Tumor-infiltrating myeloid cells activate Dll4/Notch/TGF-β signaling to drive malignant progression

Potential therapeutic targets in myeloid cell therapy for overcoming chemoresistance and immune suppression in gastrointestinal tumors

In the tumor microenvironment (TME), myeloid cells play a pivotal role. Myeloid-derived immunosuppressive cells, including tumor-associated macrophages (TAMs) and myeloid-derived suppressor cells (MDSCs), are central components in shaping the immunosuppressive milieu of the tumor. Within the TME, a majority of TAMs assume an M2 phenotype, characterized by their pro-tumoral activity. These cells promote tumor cell growth, angiogenesis, invasion, and migration. In contrast, M1 macrophages, under appropriate activation conditions, exhibit cytotoxic capabilities against cancer cells. However, an excessive M1 response may lead to pro-tumoral inflammation. As a result, myeloid cells have emerged as crucial targets in cancer therapy. This review concentrates on gastrointestinal tumors, detailing methods for targeting macrophages to enhance tumor radiotherapy and immunotherapy sensitivity. We specifically delve into monocytes and tumor-associated macrophages' various functions, establishing an immunosuppressive microenvironment, promoting tumorigenic inflammation, and fostering neovascularization and stromal remodeling. Additionally, we examine combination therapeutic strategies.

Breast Cancer Macrophage Heterogeneity and Self-renewal are Determined by Spatial Localization

Tumor-infiltrating macrophages support critical steps in tumor progression, and their accumulation in the tumor microenvironment (TME) is associated with adverse outcomes and therapeutic resistance across human cancers. In the TME, macrophages adopt diverse phenotypic alterations, giving rise to heterogeneous immune activation states and induction of cell cycle. While the transcriptional profiles of these activation states are well-annotated across human cancers, the underlying signals that regulate macrophage heterogeneity and accumulation remain incompletely understood. Here, we leveraged a novel ex vivo organotypic TME (oTME) model of breast cancer, in vivo murine models, and human samples to map the determinants of functional heterogeneity of TME macrophages. We identified a subset of F4/80highSca-1+ self-renewing macrophages maintained by type-I interferon (IFN) signaling and requiring physical contact with cancer-associated fibroblasts. We discovered that the contact-dependent self-renewal of TME macrophages is mediated via Notch4, and its inhibition abrogated tumor growth of breast and ovarian carcinomas in vivo, as well as lung dissemination in a PDX model of triple-negative breast cancer (TNBC). Through spatial multi-omic profiling of protein markers and transcriptomes, we found that the localization of macrophages further dictates functionally distinct but reversible phenotypes, regardless of their ontogeny. Whereas immune-stimulatory macrophages (CD11C+CD86+) populated the tumor epithelial nests, the stroma-associated macrophages (SAMs) were proliferative, immunosuppressive (Sca-1+CD206+PD-L1+), resistant to CSF-1R depletion, and associated with worse patient outcomes. Notably, following cessation of CSF-1R depletion, macrophages rebounded primarily to the SAM phenotype, which was associated with accelerated growth of mammary tumors. Our work reveals the spatial determinants of macrophage heterogeneity in breast cancer and highlights the disruption of macrophage self-renewal as a potential new therapeutic strategy.

Current Progress on Predictive Biomarkers for Response to Immune Checkpoint Inhibitors in Gastric Cancer: How to Maximize the Immunotherapeutic Benefit?

Gastric cancer is the fifth most prevalent cancer and the fourth leading cause of cancer death globally. Delayed diagnosis and pronounced histological and molecular variations increase the complexity and challenge of treatment. Pharmacotherapy, which for a long time was systemic chemotherapy based on 5-fluorouracil, is the mainstay of management for advanced gastric cancer. Trastuzumab and programmed cell death 1 (PD-1) inhibitors have altered the therapeutic landscape, contributing to noticeably prolonged survivorship in patients with metastatic gastric cancer. However, research has revealed that immunotherapy is only beneficial to some individuals. Biomarkers, such as programmed cell death ligand 1 (PD-L1), microsatellite instability (MSI), and tumor mutational load (TMB), have been shown to correlate with immune efficacy in numerous studies and are increasingly employed for the selection of patients most likely to respond to immunotherapy. Gut microorganisms, genetic mutations like POLE/POLD1 and NOTCH4, tumor lymphoid infiltrating cells (TILs), and other novel biomarkers have the potential to develop into new predictors. Prospective immunotherapy for gastric cancer should be guided by a biomarker-driven precision management paradigm, and multidimensional or dynamic marker testing could be the way to go.

NOTCH4 mutation as predictive biomarker for immunotherapy benefits in NRAS wildtype melanoma

Background

NRAS wildtype melanoma accounts for approximately 80% of melanomas. Previous studies have shown that NRAS wildtype melanoma had higher response rates and better prognoses than NRAS-mutant patients following immunotherapy, while as major actors in tumor cells and tumor microenvironment (TME), the association between NOTCH family genes and response to immunotherapy in NRAS wildtype melanoma remains indistinct.

Objective

We aim to explore whether NOTCH family gene variation is associated with genomic factors in immune checkpoint inhibitor (ICI) response in NRAS wildtype melanoma and with clinical results in these patients.

Method

This research used genomic data of 265 NRAS wildtype ICI-pretreatment samples from five ICI-treated melanoma cohorts to analyze the relationship between NOTCH family gene mutation and the efficacy of ICI therapy.

Results

NRAS wildtype melanomas with NOTCH4-Mut were identified to be associated with prolonged overall survival (OS) in both the discovery (HR: 0.30, 95% CI: 0.11–0.83, P = 0.01) and validation cohorts(HR: 0.21, 95% CI: 0.07–0.68, P = 0.003). Moreover, NOTCH4-Mut melanoma had a superior clinical response in the discovery cohort (ORR, 40.0% vs 13.11%, P = 0.057) and validation cohort (ORR, 68.75% vs 30.07%, P = 0.004). Further exploration found that NOTCH4-Mut tumors had higher tumor mutation burden (TMB) and tumor neoantigen burden (TNB) (P <0.05). NOTCH4-Mut tumors had a significantly increased mutation in the DNA damage response (DDR) pathway. Gene set enrichment analysis revealed NOTCH4-Mut tumor enhanced anti-tumor immunity.

Conclusion

NOTCH4 mutation may promote tumor immunity and serve as a biomarker to predict good immune response in NRAS wildtype melanoma and guide immunotherapeutic responsiveness.

Epithelial-to-Mesenchymal Transition-Derived Heterogeneity in Head and Neck Squamous Cell Carcinomas

Simple Summary

Head and neck squamous cell carcinomas (HNSCC) are common malignancies with considerable morbidity and a high death toll worldwide. Resistance towards multi-modal therapy modalities composed of surgery, irradiation, chemo- and immunotherapy represents a major obstacle in the efficient treatment of HNSCC patients. Patients frequently show nodal metastases at the time of diagnosis and endure early relapses, oftentimes in the form of local recurrences. Differentiation programs such as the epithelial-to-mesenchymal transition (EMT) allow individual tumor cells to adopt cellular functions that are central to the development of metastases and treatment resistance. In the present review article, the molecular basis and regulation of EMT and its impact on the progression of HNSCC will be addressed.

Abstract

Head and neck squamous cell carcinomas (HNSCC) are common tumors with a poor overall prognosis. Poor survival is resulting from limited response to multi-modal therapy, high incidence of metastasis, and local recurrence. Treatment includes surgery, radio(chemo)therapy, and targeted therapy specific for EGFR and immune checkpoint inhibition. The understanding of the molecular basis for the poor outcome of HNSCC was improved using multi-OMICs approaches, which revealed a strong degree of inter- and intratumor heterogeneity (ITH) at the level of DNA mutations, transcriptome, and (phospho)proteome. Single-cell RNA-sequencing (scRNA-seq) identified RNA-expression signatures related to cell cycle, cell stress, hypoxia, epithelial differentiation, and a partial epithelial-to-mesenchymal transition (pEMT). The latter signature was correlated to nodal involvement and adverse clinical features. Mechanistically, shifts towards a mesenchymal phenotype equips tumor cells with migratory and invasive capacities and with an enhanced resistance to standard therapy. Hence, gradual variations of EMT as observed in HNSCC represent a potent driver of tumor progression that could open new paths to improve the stratification of patients and to innovate approaches to break therapy resistance. These aspects of molecular heterogeneity will be discussed in the present review.

Notch-ing up knowledge on molecular mechanisms of skin fibrosis: focus on the multifaceted Notch signalling pathway

Fibrosis can be defined as an excessive and deregulated deposition of extracellular matrix proteins, causing loss of physiological architecture and dysfunction of different tissues and organs. In the skin, fibrosis represents the hallmark of several acquired (e.g. systemic sclerosis and hypertrophic scars) and inherited (i.e. dystrophic epidermolysis bullosa) diseases. A complex series of interactions among a variety of cellular types and a wide range of molecular players drive the fibrogenic process, often in a context-dependent manner. However, the pathogenetic mechanisms leading to skin fibrosis are not completely elucidated. In this scenario, an increasing body of evidence has recently disclosed the involvement of Notch signalling cascade in fibrosis of the skin and other organs. Despite its apparent simplicity, Notch represents one of the most multifaceted, strictly regulated and intricate pathways with still unknown features both in health and disease conditions. Starting from the most recent advances in Notch activation and regulation, this review focuses on the pro-fibrotic function of Notch pathway in fibroproliferative skin disorders describing molecular networks, interplay with other pro-fibrotic molecules and pathways, including the transforming growth factor-β1, and therapeutic strategies under development.

The Relevance of Notch Signaling in Cancer Progression

The Notch signaling pathway controls normal embryonic development and tissue homeostasis of many cell types. It regulates cell proliferation, fate, differentiation, and cell death by short-range signaling between nearby cells that come in contact. The Notch pathway has also been critically involved in the pathobiology of a variety of malignancies, regulating cancer initiation and development, as well as early stages of cancer progression, by adjusting conserved cellular programs. Fibroblasts, an essential for tumor growth component of stroma, have also been affected by Notch regulation. Sequencing Notch gene mutations have been identified in a number of human tumors, revealing information on the progression of specific cancer types, such as ovarian cancer and melanoma, immune-associated tumors such as myeloid neoplasms, but especially in lymphocytic leukemia. Activation of the Notch can be either oncogenic or it may contain growth-suppressive functions, acting as a tumor suppressor in other hematopoietic cells, hepatocytes, skin, and pancreatic epithelium.

Deletion of delta-like 1 homologue accelerates fibroblast-myofibroblast differentiation and induces myocardial fibrosis

AIMS

Myocardial fibrosis is associated with profound changes in ventricular architecture and geometry, resulting in diminished cardiac function. There is currently no information on the role of the delta-like homologue 1 (Dlk1) in the regulation of the fibrotic response. Here, we investigated whether Dlk1 is involved in cardiac fibroblast-to-myofibroblast differentiation and regulates myocardial fibrosis and explored the molecular mechanism underpinning its effects in this process.

METHODS AND RESULTS

Using Dlk1-knockout mice and adenoviral gene delivery, we demonstrate that overexpression of Dlk1 in cardio-fibroblasts resulted in inhibition of fibroblast proliferation and differentiation into myofibroblasts. This process is mediated by TGF-β1 signalling, since isolated fibroblasts lacking Dlk1 exhibited a higher activation of the TGF-β1/Smad-3 pathway at baseline, leading to an earlier acquisition of a myofibroblast phenotype. Likewise, Dlk1-null mice displayed increased TGF-β1/Smad3 cardiac activity, resulting in infiltration/accumulation of myofibroblasts, induction and deposition of extra-domain A-fibronectin isoform and collagen, and activation of pro-fibrotic markers. Furthermore, these profibrotic events were associated with disrupted myofibril integrity, myocyte hypertrophy, and cardiac dysfunction. Interestingly, Dlk1 expression was down-regulated in ischaemic human and porcine heart tissues. Mechanistically, miR-370 mediated Dlk1's regulation of cardiac fibroblast-myofibroblast differentiation by directly targeting TGFβ-R2/Smad-3 signalling, while the Dlk1 canonical target, Notch pathway, does not seem to play a role in this process.

CONCLUSION

These findings are the first to demonstrate an inhibitory role of Dlk1 of cardiac fibroblast-to-myofibroblast differentiation by interfering with TGFβ/Smad-3 signalling in the myocardium. Given the deleterious effects of continuous activation of this pathway, we propose Dlk1 as a new potential candidate for therapy in cases where aberrant TGFβ signalling leads to chronic fibrosis.

Subtype-specific signaling pathways and genomic aberrations associated with prognosis of glioblastoma

Background

A high heterogeneity and activation of multiple oncogenic pathways have been implicated in failure of targeted therapies in glioblastoma (GBM).

Methods

Using The Cancer Genome Atlas data, we identified subtype-specific prognostic core genes by a combined approach of genome-wide Cox regression and Gene Set Enrichment Analysis. The results were validated with 8 combined public datasets containing 608 GBMs. We further examined prognostic chromosome aberrations and mutations.

Results

In classical and mesenchymal subtypes, 2 receptor tyrosine kinases (RTKs) (MET and IGF1R), and the genes in RTK downstream pathways such as phosphatidylinositol-3 kinase (PI3K)/Akt/mammalian target of rapamycin (mTOR), and nuclear factor-kappaB (NF-kB), were commonly detected as prognostic core genes. Classical subtype-specific prognostic core genes included those in cell cycle, DNA repair, and the Janus kinase/signal transducers and activators of transcription (JAK-STAT) pathway. Immune-related genes were enriched in the prognostic genes showing negative promoter cytosine-phosphate-guanine (CpG) methylation/expression correlations. Mesenchymal subtype-specific prognostic genes were those related to mesenchymal cell movement, PI3K/Akt, mitogen-activated protein kinase (MAPK)/extracellular signal-regulated kinase (ERK), Wnt/β-catenin, and Wnt/Ca2+ pathways. In copy number alterations and mutations, 6p loss and TP53 mutation were associated with poor and good survival, respectively, in the classical subtype. In the mesenchymal subtype, patients with PIK3R1 or PCLO mutations showed poor prognosis. In the glioma CpG island methylator phenotype (G-CIMP) subtype, patients harboring 10q loss, 12p gain, or 14q loss exhibited poor survival. Furthermore, 10q loss was significantly associated with the recently recognized G-CIMP subclass showing relatively low CpG methylation and poor prognosis.

Conclusion

These subtype-specific alterations have promising potentials as new prognostic biomarkers and therapeutic targets combined with surrogate markers of GBM subtypes. However, considering the small number of events, the results of copy number alterations and mutations require further validations.

Prognostic Significance of Lymphocyte Infiltration and a Stromal Immunostaining of a Bladder Cancer Associated Diagnostic Panel in Urothelial Carcinoma

We set out to expand on our previous work in which we reported the epithelial expression pattern of a urine-based bladder cancer-associated diagnostic panel (A1AT, ANG, APOE, CA9, IL8, MMP9, MMP10, PAI1, SDC1, and VEGFA). Since many of the analytes in the bladder cancer-associated diagnostic signature were chemokines, cytokines, or secreted proteins, we set out to report the stromal staining pattern of the diagnostic signature as well as CD3⁺ (T-cell) cell and CD68⁺ (macrophage) cell staining in human bladder tumors as a snapshot of the tumor immune landscape. Immunohistochemical staining was performed on 213 tumor specimens and 74 benign controls. Images were digitally captured and quantitated using Aperio (Vista, CA). The expression patterns were correlated with tumor grade, tumor stage, and outcome measures. We noted a positive correlation of seven of the 10 proteins (excluding A1AT and IL8 which had a negative association and VEGFA had no association) in bladder cancer. The overexpression of MMP10 was associated with higher grade disease, while overexpression of MMP10, PAI1, SDC1 and ANG were associated with high stage bladder cancer and CA9 was associated with low stage bladder cancer. Increased tumor infiltration of CD68⁺ cells were associated with higher stage disease. Overall survival was significantly reduced in bladder cancer patients' whose tumors expressed eight or more of the 10 proteins that comprise the bladder cancer diagnostic panel. These findings confirm that the chemokines, cytokines, and secreted proteins in a urine-based diagnostic panel are atypically expressed, not only in the epithelial component of bladder tumors, but also in the stromal component of bladder tumors and portends a worse overall survival. Thus, when assessing immunohistochemical staining, it is important to report staining patterns within the stroma as well as the entire stroma itself.

Impaired dendritic cell functions in lung cancer: a review of recent advances and future perspectives

Lung cancer is the leading cause of cancer mortality worldwide. Dendritic cells (DCs) are the key factors providing protective immunity against lung tumors and clinical trials have proven that DC function is reduced in lung cancer patients. It is evident that the immunoregulatory network may play a key role in the failure of the immune response to terminate tumors. Lung tumors likely employ numerous strategies to suppress DC-based anti-tumor immunity. Here, we summarize the recent advances in our understanding on lung tumor-induced immunosuppression in DCs, which affects the initiation and development of T-cell responses. We also describe which existing measures to restore DC function may be useful for clinical treatment of lung tumors. Furthering our knowledge of how lung cancer cells alter DC function to generate a tumor-supportive environment will be essential in order to guide the design of new immunotherapy strategies for clinical use.

Notch signaling regulates osteosarcoma proliferation and migration through Erk phosphorylation

We used a murine spontaneous osteosarcoma cell line with high metastatic potential, the K7M2 cell line to study the role of Notch signaling in the biological manifestations of osteosarcoma, to understand its underlying mechanism in the regulation of cell proliferation and migration, and to improve patient prognosis in cases of osteosarcoma through the discovery of novel therapeutic targets, First, Notch expression in K7M2 was determined by immunostaining, and the γ-secretase inhibitor N-[N-(3,5-Difluorophenacetyl)-L-alanyl]-S-phenylglycine t-butyl ester (DAPT) was used to inhibit proteolytic cleavage of the Notch intracellular domain (NICD), resulting in the inhibition of Notch activation. By using the Sulforhodamine B assay, colony-forming units assay, Brdu and Ki67 staining, and flow cytometry assays of apoptosis and cell cycle stage, DAPT was found to inhibit K7M2 proliferation in a dose-dependent manner. By using wound healing and transwell migration assays, DAPT was found to inhibit K7M2 migration in a dose-dependent manner as well. By using a combination of micro-Raman spectroscopy and K-means clustering analysis, we found that DAPT inhibit a variety of important cell metabolism-related components in most K7M2 cell structures. Then, DAPT was found to inhibit Notch1ICD expression in a concentration-dependent manner, and this expression was directly correlated with Phospho-Erk1/2 (p-Erk) by using Western blotting. To confirm this finding, we used the Notch signaling ligand Jagged1 to activate the Notch signaling pathway, which in turn up-regulated p-Erk, resulting in increased proliferation and migration of K7M2. Using the Erk pathway inhibitor U0126, we showed that p-Erk was downregulated and the proliferation and migration of K7M2 decreased along with it. Finally, we constructed a K7M2 mouse para-tibial tumor model and lung metastatic model. We found DAPT inhibits p-Erk in vivo, effectively controls tumor growth, reduces angiogenesis, reduces metastasis to the lungs, and improves overall survival. In summary, Notch signaling plays an oncogene role and promotes metastasis in osteosarcoma through p-Erk. DAPT effectively inhibits osteosarcoma proliferation and metastasis in vivo and in vitro by inhibiting Erk phosphorylation. Therefore, the inhibition of Notch activation resulted the down-regulation of phosphorylation of Erk pathway can be used as potential therapeutic targets in clinical treatment to improve osteosarcoma prognosis.

Metastasis is impaired by endothelial-specific Dll4 loss-of-function through inhibition of epithelial-to-mesenchymal transition and reduction of cancer stem cells and circulating tumor cells

Systemic inhibition of Dll4 has been shown to thoroughly reduce cancer metastasis. The exact cause of this effect and whether it is endothelial mediated remains to be clarified. Therefore, we proposed to analyze the impact of endothelial Dll4 loss-of-function on metastasis induction on three early steps of the metastatic process, regulation of epithelial-to-mesenchymal transition (EMT), cancer stem cell (CSC) frequency and circulating tumor cell (CTC) number. For this, Lewis Lung Carcinoma (LLC) cells were used to model mouse tumor metastasis in vivo, by subcutaneous transplantation into endothelial-specific Dll4 loss-of-function mice. We observed that endothelial-specific Dll4 loss-of-function is responsible for the tumor vascular regression that leads to the reduction of tumor burden. It induces an increase in tumoral blood vessel density, but the neovessels are poorly perfused, with increased leakage and reduced perivascular maturation. Unexpectedly, although hypoxia was increased in the tumor, the number and burden of macro-metastasis was significantly reduced. This is likely to be a consequence of the observed reduction in both EMT and CSC numbers caused by the endothelial-specific Dll4 loss-of-function. This multifactorial context may explain the concomitantly observed reduction of the circulating tumor cell count. Furthermore, our results suggest that endothelial Dll4/Notch-function mediates tumor hypoxia-driven increase of EMT. Therefore, it appears that endothelial Dll4 may constitute a promising target to prevent metastasis.

Notch Signaling in the Tumor Microenvironment

The Notch signaling pathway regulates many aspects of cancer biology. Most attention has been given to its role in the transformed cell. However, it is now clear that cancer progression and metastasis depend on the bidirectional interactions between cancer cells and their environment, forming the tumor microenvironment (TME). These interactions are mediated and constantly evolve through paracrine and juxtacrine signaling. In this review, we discuss how Notch signaling takes an important part in regulating the crosstalk between the different compartments of the TME. We also address the consequences of the Notch-TME involvement from a therapeutic perspective.

Cancer Cells Exploit Notch Signaling to Redefine a Supportive Cytokine Milieu

Notch signaling is a well-known key player in the communication between adjacent cells during organ development, when it controls several processes involved in cell differentiation. Notch-mediated communication may occur through the interaction of Notch receptors with ligands on adjacent cells or by a paracrine/endocrine fashion, through soluble molecules that can mediate the communication between cells at distant sites. Dysregulation of Notch pathway causes a number of disorders, including cancer. Notch hyperactivation may be caused by mutations of Notch-related genes, dysregulated upstream pathways, or microenvironment signals. Cancer cells may exploit this aberrant signaling to "educate" the surrounding microenvironment cells toward a pro-tumoral behavior. This may occur because of key cytokines secreted by tumor cells or it may involve the microenvironment through the activation of Notch signaling in stromal cells, an event mediated by a direct cell-to-cell contact and resulting in the increased secretion of several pro-tumorigenic cytokines. Up to now, review articles were mainly focused on Notch contribution in a specific tumor context or immune cell populations. Here, we provide a comprehensive overview on the outcomes of Notch-mediated pathological interactions in different tumor settings and on the molecular and cellular mediators involved in this process. We describe how Notch dysregulation in cancer may alter the cytokine network and its outcomes on tumor progression and antitumor immune response.

Notch Signaling in Myeloid Cells as a Regulator of Tumor Immune Responses

Cancer immunotherapy, which stimulates or augments host immune responses to treat malignancies, is the latest development in the rapidly advancing field of cancer immunology. The basic principles of immunotherapies are either to enhance the functions of specific components of the immune system or to neutralize immune-suppressive signals produced by cancer cells or tumor microenvironment cells. When successful, these approaches translate into long-term survival for patients. However, durable responses are only seen in a subset of patients and so far, only in some cancer types. As for other cancer treatments, resistance to immunotherapy can also develop. Numerous research groups are trying to understand why immunotherapy is effective in some patients but not others and to develop strategies to enhance the effectiveness of immunotherapy. The Notch signaling pathway is involved in many aspects of tumor biology, from angiogenesis to cancer stem cell maintenance to tumor immunity. The role of Notch in the development and modulation of the immune response is complex, involving an intricate crosstalk between antigen-presenting cells, T-cell subpopulations, cancer cells, and other components of the tumor microenvironment. Elegant studies have shown that Notch is a central mediator of tumor-induced T-cell anergy and that activation of Notch1 in CD8 T-cells enhances cancer immunotherapy. Tumor-infiltrating myeloid cells, including myeloid-derived suppressor cells, altered dendritic cells, and tumor-associated macrophages along with regulatory T cells, are major obstacles to the development of successful cancer immunotherapies. In this article, we focus on the roles of Notch signaling in modulating tumor-infiltrating myeloid cells and discuss implications for therapeutic strategies that modulate Notch signaling to enhance cancer immunotherapy.

Bone morphogenetic protein and activin membrane-bound inhibitor overexpression inhibits gastric tumor cell invasion via the transforming growth factor-β/epithelial-mesenchymal transition signaling pathway

Gastric carcinoma is one of the most common human malignancies and remains the second leading cause of cancer-associated mortality worldwide. Gastric carcinoma is characterized by early-stage metastasis and is typically diagnosed in the advanced stage. Previous results have indicated that bone morphogenetic protein and activin membrane-bound inhibitor (BAMBI) overexpression has been demonstrated to inhibit growth and metastasis of gastric cancer cells. However, the molecular mechanisms of the BAMBI-mediated signaling pathway in the progression of gastric cancer are poorly understood. In the present study, to assess whether BAMBI overexpression inhibited the growth and aggressiveness of gastric carcinoma cells through regulation of transforming growth factor (TGF)-β/epithelial-mesenchymal transition (EMT) signaling pathway, the growth and metastasis of gastric carcinoma cells were analyzed following BAMBI overexpression and knockdown in vitro and in vivo. Molecular changes in the TGF-β/EMT signaling pathway were studied in gastric carcinoma cells following BAMBI overexpression and knockdown. DNA methylation of the gene regions encoding the TGF-β/EMT signaling pathway was investigated in gastric carcinoma cells. Tumor growth in tumor-bearing mice was analyzed after mice were subjected to endogenous overexpression of BAMBI. Results indicated that BAMBI overexpression significantly inhibited gastric carcinoma cell growth and aggressiveness, whereas knockdown of BAMBI significantly promoted its growth and metastasis compared with the control (P<0.01). The TGF-β/EMT signaling pathway was downregulated in BAMBI-overexpressed gastric carcinoma cells; however, signaling was promoted following BAMBI knockdown. In addition, it was observed that BAMBI overexpression significantly downregulated the DNA methylation of the gene regions encoding the TGF-β/EMT signaling pathway (P<0.01). Furthermore, RNA interference-mediated BAMBI overexpression also promoted apoptosis in gastric cancer cells and significantly inhibited growth of gastric tumors in murine xenografts (P<0.01). In conclusion, the present findings suggest that BAMBI overexpression inhibited the TGF-β/EMT signaling pathway and suppressed the invasiveness of gastric tumors, suggesting BAMBI may be a potential target for the treatment of gastric carcinoma via regulation of the TGF-β/EMT signaling pathway.

Notch1 signaling in melanoma cells promoted tumor-induced immunosuppression via upregulation of TGF-β1

Background

The receptors of Notch family play an important role in controlling the development, differentiation, and function of multiple cell types. The aim of this study is to investigate the role of Notch1 signaling upon immune suppression induced by melanoma cells.

Methods

Melanoma cell line B16 cells were transfected by lentivirus containing mouse Notch1 gene or Notch1 shRNA to generate B16 cell line that highly or lowly expressed Notch1. Notch1 in anti-tumor immune response was comprehensively appraised in murine B16 melanoma tumor model in immunocompetent and immunodeficient mice. The ratios of CD3⁺CD8⁺ cytotoxic T cells, CD49b⁺NK cells, CD4⁺CD25⁺FoxP3⁺ Tregs and Gr1⁺CD11b⁺ MDSCs in tumor-DLN or spleen were examined by flow cytometry. After the co-culture of B16 cells and CD8⁺ T cells, the effects of Notch1 on the proliferation and activation of T cells were assessed by CCK8 assay, CFSE dilution and Chromium-release test. The mRNA expression and supernatant secretion of immunosuppressive cytokines, TGF-β1, VEGF, IL-10 and IFN-γ were measured by RT-PCR and ELISA, respectively.

Results

Downregulation or overexpression of Notch1 in B16 melanoma cells inhibited or promoted tumor growth in immunocompetent mice, respectively. Notch1 expression in B16 melanoma cells inhibited the infiltration of CD8+ cytotoxic T lymphocytes and NK cells and reduced IFN-γ release in tumor tissue. It could also enhance B16 cell-mediated inhibition of T cell proliferation and activation, and upregulate PD-1 expression on CD4⁺ and CD8⁺ T cells. The percentage of CD4⁺CD25⁺FoxP3⁺ Tregs and Gr1⁺CD11b⁺MDSCs were significantly increased in tumor microenvironment, and all these were attributed to the upregulation of TGF-β1.

Conclusion

These findings suggested that Notch1 signaling in B16 melanoma cells might inhibit antitumor immunity by upregulation of TGF-β1.

Sinusoidal ephrin receptor EPHB4 controls hematopoietic progenitor cell mobilization from bone marrow

Hematopoietic stem and progenitor cells (HSPCs) reside in the bone marrow. Stress signals from cancer and other conditions promote HSPC mobilization into circulation and subsequent homing to tissue microenvironments. HSPC infiltration into tissue microenvironments can influence disease progression; notably, in cancer, HSPCs encourage tumor growth. Here we have uncovered a mutually exclusive distribution of EPHB4 receptors in bone marrow sinusoids and ephrin B2 ligands in hematopoietic cells. We determined that signaling interactions between EPHB4 and ephrin B2 control HSPC mobilization from the bone marrow. In mice, blockade of the EPHB4/ephrin B2 signaling pathway reduced mobilization of HSPCs and other myeloid cells to the circulation. EPHB4/ephrin B2 blockade also reduced HSPC infiltration into tumors as well as tumor progression in murine models of melanoma and mammary cancer. These results identify EPHB4/ephrin B2 signaling as critical to HSPC mobilization from bone marrow and provide a potential strategy for reducing cancer progression by targeting the bone marrow.

XTalkDB: a database of signaling pathway crosstalk

Analysis of signaling pathways and their crosstalk is a cornerstone of systems biology. Thousands of papers have been published on these topics. Surprisingly, there is no database that carefully and explicitly documents crosstalk between specific pairs of signaling pathways. We have developed XTalkDB (http://www.xtalkdb.org) to fill this very important gap. XTalkDB contains curated information for 650 pairs of pathways from over 1600 publications. In addition, the database reports the molecular components (e.g. proteins, hormones, microRNAs) that mediate crosstalk between a pair of pathways and the species and tissue in which the crosstalk was observed. The XTalkDB website provides an easy-to-use interface for scientists to browse crosstalk information by querying one or more pathways or molecules of interest.

Downregulation of CXCL12 in mesenchymal stromal cells by TGFβ promotes breast cancer metastasis

Mesenchymal stromal cells (MSCs) are one of major components of the tumour microenvironment. Recent studies have shown that MSC tumour residence and their close interactions with inflammatory factors are important factors that affect tumour progression. Among tumour-associated inflammatory factors, transforming growth factor β (TGFβ) is regarded as a key determinant of malignancy. By employing a lung metastasis model of a murine breast cancer, we show here that the prometastatic effect of MSCs was dependent on their response to TGFβ. Interestingly, we found that MSC-produced CXCL12, an important chemokine in tumour metastasis, was markedly inhibited by TGFβ. Furthermore, silencing of CXCL12 in TGFβ-unresponsive MSCs restored their ability to promote tumour metastasis. We found that 4T1 breast cancer cells expressed high levels of CXCR7, but not of CXCR4, both of which are CXCL12 receptors. In presence of CXCL12, CXCR7 expression on tumour cells was decreased. Indeed, when CXCR7 was silenced in breast cancer cells, their metastatic ability was inhibited. Therefore, our data demonstrated that sustained expression of CXCL12 by MSCs in the primary tumour site inhibits metastasis through reduction of CXCR7, while, in the presence of TGFβ, this CXCL12 effect of MSCs on tumour cells is relieved. Importantly, elevated CXCR7 and depressed CXCL12 expression levels were prominent features of clinical breast cancer lesions and were related significantly with poor survival. Our findings reveal a novel mechanism of MSC effects on malignant cells through which crosstalk between MSCs and TGFβ regulates tumour metastasis.

TNFα-activated mesenchymal stromal cells promote breast cancer metastasis by recruiting CXCR2+ neutrophils

Mesenchymal stromal cells (MSCs) tend to infiltrate into tumors and form a major component of the tumor microenvironment. Our previous work demonstrated that tumor necrosis factor α (TNFα)-activated MSCs significantly promoted tumor growth. However, the role of TNFα-treated MSCs in tumor metastasis remains elusive. Employing a lung metastasis model of murine breast cancer, we found that TNFα-activated MSCs strikingly enhanced tumor metastasis compared with normal MSCs. We analyzed the chemokine profiles and found that the expression of CCL5, CCR2 and CXCR2 ligands were enhanced in TNFα-activated MSCs. Using genetic or pharmacological strategies to inhibit CCL5 or CCR2, we demonstrated that CCL5 and CCR2 ligands were indispensable in supporting TNFα-activated MSCs to promote tumor metastasis. Analysis of immune cells revealed that CXCR2 ligands (CXCL1, CXCL 2 and CXCL5) expressed by TNFα-activated MSCs efficiently recruited CXCR2⁺ neutrophils into tumor. These neutrophils were responsible for the pro-metastatic effect of MSCs since inhibition of this chemotaxis abolished increased neutrophil recruitment and tumor metastasis. The interaction between neutrophils and tumor cells resulted in markedly elevated metastasis-related genes by tumor cells, including CXCR4, CXCR7, MMP12, MMP13, IL-6 and TGFβ. Importantly, in IL8^high human breast cancer samples, we also observed similar alterations of gene expression. Collectively, our findings demonstrate that TNFα-activated MSCs promote tumor metastasis via CXCR2⁺ neutrophil recruitment.

Anti-Cancer Stem-like Cell Compounds in Clinical Development - An Overview and Critical Appraisal

Cancer stem-like cells (CSC) represent a subpopulation of tumor cells with elevated tumor-initiating potential. Upon differentiation, they replenish the bulk of the tumor cell population. Enhanced tumor-forming capacity, resistance to antitumor drugs, and metastasis-forming potential are the hallmark traits of CSCs. Given these properties, it is not surprising that CSCs have become a therapeutic target of prime interest in drug discovery. In fact, over the last few years, an enormous number of articles describing compounds endowed with anti-CSC activities have been published. In the meanwhile, several of these compounds and also approaches that are not based on the use of pharmacologically active compounds (e.g., vaccination, radiotherapy) have progressed into clinical studies. This article gives an overview of these compounds, proposes a tentative classification, and describes their biological properties and their developmental stage. Eventually, we discuss the optimal clinical setting for these compounds, the need for biomarkers allowing patient selection, the redundancy of CSC signaling pathways and the utility of employing combinations of anti-CSC compounds and the therapeutic limitations posed by the plasticity of CSCs.

PTEN inhibits macrophage polarization from M1 to M2 through CCL2 and VEGF-A reduction and NHERF-1 synergism

PTEN has been studied in several tumor models as a tumor suppressor. In this study, we explored the role of PTEN in the inhibition state of polarized M2 subtype of macrophage in tumor microenvironment (TME) and the underlying mechanisms. To elucidate the potential effect in TME, RAW 264.7 macrophages and 4T1 mouse breast cancer cells were co-cultured to reconstruct tumor microenvironment. After PTEN was down-regulated with shRNA, the expression of CCL2 and VEGF-A, which are definited to promote the formation of M2 macrophages, have a dramatically increase on the level of both gene and protein in co-cultured RAW 264.7 macrophages. And at the same time, NHERF-1 (Na(+)/H(+) exchanger regulating factor-1), another tumor suppressor has a similar tendency to PTEN. Q-PCR and WB results suggested that PTEN and NHERF-1 were consistent with one another no matter at mRNA or protein level when exposed to the same stimulus. Coimmunoprecipitation and immunofluorescence techniques confirmed that PTEN and NHERF-1 were coprecipitated, and NHERF-1 protein expression was properly reduced with rCCL2 effect. In addition, cell immunofluorescence images revealed a profound transferance, in co-cultured RAW 264.7 macrophages, an up-regulation of NHERF-1 could promote the PTEN marked expression on the cell membrane, and this form for the interaction was not negligible. These observations illustrate PTEN with a certain synergy of NHERF-1, as well as down-regulation of CCL2 suppressing M2 macrophage transformation pathway. The results suggest that the activation of PTEN and NHERF-1 may impede the evolution of macrophages beyond the M1 into M2 phenotype in tumor microenvironment.

The Notch intracellular domain integrates signals from Wnt, Hedgehog, TGFβ/BMP and hypoxia pathways

Notch signaling is a highly conserved signal transduction pathway that regulates stem cell maintenance and differentiation in several organ systems. Upon activation, the Notch receptor is proteolytically processed, its intracellular domain (NICD) translocates into the nucleus and activates expression of target genes. Output, strength and duration of the signal are tightly regulated by post-translational modifications. Here we review the intracellular post-translational regulation of Notch that fine-tunes the outcome of the Notch response. We also describe how crosstalk with other conserved signaling pathways like the Wnt, Hedgehog, hypoxia and TGFβ/BMP pathways can affect Notch signaling output. This regulation can happen by regulation of ligand, receptor or transcription factor expression, regulation of protein stability of intracellular key components, usage of the same cofactors or coregulation of the same key target genes. Since carcinogenesis is often dependent on at least two of these pathways, a better understanding of their molecular crosstalk is pivotal.

Immune and Inflammatory Cell Composition of Human Lung Cancer Stroma

Recent studies indicate that the abnormal microenvironment of tumors may play a critical role in carcinogenesis, including lung cancer. We comprehensively assessed the number of stromal cells, especially immune/inflammatory cells, in lung cancer and evaluated their infiltration in cancers of different stages, types and metastatic characteristics potential. Immunohistochemical analysis of lung cancer tissue arrays containing normal and lung cancer sections was performed. This analysis was combined with cyto-/histomorphological assessment and quantification of cells to classify/subclassify tumors accurately and to perform a high throughput analysis of stromal cell composition in different types of lung cancer. In human lung cancer sections we observed a significant elevation/infiltration of total-T lymphocytes (CD3⁺), cytotoxic-T cells (CD8⁺), T-helper cells (CD4⁺), B cells (CD20⁺), macrophages (CD68⁺), mast cells (CD117⁺), mononuclear cells (CD11c⁺), plasma cells, activated-T cells (MUM1⁺), B cells, myeloid cells (PD1⁺) and neutrophilic granulocytes (myeloperoxidase⁺) compared with healthy donor specimens. We observed all of these immune cell markers in different types of lung cancers including squamous cell carcinoma, adenocarcinoma, adenosquamous cell carcinoma, small cell carcinoma, papillary adenocarcinoma, metastatic adenocarcinoma, and bronchioloalveolar carcinoma. The numbers of all tumor-associated immune cells (except MUM1⁺ cells) in stage III cancer specimens was significantly greater than those in stage I samples. We observed substantial stage-dependent immune cell infiltration in human lung tumors suggesting that the tumor microenvironment plays a critical role during lung carcinogenesis. Strategies for therapeutic interference with lung cancer microenvironment should consider the complexity of its immune cell composition.

Cyclic AMP Response Element Binding Protein Mediates Pathological Retinal Neovascularization via Modulating DLL4-NOTCH1 Signaling

Retinal neovascularization is the most common cause of moderate to severe vision loss in all age groups. Despite the use of anti-VEGFA therapies, this complication continues to cause blindness, suggesting a role for additional molecules in retinal neovascularization. Besides VEGFA and VEGFB, hypoxia induced VEGFC expression robustly. Based on this finding, we tested the role of VEGFC in pathological retinal angiogenesis. VEGFC induced proliferation, migration, sprouting and tube formation of human retinal microvascular endothelial cells (HRMVECs) and these responses require CREB-mediated DLL4 expression and NOTCH1 activation. Furthermore, down regulation of VEGFC levels substantially reduced tip cell formation and retinal neovascularization in vivo. In addition, we observed that CREB via modulating the DLL4-NOTCH1 signaling mediates VEGFC-induced tip cell formation and retinal neovascularization. In regard to upstream mechanism, we found that down regulation of p38β levels inhibited hypoxia-induced CREB-DLL4-NOTCH1 activation, tip cell formation, sprouting and retinal neovascularization. Based on these findings, it may be suggested that VEGFC besides its role in the regulation of lymphangiogenesis also plays a role in pathological retinal angiogenesis and this effect depends on p38β and CREB-mediated activation of DLL4-NOTCH1 signaling.

KRT6B, a key mediator of notch signaling in honokiol-induced human hepatoma cell apoptosis

The study was performed to investigate the relationship between KRT6B and Notch1 in the development and progress of hepatocellular carcinoma. The cell viability was detected by CCK8 assay. The cell apoptosis was assessed by annexin V-PI double-labeling staining on a flow cytometry. Expression of genes and proteins were analyzed by real-time PCR and Western blotting, respectively. KRT6B gene was overexpressed using a lentiviral expression vector in a human hepatoma cell line in vitro, in order to explore the mechanism by which the KRT6B promoted cell growth. The results of CCK8 and immunohistochemistry showed that honokiol induced cell death in a concentration- dependent manner, and suppressed human hepatoma cells' proliferation. The mRNA and protein expression of Notch1 was significantly lower in human hepatoma cells with honokiol treatment than that in the untreatment group. Activation of Notch-1 by exogenous transfection of Notch1 intracellular domain increased KRT6B expression in human hepatoma cells. Furthermore, cells were transfected with the wild type pLenti-KRT6B vector, the protein expression of KRT6B and NOTCH1 was significantly upregulated in human hepatoma cells with honokiol treatment. Overexpression of KRT6B promoted hepatoma cells' proliferation and showed anti-apoptosis effect. This study demonstrated that honokiol could induce human hepatoma cells' apoptosis. KRT6B, a key mediator of Notch signaling, was downregulated in honokiol-induced hepatocellular carcinoma apoptosis, suggesting that KRT6B might be a novel therapeutic target for the treatment of hepatocellular carcinoma.

Notch1/3 and p53/p21 are a potential therapeutic target for APS-induced apoptosis in non-small cell lung carcinoma cell lines

OBJECTIVE

Previous studies have shown that Astragalus polysaccharide (APS) can be applied to anti-cancer. However, the mechanism by which APS mediate this effect is unclear. In the present study, APS-mediated NSCLC cell apoptosis was investigated through the regulation of the notch signaling pathway.

METHODS

The cell viability was detected by the CCK8 assay. The mRNA and protein expression of notch1/3 and tumor suppressors were analyzed by RT-PCR and western blotting, respectively.

RESULTS

The mRNA and protein of notch1 and notch3 were significantly up-regulated in tumor tissues as compared to non-tumor adjacent tissues. Treatment of human NSCLC cells with APS induced cell death in a dose-and time-dependent manner by using CCK8 assay. The mRNA and protein expression of notch1 and notch3 were significantly lower in NSCLC cells with APS treatment than that in control group. Moreover, western blotting analysis showed that treatment of H460 cells with APS significantly increased the pro-apoptotic Bax and caspase 8 levels, decreased the anti-apoptotic Bcl-2 level. Furthermore, p53, p21 and p16 were obviously up-regulated by APS treatment in H460 cell.

CONCLUSIONS

This study demonstrated that APS-treated could inhibit proliferation and promote cell apoptosis, at least partially, through suppressing the expression of notch1 and notch3 and up-regulating the expression of tumor suppressors in H460 NSCLC cell lines.

Notch and TGFβ: Functional partners facilitating tumor progression

Cell signals integral to the tumor microenvironment influence cancer progression. Tumor-associated myeloid cells secrete pro-tumorigenic agents including, but not limited to, the potent cytokine transforming growth factor β (TGFβ). We have discovered a network of extrinsic signals including delta-like 4 (Dll4), Notch and TGFβ, linking malignant cells and tumor-infiltrating myeloid cells, a nexus portending a clinically-relevant anticancer treatment.