAMs and the complex regulatory networks within the tumor microenvironment that facilitate the polarization of TAMs toward a protumoral phenotype. More extensively, we evaluate the mechanisms by which TAMs mediate angiogenesis, metastasis, chemotherapeutic resistance and immune evasion. Lastly, we will highlight novel interventional strategies targeting TAMs in preclinical studies and in early clinical trials that have significant potential in improving efficacy of current chemotherapeutic and/or immunotherapeutic approaches.

Knockdown of miR-128a induces Lin28a expression and reverts myeloid differentiation blockage in acute myeloid leukemia

Lin28A is a highly conserved RNA-binding protein that concurs to control the balance between stemness and differentiation in several tissue lineages. Here, we report the role of miR-128a/Lin28A axis in blocking cell differentiation in acute myeloid leukemia (AML), a genetically heterogeneous disease characterized by abnormally controlled proliferation of myeloid progenitor cells accompanied by partial or total inability to undergo terminal differentiation. First, we found Lin28A underexpressed in blast cells from AML patients and AML cell lines as compared with CD34+ normal precursors. In vitro transfection of Lin28A in NPM1-mutated OCI-AML3 cell line significantly triggered cell-cycle arrest and myeloid differentiation, with increased expression of macrophage associate genes (EGR2, ZFP36 and ANXA1). Furthermore, miR-128a, a negative regulator of Lin28A, was found overexpressed in AML cells compared with normal precursors, especially in acute promyelocytic leukemia (APL) and in ‘AML with maturation’ (according to 2016 WHO classification of myeloid neoplasms and acute leukemia). Its forced overexpression by lentiviral infection in OCI-AML3 downregulated Lin28A with ensuing repression of macrophage-oriented differentiation. Finally, knockdown of miR-128a in OCI-AML3 and in APL/AML leukemic cells (by transfection and lentiviral infection, respectively) induced myeloid cell differentiation and increased expression of Lin28A, EGR2, ZFP36 and ANXA1, reverting myeloid differentiation blockage. In conclusion, our findings revealed a new mechanism for AML differentiation blockage, suggesting new strategies for AML therapy based upon miR-128a inhibition.

Angiopoietin-1 enhances neutrophil chemotaxis in vitro and migration in vivo through interaction with CD18 and release of CCL4

Angiopoietins are a family of growth factors that are ligands for the tyrosine kinase receptor, Tie2. Angiopoietin 1 (Ang-1) is agonistic for Tie2, plays a key role in blood vessel maturation and stability and has been shown to possess anti-inflammatory properties. However, Tie2 expression has been demonstrated on human neutrophils and the observation that neutrophils migrate in response to Ang-1 in vitro has confounded research into its exact role in inflammation as well as its potential use as a therapeutic agent. We used a mouse model of peritoneal neutrophilic inflammation to determine if Ang-1 could stimulate neutrophil migration in vivo. Tie2 expression was demonstrated on mouse neutrophils. In addition, recombinant human Ang-1 induced significant chemotaxis of isolated mouse neutrophils in a Tie2- and CD18-dependent manner. Subsequently, co-immunoprecipitation of Ang-1 and CD18 demonstrated their interaction. Intraperitoneal injection of an engineered angiopoietin-1, MAT.Ang-1, induced significant neutrophil migration into the peritoneum and a significant increase in the levels of CCL4 in peritoneal lavage fluid. Depletion of resident peritoneal macrophages prior to, or concomitant injections of an anti-CCL4 antibody with MAT.Ang-1 resulted in a significant reduction in neutrophil recruitment. These data indicate a pro-inflammatory role for Ang-1 with respect to neutrophil recruitment.

The Sabotaging Role of Myeloid Cells in Anti-Angiogenic Therapy: Coordination of Angiogenesis and Immune Suppression by Hypoxia

Tumor angiogenesis has become a promising target for anti-tumor therapy. Unfortunately, the somewhat inevitable occurrence of resistance has limited the efficacy of anti-angiogenic therapy. In addition to their well-established role in immune suppression, bone marrow-derived myeloid cells actively contribute to tumor angiogenesis. More importantly, myeloid cells constitute one of the major mechanisms of resistance to angiogenesis inhibition. As the most pervasive feature in tumor microenvironment, hypoxia is able to initiate both pro-angiogenic and immunosuppressive capacities of myeloid cells. Tumor adapts to hypoxic stress primarily through signaling mediated by hypoxic inducible factors (HIFs) and consequently utilizes hypoxia to its own advantage. In this regard, hypoxia orchestrates both angiogenesis and immune evasion to support tumor growth. In this article, we will review available information on the sabotaging role of myeloid cells in anti-angiogenic therapy. We will also discuss how hypoxia coordinates the dual-role cellular and molecular participants in microenvironment to maximize the efficiency of angiogenesis and immunosuppression to promote tumor progression. J. Cell. Physiol. 232: 2312-2322, 2017. © 2016 Wiley Periodicals, Inc.

TIE-2 expressing monocytes in human cancers

Tumor-associated macrophages (TAM) are well known as a key player in the tumor microenvironment, which support cancer progression. More recently, a lineage of monocytes characterized by the expression of the TIE-2/Tek angiopoietin receptor identified a subset of circulating and tumor-associated monocytes endowed with proangiogenic activity. TIE-2 expressing monocytes (TEM) were found both in humans and mice. Here, we review the phenotypes and functions of TEM reported so far in human cancer and their potential use as markers of cancer progression and metastasis. Finally, we discuss the therapeutic approaches currently used or proposed to target TEM.

Human Tumor-Infiltrating Myeloid Cells: Phenotypic and Functional Diversity

Our current understanding of human tumor-resident myeloid cells is, for the most part, based on a large body of work in murine models or studies enumerating myeloid cells in patient tumor samples using immunohistochemistry (IHC). This has led to the establishment of the theory that, by and large, tumor-resident myeloid cells are either “protumor” M2 macrophages or myeloid-derived suppressor cells (MDSC). This concept has accelerated our understanding of myeloid cells in tumor progression and enabled the elucidation of many key regulatory mechanisms involved in cell recruitment, polarization, and activation. On the other hand, this paradigm does not embrace the complexity of the tumor-resident myeloid cell phenotype (IHC can only measure 1 or 2 markers per sample) and their possible divergent function in the hostile tumor microenvironment. Here, we examine the criteria that define human tumor-infiltrating myeloid cell subsets and provide a comprehensive and critical review of human myeloid cell nomenclature in cancer. We also highlight new evidence characterizing their contribution to cancer pathogenesis based on evidence derived from clinical studies drawing comparisons with murine studies where necessary. We then review the mechanisms in which myeloid cells are regulated by tumors in humans and how these are being targeted therapeutically.

Angiopoietin-2 as a Biomarker and Target for Immune Checkpoint Therapy

Immune checkpoint therapies targeting CTLA-4 and PD-1 have proven effective in cancer treatment. However, the identification of biomarkers for predicting clinical outcomes and mechanisms to overcome resistance remain as critical needs. Angiogenesis is increasingly appreciated as an immune modulator with potential for combinatorial use with checkpoint blockade. Angiopoietin-2 (ANGPT2) is an immune target in patients and is involved in resistance to anti-VEGF treatment with the monoclonal antibody bevacizumab. We investigated the predictive and prognostic value of circulating ANGPT2 in metastatic melanoma patients receiving immune checkpoint therapy. High pretreatment serum ANGPT2 was associated with reduced overall survival in CTLA-4 and PD-1 blockade-treated patients. These treatments also increased serum ANGPT2 in many patients early after treatment initiation, whereas ipilimumab plus bevacizumab treatment decreased serum concentrations. ANGPT2 increases were associated with reduced response and/or overall survival. Ipilimumab increased, and ipilimumab plus bevacizumab decreased, tumor vascular ANGPT2 expression in a subset of patients, which was associated with increased and decreased tumor infiltration by CD68⁺ and CD163⁺ macrophages, respectively. In vitro, bevacizumab blocked VEGF-induced ANGPT2 expression in tumor-associated endothelial cells, whereas ANGPT2 increased PD-L1 expression on M2-polarized macrophages. Treatments elicited long-lasting and functional antibody responses to ANGPT2 in a subset of patients receiving clinical benefit. Our findings suggest that serum ANGPT2 may be considered as a predictive and prognostic biomarker for immune checkpoint therapy and may contribute to treatment resistance via increasing proangiogenic and immunosuppressive activities in the tumor microenvironment. Targeting ANGPT2 provides a rational combinatorial approach to improve the efficacy of immune therapy. Cancer Immunol Res; 5(1); 17-28. ©2016 AACR.

Novel TIE-2 inhibitor BAY-826 displays in vivo efficacy in experimental syngeneic murine glioma models

Targeting the vascular endothelial growth factor signaling axis in glioblastoma inevitably leads to tumor recurrence and a more aggressive phenotype. Therefore, other angiogenic pathways, like the angiopoietin/tunica interna endothelial cell kinase (TIE) signaling axis, have become additional targets for therapeutic intervention. Here, we explored whether targeting the receptor tyrosine kinase TIE-2 using a novel, highly potent, orally available small molecule TIE-2 inhibitor (BAY-826) improves tumor control in syngeneic mouse glioma models. BAY-826 inhibits TIE-2 phosphorylation in vitro and in vivo as demonstrated by suppression of Angiopoietin-1- or Na₃ VO₄ -induced TIE-2 phosphorylation in glioma cells or extracts of lungs from BAY-826-treated mice. There was a trend toward prolonged survival upon single-agent treatment in two of four models (SMA-497 and SMA-540) and there was a significant survival benefit in one model (SMA-560). Co-treatment with BAY-826 and irradiation was ineffective in one model (SMA-497), but provided synergistic prolongation of survival in another (SMA-560). Decreased vessel densities and increased leukocyte infiltration were observed, but might be independent processes as the effect was also observed in single treatment modalities. These data demonstrate that TIE-2 inhibition may improve tumor response to treatment in highly vascularized tumors such as glioblastoma.

ILs-3, 6 and 11 increase, but ILs-10 and 24 decrease stemness of human prostate cancer cells in vitro

Cancer stem cells (CSCs) are associated with cancer recurrence and metastasis. Prostate cancer cells often metastasize to the bone with a complex microenvironment of cytokines favoring cell survival. In this study, the cell stemness influence of a group of interleukins including IL-3, 6, 10, 11 and 24 on human prostate cancer cell lines LNCaP and PC-3 was explored in vitro. Sulforhodamine B(SRB) and 5-ethynyl-2′-deoxyuridine (EdU) assays were applied to examine the effect on cell proliferation, and wound healing and transwell assays were used for migration and invasion studies, in addition to colony formation, Western blotting and flowcytometry for the expression of stemness factors and chemotherapy sensitivity. We observed that ILs-3, 6 and 11 stimulated while ILs-10 and 24 inhibited the growth, invasion and migration of both cell lines. Interestingly, ILs-3, 6 and 11 significantly promoted colony formation and increased the expression of SOX2, CD44 and ABCG2 in both prostate cancer cell lines. However, ILs-10 and 24 showed the opposite effect on the expression of these factors. In line with the above findings, treatment with either IL-3 or IL-6 or IL-11 decreased the chemosensitivity to docetaxel while treatment with either IL-10 or IL-24 increased the sensitivity of docetaxel chemotherapy. In conclusion, our results suggest that ILs-3, 6 and 11 function as tumor promoters while ILs-10 and 24 function as tumor suppressors in the prostate cancer cell lines PC-3 and LNCaP in vitro, and such differences may attribute to their different effect on the stemness of PCa cells.

Monocytopenia; Induction by Vinorelbine, Cisplatin and Doxorubicin in Breast, Non-Small Cell Lung and Cervix Cancer Patients

BACKGROUND

The neoplasm is still a potential threat for breast, Non-Small Cell Lung (NSCL) and cervix cancer patients. Those gradually invade into other body organs, inducing complex pathological complications. Whereas, the anticancer drugs suppress the bone marrow, resulting serious hematological toxicities. Thus, the monocytic toxicity may the chance of infections, particularly in AID's patients.

OBJECTIVE

We aimed this retrospective study to investigate the monocytopenia induced by vinorelbine following chemotherapy in cancer patients.

PATIENTS AND METHOD

A total 60 adult cancer patients were divided into two groups; Group-1 patients received the treatment of Vinorelbine alone while group 2 patients received Vinorelbine based combination chemotherapy.

RESULT

The overall comparison of mean monocyte count (×10³ per μl) with time showed a significant statistical difference (p value <0.001) for G-I and no significant difference for G-II (p value <0.08). The independent comparison of mean values for two groups at every week confirms the non-significant statistical difference during all of the five weeks (p values 0.551, 0.112, 0.559, 0.372, 0.468 respectively). In addition of that, the comparison of mean values observed before therapy with that of week 4 (after therapy) showed significant difference in G-I (p value <0.001) and non-significant in G-II (p value 0.053).

CONCLUSION

Monocytopenia is induced in both of the chemotherapy protocols allows the clinical oncologists and consultant physicians to select either of the chemotherapy protocol. The therapeutic efficacy should constitute the intervening consideration to treat the breast, cervix and NSCL (Non-Small Cell Lung's) cancers.

Chemokines CCL2, 3, 14 stimulate macrophage bone marrow homing, proliferation, and polarization in multiple myeloma

We previously showed that macrophages (MΦs) infiltrate the bone marrow (BM) of patients with myeloma and may play a role in drug resistance. This study analyzed chemokines expressed by myeloma BM that are responsible for recruiting monocytes to the tumor bed. We found that chemokines CCL3, CCL14, and CCL2 were highly expressed by myeloma and BM cells, and the levels of CCL14 and CCL3 in myeloma BM positively correlated with the percentage of BM-infiltrating MΦs. In vitro, these chemokines were responsible for chemoattracting human monocytes to tumor sites and in vivo for MΦ infiltration into myeloma-bearing BM in the 5TGM1 mouse model. Surprisingly, we also found that these chemokines stimulated MΦ in vitro proliferation induced by myeloma cells and in vivo in a human myeloma xenograft SCID mouse model. The chemokines also activated normal MΦ polarization and differentiation into myeloma-associated MΦs. Western blot analysis revealed that these chemokines promoted growth and survival signaling in MΦs via activating the PI3K/Akt and ERK MAPK pathways and c-myc expression. Thus, this study provides novel insight into the mechanism of MΦ infiltration of BM and also potential targets for improving the efficacy of chemotherapy in myeloma.

The impact of hypoxia on tumor-associated macrophages

The role of tumor-associated macrophages (TAMs) in cancer is often correlated with poor prognosis, even though this statement should be interpreted with care, as the effects of macrophages primarily depend on their localization within the tumor. This versatile cell type orchestrates a broad spectrum of biological functions and exerts very complex and even opposing functions on cell death, immune stimulation or suppression, and angiogenesis, resulting in an overall pro- or antitumoral effect. We are only beginning to understand the environmental cues that contribute to transient retention of macrophages in a specific phenotype. It has become clear that hypoxia shapes and induces specific macrophage phenotypes that serve tumor malignancy, as hypoxia promotes immune evasion, angiogenesis, tumor cell survival, and metastatic dissemination. Additionally, TAMs in the hypoxic niches within the tumor are known to mediate resistance to several anticancer treatments and to promote cancer relapse. Thus, a careful characterization and understanding of this macrophage differentiation state is needed in order to efficiently tailor cancer therapy.