Myeloid-derived suppressor cells and tumor escape from immune surveillance

Hypoxia as a critical player in extracellular vesicles-mediated intercellular communication between tumor cells and their surrounding microenvironment

In the past years, increasing attention has been paid to the role of extracellular vesicles (EVs) as mediators of intercellular communication in cancer. These small size particles mediate the intercellular transfer of important bioactive molecules involved in malignant initiation and progression. Hypoxia, or low partial pressure of oxygen, is recognized as a remarkable feature of solid tumors and has been demonstrated to exert a profound impact on tumor prognosis and therapeutic efficacy. Indeed, the high-pitched growth rate and chaotic neovascular architecture that embodies solid tumors results in a profound reduction in oxygen pressure within the tumor microenvironment (TME). In response to oxygen-deprived conditions, tumor cells and their surrounding milieu develop homeostatic adaptation mechanisms that contribute to the establishment of a pro-tumoral phenotype. Latest evidence suggests that the hypoxic microenvironment that surrounds the tumor bulk may be a clincher for the observed elevated levels of circulating EVs in cancer patients. Thus, it is proposed that EVs may play a role in mediating intercellular communication in response to hypoxic conditions. This review focuses on the EVs-mediated crosstalk that is established between tumor cells and their surrounding immune, endothelial, and stromal cell populations, within the hypoxic TME.

FXa-mediated PAR-2 promotes the efficacy of immunotherapy for hepatocellular carcinoma through immune escape and anoikis resistance by inducing PD-L1 transcription

BACKGROUND

The high metastasis rate is one of the main reasons for the poor prognosis of patients with hepatocellular carcinoma (HCC). Coagulation factor Xa (FXa) and its receptor proteinase-activated receptor-2 (PAR-2) proven to promote tumor metastasis in other forms of cancer. Here, we explore the role and mechanism of FXa in the regulation of resistance of anoikis and immune escape of HCC.

METHODS

In vitro and in vivo experiments were conducted to explore the role of FXa in HCC metastasis and its potential mechanism. The effects of FXa inhibitor rivaroxaban on HCC immunotherapy were evaluated using intrahepatic metastasis animal models and clinical trial (No. ChiCTR20000040540). We investigated the potential of FXa inhibition as a treatment for HCC.

RESULTS

FXa was highly expressed in HCC and promoted metastasis by activating PAR-2. Mechanistically, FXa-activated PAR-2 endows HCC cells with the ability of anoikis resistance to survive in the circulating blood by inhibiting the extrinsic apoptosis pathway. Furthermore, suspension stimulation-induced phosphorylation of STAT2, which promotes programmed death-ligand 1 (PD-L1) transcription and inhibits the antitumor effects of immune cells by inhibiting the infiltration of CD8+T cells in tumors and the levels of secreted cytokines. In vivo inhibition of FXa with rivaroxaban reduced HCC metastasis by decreasing PD-L1 expression and exhausting tumor-infiltrating lymphocytes. Notably, the combination of rivaroxaban and anti-programmed death-1 monoclonal antibody (anti-PD-1) programmed Death-1 monoclonal antibody (anti-PD-1) induced synergistic antitumor effects in animal models. Most importantly, rivaroxaban improved the objective response rate of patients with HCC to immune checkpoint inhibitors and prolonged overall survival time.

CONCLUSIONS

FXa-activated PAR-2 promotes anoikis resistance and immune escape in HCC, suggesting the potential for combining coagulation inhibitors and PD-1/PD-L1 immune checkpoint blockade to enhance the therapeutic efficacy of HCC.

Nerve-tumor crosstalk in tumor microenvironment: From tumor initiation and progression to clinical implications

The autonomic nerve system (ANS) innervates organs and tissues throughout the body and maintains functional balance among various systems. Further investigations have shown that excessive activation of ANS not only causes disruption of homeostasis, but also may promote tumor formation. In addition, the dynamic interaction between nerve and tumor cells in the tumor microenvironment also regulate tumor progression. On the one hand, nerves are passively invaded by tumor cells, that is, perineural invasion (PNI). On the other hand, compared with normal tissues, tumor tissues are subject to more abundant innervation, and nerves can influence tumor progression through regulating tumor proliferation, metastasis and drug resistance. A large number of studies have shown that nerve-tumor crosstalk, including PNI and innervation, is closely related to the prognosis of patients, and contributes to the formation of cancer pain, which significantly deteriorates the quality of life for patients. These findings suggest that nerve-tumor crosstalk represents a potential target for anti-tumor therapies and the management of cancer pain in the future. In this review, we systematically describe the mechanism by which nerve-tumor crosstalk regulates tumorigenesis and progression.

RNAi mediated silencing of STAT3/PD-L1 in tumor-associated immune cells induces robust anti-tumor effects in immunotherapy resistant tumors

Malignant tumors are often associated with an immunosuppressive tumor microenvironment (TME), rendering most of them resistant to standard-of-care immune checkpoint inhibitors (CPIs). Signal transducer and activator of transcription 3 (STAT3), a ubiquitously expressed transcription factor, has well-defined immunosuppressive functions in several leukocyte populations within the TME. Since the STAT3 protein has been challenging to target using conventional pharmaceutical modalities, we investigated the feasibility of applying systemically delivered RNA interference (RNAi) agents to silence its mRNA directly in tumor-associated immune cells. In preclinical rodent tumor models, chemically stabilized acylated small interfering RNAs (siRNAs) selectively silenced Stat3 mRNA in multiple relevant cell types, reduced STAT3 protein levels, and increased cytotoxic T cell infiltration. In a murine model of CPI-resistant pancreatic cancer, RNAi-mediated Stat3 silencing resulted in tumor growth inhibition, which was further enhanced in combination with CPIs. To further exemplify the utility of RNAi for cancer immunotherapy, this technology was used to silence Cd274, the gene encoding the immune checkpoint protein programmed death-ligand 1 (PD-L1). Interestingly, silencing of Cd274 was effective in tumor models that are resistant to PD-L1 antibody therapy. These data represent the first demonstration of systemic delivery of RNAi agents to the TME and suggest applying this technology for immuno-oncology applications.

Macrophages and tumor-associated macrophages in the senescent microenvironment: From immunosuppressive TME to targeted tumor therapy

In-depth studies of the tumor microenvironment (TME) have helped to elucidate its cancer-promoting mechanisms and inherent characteristics. Cellular senescence, which acts as a response to injury and can the release of senescence-associated secretory phenotypes (SASPs). These SASPs release various cytokines, chemokines, and growth factors, remodeling the TME. This continual development of a senescent environment could be associated with chronic inflammation and immunosuppressive TME. Additionally, SASPs could influence the phenotype and function of macrophages, leading to the recruitment of tumor-associated macrophages (TAMs). This contributes to tumor proliferation and metastasis in the senescent microenvironment, working in tandem with immune regulation, angiogenesis, and therapeutic resistance. This comprehensive review covers the evolving nature of the senescent microenvironment, macrophages, and TAMs in tumor development. We also explored the links between chronic inflammation, immunosuppressive TME, cellular senescence, and macrophages. Moreover, we compiled various tumor-specific treatment strategies centered on cellular senescence and the current challenges in cellular senescence research. This study aimed to clarify the mechanism of macrophages and the senescent microenvironment in tumor progression and advance the development of targeted tumor therapies.

Extracellular vesicle-derived non-coding RNAs in remodeling melanoma

Melanoma is one of the most lethal cutaneous malignancies. Despite great advances in radiotherapy, chemotherapy, and immunotherapy, the survival rate and prognosis of patients with melanoma remain poor. The abundant and sophisticated reciprocal communication network between melanoma cells and non-tumor cells contributes to the high heterogeneity of the melanoma microenvironment and is intimately related to varying treatment responses and clinical courses. Extracellular vesicles (EVs) are membrane structures generated by nearly all cell types. EVs contain biologically active molecules, mainly comprising proteins, lipids, and RNAs, and undoubtedly play multifaceted roles in numerous diseases, represented by melanoma. Non-coding RNAs (ncRNAs) mainly encompass long non-coding RNAs, microRNAs, and circular RNAs and constitute the majority of the human transcriptome. Multiple ncRNAs encapsulated in EVs coordinate various pathophysiological processes in melanoma. This review summarizes the mechanisms by which EV-ncRNAs modulate biological behaviors and immunity, and their potential diagnostic and therapeutic applications in melanoma. Undoubtedly, further insight into EV-ncRNAs and their functions in melanoma will contribute to the clinical treatment of melanoma and the implementation of precision medicine.

Photodynamic Therapy and Adaptive Immunity Induced by Reactive Oxygen Species: Recent Reports

Cancer is one of the most significant causes of death worldwide. Despite the rapid development of modern forms of therapy, results are still unsatisfactory. The prognosis is further worsened by the ability of cancer cells to metastasize. Thus, more effective forms of therapy, such as photodynamic therapy, are constantly being developed. The photodynamic therapeutic regimen involves administering a photosensitizer that selectively accumulates in tumor cells or is present in tumor vasculature prior to irradiation with light at a wavelength corresponding to the photosensitizer absorbance, leading to the generation of reactive oxygen species. Reactive oxygen species are responsible for the direct and indirect destruction of cancer cells. Photodynamically induced local inflammation has been shown to have the ability to activate an adaptive immune system response resulting in the destruction of tumor lesions and the creation of an immune memory. This paper focuses on presenting the latest scientific reports on the specific immune response activated by photodynamic therapy. We present newly discovered mechanisms for the induction of the adaptive response by analyzing its various stages, and the possible difficulties in generating it. We also present the results of research over the past 10 years that have focused on improving the immunological efficacy of photodynamic therapy for improved cancer therapy.

Prognostic marker CXCL5 in glioblastoma polyformis and its mechanism of immune invasion

Glioblastoma multiforme (GBM) is the most aggressive brain cancer with a poor prognosis. Therefore, the correlative molecular markers and molecular mechanisms should be explored to assess the occurrence and treatment of glioma.WB and qPCR assays were used to detect the expression of CXCL5 in human GBM tissues. The relationship between CXCL5 expression and clinicopathological features was evaluated using logistic regression analysis, Wilcoxon symbolic rank test, and Kruskal-Wallis test. Univariate, multivariate Cox regression and Kaplan-Meier methods were used to assess CXCL5 and other prognostic factors of GBM. Gene set enrichment analysis (GSEA) was used to identify pathways associated with CXCL5. The correlation between CXCL5 and tumor immunoinfiltration was investigated using single sample gene set enrichment analysis (ssGSEA) of TCGA data. Cell experiments and mouse subcutaneous transplanted tumor models were used to evaluate the role of CXCL5 in GBM. WB, qPCR, immunofluorescence, and immunohistochemical assays showed that CXCL5 expression was increased in human GBM tissues. Furthermore, high CXCL5 expression was closely related to poor disease-specific survival and overall survival of GBM patients. The ssGSEA suggested that CXCL5 is closely related to the cell cycle and immune response through PPAR signaling pathway. GSEA also showed that CXCL5 expression was positively correlated with macrophage cell infiltration level and negatively correlated with cytotoxic cell infiltration level. CXCL5 may be associated with the prognosis and immunoinfiltration of GBM.

Development of an immune-related gene prognostic risk model and identification of an immune infiltration signature in the tumor microenvironment of colon cancer

BACKGROUND

Colon cancer is a common and highly malignant tumor. Its incidence is increasing rapidly with poor prognosis. At present, immunotherapy is a rapidly developing treatment for colon cancer. The aim of this study was to construct a prognostic risk model based on immune genes for early diagnosis and accurate prognostic prediction of colon cancer.

METHODS

Transcriptome data and clinical data were downloaded from the cancer Genome Atlas database. Immunity genes were obtained from ImmPort database. The differentially expressed transcription factors (TFs) were obtained from Cistrome database. Differentially expressed (DE) immune genes were identified in 473 cases of colon cancer and 41 cases of normal adjacent tissues. An immune-related prognostic model of colon cancer was established and its clinical applicability was verified. Among 318 tumor-related transcription factors, differentially expressed transcription factors were finally obtained, and a regulatory network was constructed according to the up-down regulatory relationship.

RESULTS

A total of 477 DE immune genes (180 up-regulated and 297 down-regulated) were detected. We developed and validated twelve immune gene models for colon cancer, including SLC10A2, FABP4, FGF2, CCL28, IGKV1-6, IGLV6-57, ESM1, UCN, UTS2, VIP, IL1RL2, NGFR. The model was proved to be an independent prognostic variable with good prognostic ability. A total of 68 DE TFs (40 up-regulated and 23 down-regulated) were obtained. The regulation network between TF and immune genes was plotted by using TF as source node and immune genes as target node. In addition, Macrophage, Myeloid Dendritic cell and CD4+ T cell increased with the increase of risk score.

CONCLUSION

We developed and validated twelve immune gene models for colon cancer, including SLC10A2, FABP4, FGF2, CCL28, IGKV1-6, IGLV6-57, ESM1, UCN, UTS2, VIP, IL1RL2, NGFR. This model can be used as a tool variable to predict the prognosis of colon cancer.

NK cells and solid tumors: therapeutic potential and persisting obstacles

Natural killer (NK) cells, which are innate lymphocytes endowed with potent cytotoxic activity, have recently attracted attention as potential anticancer therapeutics. While NK cells mediate encouraging responses in patients with leukemia, the therapeutic effects of NK cell infusion in patients with solid tumors are limited. Preclinical and clinical data suggest that the efficacy of NK cell infusion against solid malignancies is hampered by several factors including inadequate tumor infiltration and persistence/activation in the tumor microenvironment (TME). A number of metabolic features of the TME including hypoxia as well as elevated levels of adenosine, reactive oxygen species, and prostaglandins negatively affect NK cell activity. Moreover, cancer-associated fibroblasts, tumor-associated macrophages, myeloid-derived suppressor cells, and regulatory T cells actively suppress NK cell-dependent anticancer immunity. Here, we review the metabolic and cellular barriers that inhibit NK cells in solid neoplasms as we discuss potential strategies to circumvent such obstacles towards superior therapeutic activity.

Arginase-2-specific cytotoxic T cells specifically recognize functional regulatory T cells

Background

High expression of the metabolic enzyme arginase-2 (ARG2) by cancer cells, regulatory immune cells, or cells of the tumor stroma can reduce the availability of arginine (L-Arg) in the tumor microenvironment (TME). Depletion of L-Arg has detrimental consequences for T cells and leads to T-cell dysfunction and suppression of anticancer immune responses. Previous work from our group has demonstrated the presence of proinflammatory ARG2-specific CD4 T cells that inhibited tumor growth in murine models on activation with ARG2-derived peptides. In this study, we investigated the natural occurrence of ARG2-specific CD8 T cells in both healthy donors (HDs) and patients with cancer, along with their immunomodulatory capabilities in the context of the TME.

Materials and methods

A library of 15 major histocompatibility complex (MHC) class I-restricted ARG2-derived peptides were screened in HD peripheral blood mononuclear cells using interferon gamma (IFN-γ) ELISPOT. ARG2-specific CD8 T-cell responses were identified using intracellular cytokine staining and ARG2-specific CD8 T-cell cultures were established by enrichment and rapid expansion following in vitro peptide stimulation. The reactivity of the cultures toward ARG2-expressing cells, including cancer cell lines and activated regulatory T cells (Tregs), was assessed using IFN-γ ELISPOT and a chromium release assay. The Treg signature was validated based on proliferation suppression assays, flow cytometry and quantitative reverse transcription PCR (RT-qPCR). In addition, vaccinations with ARG2-derived epitopes were performed in the murine Pan02 tumor model, and induction of ARG2-specific T-cell responses was evaluated with IFN-γ ELISPOT. RNAseq and subsequent GO-term and ImmuCC analysis was performed on the tumor tissue.

Results

We describe the existence of ARG2-specific CD8⁺ T cells and demonstrate these CD8⁺ T-cell responses in both HDs and patients with cancer. ARG2-specific T cells recognize and react to an ARG2-derived peptide presented in the context of HLA-B8 and exert their cytotoxic function against cancer cells with endogenous ARG2 expression. We demonstrate that ARG2-specific T cells can specifically recognize and react to activated Tregs with high ARG2 expression. Finally, we observe tumor growth suppression and antitumorigenic immunomodulation following ARG2 vaccination in an in vivo setting.

Conclusion

These findings highlight the ability of ARG2-specific T cells to modulate the immunosuppressive TME and suggest that ARG2-based immunomodulatory vaccines may be an interesting option for cancer immunotherapy.

Tumor microenvironment antigens

The identification and characterization of tumor antigens are central objectives in developing anti-cancer immunotherapy. Traditionally, tumor-associated antigens (TAAs) are considered relatively restricted to tumor cells (i.e., overexpressed proteins in tumor cells), whereas tumor-specific antigens (TSAs) are considered unique to tumor cells. Recent studies have focused on identifying patient-specific neoantigens, which might be highly immunogenic because they are not expressed in normal tissues. The opposite strategy has emerged with the discovery of anti-regulatory T cells (anti-Tregs) that recognize and attack many cell types in the tumor microenvironment, such as regulatory immune cells, in addition to tumor cells. The term proposed in this review is "tumor microenvironment antigens" (TMAs) to describe the antigens that draw this attack. As therapeutic targets, TMAs offer several advantages that differentiate them from more traditional tumor antigens. Targeting TMAs leads not only to a direct attack on tumor cells but also to modulation of the tumor microenvironment, rendering it immunocompetent and tumor-hostile. Of note, in contrast to TAAs and TSAs, TMAs also are expressed in non-transformed cells with consistent human leukocyte antigen (HLA) expression. Inflammation often induces HLA expression in malignant cells, so that targeting TMAs could additionally affect tumors with no or very low levels of surface HLA expression. This review defines the characteristics, differences, and advantages of TMAs compared with traditional tumor antigens and discusses the use of these antigens in immune modulatory vaccines as an attractive approach to immunotherapy. Different TMAs are expressed by different cells and could be combined in anti-cancer immunotherapies to attack tumor cells directly and modulate local immune cells to create a tumor-hostile microenvironment and inhibit tumor angiogenesis. Immune modulatory vaccines offer an approach for combinatorial therapy with additional immunotherapy including checkpoint blockade, cellular therapy, or traditional cancer vaccines. These combinations would increase the number of patients who can benefit from such therapeutic measures, which all have optimal efficiency in inflamed tumors.

Anti-Gr-1 Antibody Provides Short-Term Depletion of MDSC in Lymphodepleted Mice with Active-Specific Melanoma Therapy

Lymphodepletion, reconstitution and active-specific tumor cell vaccination (LRAST) enhances the induction of tumor-specific T cells in a murine melanoma model. Myeloid-derived suppressor cells (MDSC) may counteract the induction of tumor-reactive T cells and their therapeutic efficacy. Thus, the aim of the study was to evaluate a possible benefit of MDSC depletion using anti-Gr-1 antibodies (Ab) in combination with LRAST. Female C57BL/6 mice with 3 days established subcutaneous (s.c.) D5 melanoma were lymphodepleted with cyclophosphamide and reconstituted with naive splenocytes. Vaccination was performed with irradiated syngeneic mGM-CSF-secreting D5G6 melanoma cells. MDSC depletion was performed using anti-Gr-1 Ab (clone RB6-8C5). Induction of tumor-specific T cells derived from tumor vaccine draining lymph nodes (TVDLN) was evaluated by the amount of tumor-specific interferon (IFN)-γ release. LRAST combined with anti-Gr-1 mAb administration enhanced the induction of tumor-specific T cells in TVDLN capable of releasing IFN-γ in a tumor-specific manner. Additional anti-Gr-1 mAb administration in LRAST-treated mice delayed growth of D5 melanomas by two weeks. Furthermore, we elucidate the impact of anti-Gr-1-depleting antibodies on the memory T cell compartment. Our data indicate that standard of care treatment regimens against cancer can be improved by implementing agents, e.g., depleting antibodies, which target and eliminate MDSC.

Nanozyme-Based Enhanced Cancer Immunotherapy

Catalytic nanoparticles with natural enzyme-mimicking properties, known as nanozymes, have emerged as excellent candidate materials for cancer immunotherapy. Owing to their enzymatic activities, artificial nanozymes not only serve as responsive carriers to load drugs and therapeutic molecules for cancer treatment, but also act as enzymes for modulating the immunosuppression of the tumor microenvironment (TME) via the catalytic activities of catalase, peroxidase, superoxide dismutase, and oxidase. The immunosuppressive pro-tumor TME can be reversed to the immunoactive anti-tumor TME by utilizing both reactive oxygen species (ROS)-generating and ROS-scavenging nanozymes, which enhance the efficacy of cancer immunotherapy. In this review, we introduce representative ROS-generating and ROS-scavenging nanozymes and discuss how artificial nanozymes respond to the conditions of the TME. Based on the mutual interaction between nanozymes and TME, recent therapeutic pathways to provoke anti-cancer immune responses using nanozymes are discussed.

Analysis of the myeloid-derived suppressor cells and annexin A1 in multibacillary leprosy and reactional episodes

Background

Leprosy is a chronic infectious disease caused by Mycobacterium leprae. Patients have distinct clinical forms, and the host´s immunological response regulate those manifestations. In this work, the presence of the myeloid-derived suppressor cell and the regulatory protein annexin A1 is described in patients with multibacillary leprosy and with type 1 and 2 reactions.

Methods

Patients were submitted to skin biopsy for histopathological analysis to obtain a bacilloscopic index. Immunofluorescence was used to detect myeloid-derived suppressor cells and annexin A1.

Results

The data demonstrated that the presence of granulocytic and monocytic myeloid-derived suppressor cells in leprosy patients. A high number of monocytic myeloid-derived suppressor cells were observed in lepromatous leprosy and type 2 reactional patients. The presence of annexin A1 was observed in all myeloid-derived suppressor cells. In particular, the monocytic myeloid-derived suppressor cell in the lepromatous patients has higher levels of this protein when compared to the reactional patients. This data suggest that the higher expression of this protein may be related to regulatory response against a severe infection, contributing to anergic response. In type 1 reactional patients, the expression of annexin A1 was reduced.

Conclusions

Myeloid-derived suppressor cell are present in leprosy patients and annexin A1 might be regulated the host response against Mycobacterium leprae.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12879-021-06744-x.

Current status of research on exosomes in general, and for the diagnosis and treatment of kidney cancer in particular

Kidney cancer is a common urological tumour. Owing to its high prevalence and mortality rate, it is the third most malignant tumour of the urinary system, followed by prostate and bladder cancers. It exerts a high degree of malignancy, and most of the distant metastasis occurs at an early stage; it is insensitive to chemoradiotherapy and easily develops drug resistance. The current treatment for kidney cancer mainly includes surgery, interventional embolization and targeted therapy; however, the treatment efficacy is poor. In recent years, the role of exosomes as mediators of intercellular communication and information exchange in the tumour microenvironment in tumour pathogenesis has attracted much attention. Exosomes are rich in bioactive substances such as nucleic acids, proteins and lipids and are involved in angiogenesis, immune regulation, drug resistance, formation of pre-metastatic niche, invasion and metastasis. This article reviews the ongoing research and applications of exosomes for the diagnosis and treatment of kidney cancer.

Arginase 1-Based Immune Modulatory Vaccines Induce Anticancer Immunity and Synergize with Anti-PD-1 Checkpoint Blockade

Expression of the L-arginine catabolizing enzyme arginase 1 (ARG1) is a central immunosuppressive mechanism mediated by tumor-educated myeloid cells. Increased activity of ARG1 promotes the formation of an immunosuppressive microenvironment and leads to a more aggressive phenotype in many cancers. Intrinsic T-cell immunity against ARG1-derived epitopes in the peripheral blood of cancer patients and healthy subjects has previously been demonstrated. To evaluate the antitumor efficacy of ARG1-derived peptide vaccines as a monotherapy and as a combinational therapy with checkpoint blockade, different in vivo syngeneic mouse tumor models were utilized. To evaluate the antitumor effects, flow cytometry analysis and IHC were performed on tumors, and ELISPOT assays were performed to characterize immune responses. We show that ARG1-targeting therapeutic vaccines were able to activate endogenous antitumor immunity in several in vivo syngeneic mouse tumor models and to modulate the cell composition of the tumor microenvironment without causing any associated side effects or systemic toxicity. ARG1-targeting vaccines in combination with anti-PD-1 also resulted in increased T-cell infiltration, decreased ARG1 expression, reduced suppressive function of tumor-educated myeloid cells, and a shift in the M1/M2 ratio of tumor-infiltrating macrophages. These results indicated that the induced shift toward a more proinflammatory microenvironment by ARG1-targeting immunotherapy favors effective tumor control when combined with anti-PD-1 checkpoint blockade. Our data illustrate the ability of ARG1-based immune modulatory vaccination to elicit antigen-specific immunosurveillance and imply the feasibility of this novel immunotherapeutic approach for clinical translation.

Extracellular Vesicles Secreted by Tumor Cells Promote the Generation of Suppressive Monocytes

Monocytes are among the first cells to infiltrate the tumor microenvironment. The conversion of monocytes to suppressor cells in the tumor microenvironment is crucial in evasion of the immune response and tumor maintenance. Tumor cells may secrete products that promote the conversion of monocytes to suppressor cells. Cells secrete extracellular vesicles (EVs) containing cargos of genetic materials and proteins as a way to communicate with neighboring cells. During pathologic conditions like cancers, tumor cells increase their EVs production containing microRNA, RNA, and proteins that may affect the immune cell response, contributing to the immunosuppressive microenvironment. Our studies show that EVs secreted by a wide range of murine tumor cells, including osteosarcoma, glioma, colon carcinoma, sarcoma, and melanoma, can be taken up by bone marrow-derived monocytes. The monocytes that took up the EVs secreted by tumor cells matured toward an immune-suppressive phenotype by upregulating the expression of suppressive cytokines and effector molecules. The monocytes also downregulated MHC class II and costimulatory molecules while increasing the expression of PD-L1 on their surface after taking up EVs from tumor cells. Most importantly, monocytes exposed to EVs secreted by tumor cells suppressed activated Ag-specific CD4+ T cells. These results show that tumor cells from several different tumor types secrete EVs which promote the conversion of monocytes into suppressor cells, thus promoting immune evasion. These studies suggest that EVs secreted by tumors are potentially a new target for future cancer therapy.

Modulating Repolarization of Tumor-Associated Macrophages with Targeted Therapeutic Nanoparticles as a Potential Strategy for Cancer Therapy

There are always some components in the tumor microenvironment (TME), such as tumor-associated macrophages (TAMs), that help tumor cells escape the body's immune surveillance. Therefore, this situation can lead to tumor growth, progression, and metastasis, resulting in low response rates for cancer therapy. Macrophages play an important role with strong plasticity and functional diversity. Facing different microenvironmental stimulations, macrophages undergo a dynamic change in phenotype and function into two major macrophage subpopulations, namely classical activation/inflammation (M1) and alternative activation/regeneration (M2) type. Through various signaling pathways, macrophages polarize into complex groups, which can perform different immune functions. In this review, we emphasize the use of nanopreparations for macrophage related immunotherapy based on the pathological knowledge of TAMs phenotype. These macrophages targeted nanoparticles re-edit and re-educate macrophages by attenuating M2 macrophages and reducing aggregation to the TME, thereby relieving or alleviating immunosuppression. Among them, we describe in detail the cellular mechanisms and regulators of several major signaling pathways involved in the plasticity and polarization functions of macrophages. The advantages and challenges of those nanotherapeutics for these pathways have been elucidated, providing the basis and insights for the diagnosis and treatment strategies of various diseases centered on macrophages.

Understanding Immune Thrombocytopenia: Looking Out of the Box

The pathogenesis of immune thrombocytopenia (ITP) is increasingly being elucidated, and its etiology is becoming more frequently identified, leading to a diagnostic shift from primary to secondary ITP. The overlap between autoimmunity, immunodeficiency, and cancer is evident, implying more interdisciplinarity in daily care. This mini-review is based on an expert meeting on ITP organized by the Intercontinental Cooperative ITP Study Group and presents the challenges of hematologists in understanding and investigating "out of the box" concepts associated with ITP.

Immune Responses against Disseminated Tumor Cells

Most cancer-related deaths are a consequence of metastases, a series of linear events, notably the invasion-metastasis cascade. The current understanding of cancer immune surveillance derives from studies in primary tumors, but disseminated cancer cells acquire mutations and, in some cases, appear to progress independently after spreading from primary sites. An early step in this process is micrometastatic dissemination. As such, the equilibrium between the immune system and disseminated cancer cells controls the fate of the cancer. Immune checkpoint inhibitors (ICIs) exhibit significant clinical activity in patients, but the efficacy of ICIs depends on both the tumor and its microenvironment. Data often suggest that disseminated cancer cells are not adequately targeted by the immune system. In this review, we summarize the main basic findings of immune responses against disseminated tumor cells and their organ-specific characteristics. Such studies may provide new directions for cancer immune therapy.

Feed-forward regulation between cellular senescence and immunosuppression promotes the aging process and age-related diseases

Aging is a progressive degenerative process involving a chronic low-grade inflammation and the accumulation of senescent cells. One major issue is to reveal the mechanisms which promote the deposition of pro-inflammatory senescent cells within tissues. The accumulation involves mechanisms which increase cellular senescence as well as those inhibiting the clearance of senescent cells from tissues. It is known that a persistent inflammatory state evokes a compensatory immunosuppression which inhibits pro-inflammatory processes by impairing the functions of effector immune cells, e.g., macrophages, T cells and natural killer (NK) cells. Unfortunately, these cells are indispensable for immune surveillance and the subsequent clearance of senescent cells, i.e., the inflammation-induced counteracting immunosuppression prevents the cleansing of host tissues. Moreover, senescent cells can also repress their own clearance by expressing inhibitors of immune surveillance and releasing the ligands of NKG2D receptors which impair their surveillance by NK and cytotoxic CD8⁺ T cells. It seems that cellular senescence and immunosuppression establish a feed-forward process which promotes the aging process and age-related diseases. I will examine in detail the immunosuppressive mechanisms which impair the surveillance and clearance of pro-inflammatory senescent cells with aging. In addition, I will discuss several therapeutic strategies to halt the degenerative feed-forward circuit associated with the aging process and age-related diseases.

Current Advance of Immune Evasion Mechanisms and Emerging Immunotherapies in Renal Cell Carcinoma

Renal cell carcinoma is a highly heterogeneous cancer group, and the complex microenvironment of the tumor provides appropriate immune evasion opportunities. The molecular mechanism of immune escape in renal cell carcinoma is currently a hot issue, focusing primarily on the major complex of histocompatibility, immunosuppressive cells, their secreted immunosuppressive cytokines, and apoptosis molecule signal transduction. Immunotherapy is the best treatment option for patients with metastatic or advanced renal cell carcinoma and combination immunotherapy based on a variety of principles has shown promising prospects. Comprehensive and in-depth knowledge of the molecular mechanism of immune escape in renal cell carcinoma is of vital importance for the clinical implementation of effective therapies. The goal of this review is to address research into the mechanisms of immune escape in renal cell carcinoma and the use of the latest immunotherapy. In addition, we are all looking forward to the latest frontiers of experimental combination immunotherapy.

Myeloid-Derived Suppressor Cells: Facilitators of Cancer and Obesity-Induced Cancer

Immature myeloid cells at varied stages of differentiation, known as myeloid-derived suppressor cells (MDSC), are present in virtually all cancer patients. MDSC are profoundly immune-suppressive cells that impair adaptive and innate antitumor immunity and promote tumor progression through nonimmune mechanisms. Their widespread presence combined with their multitude of protumor activities makes MDSC a major obstacle to cancer immunotherapies. MDSC are derived from progenitor cells in the bone marrow and traffic through the blood to infiltrate solid tumors. Their accumulation and suppressive potency are driven by multiple tumor- and host-secreted proinflammatory factors and adrenergic signals that act via diverse but sometimes overlapping transcriptional pathways. MDSC also accumulate in response to the chronic inflammation and lipid deposition characteristic of obesity and contribute to the more rapid progression of cancers in obese individuals. This article summarizes the key aspects of tumor-induced MDSC with a focus on recent progress in the MDSC field.

Chinese Medicine Formula PSORI-CM02 Alleviates Psoriatic Dermatitis via M-MDSCs and Th17 Crosstalk

Psoriasis is a chronic inflammatory skin disease that is associated with multiple coexisting conditions. Extensive literature suggests that psoriasis is a T-cell-mediated condition, and its pathogenesis is related to dysfunction of the immune system. Myeloid-derived suppressor cells (MDSCs) are a group of heterogeneous myeloid cells that have suppressive effects on T cells. MDSCs are present at very low levels in healthy individuals but can substantially expand in tumours or inflammatory conditions. PSORI-CM02, a Chinese medical formula designed based on the Chinese medicine theory (Blood Stasis), has been prescribed extensively for psoriasis therapy and shows a stable clinical effect and safety. This study discusses the mechanisms of MDSCs involved in disease development and therapeutic progress. Our data provides evidence that monocytic myeloid-derived suppressor cells (M-MDSCs) play a role in IMQ-induced psoriatic dermatitis. Functional characterization and correlation analysis indicated that MDSCs are positively correlated with Th17 cells. PSORI-CM02 alleviated IMQ-induced psoriatic dermatitis and suppressed the proliferation of Th17 cells via M-MDSC-induced Arg1 upregulation, suggesting M-MDSCs could be a novel therapeutic target for psoriasis, and PSORI-CM02 exerted its effects via the perturbation of M-MDSCs and Th17 cell crosstalk.

Potential therapeutic effect of low-dose paclitaxel in melanoma patients resistant to immune checkpoint blockade: A pilot study

The low dose application of chemotherapeutic agents such as paclitaxel was previously shown to initiate anti-tumor activity by neutralizing myeloid-derived suppressor cells (MDSCs) in melanoma mouse models. Here, we investigated immunomodulating effects of low-dose paclitaxel in 9 metastatic melanoma patients resistant to prior treatments. Three patients showed response to therapy (two partial responses and one stable disease). In responding patients, paclitaxel decreased the frequency and immunosuppressive pattern of MDSCs in the peripheral blood and skin metastases. Furthermore, paclitaxel modulated levels of inflammatory mediators in the serum. In addition, responders displayed enhanced frequencies of tumor-infiltrating CD8⁺ T cells and their activity indicated by the upregulation of CD25 and TCR ζ-chain expression. Our study suggests that low-dose paclitaxel treatment could improve clinical outcome of some advanced melanoma patients by enhancing anti-tumor immunity and might be proposed for combined melanoma immunotherapy.

Circulating Monocytic Myeloid-Derived Suppressor Cells Are Elevated and Associated with Poor Prognosis in Acute Myeloid Leukemia

Background

Monocytic myeloid-derived suppressor cells (M-MDSCs) characterized with the phenotype of CD14⁺HLA-DR^low/- have attracted a lot of attention in the field of human tumor immunology. However, little is known about the roles of M-MDSCs in acute myeloid leukemia (AML) as opposed to their multiple roles in solid tumors.

Methods

We examined the frequencies of M-MDSCs identified for CD14⁺HLA-DR^low/- by flow cytometry in the peripheral circulating blood of 109 newly diagnosed adult patients with AML and 30 healthy controls (HC). Then, we, respectively, validated the clinic significance of circulating M-MDSCs on the relevance of spectral features for diagnostic stratification, induction therapy response, treatment effect maintenance, and long-term survival in AML.

Results

Circulating M-MDSC frequencies of AML were significantly higher than those of HC both in CD14⁺ monocytes (46.22% ± 2.95% vs. 1.07% ± 0.17%, p < 0.01) and peripheral blood mononuclear cells (PBMCs) (4.21% ± 0.80% vs. 0.17% ± 0.03%, p < 0.01). Elevated circulating M-MDSCs in patients with AML were significantly associated with low complete remission (CR) rate, high relapse/refractory rate, and poor long-term survival, but had no correlation with common clinic risks and cytogenetic molecular risk categories.

Conclusions

It was demonstrated that circulating M-MDSCs are elevated and associated with poor prognosis in AML, suggesting M-MDSCs might be a prognostic indicator for AML.

The role of tumor-associated macrophages (TAMs) in tumor progression and relevant advance in targeted therapy

Macrophages have a leading position in the tumor microenvironment (TME) which paves the way to carcinogenesis. Initially, monocytes and macrophages are recruited to the sites where the tumor develops. Under the guidance of different microenvironmental signals, macrophages would polarize into two functional phenotypes, named as classically activated macrophages (M1) and alternatively activated macrophages (M2). Contrary to the anti-tumor effect of M1, M2 exerts anti-inflammatory and tumorigenic characters. In progressive tumor, M2 tumor-associated macrophages (TAMs) are in the majority, being vital regulators reacting upon TME. This review elaborates on the role of TAMs in tumor progression. Furthermore, prospective macrophage-focused therapeutic strategies, including drugs not only in clinical trials but also at primary research stages, are summarized followed by a discussion about their clinical application values. Nanoparticulate systems with efficient drug delivery and improved antitumor effect are also summed up in this article.

Prognostic values of GPNMB identified by mining TCGA database and STAD microenvironment

The survival rate of stomach adenocarcinoma patients with immune and stromal scores and different clinicopathological features obtained from the TCGA datasets was systematically compared. A list of genes that are correlated with stomach adenocarcinoma microenvironment were extracted using the TCGA database to predict the prognosis and survival. In addition, the differentially expressed genes were extracted by comparing the immune and stromal scores of the groups. The protein-protein interaction network, and functional and pathway enrichment analyses of differentially expressed genes were performed. A total of 8 hub genes were selected from the differentially expressed genes to predict the overall survival and disease-free survival rates. GPNMB was selected from the hub genes based on the survival and prognosis analyses. A nomogram was built by including the potential risk factors based on multivariate Cox analysis. Cell function experiments and xenograft tumors were conducted in vivo to further verify the role of GPNMB in tumor progression. The predicted microRNA, miR-30b-3p, might act as upstream negative regulator and binding to 3’ UTR of GPNMB, confirming by fluorescent enzyme reporter gene experiment. In summary, immune-related scores are crucial factors in the malignant progression of stomach adenocarcinoma and GPNMB acts as a potentially useful prognostic factor for stratification and in developing the treatment strategy

Role of tumor-associated immune cells in prostate cancer: angel or devil?

Prostate cancer is the most common malignancy in the reproductive system of older males. Androgen deprivation therapy (ADT) is an important treatment for prostate cancer patients. However, almost all prostate cancer patients unavoidably progress to the castration-resistant stage after ADT treatment. Recent studies have shown that tumor-associated immune cells play major roles in the initiation, progression, and metastasis of prostate cancer. Various phenotypes of tumor-associated immune cells have tumor-promoting or antitumor functions mediated by interacting with tumor cells. Here, we review the current knowledge of tumor-associated immune cells in prostate cancer.

Research progress of PD-1/PD-L1 immunotherapy in gastrointestinal tumors

Gastrointestinal tumor (GIT) is a common malignant tumor of the digestive system, which seriously threatens people's health and life. With the deepening of the study on the mechanism of tumor immune escape, programmed death receptor ligand 1 (PD-L1) has been proved to interact with the tumor microenvironment to mediate tumor immune escape. PD-L1 inhibitor is a hot spot in tumor immunotherapy in recent years, which can restore the activity of T cells, enhance the body's ability of immune response, and ultimately enable the immune system to effectively identify and kill gastric cancer cells, then achieve long-term tumor remission in patients with GITs. At present, variety of PD-L1 inhibitors such as pembrolizumab, nivolumab and avelumab have been approved for the market, and they have achieved good results in clinical studies on the GIT. This paper reviews the progress of PD-1/PD-L1 immunotherapy in GITs which include gastric cancer, colon cancer and rectal cancer.

Evaluation of Exosomal miRNA in Blood as a Potential Diagnostic Biomarker for Human Non-Small Cell Lung Cancer

Background

Tumor-derived exosomes have been used as diagnostic biomarkers to discriminate between tumor patients and healthy people. This study explored the roles of exosomal miRNAs in lung adenocarcinoma metastasis by microarray and developed a novel method for diagnosis of lung adenocarcinoma.

Material/Methods

Four lung adenocarcinoma patients’ peripheral blood, including 2 metastasis and 2 N-metastasis, were used for exosomes miRNA microarray analysis. Exosomes were extracted by ultracentrifugation and identified by transmission electron microscopy. All the raw data were normalized by R software with limma packet. qRT-PCR was used to validate the microarray results. A549 cells were used to identify the functions of miR-4448. Western blot, qRT-PCR, RNAi, CCK8, and transwell invasion assay were used to verify the metastasis and proliferation abilities.

Results

miR-4436a and miR-4687-5p were upregulated between the metastasis and N-metastasis group, while miR-22-3p, miR-3666, miR-4448, miR-4449, miR-6751-5p and miR-92a-3p were downregulated. miR-4448 was also downregulated between the metastasis and control group, whereas there was no significant difference between the N-metastasis group and control group. qRT-PCR confirmed the downregulation of miR-4448 in exosomes from lung adenocarcinoma patients compared with N-metastasis patients and healthy people. CCK8 and transwell invasion assay showed that A549 cells transfected with miR-4448 inhibitor had higher proliferation and metastasis ability. qRT-PCR and Western blot confirmed the high expression of MMP2 and MMP9 in A549 cells transfected with miR-4448 inhibitor.

Conclusions

miR-4448 can inhibit A549 cell proliferation and metastasis. miR-4448 in exosomes has the potential to serve as a diagnostic marker of patients with adenocarcinoma metastasis.

Transimmunization restores immune surveillance and prevents recurrence in a syngeneic mouse model of ovarian cancer

Ovarian cancer accounts for most deaths from gynecologic malignancies. Although more than 80% of patients respond to first-line standard of care, most of these responders present with recurrence and eventually succumb to carcinomatosis and chemotherapy-resistant disease. To improve patient survival, new modalities must, therefore, target or prevent recurrent disease. Here we describe for the first time a novel syngeneic mouse model of recurrent high-grade serous ovarian cancer (HGSOC), which allows immunotherapeutic interventions in a time course relevant to human carcinomatosis and disease course. Using this model, we demonstrate the efficacy of Transimmunization (TI), a dendritic cell (DC) vaccination strategy that uses autologous and physiologically derived DC loaded with autologous whole tumor antigens. TI has been proven successful in the treatment of human cutaneous T cell lymphoma and we report for the first time its in vivo efficacy against an intra-peritoneal solid tumor. Given as a single therapy, TI is able to elicit an effective anti-tumor immune response and inhibit immune-suppressive crosstalks with sufficient power to curtail tumor progression and establishment of carcinomatosis and recurrent disease. Specifically, TI is able to inhibit the expansion of tumor-associated macrophages as well as myeloid-derived suppressive cells consequently restoring T cell immune-surveillance. These results demonstrate the possible value of TI in the management of ovarian cancer and other intra-peritoneal tumors.

Increased Expression of Myeloid-Derived Suppressor Cells in Patients with HBV-Related Hepatocellular Carcinoma

METHODS

The percentages of MDSCs, IFN-γ-producing CD4 and CD8 T cells in the peripheral blood of HCC patients, chronic hepatitis B (CHB) patients, and healthy controls (HC) were determined by flow cytometry. The serum concentrations of IL-10 and TNF-α were determined by ELISA. The association of the percentages of MDSCs with tumor burden, liver function parameters, systemic inflammation-related indexes, and IFN-γ-producing T cells was assessed.

RESULTS

The percentages of MDSCs and PMN-MDSCs were significantly higher in HCC patients than those in CHB patients and HC. The level of MDSCs was correlated with indirect bilirubin and prealbumin, as well as systemic inflammation response index, monocyte/lymphocyte ratio, and monocyte counts. The frequency of IFN-γ-producing CD8 T cells of HCC patients was lower than that of HC. However, there was no relationship between MDSCs and IFN-γ-producing CD8 T cells. The level of IL-10 in HCC patients was significantly higher than that in CHB patients.

CONCLUSION

MDSCs seem to play an important role in the process leading from chronic HBV infection to HCC. Early inhibiting these cells could affect tumor progression.

Metabolic changes and interaction of tumor cell, myeloid-derived suppressor cell and T cell in hypoxic microenvironment

It is universally acknowledged that a large number of immune cells, as well as inflammatory factors, regulatory factors and metabolites, accumulate in the tumor microenvironment to jointly promote tumor escape, development and metastasis. Hypoxia is one of the characteristics in tumor microenvironment and is a common phenomenon in all solid tumors. In tumor hypoxia response, there is a key regulator called HIF-1a, which is a key transcriptional regulatory protein that regulates many critical genes. In this paper, the effects of hypoxia on glucose metabolism of tumor cells, myeloid-derived suppressor cells and T cells in tumor microenvironment were reviewed, and the interaction among the three was also described.

Tumor-targeted IL-12 combined with tumor resection yields a survival-favorable immune profile

BACKGROUND

Although accumulated evidence provides a strong scientific premise for using immune profiles to predict survival in patients with cancer, a universal immune profile across tumor types is still lacking, and how to achieve a survival-associated immune profile remains to be evaluated.

METHODS

We analyzed datasets from The Cancer Genome Atlas to identify an immune profile associated with prolonged overall survival in multiple tumor types and tested the efficacy of tumor cell-surface vimentin-targeted interleukin 12 (ttIL-12) in inducing that immune profile and prolonging survival in both mouse and patient-derived xenograft tumor models.

RESULTS

We identified an immune profile (IFNγHiCD8HiFOXP3LowCD33Low) associated with prolonged overall survival across several human tumor types. ttIL-12 in combination with surgical resection of the primary tumor transformed tumors to this immune profile. Intriguingly, this immune profile transformation led to inhibition of metastasis and to prolonged survival in both mouse and patient-derived xenograft malignant models. Wild-type IL-12 combined with surgery was significantly less effective. In the IL-12-sensitive C3H mouse strain, in fact, wild-type IL-12 and surgery resulted in shorter overall survival than in mice treated with control pDNA; this surprising result is believed to be attributable to IL-12 toxicity, which was absent in the mice treated with ttIL-12. The ttIL-12-induced immune profile associated with longer overall survival was also associated with a greater accumulation of CD8+ T cells and reduced infiltration of regulatory T cells, myeloid-derived suppressor cells, and tumor-associated macrophages. The underlying mechanism for this transformation by ttIL-12 treatment was induction of expression of CXCL9 and reduction of expression of CXCL2 and CCL22 in tumors.

CONCLUSIONS

ttIL-12 when combined with surgery led to conversion to the IFNγHiCD8HiFOXP3LowCD33Low immune profile, eliminated relapse and metastasis, and prolonged overall survival.

Increased CD14+HLA-DR-/low Myeloid-Derived Suppressor Cells Correlate With Disease Severity in Systemic Lupus Erythematosus Patients in an iNOS-Dependent Manner

Myeloid-derived suppressor cells (MDSCs) comprise of a population of cells, which suppress the innate and adaptive immune system via different mechanisms. MDSCs are accumulated under pathological conditions. The present study aimed to clarify the pathological role of MDSCs in systemic lupus erythematosus (SLE) patients. Consequently, the level of circulating M-MDSCs was significantly increased in newly diagnosed SLE patients as compared to healthy controls. An elevated level of M-MDSCs was positively correlated with the disease severity in SLE patients and an immunosuppressive role was exerted in an iNOS-dependent manner. The decrease in the number of M-MDSCs after therapy rendered them as an indicator for the efficacy of treatment. These results demonstrated that M-MDSCs participated in the pathological progress in SLE patients. Thus, MDSCs are attractive biomarkers and therapeutic targets for SLE patients.

AMPK activation inhibits the functions of myeloid-derived suppressor cells (MDSC): impact on cancer and aging

AMP-activated protein kinase (AMPK) has a crucial role not only in the regulation of tissue energy metabolism but it can also control immune responses through its cooperation with immune signaling pathways, thus affecting immunometabolism and the functions of immune cells. It is known that AMPK signaling inhibits the activity of the NF-κB system and thus suppresses pro-inflammatory responses. Interestingly, AMPK activation can inhibit several major immune signaling pathways, e.g., the JAK-STAT, NF-κB, C/EBPβ, CHOP, and HIF-1α pathways, which induce the expansion and activation of myeloid-derived suppressor cells (MDSC). MDSCs induce an immunosuppressive microenvironment in tumors and thus allow the escape of tumor cells from immune surveillance. Chronic inflammation has a key role in the expansion and activation of MDSCs in both tumors and inflammatory disorders. The numbers of MDSCs also significantly increase during the aging process concurrently with the immunosenescence associated with chronic low-grade inflammation. Increased fatty acid oxidation and lactate produced by aerobic glycolysis are important immunometabolic enhancers of MDSC functions. However, it seems that AMPK signaling regulates the functions of MDSCs in a context-dependent manner. Currently, the activators of AMPK signaling are promising drug candidates for cancer therapy and possibly for the extension of healthspan and lifespan. We will describe in detail the AMPK-mediated regulation of the signaling pathways controlling the expansion and activation of immunosuppressive MDSCs. We will propose that the beneficial effects mediated by AMPK activation, e.g., in cancers and the aging process, could be induced by the inhibition of MDSC functions.

Natural killer cells involved in tumour immune escape of hepatocellular carcinomar

Natural killer cells are the first line of host immune surveillance and play major roles in the defence against infection and tumours. Hepatic NK cells exhibit unique phenotypic and functional characteristics compared to circulating and spleen NK cells, such as higher levels of cytolytic activity and cytotoxicity mediators against tumour cells. However, the activities of NK cells may be reversed during tumour progression. Recent studies demonstrated that hepatic NK cells were exhausted in hepatocellular carcinoma (HCC) and exhibited impaired cytolytic activity and decreased production of effector cytokines. The present review discusses current knowledge on the role of exhausted NK cells in promoting HCC development and the mechanisms contributing to tumour immune escape, including an imbalance of activating and inhibitory receptors on NK cells, abnormal receptor-ligand interaction, and cross-talk with immune cells and other stromal cells in the tumour environment. We provide a fundamental basis for further study of innate immunity in tumour progression and serve the purpose of exploring new HCC treatment strategies.

Myeloid Derived Suppressor Cells Interactions With Natural Killer Cells and Pro-angiogenic Activities: Roles in Tumor Progression

Myeloid-derived suppressor cells (MDSCs) contribute to the induction of an immune suppressive/anergic, tumor permissive environment. MDSCs act as immunosuppression orchestrators also by interacting with several components of both innate and adaptive immunity. Natural killer (NK) cells are innate lymphoid cells functioning as primary effector of immunity, against tumors and virus-infected cells. Apart from the previously described anergy and hypo-functionality of NK cells in different tumors, NK cells in cancer patients show pro-angiogenic phenotype and functions, similar to decidual NK cells. We termed the pro-angiogenic NK cells in the tumor microenvironment "tumor infiltrating NK" (TINKs), and peripheral blood NK cells in cancer patients "tumor associated NK" (TANKs). The contribution of MDSCs in regulating NK cell functions in tumor-bearing host, still represent a poorly explored topic, and even less is known on NK cell regulation of MDSCs. Here, we review whether the crosstalk between MDSCs and NK cells can impact on tumor onset, angiogenesis and progression, focusing on key cellular and molecular interactions. We also propose that the similarity of the properties of tumor associated/tumor infiltrating NK and MDSC with those of decidual NK and decidual MDSCs during pregnancy could hint to a possible onco-fetal origin of these pro-angiogenic leukocytes.

Interactions among myeloid regulatory cells in cancer

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

Low-Dose Total Body Irradiation Can Enhance Systemic Immune Related Response Induced by Hypo-Fractionated Radiation

A systemic immune related response (SIME) of radiotherapy has been occasionally observed on metastatic tumors, but the clinical outcomes remain poor. Novel treatment approaches are therefore needed to improve SIME ratio. We used a combination of hypo-fractionated radiation therapy (H-RT) with low-dose total body irradiation (L-TBI) in a syngeneic mouse model of breast and colon carcinoma. The combination therapy of H-RT and L-TBI potentially enhanced SIME by infiltration of CD8⁺ T cell and altering the immunosuppressive microenvironment in non-irradiated subcutaneous tumor lesions. The frequency of IFN-γ, as a tumor-specific CD8⁺ T cells producing, significantly inhibited the secondary tumor growth of breast and colon. Our findings suggest that L-TBI could serve as a potential therapeutic agent for metastatic breast and colon cancer and, together with H-RT, their therapeutic potential is enhanced significantly.

An update on extracellular vesicles in multiple myeloma: a focus on their role in cell-to-cell cross-talk and as potential liquid biopsy biomarkers

INTRODUCTION

Multiple myeloma (MM) is characterized by a clonal proliferation of neoplastic plasma cells (PCs) in bone marrow (BM) and the interplay between MM PCs and the BM microenvironment, which plays a relevant role in its pathogenesis. In this important cross-talk, extracellular vesicles (EVs) are active. EVs, including small and medium/large EVs, are lipid bi-layer particles released in circulation by normal and neoplastic cells. A selected cargo of lipids, proteins, and nucleic acids is loaded into EVs, and delivered locally and to distant sites, thus influencing the physiology of recipient cells. In the 'liquid biopsy' context, EVs can be isolated from human biofluids proving to be powerful markers in cancer. Areas covered: Here, we summarize the recent advances on EVs in MM field. Expert commentary: EVs from MM PCs: i) enhance malignant cell proliferation and aggressiveness through an autocrine loop; ii) are able to transfer drug resistance in sensitive-drug cells; iii) stimulate angiogenesis; iv) increase the activity of osteoclasts; v) have immunosuppressive effects. In addition, EVs from MM stromal cells also promote MM cell proliferation and drug resistance. Finally, we underline the importance of EVs as MM potential biomarkers in 'cancer liquid biopsy' and as a potential new therapeutic target.

The role of endothelial colony forming cells in kidney cancer's pathogenesis, and in resistance to anti-VEGFR agents and mTOR inhibitors: A speculative review

Renal cell carcinoma (RCC) is highly dependent on angiogenesis, due to the overactivation of the VHL/HIF/VEGF/VEGFRs axis; this justifies the marked sensitivity of this neoplasm to antiangiogenic agents which, however, ultimately fail to control tumor growth. RCC also frequently shows alterations in the mTOR signaling pathway, and mTOR inhibitors have shown a similar pattern of initial activity/late failure as pure antiangiogenic agents. Understanding mechanisms of resistance to these agents would be key to improve the outcome of our patients. Circulating endothelial cells are a family of mainly bone marrow-derived progenitors, which have been postulated to be responsible of the reactivation of angiogenesis in different tumors. In this review, we shall discuss the complex nature and function of these cells, the evidence pro and contra their contribution to tumor vascularization, especially as far as RCC is concerned, and their possible role in determining resistance to presently available treatments.

Cigarette Smoke-Induced Emphysema Exhausts Early Cytotoxic CD8+ T Cell Responses against Nascent Lung Cancer Cells

Chronic obstructive pulmonary disease is a chronic inflammatory disorder with an increased incidence of lung cancer. The emphysema component of chronic obstructive pulmonary disease confers the greatest proportion to lung cancer risk. Although tumors create inflammatory conditions to escape immunity, the immunological responses that control growth of nascent cancer cells in pre-established inflammatory microenvironments are unknown. In this study, we addressed this issue by implanting OVA-expressing cancer cells in the lungs of mice with cigarette smoke-induced emphysema. Emphysema augmented the growth of cancer cells, an effect that was dependent on T cytotoxic cells. OVA-specific OTI T cells showed early signs of exhaustion upon transfer in emphysema tumor hosts that was largely irreversible because sorting, expansion, and adoptive transfer failed to restore their antitumor activity. Increased numbers of PD-L1- and IDO-positive CD11c⁺ myeloid dendritic cells (DCs) infiltrated emphysema tumors, whereas sorted emphysema tumor DCs poorly stimulated OTI T cells. Upon adoptive transfer in immunocompetent hosts, T cells primed by emphysema tumor DCs were unable to halt tumor growth. DCs exposed to the emphysema tumor microenvironment downregulated MHC class II and costimulatory molecules, whereas they upregulated PD-L1/IDO via oxidative stress-dependent mechanisms. T cell activation increased upon PD-L1 blockade in emphysema DC-T cell cocultures and in emphysema tumor hosts in vivo. Analysis of the transcriptome of primary human lung tumors showed a strong association between computed tomography-based emphysema scoring and downregulation of immunogenic processes. Thus, suppression of adaptive immunity against lung cancer cells links a chronic inflammatory disorder, emphysema, to cancer, with clinical implications for emphysema patients to be considered optimal candidates for cancer immunotherapies.

Spontaneous T-cell responses against Arginase-1 in the chronic myeloproliferative neoplasms relative to disease stage and type of driver mutation

Compelling evidence supports the existence of a profound immune dysregulation in patients with chronic myeloproliferative neoplasms (MPN). Increased Arginase-1 expression has been described in MPN patients and in solid cancers. This increase contributes to an immunosuppressive tumor microenvironment in MPN patients because of L-arginine depletion by Arginase-1-expressing regulatory cells and cancer cells, which subsequently limits the activation of circulating effector cells. In the present study, we demonstrate that Arginase-1-derived peptides are recognized by T cells among peripheral mononuclear blood cells from MPN patients. We characterized the Arginase-1-specific T cells as being CD4⁺ and found that the magnitude of response to the Arginase-1 peptides depends on disease stage. Activation of Arginase-1-specific T cells by vaccination could be an attractive novel immunotherapeutic approach to targeting malignant and suppressive cells in MPN patients in combination with other immunotherapeutics.