Tumor-induced STAT3 activation in monocytic myeloid-derived suppressor cells enhances stemness and mesenchymal properties in human pancreatic cancer. Cancer Immunol Immunother. 2014;63:513-528. [PMID: 24652403 PMCID: PMC3994288 DOI: 10.1007/s00262-014-1527-x]

Glucocorticoid Receptor-Targeted Nanoliposome for STAT3 Inhibition-Led Myeloid-Derived Suppressor Cell Modulation and Efficient Colon Cancer Treatment

STAT3 is an important protein responsible for cellular proliferation, motility, and immune tolerance and is hyperactive in colorectal cancer, instigating metastasis, cellular proliferation, migration, as well as inhibition. It helps in proliferation of myeloid-derived suppressor cells (MDSCs), which within the tumor microenvironment (TME) suppress T cells to encourage tumor growth, metastasis, and resistance to immunotherapy, besides playing dynamic role in regulating macrophages within the tumor. Thus, MDSC is a potential target to augment immune surveillance within the TME. Herein, we report targeting both colorectal cancer and MDSCs using a glucocorticoid receptor (GR)-targeted nanoliposomal formulation carrying GR-ligand, dexamethasone (Dex), and a STAT3 inhibitor, niclosamide (N). Our main objective was to selectively inhibit STAT3, the key immunomodulatory factor in most TME-associated cells including MDSCs, and also repurpose the use of this antihelminthic, low-cost drug N for cancer treatment. The resultant formulation D1XN exhibited better tumor regression and survivability compared to GR nontargeted formulation. Further, bone marrow cell-derived MDSCs were engineered by D1XN treatment ex vivo and were inoculated back to tumor-bearing mice. Significant tumor growth inhibition with enhanced antiproliferative immune cell signatures, such as T cell infiltration, decrease in Treg cells, and increased M1/M2 macrophage ratio within the TME were observed. This reveals the effectiveness of engineered MDSCs to modulate tumor surveillance besides reversing the aggressiveness of the tumor. Therefore, D1XN and D1XN-mediated engineered MDSCs alone or in combination can be considered as potent selective chemo-immunotherapeutic nanoliposomal agent(s) against colorectal cancer.

Myeloid-Derived Suppressor Cells: Implications in Cancer Immunology and Immunotherapy

Myeloid-derived suppressor cells (MDSCs) are believed to be key promoters of tumor development and are recognized as a hallmark of cancer cells' ability to evade the immune system evasion. MDSC levels often increase in peripheral blood and the tumor microenvironment (TME). These cells exert immunosuppressive functions, weakening the anticancer immune surveillance system, in part by repressing T-cell immunity. Moreover, MDSCs may promote tumor progression and interact with cancer cells, increasing MDSC expansion and favoring an immunotolerant TME. This review analyzes the primary roles of MDSCs in cancer and T-cell immunity, discusses the urgent need to develop effective MDSC-targeted therapies, and highlights the potential synergistic combination of MDSC targeting with chimeric antigen receptors and immune checkpoint inhibitors.

The characteristics of the tumor immune microenvironment in colorectal cancer with different MSI status and current therapeutic strategies

Colorectal cancer (CRC) remains a significant cause of cancer-related mortality worldwide. Despite advancements in surgery, chemotherapy, and radiotherapy, the effectiveness of these conventional treatments is limited, particularly in advanced cases. Therefore, transition to novel treatment is urgently needed. Immunotherapy, especially immune checkpoint inhibitors (ICIs), has shown promise in improving outcomes for CRC patients. Notably, patients with deficient mismatch repair (dMMR) or microsatellite instability-high (MSI-H) tumors often benefit from ICIs, while the majority of CRC cases, which exhibit proficient mismatch repair (pMMR) or microsatellite-stable (MSS) status, generally show resistance to this approach. It is assumed that the MSI phenotype cause some changes in the tumor microenvironment (TME), thus triggering antitumor immunity and leading to response to immunotherapy. Understanding these differences in the TME relative to MSI status is essential for developing more effective therapeutic strategies. This review provides an overview of the TME components in CRC and explores current approaches aimed at enhancing ICI efficacy in MSS CRC.

Toll-Like receptor 3-mediated interferon-β production is suppressed by oncostatin m and a broader epithelial-mesenchymal transition program

BACKGROUND

Patients with Triple Negative Breast Cancer (TNBC) currently lack targeted therapies, and consequently face higher mortality rates when compared to patients with other breast cancer subtypes. The tumor microenvironment (TME) cytokine Oncostatin M (OSM) reprograms TNBC cells to a more stem-like/mesenchymal state, conferring aggressive cancer cell properties such as enhanced migration and invasion, increased tumor-initiating capacity, and intrinsic resistance to the current standards of care. In contrast to OSM, Interferon-β (IFN-β) promotes a more differentiated, epithelial cell phenotype in addition to its role as an activator of anti-tumor immunity. Importantly, OSM suppresses the production of IFN-β, although the mechanism of IFN-β suppression has not yet been elucidated.

METHODS

IFN-β production and downstream autocrine signaling were assessed via quantitative real-time PCR (qRT-PCR) and Western blotting in TNBC cells following exposure to OSM. RNA-sequencing (RNA-seq) was used to assess an IFN-β metagene signature, and to assess the expression of innate immune sensors, which are upstream activators of IFN-β. Cell migration was assessed using an in vitro chemotaxis assay. Additionally, TNBC cells were exposed to TGF-β1, Snail, and Zeb1, and IFN-β production and downstream autocrine signaling were assessed via RNA-seq, qRT-PCR, and Western blotting.

RESULTS

Here, we identify the repression of Toll-like Receptor 3 (TLR3), an innate immune sensor, as the key molecular event linking OSM signaling and the repression of IFN-β transcription, production, and autocrine IFN signaling. Moreover, we demonstrate that additional epithelial-mesenchymal transition-inducing factors, such as TGF-β1, Snail, and Zeb1, similarly suppress TLR3-mediated IFN-β production and signaling.

CONCLUSIONS

Our findings provide a novel insight into the regulation of TLR3 and IFN-β production in TNBC cells, which are known indicators of treatment responses to DNA-damaging therapies. Furthermore, strategies to stimulate TLR3 in order to increase IFN-β within the TME may be ineffective in stem-like/mesenchymal cells, as TLR3 is strongly repressed. Rather, we propose that therapies targeting OSM or OSM receptor would reverse the stem-like/mesenchymal program and restore TLR3-mediated IFN-β production within the TME, facilitating improved responses to current therapies.

Cancer stem cells: advances in knowledge and implications for cancer therapy

Cancer stem cells (CSCs), a small subset of cells in tumors that are characterized by self-renewal and continuous proliferation, lead to tumorigenesis, metastasis, and maintain tumor heterogeneity. Cancer continues to be a significant global disease burden. In the past, surgery, radiotherapy, and chemotherapy were the main cancer treatments. The technology of cancer treatments continues to develop and advance, and the emergence of targeted therapy, and immunotherapy provides more options for patients to a certain extent. However, the limitations of efficacy and treatment resistance are still inevitable. Our review begins with a brief introduction of the historical discoveries, original hypotheses, and pathways that regulate CSCs, such as WNT/β-Catenin, hedgehog, Notch, NF-κB, JAK/STAT, TGF-β, PI3K/AKT, PPAR pathway, and their crosstalk. We focus on the role of CSCs in various therapeutic outcomes and resistance, including how the treatments affect the content of CSCs and the alteration of related molecules, CSCs-mediated therapeutic resistance, and the clinical value of targeting CSCs in patients with refractory, progressed or advanced tumors. In summary, CSCs affect therapeutic efficacy, and the treatment method of targeting CSCs is still difficult to determine. Clarifying regulatory mechanisms and targeting biomarkers of CSCs is currently the mainstream idea.

Modulatory effects of cancer stem cell-derived extracellular vesicles on the tumor immune microenvironment

Cancer stem cells (CSCs), accounting for only a minor cell proportion (< 1%) within tumors, have profound implications in tumor initiation, metastasis, recurrence, and treatment resistance due to their inherent ability of self-renewal, multi-lineage differentiation, and tumor-initiating potential. In recent years, accumulating studies indicate that CSCs and tumor immune microenvironment act reciprocally in driving tumor progression and diminishing the efficacy of cancer therapies. Extracellular vesicles (EVs), pivotal mediators of intercellular communications, build indispensable biological connections between CSCs and immune cells. By transferring bioactive molecules, including proteins, nucleic acids, and lipids, EVs can exert mutual influence on both CSCs and immune cells. This interaction plays a significant role in reshaping the tumor immune microenvironment, creating conditions favorable for the sustenance and propagation of CSCs. Deciphering the intricate interplay between CSCs and immune cells would provide valuable insights into the mechanisms of CSCs being more susceptible to immune escape. This review will highlight the EV-mediated communications between CSCs and each immune cell lineage in the tumor microenvironment and explore potential therapeutic opportunities.

Myeloid-derived suppressor cells in cancer and cancer therapy

Anticancer agents continue to dominate the list of newly approved drugs, approximately half of which are immunotherapies. This trend illustrates the considerable promise of cancer treatments that modulate the immune system. However, the immune system is complex and dynamic, and can have both tumour-suppressive and tumour-promoting effects. Understanding the full range of immune modulation in cancer is crucial to identifying more effective treatment strategies. Myeloid-derived suppressor cells (MDSCs) are a heterogeneous population of myeloid cells that develop in association with chronic inflammation, which is a hallmark of cancer. Indeed, MDSCs accumulate in the tumour microenvironment, where they strongly inhibit anticancer functions of T cells and natural killer cells and exert a variety of other tumour-promoting effects. Emerging evidence indicates that MDSCs also contribute to resistance to cancer treatments, particularly immunotherapies. Conversely, treatment approaches designed to eliminate cancer cells can have important additional effects on MDSC function, which can be either positive or negative. In this Review, we discuss the interplay between MDSCs and various other cell types found in tumours as well as the mechanisms by which MDSCs promote tumour progression. We also discuss the relevance and implications of MDSCs for cancer therapy.

Reciprocal relationship between cancer stem cells and myeloid-derived suppressor cells: implications for tumor progression and therapeutic strategies

Recently, there has been an increased focus on cancer stem cells (CSCs) due to their resilience, making them difficult to eradicate. This resilience often leads to tumor recurrence and metastasis. CSCs adeptly manipulate their surroundings to create an environment conducive to their survival. In this environment, myeloid-derived suppressor cells (MDSCs) play a crucial role in promoting epithelial-mesenchymal transition and bolstering CSCs' stemness. In response, CSCs attract MDSCs, enhancing their infiltration, expansion and immunosuppressive capabilities. This interaction between CSCs and MDSCs increases the difficulty of antitumor therapy. In this paper, we discuss the interplay between CSCs and MDSCs based on current research and highlight recent therapeutic strategies targeting either CSCs or MDSCs that show promise in achieving effective antitumor outcomes.

Forces at play: exploring factors affecting the cancer metastasis

Metastatic disease, a leading and lethal indication of deaths associated with tumors, results from the dissemination of metastatic tumor cells from the site of primary origin to a distant organ. Dispersion of metastatic cells during the development of tumors at distant organs leads to failure to comply with conventional treatments, ultimately instigating abrupt tissue homeostasis and organ failure. Increasing evidence indicates that the tumor microenvironment (TME) is a crucial factor in cancer progression and the process of metastatic tumor development at secondary sites. TME comprises several factors contributing to the initiation and progression of the metastatic cascade. Among these, various cell types in TME, such as mesenchymal stem cells (MSCs), lymphatic endothelial cells (LECs), cancer-associated fibroblasts (CAFs), myeloid-derived suppressor cells (MDSCs), T cells, and tumor-associated macrophages (TAMs), are significant players participating in cancer metastasis. Besides, various other factors, such as extracellular matrix (ECM), gut microbiota, circadian rhythm, and hypoxia, also shape the TME and impact the metastatic cascade. A thorough understanding of the functions of TME components in tumor progression and metastasis is necessary to discover new therapeutic strategies targeting the metastatic tumor cells and TME. Therefore, we reviewed these pivotal TME components and highlighted the background knowledge on how these cell types and disrupted components of TME influence the metastatic cascade and establish the premetastatic niche. This review will help researchers identify these altered components' molecular patterns and design an optimized, targeted therapy to treat solid tumors and restrict metastatic cascade.

Tumor-educated Gr1+CD11b+ cells drive breast cancer metastasis via OSM/IL-6/JAK-induced cancer cell plasticity

Cancer cell plasticity contributes to therapy resistance and metastasis, which represent the main causes of cancer-related death, including in breast cancer. The tumor microenvironment drives cancer cell plasticity and metastasis, and unraveling the underlying cues may provide novel strategies for managing metastatic disease. Using breast cancer experimental models and transcriptomic analyses, we show that stem cell antigen-1 positive (SCA1+) murine breast cancer cells enriched during tumor progression and metastasis had higher in vitro cancer stem cell-like properties, enhanced in vivo metastatic ability, and generated tumors rich in Gr1hiLy6G+CD11b+ cells. In turn, tumor-educated Gr1+CD11b+ (Tu-Gr1+CD11b+) cells rapidly and transiently converted low metastatic SCA1- cells into highly metastatic SCA1+ cells via secreted oncostatin M (OSM) and IL-6. JAK inhibition prevented OSM/IL-6-induced SCA1+ population enrichment, while OSM/IL-6 depletion suppressed Tu-Gr1+CD11b+-induced SCA1+ population enrichment in vitro and metastasis in vivo. Moreover, chemotherapy-selected highly metastatic 4T1 cells maintained high SCA1+ positivity through autocrine IL-6 production, and in vitro JAK inhibition blunted SCA1 positivity and metastatic capacity. Importantly, Tu-Gr1+CD11b+ cells invoked a gene signature in tumor cells predicting shorter overall survival (OS), relapse-free survival (RFS), and lung metastasis in breast cancer patients. Collectively, our data identified OSM/IL-6/JAK as a clinically relevant paracrine/autocrine axis instigating breast cancer cell plasticity and triggering metastasis.

Tumor Microenvironment: A Niche for Cancer Stem Cell Immunotherapy

Tumorigenic Cancer Stem Cells (CSCs), often called tumor-initiating cells (TICs), represent a unique subset of cells within the tumor milieu. They stand apart from the bulk of tumor cells due to their exceptional self-renewal, metastatic, and differentiation capabilities. Despite significant progress in classifying CSCs, these cells remain notably resilient to conventional radiotherapy and chemotherapy, contributing to cancer recurrence. In this review, our objective is to explore novel avenues of research that delve into the distinctive characteristics of CSCs within their surrounding tumor microenvironment (TME). We will start with an overview of the defining features of CSCs and then delve into their intricate interactions with cells from the lymphoid lineage, namely T cells, B cells, and natural killer (NK) cells. Furthermore, we will discuss their dynamic interplay with myeloid lineage cells, including macrophages, neutrophils, and myeloid-derived suppressor cells (MDSCs). Moreover, we will illuminate the crosstalk between CSCs and cells of mesenchymal origin, specifically fibroblasts, adipocytes, and endothelial cells. Subsequently, we will underscore the pivotal role of CSCs within the context of the tumor-associated extracellular matrix (ECM). Finally, we will highlight pre-clinical and clinical studies that target CSCs within the intricate landscape of the TME, including CAR-T therapy, oncolytic viruses, and CSC-vaccines, with the ultimate goal of uncovering novel avenues for CSC-based cancer immunotherapy.

Improving cancer immunotherapy by preventing cancer stem cell and immune cell linking in the tumor microenvironment

Cancer stem cells are the key link between malignant tumor progression and drug resistance. This cell population has special properties that are different from those of conventional tumor cells, and the role of cancer stem cell-related exosomes in progression of tumor malignancy is becoming increasingly clear. Cancer stem cell-derived exosomes carry a variety of functional molecules involved in regulation of the microenvironment, especially with regard to immune cells, but how these exosomes exert their functions and the specific mechanisms need to be further clarified. Here, we summarize the role of cancer stem cell exosomes in regulating immune cells in detail, aiming to provide new insights for subsequent targeted drug development and clinical strategy formulation.

Obesity associated pancreatic ductal adenocarcinoma: Therapeutic challenges

Obesity is a prominent health issue worldwide and directly impacts pancreatic health, with obese individuals exhibiting a significant risk for increasing pancreatic ductal adenocarcinoma (PDAC). Several factors potentially explain the increased risk for the development of PDAC, including obesity-induced chronic inflammation within and outside of the pancreas, development of insulin resistance and metabolic dysfunction, promotion of immune suppression within the pancreas during inflammation, pre- and malignant stages, variations in hormones levels (adiponectin, ghrelin, and leptin) produced from the adipose tissue, and acquisition of somatic mutations in tumor once- and suppressor proteins critical for pancreatic tumorigenesis. In this manuscript, we will explore the broad impact of these obesity-induced risk factors on the development and progression of PDAC, focusing on changes within the tumor microenvironment (TME) as they pertain to prevention, current therapeutic strategies, and future directions for targeting obesity management as they relate to the prevention of pancreatic tumorigenesis.

Immunobiology of cancer stem cells and their immunoevasion mechanisms

Cancer stem cells (CSCs) defined as a small fraction of cells within malignancies have been isolated from tumors with different histological origins with stem related characteristics such as self-replicating potential, tumorigenesis, and therapy resistance. The dynamic communication between CSCs and tumor microenvironment particularly immune cells orchestrates their fate and plasticity as well as the patient outcome. According to recent evidence, it has been reported that they harness different immunological pathways to escape immunosurveillance and express aberrantly immunomodulatory agents or decreased levels of factors forming antigen presenting machinery (APM), subsequently followed by impaired antigen presentation and suppressed immune detection. As effective therapies are expected to be able to eradicate CSCs, mechanistic understanding of such interactions can provide insights into causes of therapy failure particularly in immunotherapy. Also, it can contribute to enhance the practical interventions against CSCs and their immunomodulatory features resulting in CSCs eradication and improving patient clinical outcome. The aim of this review is to explain the present knowledge regarding the immunobiology of CSCs and the immunoevasion mechanisms they use.

Rough neighborhood: Intricacies of cancer stem cells and infiltrating immune cell interaction in tumor microenvironment and potential in therapeutic targeting

Ongoing research on cellular heterogeneity of Cancer stem cells (CSCs) and its synergistic involvement with tumor milieu reveals enormous complexity, resulting in diverse hindrance in immune therapy. CSCs has captured attention for their contribution in shaping of tumor microenvironment and as target for therapeutic intervention. Recent studies have highlighted cell-extrinsic and intrinsic mechanisms of reciprocal interaction between tumor stroma constituents and CSCs. Therapeutic targeting requires an in-depth understanding of the underlying mechanisms involved with the rate limiting factors in tumor aggressiveness and pinpoint role of CSCs. Some of the major constituents of tumor microenvironment includes resident and infiltrating immune cell, both innate and adaptive. Some of these immune cells play crucial role as adjustors of tumor immune response. Tumor-adjustor immune cell interaction confer plasticity and features enabling tumor growth and metastasis in one hand and on the other hand blunts anti-tumor immunity. Detail understanding of CSC and TME resident immune cells interaction can shape new avenues for cancer immune therapy. In this review, we have tried to summarize the development of knowledge on cellular, molecular and functional interaction between CSCs and tumor microenvironment immune cells, highlighting immune-mediated therapeutic strategies aimed at CSCs. We also discussed developing a potential CSC and TME targeted therapeutic avenue.

Regulation of T cells by myeloid-derived suppressor cells: emerging immunosuppressor in lung cancer

Myeloid-derived suppressor cells (MDSCs), major components maintaining the immune suppressive microenvironment in lung cancer, are relevant to the invasion, metastasis, and poor prognosis of lung cancer, through the regulation of epithelial-mesenchymal transition, remodeling of the immune microenvironment, and regulation of angiogenesis. MDSCs regulate T-cell immune functions by maintaining a strong immunosuppressive microenvironment and promoting tumor invasion. This raises the question of whether reversing the immunosuppressive effect of MDSCs on T cells can improve lung cancer treatment. To understand this further, this review explores the interactions and specific mechanisms of different MDSCs subsets, including regulatory T cells, T helper cells, CD8 + T cells, natural killer T cells, and exhausted T cells, as part of the lung cancer immune microenvironment. Second, it focuses on the guiding significance confirmed via clinical liquid biopsy and tissue biopsy that different MDSC subsets improve the prognosis of lung cancer. Finally, we conclude that targeting MDSCs through action targets or signaling pathways can help regulate T-cell immune functions and suppress T-cell exhaustion. In addition, immune checkpoint inhibitors targeting MDSCs may serve as a new approach for enhancing the efficiency of immunotherapy and targeted therapy for lung cancer in the future, providing better comprehensive options for lung cancer treatment.

Role of the tumor microenvironment in the lymphatic metastasis of cervical cancer (Review)

Lymphatic metastasis is the primary type of cervical cancer metastasis and is associated with an extremely poor prognosis in patients. The tumor microenvironment primarily includes cancer-associated fibroblasts, tumor-associated macrophages, myeloid-derived suppressor cells, immune and inflammatory cells, and blood and lymphatic vascular networks, which can promote the establishment of lymphatic metastatic sites within immunosuppressive microenvironments or promote lymphatic metastasis by stimulating lymphangiogenesis and epithelial-mesenchymal transformation. As the most important feature of the tumor microenvironment, hypoxia plays an essential role in lymph node metastasis. In this review, the known mechanisms of hypoxia, and the involvement of stromal components and immune inflammatory cells in the tumor microenvironment of lymphatic metastasis of cervical cancer are discussed. Additionally, a summary of the clinical trials targeting the tumor microenvironment for the treatment of cervical cancer is provided, emphasizing the potential and challenges of immunotherapy.

Induction of cancer neoantigens facilitates development of clinically relevant models for the study of pancreatic cancer immunobiology

Neoantigen burden and CD8 T cell infiltrate are associated with clinical outcome in pancreatic ductal adenocarcinoma (PDAC). A shortcoming of many genetic models of PDAC is the lack of neoantigen burden and limited T cell infiltrate. The goal of the present study was to develop clinically relevant models of PDAC by inducing cancer neoantigens in KP2, a cell line derived from the KPC model of PDAC. KP2 was treated with oxaliplatin and olaparib (OXPARPi), and a resistant cell line was subsequently cloned to generate multiple genetically distinct cell lines (KP2-OXPARPi clones). Clones A and E are sensitive to immune checkpoint inhibition (ICI), exhibit relatively high T cell infiltration, and have significant upregulation of genes involved in antigen presentation, T cell differentiation, and chemokine signaling pathways. Clone B is resistant to ICI and is similar to the parental KP2 cell line in terms of relatively low T cell infiltration and no upregulation of genes involved in the pathways noted above. Tumor/normal exome sequencing and in silico neoantigen prediction confirms successful generation of cancer neoantigens in the KP2-OXPARPi clones and the relative lack of cancer neoantigens in the parental KP2 cell line. Neoantigen vaccine experiments demonstrate that a subset of candidate neoantigens are immunogenic and neoantigen synthetic long peptide vaccines can restrain Clone E tumor growth. Compared to existing models, the KP2-OXPARPi clones better capture the diverse immunobiology of human PDAC and may serve as models for future investigations in cancer immunotherapies and strategies targeting cancer neoantigens in PDAC.

TNF+ regulatory T cells regulate the stemness of gastric cancer cells through the IL13/STAT3 pathway

Regulatory T cells (Tregs) are an important component of the tumor microenvironment; however, the interaction between Tregs and gastric cancer cells is not completely understood. Recent studies have shown that Tregs participate in cancer cell stemness maintenance. In this study, we performed single-cell RNA sequencing of gastric cancer and adjacent tissues and found that Tregs with high TNF expression were recruited to gastric cancer tissues and were significantly correlated with patient survival. TNF+ Tregs significantly contribute to tumor growth and progression. Our studies have further demonstrated that TNF+ Tregs promote the stemness of gastric cancer cells through the IL13/STAT3 pathway. Therefore, blocking the interaction between TNF+ Tregs and gastric cancer cells may be a new approach in the treatment of gastric cancer.

G-CSF rescue of FOLFIRINOX-induced neutropenia leads to systemic immune suppression in mice and humans

BACKGROUND

Recombinant granulocyte colony-stimulating factor (G-CSF) is routinely administered for prophylaxis or treatment of chemotherapy-induced neutropenia. Chronic myelopoiesis and granulopoiesis in patients with cancer has been shown to induce immature monocytes and neutrophils that contribute to both systemic and local immunosuppression in the tumor microenvironment. The effect of recombinant G-CSF (pegfilgrastim or filgrastim) on the production of myeloid-derived suppressive cells is unknown. Here we examined patients with pancreatic cancer, a disease known to induce myeloid-derived suppressor cells (MDSCs), and for which pegfilgrastim is routinely administered concurrently with FOLFIRINOX but not with gemcitabine-based chemotherapy regimens.

METHODS

Serial blood was collected from patients with pancreatic ductal adenocarcinoma newly starting on FOLFIRINOX or gemcitabine/n(ab)paclitaxel combination chemotherapy regimens. Neutrophil and monocyte frequencies were determined by flow cytometry from whole blood and peripheral blood mononuclear cell fractions. Serum cytokines were evaluated pretreatment and on-treatment. Patient serum was used in vitro to differentiate healthy donor monocytes to MDSCs as measured by downregulation of major histocompatibility complex II (HLA-DR) and the ability to suppress T-cell proliferation in vitro. C57BL/6 female mice with pancreatic tumors were treated with FOLFIRINOX with or without recombinant G-CSF to directly assess the role of G-CSF on induction of immunosuppressive neutrophils.

RESULTS

Patients receiving FOLFIRINOX with pegfilgrastim had increased serum G-CSF that correlated with an induction of granulocytic MDSCs. This increase was not observed in patients receiving gemcitabine/n(ab)paclitaxel without pegfilgrastim. Interleukin-18 also significantly increased in serum on FOLFIRINOX treatment. Patient serum could induce MDSCs as determined by in vitro functional assays, and this suppressive effect increased with on-treatment serum. Induction of MDSCs in vitro could be recapitulated by addition of recombinant G-CSF to healthy serum, indicating that G-CSF is sufficient for MDSC differentiation. In mice, neutrophils isolated from spleen of G-CSF-treated mice were significantly more capable of suppressing T-cell proliferation.

CONCLUSIONS

Pegfilgrastim use contributes to immune suppression in both humans and mice with pancreatic cancer. These results suggest that use of recombinant G-CSF as supportive care, while critically important for mitigating neutropenia, may complicate efforts to induce antitumor immunity.

Pancreatic cancer stemness: dynamic status in malignant progression

Pancreatic cancer (PC) is one of the most aggressive malignancies worldwide. Increasing evidence suggests that the capacity for self-renewal, proliferation, and differentiation of pancreatic cancer stem cells (PCSCs) contribute to major challenges with current PC therapies, causing metastasis and therapeutic resistance, leading to recurrence and death in patients. The concept that PCSCs are characterized by their high plasticity and self-renewal capacities is central to this review. We focused specifically on the regulation of PCSCs, such as stemness-related signaling pathways, stimuli in tumor cells and the tumor microenvironment (TME), as well as the development of innovative stemness-targeted therapies. Understanding the biological behavior of PCSCs with plasticity and the molecular mechanisms regulating PC stemness will help to identify new treatment strategies to treat this horrible disease.

SLC14A1 is a new biomarker in renal cancer

BACKGROUND

Renal cancer is one of the common malignant tumors of the urinary tract, prone to distant metastasis and drug resistance, with a poor clinical prognosis. SLC14A1 belongs to the solute transporter family, which plays a role in urinary concentration and urea nitrogen recycling in the renal, and is closely associated with the development of a variety of tumors.

METHODS

Transcription data for renal clear cell carcinoma (KIRC) were obtained from the public databases Gene Expression Omnibus database (GEO) and The Cancer Genome Atlas (TCGA), and we investigated the differences in SLC14A1 expression in cancerous and normal tissues of renal cancer, its correlation with the clinicopathological features of renal cancer patients. Then, we verified the expression levels of SLC14A1 in renal cancer tissues and their Paracancerous tissues using RT-PCR, Western-blotting and immunohistochemistry. Finally, we used renal endothelial cell line HEK-293 and renal cancer cell lines 786-O and ACHN to explore the effects of SLC14A1 on the biological behaviors of renal cancer cell proliferation, invasion and metastasis using EDU, MTT proliferation assay, Transwell invasion assay and scratch healing assay.

RESULTS

SLC14A1 was lowly expressed in renal cancer tissues and this was further validated by RT-PCR, Western blotting, and immunohistochemistry in our clinical samples. Analysis of KIRC single-cell data suggested that SLC14A1 was mainly expressed in endothelial cells. Survival analysis showed that low levels of SLC14A1 expression were associated with a better clinical prognosis. In biological behavioral studies, we found that upregulation of SLC14A1 expression levels inhibited the proliferation, invasion, and metastatic ability of renal cancer cells.

CONCLUSION

SLC14A1 plays an important role in the progression of renal cancer and has the potential to become a new biomarker for renal cancer.

Cancer Stem Cell Relationship with Pro-Tumoral Inflammatory Microenvironment

Inflammatory processes and cancer stem cells (CSCs) are increasingly recognized as factors in the development of tumors. Emerging evidence indicates that CSCs are associated with cancer properties such as metastasis, treatment resistance, and disease recurrence. However, the precise interaction between CSCs and the immune microenvironment remains unexplored. Although evasion of the immune system by CSCs has been extensively studied, new research demonstrates that CSCs can also control and even profit from the immune response. This review provides an overview of the reciprocal interplay between CSCs and tumor-infiltrating immune cells, collecting pertinent data about how CSCs stimulate leukocyte reprogramming, resulting in pro-tumor immune cells that promote metastasis, chemoresistance, tumorigenicity, and even a rise in the number of CSCs. Tumor-associated macrophages, neutrophils, Th17 and regulatory T cells, mesenchymal stem cells, and cancer-associated fibroblasts, as well as the signaling pathways involved in these pro-tumor activities, are among the immune cells studied. Although cytotoxic leukocytes have the potential to eliminate CSCs, immune evasion mechanisms in CSCs and their clinical implications are also known. We intended to compile experimental findings that provide direct evidence of interactions between CSCs and the immune system and CSCs and the inflammatory milieu. In addition, we aimed to summarize key concepts in order to comprehend the cross-talk between CSCs and the tumor microenvironment as a crucial process for the effective design of anti-CSC therapies.

The STAT family: Key transcription factors mediating crosstalk between cancer stem cells and tumor immune microenvironment

Signal transducer and activator of transcription (STAT) proteins compose a family of transcription factors critical for cancer stem cells (CSCs), and they are involved in maintaining stemness properties, enhancing cell proliferation, and promoting metastasis. Recent studies suggest that STAT proteins engage in reciprocal communication between CSCs and infiltrate immune cell populations in the tumor microenvironment (TME). Emerging evidence has substantiated the influence of immune cells, including macrophages, myeloid-derived suppressor cells, and T cells, on CSC survival through the regulation of STAT signaling. Conversely, dysregulation of STATs in CSCs or immune cells contributes to the establishment of an immunosuppressive TME. Thus, STAT proteins are promising therapeutic targets for cancer treatment, especially when used in combination with immunotherapy. From this perspective, we discuss the complex roles of STATs in CSCs and highlight their functions in the crosstalk between CSCs and the immune microenvironment. Finally, cutting-edge clinical trial progress with STAT signaling inhibitors is summarized.

Current understanding of cancer stem cells: Immune evasion and targeted immunotherapy in gastrointestinal malignancies

As a relatively rare population of cancer cells existing in the tumor microenvironment, cancer stem cells (CSCs) possess properties of immune privilege to evade the attack of immune system, regulated by the microenvironment of CSCs, the so-called CSCs niche. The bidirectional interaction of CSCs with tumor microenvironment (TME) components favors an immunosuppressive shelter for CSCs' survival and maintenance. Gastrointestinal cancer stem cells (GCSCs) are broadly regarded to be intimately involved in tumor initiation, progression, metastasis and recurrence, with elevated tumor resistance to conventional therapies, which pose a major hindrance to the clinical efficacy for treated patients with gastrointestinal malignancies. Thus, a multitude of efforts have been made to combat and eradicate GCSCs within the tumor mass. Among diverse methods of targeting CSCs in gastrointestinal malignancies, immunotherapy represents a promising strategy. And the better understanding of GCSCs immunomodulation and immunoresistance mechanisms is beneficial to guide and design novel GCSCs-specific immunotherapies with enhanced immune response and clinical efficacy. In this review, we have gathered available and updated information to present an overview of the immunoevasion features harbored by cancer stem cells, and we focus on the description of immune escape strategies utilized by CSCs and microenvironmental regulations underlying CSCs immuno-suppression in the context of gastrointestinal malignancies. Importantly, this review offers deep insights into recent advances of CSC-targeting immunotherapeutic approaches in gastrointestinal cancers.

Regulation of epithelial-mesenchymal transition by tumor microenvironmental signals and its implication in cancer therapeutics

Epithelial-mesenchymal transition (EMT) has been implicated in various aspects of tumor development, including tumor invasion and metastasis, cancer stemness, and therapy resistance. Diverse stroma cell types along with biochemical and biophysical factors in the tumor microenvironment impinge on the EMT program to impact tumor progression. Here we provide an in-depth review of various tumor microenvironmental signals that regulate EMT in cancer. We discuss the molecular mechanisms underlying the role of EMT in therapy resistance and highlight new therapeutic approaches targeting the tumor microenvironment to impact EMT and tumor progression.

Tumor microenvironment enriches the stemness features: the architectural event of therapy resistance and metastasis

Cancer divergence has many facets other than being considered a genetic term. It is a tremendous challenge to understand the metastasis and therapy response in cancer biology; however, it postulates the opportunity to explore the possible mechanism in the surrounding tumor environment. Most deadly solid malignancies are distinctly characterized by their tumor microenvironment (TME). TME consists of stromal components such as immune, inflammatory, endothelial, adipocytes, and fibroblast cells. Cancer stem cells (CSCs) or cancer stem-like cells are a small sub-set of the population within cancer cells believed to be a responsible player in the self-renewal, metastasis, and therapy response of cancer cells. The correlation between TME and CSCs remains an enigma in understanding the events of metastasis and therapy resistance in cancer biology. Recent evidence suggests that TME dictates the CSCs maintenance to arbitrate cancer progression and metastasis. The immune, inflammatory, endothelial, adipocyte, and fibroblast cells in the TME release growth factors, cytokines, chemokines, microRNAs, and exosomes that provide cues for the gain and maintenance of CSC features. These intricate cross-talks are fueled to evolve into aggressive, invasive, migratory phenotypes for cancer development. In this review, we have abridged the recent developments in the role of the TME factors in CSC maintenance and how these events influence the transition of tumor progression to further translate into metastasis and therapy resistance in cancer.

Recombinant Viral Vectors for Therapeutic Programming of Tumour Microenvironment: Advantages and Limitations

Viral vectors have been widely investigated as tools for cancer immunotherapy. Although many preclinical studies demonstrate significant virus-mediated tumour inhibition in synergy with immune checkpoint molecules and other drugs, the clinical success of viral vector applications in cancer therapy currently is limited. A number of challenges have to be solved to translate promising vectors to clinics. One of the key elements of successful virus-based cancer immunotherapy is the understanding of the tumour immune state and the development of vectors to modify the immunosuppressive tumour microenvironment (TME). Tumour-associated immune cells, as the main component of TME, support tumour progression through multiple pathways inducing resistance to treatment and promoting cancer cell escape mechanisms. In this review, we consider DNA and RNA virus vectors delivering immunomodulatory genes (cytokines, chemokines, co-stimulatory molecules, antibodies, etc.) and discuss how these viruses break an immunosuppressive cell development and switch TME to an immune-responsive "hot" state. We highlight the advantages and limitations of virus vectors for targeted therapeutic programming of tumour immune cell populations and tumour stroma, and propose future steps to establish viral vectors as a standard, efficient, safe, and non-toxic cancer immunotherapy approach that can complement other promising treatment strategies, e.g., checkpoint inhibitors, CAR-T, and advanced chemotherapeutics.

Pharmacological modulation of myeloid-derived suppressor cells to dampen inflammation

Myeloid-derived suppressor cells (MDSCs) are a heterogeneous cell population with potent suppressive and regulative properties. MDSCs’ strong immunosuppressive potential creates new possibilities to treat chronic inflammation and autoimmune diseases or induce tolerance towards transplantation. Here, we summarize and critically discuss different pharmacological approaches which modulate the generation, activation, and recruitment of MDSCs in vitro and in vivo, and their potential role in future immunosuppressive therapy.

Exosomes derived from myeloid-derived suppressor cells facilitate castration-resistant prostate cancer progression via S100A9/circMID1/miR-506-3p/MID1

Background

Castration-resistant prostate cancer (CRPC) is a major cause of recurrence and mortality among prostate cancer (PCa) patients. Myeloid-derived suppressor cells (MDSCs) regulate castration resistance in PCa. Previously, it was shown that intercellular communication was efficiently mediated by exosomes (Exos), but the role and the mechanism of MDSC-derived Exos in CRPC progression was unclear.

Methods

In this study, the circRNA expression profiles in PC3 cells treated with MDSC-Exo and control cells were investigated using a circRNA microarray.

Results

The data showed that circMID1 (hsa_circ_0007718) expression was elevated in PC3 cells treated with MDSC-Exo. Moreover, high circMID1 expression was found in PCa compared with benign prostatic hyperplasia (BPH) tissues and in CRPC patients compared with hormone sensitive prostate cancer (HSPC) patients. Further studies showed that MDSC-Exo accelerated PCa cell proliferation, migration, and invasion, while circMID1 deficiency inhibited MDSC-Exo-regulated CRPC progression in vitro and in vivo. Mechanistically, MDSC-derived exosomal S100A9 increased circMID1 expression to sponge miR-506-3p, leading to increased MID1 expression and accelerated tumor progression.

Conclusion

Together, our results showed that a S100A9/circMID1/miR-506-3p/MID1 axis existed in MDSC-Exo-regulated CRPC progression, which provided novel insights into MDSC-Exo regulatory mechanisms in CRPC progression.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12967-022-03494-5.

The immunoregulation effect of tumor microenvironment in pancreatic ductal adenocarcinoma

Pancreatic cancer has the seventh highest death rate of all cancers. The absence of any serious symptoms, coupled with a lack of early prognostic and diagnostic markers, makes the disease untreatable in most cases. This leads to a delay in diagnosis and the disease progresses so there is no cure. Only about 20% of cases are diagnosed early. Surgical removal is the preferred treatment for cancer, but chemotherapy is standard for advanced cancer, although patients can eventually develop drug resistance and serious side effects. Chemoresistance is multifactorial because of the interaction among pancreatic cancer cells, cancer stem cells, and the tumor microenvironment (TME). Nevertheless, more pancreatic cancer patients will benefit from precision treatment and targeted drugs. This review focuses on the immune-related components of TME and the interactions between tumor cells and TME during the development and progression of pancreatic cancer, including immunosuppression, tumor dormancy and escape. Finally, we discussed a variety of immune components-oriented immunotargeting drugs in TME from a clinical perspective.

The metabolic addiction of cancer stem cells

Cancer stem cells (CSC) are the minor population of cancer originating cells that have the capacity of self-renewal, differentiation, and tumorigenicity (when transplanted into an immunocompromised animal). These low-copy number cell populations are believed to be resistant to conventional chemo and radiotherapy. It was reported that metabolic adaptation of these elusive cell populations is to a large extent responsible for their survival and distant metastasis. Warburg effect is a hallmark of most cancer in which the cancer cells prefer to metabolize glucose anaerobically, even under normoxic conditions. Warburg's aerobic glycolysis produces ATP efficiently promoting cell proliferation by reprogramming metabolism to increase glucose uptake and stimulating lactate production. This metabolic adaptation also seems to contribute to chemoresistance and immune evasion, a prerequisite for cancer cell survival and proliferation. Though we know a lot about metabolic fine-tuning in cancer, what is still in shadow is the identity of upstream regulators that orchestrates this process. Epigenetic modification of key metabolic enzymes seems to play a decisive role in this. By altering the metabolic flux, cancer cells polarize the biochemical reactions to selectively generate "onco-metabolites" that provide an added advantage for cell proliferation and survival. In this review, we explored the metabolic-epigenetic circuity in relation to cancer growth and proliferation and establish the fact how cancer cells may be addicted to specific metabolic pathways to meet their needs. Interestingly, even the immune system is re-calibrated to adapt to this altered scenario. Knowing the details is crucial for selective targeting of cancer stem cells by choking the rate-limiting stems and crucial branch points, preventing the formation of onco-metabolites.

Toll-like receptor 7/8 agonist R848 alters the immune tumor microenvironment and enhances SBRT-induced antitumor efficacy in murine models of pancreatic cancer

BACKGROUND

Stereotactic body radiotherapy (SBRT) has been increasingly used as adjuvant therapy in pancreatic ductal adenocarcinoma (PDAC), and induces immunogenic cell death, which leads to the release of tumor antigen and damage-associated molecular patterns. However, this induction often fails to generate sufficient response to overcome pre-existing tumor microenvironment (TME) immunosuppression. Toll-like receptor (TLR) 7/8 ligands, such as R848, can amplify the effect of tumor vaccines, with recent evidence showing its antitumor effect in pancreatic cancer by modulating the immunosuppressive TME. Therefore, we hypothesized that the combination of R848 and SBRT would improve local and systemic antitumor immune responses by potentiating the antitumor effects of SBRT and reversing the immunosuppressive nature of the PDAC TME.

METHODS

Using murine models of orthotopic PDAC, we assessed the combination of intravenous TLR7/8 agonist R848 and local SBRT on tumor growth and immune response in primary pancreatic tumors. Additionally, we employed a hepatic metastatic model to investigate if the combination of SBRT targeting only the primary pancreatic tumor and systemic R848 is effective in controlling established liver metastases.

RESULTS

We demonstrated that intravenous administration of the TLR7/8 agonist R848, in combination with local SBRT, leads to superior tumor control compared with either treatment alone. The combination of R848 and SBRT results in significant immune activation of the pancreatic TME, including increased tumor antigen-specific CD8+ T cells, decreased regulatory T cells, and enhanced antigen-presenting cells maturation, as well as increased interferon gamma, granzyme B, and CCL5 along with decreased levels of interleukin 4 (IL-4), IL-6, and IL-10. Importantly, the combination of SBRT and systemic R848 also resulted in similar immunostimulatory changes in liver metastases, leading to improved metastatic control. CD8+ T cell depletion studies highlighted the necessity of these effector cells at both the local and hepatic metastatic sites. T cell receptor (TCR) clonotype analysis indicated that systemic R848 not only diversified the TCR repertoire but also conditioned the metastatic foci to facilitate entry of CD8+ T cells generated by SBRT therapy.

CONCLUSIONS

These findings suggest that systemic administration of TLR7/8 agonists in combination with SBRT may be a promising avenue for metastatic PDAC treatment.

The role of pyroptosis in modulating the tumor immune microenvironment

The tumor immune microenvironment (TIME) plays a key role in immunosuppression in cancer, which results in tumorigenesis and tumor progression, and contributes to insensitivity to chemotherapy and immunotherapy. Understanding the mechanism of TIME formation is critical for overcoming cancer. Pyroptosis exerts a dual role in modulating the TIME. In this review, we summarize the regulatory mechanisms of pyroptosis in modulating the TIME and the potential application of targeted pyroptosis therapy in the clinic. Several treatments targeting pyroptosis have been developed; however, the majority of treatments are still in preclinical studies. Only a few agents have been used in clinic, but the outcomes are unsatisfactory. More studies are necessary to determine the role of pyroptosis in cancer, and more research is required to realize the application of treatments targeting pyroptosis in the clinic.

MDSCs might be "Achilles heel" for eradicating CSCs

During tumor initiation and progression, the complicated role of immune cells in the tumor immune microenvironment remains a concern. Myeloid-derived suppressor cells (MDSCs) are a group of immune cells that originate from the bone marrow and have immunosuppressive potency in various diseases, including cancer. In recent years, the key role of cancer stemness has received increasing attention in cancer development and therapy. Several studies have demonstrated the important regulatory relationship between MDSCs and cancer stem cells (CSCs). However, there is still no clear understanding regarding the complex interacting regulation of tumor malignancy, and current research progress is limited. In this review, we summarize the complicated role of MDSCs in the modulation of cancer stemness, evaluate the mechanism of the relationship between CSCs and MDSCs, and discuss potential strategies for eradicating CSCs with respect to MDSCs.

CCR4+ monocytic myeloid-derived suppressor cells are associated with the increased epithelial-mesenchymal transition in pancreatic adenocarcinoma patients

Among all the cancer-related deaths globally, pancreatic ductal adenocarcinoma (PDAC) accounts for the seventh leading cause of mortality. A dysregulated immune system disrupts anti-tumor immunity by abnormal accumulation of myeloid-derived suppressor cells (MDSCs), but the underlying mechanisms are still inconclusive. To gain new insights into the role of MDSCs in tumor settings, we aimed to determine the mechanism of expansion of various subsets of MDSCs in PDAC patients and their role in promoting invasiveness. We assessed the load of MDSCs, chemokines responsible for the recruitment of MDSCs in PDAC patients by flow cytometry. We investigated the chemokine profile of tumor tissue using qRT-PCR and the status of epithelial-mesenchymal transition (EMT) related markers E-Cadherin, N-Cadherin, Snail, and ZEB1 by qRT-PCR and immunohistochemistry. We found a higher frequency of tumor infiltrated MDSCs in PDAC patients. Chemokine ligands CCL2 and the receptor CCR4 were markedly elevated in the PDAC tumor, while CCR4+ monocytic MDSCs (M-MDSCs) were found significantly elevated in peripheral blood and tumor tissue. In tumor tissue, expression of E-Cadherin was significantly reduced, while N-Cadherin, Snail, and ZEB1 were markedly raised. The frequency of CCR4+ M-MDSCs significantly correlated with the expression of mesenchymal transition markers N-Cadherin, Snail, and ZEB1. Collectively, these results suggest that the CCL2-CCR4 axis plays a crucial role in driving the recruitment of M-MDSCs, which is associated with increased invasiveness in PDAC. This study sheds light on the expansion mechanism of MDSCs, which can serve as a crucial target of future anti-cancer strategies to inhibit tumor cell invasiveness.

Roles of the Exosomes Derived From Myeloid-Derived Suppressor Cells in Tumor Immunity and Cancer Progression

Tumor immunity is involved in malignant tumor progression. Myeloid-derived suppressor cells (MDSCs) play an irreplaceable role in tumor immunity. MDSCs are composed of immature myeloid cells and exhibit obvious immunomodulatory functions. Exosomes released by MDSCs (MDSCs-Exos) have similar effects to parental MDSCs in regulating tumor immunity. In this review, we provided a comprehensive description of the characteristics, functions and mechanisms of exosomes. We analyzed the immunosuppressive, angiogenesis and metastatic effects of MDSCs-Exos in different tumors through multiple perspectives. Immunotherapy targeting MDSCs-Exos has demonstrated great potential in cancers and non-cancerous diseases.

The Role of Myeloid-Derived Suppressor Cells in Tumor Growth and Metastasis

Myeloid-derived suppressor cells (MDSCs) are immature bone marrow-derived suppressive cells that are an important component of the pathological immune response associated with cancer. Expansion of MDSCs has been linked to poor disease outcome and therapeutic resistance in patients with various malignancies, making these cells potential targets for next-generation treatment strategies. MDSCs are classified into monocytic (M-MDSC) and polymorphonuclear/granulocytic (PMN-MDSC) subtypes that undertake distinct and numerous roles in the tumor microenvironment or systemically to drive disease progression. In this chapter, we will discuss how MDSC subsets contribute to the growth of primary tumors and induce metastatic spread by suppressing the antitumor immune response, supporting cancer stem cell (CSC)/epithelial-to-mesenchymal transition (EMT) phenotypes and promoting angiogenesis. We will also summarize the signaling networks involved in the crosstalk between cancer cells and MDSCs that could represent putative immunotherapy targets.

Specific targeting of cancer stem cells by immunotherapy: A possible stratagem to restrain cancer recurrence and metastasis

Cancer stem cells (CSCs), the tumor-initiating cells playing a crucial role in cancer progression, recurrence, and metastasis, have the intrinsic property of self-renewal and therapy resistance. The tumorigenic properties of these cells include generation of cellular heterogeneity and immuno-suppressive tumor microenvironment (TME), conferring them the capability to resist a variety of anti-cancer therapeutics. Further, CSCs possess several unique immunological properties that help them escape recognition by the innate and adaptive immune system and shape a TME into a pro-tumorigenic and immunosuppressive landscape. In this context, immunotherapy is considered one of the best therapeutic options for eliminating CSCs to halt cancer recurrence and metastasis. In this review, we discuss the various immunomodulatory properties of CSCs and the interaction of CSCs with the immune system enabling immune evasion. In addition, we also highlight the present research update on immunotherapeutic targeting of CSCs and the possible further scope of research on this topic. We believe that a deeper understanding of CSCs' immunological properties and the crosstalk between CSCs and the immune system can develop better innovative immune-therapeutics and enhance the efficacy of current therapy-resistant cancer treatments.

Peripheral blood monocytes predict clinical prognosis and support tumor invasiveness through NF-κB-dependent upregulation of Snail in pancreatic cancer

Background

The tumor inflammatory microenvironment plays a vital role in the initiation and progression of pancreatic cancer (PC). Both the lymphocyte-to-monocyte ratio (LMR) and preoperative peripheral blood monocytes are related to the prognosis of PC patients. However, the direct effect of monocytes on PC cells is not fully understood. The current study aimed to assess the effect of monocytes on PC and explore its potential mechanism.

Methods

The cutoff value of peripheral blood monocytes was evaluated by the receiver operating characteristic (ROC) curve. Transwell migration and invasion assays were used to detect the mobility of PC cells. The cytokines derived from monocytes were measured by quantitative real-time polymerase chain reaction (qRT-PCR). Western blotting was utilized to assess the expression of epithelial-mesenchymal transition (EMT) related markers. The expression level of Snail in PC tissue was determined by immunohistochemical (IHC) staining.

Results

A high monocyte count was inversely correlated with lymph node status and 5-year overall survival in PC. The PC cells underwent a cellular morphology change and increased cell motility after coculture with THP-1 monocytes. The THP-1 monocytes secreted various proinflammatory cytokines, including tumor necrosis factor-α (TNF-α) and interleukin-1α (IL-1α), which activated the nuclear factor-κB (NF-κB) signaling pathway leading to the upregulation of Snail and thereby promoting the EMT of PC cells. The expression level of Snail correlated significantly with the density of peripheral blood monocytes, and their level status was significantly associated with 5-year overall survival.

Conclusions

These findings indicated that elevated monocytes counts were a poor prognostic marker in PC, and monocytes could directly induce the EMT process of PC cells by upregulating Snail expression through the NF-κB signaling pathway.

Evolution and Targeting of Myeloid Suppressor Cells in Cancer: A Translational Perspective

Simple Summary

Immunotherapy is achieving impressive results in the treatment of several cancers. While the main strategies aim to re-invigorate the specific lymphocyte anti-tumor response, many studies underline that altered myeloid cell frequency and functions can dramatically interfere with the responsiveness to cancer therapies. Therefore, many novel strategies targeting TAMs and MDSCs in combination with classical treatments are under continuous evolution at both pre-clinical and clinical levels, showing encouraging results. Herein, we depict a comprehensive overview of myeloid cell generation and function in a cancer setting, and the most relevant strategies for their targeting that are currently in clinical use or under pre-clinical development.

Abstract

In recent years, the immune system has emerged as a critical regulator of tumor development, progression and dissemination. Advanced therapeutic approaches targeting immune cells are currently under clinical use and improvement for the treatment of patients affected by advanced malignancies. Among these, anti-PD1/PD-L1 and anti-CTLA4 immune checkpoint inhibitors (ICIs) are the most effective immunotherapeutic drugs at present. In spite of these advances, great variability in responses to therapy exists among patients, probably due to the heterogeneity of both cancer cells and immune responses, which manifest in diverse forms in the tumor microenvironment (TME). The variability of the immune profile within TME and its prognostic significance largely depend on the frequency of the infiltrating myeloid cells, which often represent the predominant population, characterized by high phenotypic heterogeneity. The generation of heterogeneous myeloid populations endowed with tumor-promoting activities is typically promoted by growing tumors, indicating the sequential levels of myeloid reprogramming as possible antitumor targets. This work reviews the current knowledge on the events governing protumoral myelopoiesis, analyzing the mechanisms that drive the expansion of major myeloid subsets, as well as their functional properties, and highlighting recent translational strategies for clinical developments.

Myeloid-Derived Suppressor Cells: A Multifaceted Accomplice in Tumor Progression

Myeloid-derived suppressor cell (MDSC) is a heterogeneous population of immature myeloid cells, has a pivotal role in negatively regulating immune response, promoting tumor progression, creating pre-metastases niche, and weakening immunotherapy efficacy. The underlying mechanisms are complex and diverse, including immunosuppressive functions (such as inhibition of cytotoxic T cells and recruitment of regulatory T cells) and non-immunological functions (mediating stemness and promoting angiogenesis). Moreover, MDSC may predict therapeutic response as a poor prognosis biomarker among multiple tumors. Accumulating evidence indicates targeting MDSC can reverse immunosuppressive tumor microenvironment, and improve therapeutic response either single or combination with immunotherapy. This review summarizes the phenotype and definite mechanisms of MDSCs in tumor progression, and provide new insights of targeting strategies regarding to their clinical applications.

The Role of Myeloid-Derived Suppressor Cells in the Treatment of Pancreatic Cancer

Pancreatic cancer has the highest mortality rate of all major cancers, with a 5-year survival rate of about 10%. Early warning signs and symptoms of pancreatic cancer are vague or nonexistent, and most patients are diagnosed in Stage IV, when surgery is not an option for about 80%-85% of patients. For patients with inoperable pancreatic cancer, current conventional treatment modalities such as chemotherapy and radiotherapy (RT) have suboptimal efficacy. Tumor progression is closely associated with the tumor microenvironment, which includes peripheral blood vessels, bone marrow-derived inflammatory cells, fibroblasts, immune cells, signaling molecules, and extracellular matrix. Tumor cells affect the microenvironment by releasing extracellular signaling molecules, inducing peripheral immune tolerance, and promoting tumor angiogenesis. In turn, the immune cells of the tumor affect the survival and proliferation of cancer cells. Myeloid-derived suppressor cells are key cellular components in the tumor microenvironment and exert immunosuppressive functions by producing cytokines, recognizing other immune cells, and promoting tumor growth and metastasis. Myeloid-derived suppressor cells are the main regulator of the tumor immune response and a key target for tumor treatments. Since the combination of RT and immunotherapy is the main strategy for the treatment of pancreatic cancer, it is very important to understand the immune mechanisms which lead to MDSCs generation and the failure of current therapies in order to develop new target-based therapies. This review summarizes the research advances on the role of Myeloid-derived suppressor cells in the progression of pancreatic cancer and its treatment application in recent years.

ADAMTS9-AS1 Constrains Breast Cancer Cell Invasion and Proliferation via Sequestering miR-301b-3p

Objective: For determination of how ADAMTS9-AS1/miR-301b-3p/TGFBR2/JAK STAT signaling axis modulates progression of breast cancer cells.

Methods: Target lncRNA was determined by differential analysis of breast cancer expression data and survival analysis. Differentially expressed miRNAs and target mRNAs that had binding sites with target lncRNA were predicted. GSEA software was used to carry out pathway enrichment analysis for mRNAs. Binding of the researched genes were tested with RNA binding protein immunoprecipitation (RIP). How miR-301b-3p bound TGFBR2 mRNA was tested by dual-luciferase method. Transwell, colony formation, EdU approaches were employed for verification of invasion and proliferation of breast cancer cells in each treatment group.

Results: Markedly inactivated ADAMTS9-AS1 in breast cancer pertained to patient’s prognosis. MiR-301b-3p was capable of binding TGFBR2/ADAMTS9-AS1. However, overexpression of ADAMTS9-AS1 stimulated miR-301b-3p binding ADAMTS9-AS1 and repressed miR-301b-3p binding TGFBR2 mRNA. ADAMTS9-AS1 interference enhanced cancer proliferation and invasion, facilitated levels of KI67, PCNA, MMP-9 and MMP-2, and activated the JAK STAT signaling pathway. While silencing miR-301b-3p reversed the effect of ADAMTS9-AS1 interference. In addition, TGFBR2 interference or restraining JAK STAT signaling counteracted the effect of ADAMTS9-AS1.

Conclusion: ADAMTS9-AS1 could sequester miR-301b-3p to inhibit progression of breast cancer via TGFBR2/JAK STAT pathway. This study supplies a rationale for incremental apprehension of ADAMTS9-AS1 in breast cancer progression.

IL-6 is associated with expansion of myeloid-derived suppressor cells and enhanced immunosuppression in pancreatic adenocarcinoma patients

Chronic inflammation favours the expansion of myeloid-derived suppressor cells (MDSCs) by secreting pro-inflammatory mediators. The role of MDSCs in mediating immunosuppression in pancreatic adenocarcinoma and in defining a premalignant route from chronic pancreatitis remains unclear. We aimed to study the immunosuppressive potential of all subsets of MDSCs and their correlation with inflammatory cytokines in pancreatic adenocarcinoma and chronic pancreatitis. Relative frequencies of MDSCs, immunosuppressive markers arginase-1 (ARG-1), programmed death-ligand 1 (PD-L1), reactive oxygen species (ROS) and cytokines in circulation and surgically resected local pancreatic tissue of chronic pancreatitis and pancreatic adenocarcinoma patients were analysed by multicolour flow cytometry and cytokine bead array, respectively. Levels of cytokines involved in MDSCs activation were analysed by ELISA, and the immunosuppressive nature of MDSCs was confirmed by T-cell suppression assay. Frequencies of circulating MDSCs and ARG-1, PD-L1, and ROS were significantly higher in pancreatic adenocarcinoma than healthy controls and showed a significant positive correlation with MDSCs burden in cancer tissue. Serum levels of cytokines IL-6, IL-8 and IL-10 were significantly elevated in pancreatic adenocarcinoma. IL-6 serum levels showed a significant positive correlation with frequencies of circulating MDSCs in pancreatic adenocarcinoma patients, and MDSCs mediated suppression of T-cell proliferation in vitro was associated with elevated IL-6 levels in the cell culture medium. Collectively, our results suggest that IL-6 plays a crucial role in the expansion of MDSCs and activating their immunosuppressive nature in pancreatic adenocarcinoma. The relative frequency of MDSCs in circulation can be used as a potential diagnostic biomarker for pancreatic cancer.

The Role of the Innate Immune System in Cancer Dormancy and Relapse

Metastatic spread and recurrence are intimately linked to therapy failure, which remains an overarching clinical challenge for patients with cancer. Cancer cells often disseminate early in the disease process and can remain dormant for years or decades before re-emerging as metastatic disease, often after successful treatment. The interactions of dormant cancer cells and their metastatic niche, comprised of various stromal and immune cells, can determine the length of time that cancer cells remain dormant, as well as when they reactivate. New studies are defining how innate immune cells in the primary tumor may be corrupted to help facilitate many aspects of dissemination and re-emergence from a dormant state. Although the scientific literature has partially shed light on the drivers of immune escape in cancer, the specific mechanisms regulating metastasis and dormancy in the context of anti-tumor immunity are still mostly unknown. This review follows the journey of metastatic cells from dissemination to dormancy and the onset of metastatic outgrowth and recurrent tumor development, with emphasis on the role of the innate immune system. To this end, further research identifying how immune cells interact with cancer cells at each step of cancer progression will pave the way for new therapies that target the reactivation of dormant cancer cells into recurrent, metastatic cancers.

The tumor microenvironment in pancreatic ductal adenocarcinoma: current perspectives and future directions

Pancreatic ductal adenocarcinoma (PDAC) is among the most lethal malignancies and is characterized by a unique tumor microenvironment (TME) consisting of an abundant stromal component. Many features contained with the PDAC stroma contribute to resistance to cytotoxic and immunotherapeutic regimens, as well as the propensity for this tumor to metastasize. At the cellular level, PDAC cells crosstalk with a complex mixture of non-neoplastic cell types including fibroblasts, endothelial cells, and immune cells. These intricate interactions fuel the progression and therapeutic resistance of this aggressive cancer. Moreover, data suggest the polarization of these cell types, in particular immune and fibroblast populations, dictate how PDAC tumors grow, metastasize, and respond to therapy. As a result, current research is focused on how to best target these populations to render tumors responsive to treatment. Herein, we summarize the cell populations implicated in providing a supporting role for the development and progression of PDAC. We focus on stromal fibroblasts and immune subsets that have been widely researched. We discuss factors which govern the phenotype of these populations and provide insight on how they have been targeted therapeutically. This review provides an overview of the tumor microenvironment and postulates that cellular and soluble factors within the microenvironment can be specifically targeted to improve patient outcomes.

Systematic analysis of the relationship between ovarian cancer prognosis and alternative splicing

Background

Ovarian cancer(OC) is the gynecological tumor with the highest mortality rate, effective biomarkers are of great significance in improving its prognosis. In recent years, there have been many studies on alternative splicing (AS) events, and the role of AS events in tumor has become a focus of attention.

Methods

Data were downloaded from the TCGA database and Univariate Cox regression analysis was performed to determine AS events associated with OC prognosis.Eight prognostic models of OC were constructed in R package, and the accuracy of the models were evaluated by the time-dependent receiver operating characteristic (ROC) curves.Eight types of survival curves were drawn to evaluate the differences between the high and low risk groups.Independent prognostic factors of OC were analyzed by single factor independent analysis and multi-factor independent prognostic analysis.Again, Univariate Cox regression analysis was used to analyze the relationship between splicing factors(SF) and AS events, and Gene Ontology(GO) and Kyoto Encyclopedia of Genes and Genomes(KEGG) enrichment analysis were performed on OS-related SFs to understand the pathways.

Results

Univariate Cox regression analysis showed that among the 15,278 genes, there were 31,286 overall survival (OS) related AS events, among which 1524 AS events were significantly correlated with OS. The area under the time-dependent receiver operating characteristic curve (AUC) of AT and ME were the largest and the RI was the smallest,which were 0.757 and 0.68 respectively. The constructed models have good value for the prognosis assessment of OC patients. Among the eight survival curves, AP was the most significant difference between the high and low risk groups, with a P value of 1.61e − 1.The results of single factor independent analysis and multi-factor independent prognostic analysis showed that risk score calculated by the model and age could be used as independent risk factors.According to univariate COX regression analysis,109 SFs were correlated with AS events and adjusted in two ways: positive and negative.

Conclusions

SFs and AS events can directly or indirectly affect the prognosis of OC patients. It is very important to find effective prognostic markers to improve the survival rate of OC.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13048-021-00866-1.

Chemokine-Directed Tumor Microenvironment Modulation in Cancer Immunotherapy

Chemokines are a large family of small chemotactic cytokines that coordinates immune cell trafficking. In cancer, they have a pivotal role in the migration pattern of immune cells into the tumor, thereby shaping the tumor microenvironment immune profile, often towards a pro-tumorigenic state. Furthermore, chemokines can directly target non-immune cells in the tumor microenvironment, including cancer, stromal and vascular endothelial cells. As such, chemokines participate in several cancer development processes such as angiogenesis, metastasis, cancer cell proliferation, stemness and invasiveness, and are therefore key determinants of disease progression, with a strong influence in patient prognosis and response to therapy. Due to their multifaceted role in the tumor immune response and tumor biology, the chemokine network has emerged as a potential immunotherapy target. Under the present review, we provide a general overview of chemokine effects on several tumoral processes, as well as a description of the currently available chemokine-directed therapies, highlighting their potential both as monotherapy or in combination with standard chemotherapy or other immunotherapies. Finally, we discuss the most critical challenges and prospects of developing targeted chemokines as therapeutic options.

Cancer stem cell-immune cell crosstalk in tumour progression

Cellular heterogeneity and an immunosuppressive tumour microenvironment are independent yet synergistic drivers of tumour progression and underlie therapeutic resistance. Recent studies have highlighted the complex interaction between these cell-intrinsic and cell-extrinsic mechanisms. The reciprocal communication between cancer stem cells (CSCs) and infiltrating immune cell populations in the tumour microenvironment is a paradigm for these interactions. In this Perspective, we discuss the signalling programmes that simultaneously induce CSCs and reprogramme the immune response to facilitate tumour immune evasion, metastasis and recurrence. We further highlight biological factors that can impact the nature of CSC-immune cell communication. Finally, we discuss targeting opportunities for simultaneous regulation of the CSC niche and immunosurveillance.