Hypoxia shifts activity of neuropeptide Y in Ewing sarcoma from growth-inhibitory to growth-promoting effects

Hypoxia-Inducible Factor-Dependent and Independent Mechanisms Underlying Chemoresistance of Hypoxic Cancer Cells

In hypoxic regions of malignant solid tumors, cancer cells acquire resistance to conventional therapies, such as chemotherapy and radiotherapy, causing poor prognosis in patients with cancer. It is widely recognized that some of the key genes behind this are hypoxia-inducible transcription factors, e.g., hypoxia-inducible factor 1 (HIF-1). Since HIF-1 activity is suppressed by two representative 2-oxoglutarate-dependent dioxygenases (2-OGDDs), PHDs (prolyl-4-hydroxylases), and FIH-1 (factor inhibiting hypoxia-inducible factor 1), the inactivation of 2-OGDD has been associated with cancer therapy resistance by the activation of HIF-1. Recent studies have also revealed the importance of hypoxia-responsive mechanisms independent of HIF-1 and its isoforms (collectively, HIFs). In this article, we collate the accumulated knowledge of HIF-1-dependent and independent mechanisms responsible for resistance of hypoxic cancer cells to anticancer drugs and briefly discuss the interplay between hypoxia responses, like EMT and UPR, and chemoresistance. In addition, we introduce a novel HIF-independent mechanism, which is epigenetically mediated by an acetylated histone reader protein, ATAD2, which we recently clarified.

Involvement of neuronal factors in tumor angiogenesis and the shaping of the cancer microenvironment

Emerging evidence suggests that nerves within the tumor microenvironment play a crucial role in regulating angiogenesis. Neurotransmitters and neuropeptides released by nerves can interact with nearby blood vessels and tumor cells, influencing their behavior and modulating the angiogenic response. Moreover, nerve-derived signals may activate signaling pathways that enhance the production of pro-angiogenic factors within the tumor microenvironment, further supporting blood vessel growth around tumors. The intricate network of communication between neural constituents and the vascular system accentuates the potential of therapeutically targeting neural-mediated pathways as an innovative strategy to modulate tumor angiogenesis and, consequently, neoplastic proliferation. Hereby, we review studies that evaluate the precise molecular interplay and the potential clinical ramifications of manipulating neural elements for the purpose of anti-angiogenic therapeutics within the scope of cancer treatment.

Neuropeptide Y and its receptors in prostate cancer: associations with cancer invasiveness and perineural spread

PURPOSE

Neuropeptide Y (NPY) is a pleiotropic peptide, which is involved in many biological mechanisms important in regulation of cell growth and survival. The aim of this study was a comprehensive analysis of the NPY system in prostate pathology.

METHODS

The study was based on immunohistochemical analysis of NPY and its receptors, Y1R, Y2R and Y5R, in tissue samples from benign prostate (BP), primary prostate cancer (PCa) and PCa bone metastases. Tissue microarray (TMA) technique was employed, with analysis of multiple cores from each specimen. Intensity of the immunoreactivity and expression index (EI), as well as distribution of the immunostaining in neoplastic cells and stromal elements were evaluated. Perineural invasion (PNI) and extraprostatic extension (EPE) were areas of special interests. Moreover, a transwell migration assay on the LNCaP PCa cell line was used to assess the chemotactic properties of NPY.

RESULTS

Morphological analysis revealed homogeneous membrane and cytoplasmic pattern of NPY staining in cancer cells and its membrane localization with apical accentuation in BP glands. All elements of the NPY system were upregulated in pre-invasive prostate intraepithelial neoplasia, PCa and metastases. EI and staining intensity of NPY receptors were significantly higher in PCa then in BP with correlation between Y2R and Y5R. The strength of expression of the NPY system was further increased in the PNI and EPE areas. In bone metastases, Y1R and Y5R presented high expression scores.

CONCLUSION

The results of our study suggest that the NPY system is involved in PCa, starting from early stages of its development to disseminated states of the disease, and participates in the invasion of PCa into the auto and paracrine matter.

Neuropeptide Y Peptide Family and Cancer: Antitumor Therapeutic Strategies

Currently available data on the involvement of neuropeptide Y (NPY), peptide YY (PYY), and pancreatic polypeptide (PP) and their receptors (YRs) in cancer are updated. The structure and dynamics of YRs and their intracellular signaling pathways are also studied. The roles played by these peptides in 22 different cancer types are reviewed (e.g., breast cancer, colorectal cancer, Ewing sarcoma, liver cancer, melanoma, neuroblastoma, pancreatic cancer, pheochromocytoma, and prostate cancer). YRs could be used as cancer diagnostic markers and therapeutic targets. A high Y1R expression has been correlated with lymph node metastasis, advanced stages, and perineural invasion; an increased Y5R expression with survival and tumor growth; and a high serum NPY level with relapse, metastasis, and poor survival. YRs mediate tumor cell proliferation, migration, invasion, metastasis, and angiogenesis; YR antagonists block the previous actions and promote the death of cancer cells. NPY favors tumor cell growth, migration, and metastasis and promotes angiogenesis in some tumors (e.g., breast cancer, colorectal cancer, neuroblastoma, pancreatic cancer), whereas in others it exerts an antitumor effect (e.g., cholangiocarcinoma, Ewing sarcoma, liver cancer). PYY or its fragments block tumor cell growth, migration, and invasion in breast, colorectal, esophageal, liver, pancreatic, and prostate cancer. Current data show the peptidergic system's high potential for cancer diagnosis, treatment, and support using Y2R/Y5R antagonists and NPY or PYY agonists as promising antitumor therapeutic strategies. Some important research lines to be developed in the future will also be suggested.

Pharmacological inhibition of neuropeptide Y receptors Y1 and Y5 reduces hypoxic breast cancer migration, proliferation, and signaling

BACKGROUND

Neuropeptide Y (NPY) is an abundant neurohormone in human breast carcinomas that acts on a class of G-protein coupled receptors, of which NPY1R and NPY5R are the most highly expressed. This abundance is exploited for cancer imaging, but there is interest in pharmacological inhibition of the NPYRs to interrogate their functional relevance in breast cancer. We previously reported that NPY1R and NPY5R mRNA abundance is increased by hypoxia inducible factors, which sensitizes these receptors to NPY stimulation leading to enhanced migration and proliferation.

METHODS/RESULTS

Here, we measured the effects of NPY1R and NPY5R antagonists in normoxia and hypoxia on migration, proliferation, invasion, and signaling in 2D and 3D models of breast cancer cell lines MDA-MB-231 and MCF7. Antagonizing NPY1R and/or NPY5R in hypoxia compared to normoxia more greatly reduced MAPK signaling, cell proliferation, cell migration and invasion, and spheroid growth and invasion. The estrogen receptor positive MCF7 cells were significantly less invasive in 3D spheres when NPY5R was specifically inhibited. There were some discrepancies in the responses of each cell line to the isoform-specific antagonists and oxygen availability, therefore further investigations are required to dissect the intricacies of NPYR signaling dynamics. In human breast tumor tissue, we show via immunofluorescence that NPY5R protein levels and colocalization with hypoxia correlate with advanced cancer, and NPY1R protein correlates with adverse outcomes.

CONCLUSIONS

Antagonizing the NPYRs has been implicated as a treatment for a wide variety of diseases. Therefore, these antagonists may aid in the development of novel cancer therapeutics and patient-based treatment plans.

Hypoxia and HIFs in Ewing sarcoma: new perspectives on a multi-facetted relationship

Hypoxia develops during the growth of solid tumors and influences tumoral activity in multiple ways. Low oxygen tension is also present in the bone microenvironment where Ewing sarcoma (EwS) - a highly aggressive pediatric cancer - mainly arises. Hypoxia inducible factor 1 subunit alpha (HIF-1-a) is the principal molecular mediator of the hypoxic response in cancer whereas EWSR1::FLI1 constitutes the oncogenic driver of EwS. Interaction of the two proteins has been shown in EwS. Although a growing body of studies investigated hypoxia and HIFs in EwS, their precise role for EwS pathophysiology is not clarified to date. This review summarizes and structures recent findings demonstrating that hypoxia and HIFs play a role in EwS at multiple levels. We propose to view hypoxia and HIFs as independent protagonists in the story of EwS and give a perspective on their potential clinical relevance as prognostic markers and therapeutic targets in EwS treatment.

Correlation of Transcriptomics and FDG-PET SUVmax Indicates Reciprocal Expression of Stemness-Related Transcription Factor and Neuropeptide Signaling Pathways in Glucose Metabolism of Ewing Sarcoma

BACKGROUND

In Ewing sarcoma (EwS), long-term treatment effects and poor survival rates for relapsed or metastatic cases require individualization of therapy and the discovery of new treatment methods. Tumor glucose metabolic activity varies significantly between patients, and FDG-PET signals have been proposed as prognostic factors. However, the biological basis for the generally elevated but variable glucose metabolism in EwS is not well understood.

METHODS

We retrospectively included 19 EwS samples (17 patients). Affymetrix gene expression was correlated with maximal standardized uptake value (SUVmax) using machine learning, linear regression modelling, and gene set enrichment analyses for functional annotation.

RESULTS

Expression of five genes correlated (MYBL2, ELOVL2, NETO2) or anticorrelated (FAXDC2, PLSCR4) significantly with SUVmax (adjusted p-value ≤ 0.05). Additionally, we identified 23 genes with large SUVmax effect size, which were significantly enriched for "neuropeptide Y receptor activity (GO:0004983)" (adjusted p-value = 0.0007). The expression of the members of this signaling pathway (NPY, NPY1R, NPY5R) anticorrelated with SUVmax. In contrast, three transcription factors associated with maintaining stemness displayed enrichment of their target genes with higher SUVmax: RNF2, E2F family, and TCF3.

CONCLUSION

Our large-scale analysis examined comprehensively the correlations between transcriptomics and tumor glucose utilization. Based on our findings, we hypothesize that stemness may be associated with increased glucose uptake, whereas neuroectodermal differentiation may anticorrelate with glucose uptake.

Hypoxia-activated neuropeptide Y/Y5 receptor/RhoA pathway triggers chromosomal instability and bone metastasis in Ewing sarcoma

Adverse prognosis in Ewing sarcoma (ES) is associated with the presence of metastases, particularly in bone, tumor hypoxia and chromosomal instability (CIN). Yet, a mechanistic link between these factors remains unknown. We demonstrate that in ES, tumor hypoxia selectively exacerbates bone metastasis. This process is triggered by hypoxia-induced stimulation of the neuropeptide Y (NPY)/Y5 receptor (Y5R) pathway, which leads to RhoA over-activation and cytokinesis failure. These mitotic defects result in the formation of polyploid ES cells, the progeny of which exhibit high CIN, an ability to invade and colonize bone, and a resistance to chemotherapy. Blocking Y5R in hypoxic ES tumors prevents polyploidization and bone metastasis. Our findings provide evidence for the role of the hypoxia-inducible NPY/Y5R/RhoA axis in promoting genomic changes and subsequent osseous dissemination in ES, and suggest that targeting this pathway may prevent CIN and disease progression in ES and other cancers rich in NPY and Y5R.

Ewing sarcoma tumour cells frequently metastasize to the bone but the molecular mechanisms governing this process are not well understood. Here, the authors show that neuropeptide Y/Y5 receptor pathway is activated in the hypoxic tumour microenvironment, which results in cytokinesis defects and chromosomal instability, leading to bone invasion.

Expression of hypoxia inducible factor-dependent Neuropeptide Y Receptors Y1 and Y5 sensitizes hypoxic cells to NPY stimulation

Neuropeptide Y (NPY) is an abundant neurohormone in the central and peripheral nervous system involved in feeding behavior, energy balance, nociception, and anxiety. Several NPY receptor (NPYR) subtypes display elevated expression in many cancers including in breast tumors where it is exploited for imaging and diagnosis. Here, we address how hypoxia, a common feature of the tumor microenvironment, influences the expression of the NPYRs. We show that NPY1R and NPY5R mRNA abundance is induced by hypoxia in a hypoxia inducible factor (HIF)-dependent manner in breast cancer cell lines MCF7 and MDA-MB-231. We demonstrate that HIFs bind to several genomic regions upstream of the NPY1R and NPY5R transcription start sites. In addition, the MAPK/ERK pathway is activated more rapidly upon NPY5R stimulation in hypoxic cells compared with normoxic cells. This pathway requires insulin-like growth factor 1 receptor (IGF1R) activity in normoxia, but not in hypoxic cells, which display resistance to the radiosensitizer and IGF1R inhibitor AG1024. Furthermore, hypoxic cells proliferate and migrate more when stimulated with NPY relative to normoxic cells and exhibit a more robust response to a Y5-specific agonist. Our data suggest that hypoxia-induced NPYRs render hypoxic cells more sensitive to NPY stimulation. Considering that breast tissue receives a constant supply of NPY, hypoxic breast tumors are the perfect storm for hyperactive NPYR. This study not only highlights a new relationship between the HIFs and NPYR expression and activity but may inform the use of chemotherapeutics targeting NPYRs and hypoxic cells.

One oncogene, several vulnerabilities: EWS/FLI targeted therapies for Ewing sarcoma

EWS/FLI is the defining mutation of Ewing sarcoma. This oncogene drives malignant transformation and progression and occurs in a genetic background characterized by few other recurrent cooperating mutations. In addition, the tumor is absolutely dependent on the continued expression of EWS/FLI to maintain the malignant phenotype. However, EWS/FLI is a transcription factor and therefore a challenging drug target. The difficulty of directly targeting EWS/FLI stems from unique features of this fusion protein as well as the network of interacting proteins required to execute the transcriptional program. This network includes interacting proteins as well as upstream and downstream effectors that together reprogram the epigenome and transcriptome. While the vast number of proteins involved in this process challenge the development of a highly specific inhibitors, they also yield numerous therapeutic opportunities. In this report, we will review how this vast EWS-FLI transcriptional network has been exploited over the last two decades to identify compounds that directly target EWS/FLI and/or associated vulnerabilities.

The hypoxia response and nutritional peptides

Hypoxia controls metabolism at several levels, e.g., via mitochondrial ATP production, glucose uptake and glycolysis. Hence it is likely that hypoxia also affects the action and/or production of many peptide hormones linked to food intake and appetite control. Many of those are produced in the gastrointestinal tract, endocrine pancreas, adipose tissue, and selective areas in the brain which modulate and concert their actions. However, the complexity of the hypoxia response and the links to peptides/hormones involved in food intake and appetite control in the different organs are not well known. This review summarizes the role of the hypoxia response and its effects on major peptides linked to appetite regulation, nutrition and metabolism.

Neuropeptide Y/Y5 Receptor Pathway Stimulates Neuroblastoma Cell Motility Through RhoA Activation

Neuropeptide Y (NPY) has been implicated in the regulation of cellular motility under various physiological and pathological conditions, including cancer dissemination. Yet, the exact signaling pathways leading to these effects remain unknown. In a pediatric malignancy, neuroblastoma (NB), high NPY release from tumor tissue associates with metastatic disease. Here, we have shown that NPY stimulates NB cell motility and invasiveness and acts as a chemotactic factor for NB cells. We have also identified the Y5 receptor (Y5R) as the main NPY receptor mediating these actions. In NB tissues and cell cultures, Y5R is highly expressed in migratory cells and accumulates in regions of high RhoA activity and dynamic cytoskeleton remodeling. Y5R stimulation activates RhoA and results in Y5R/RhoA-GTP interactions, as shown by pull-down and proximity ligation assays, respectively. This is the first demonstration of the role for the NPY/Y5R axis in RhoA activation and the subsequent cytoskeleton remodeling facilitating cell movement. These findings implicate Y5R as a target in anti-metastatic therapies for NB and other cancers expressing this receptor.

Neuropeptide Y nerve paracrine regulation of prostate cancer oncogenesis and therapy resistance

BACKGROUND

Nerves are key factors in prostate cancer (PCa) progression. Here, we propose that neuropeptide Y (NPY) nerves are key regulators of cancer-nerve interaction.

METHODS

We used in vitro models for NPY inhibition studies and subsequent metabolomics, apoptotic and migration assays, and nuclear transcription factor-κB (NF-κB) translocation studies. Human naïve and radiated PCa tissues were used for NPY nerve density biomarker studies. Tissues derived from a Botox denervation clinical trial were used to corroborate metabolomic changes in humans.

RESULTS

Cancer cells increase NPY positive nerves in vitro and in preneoplastic human tissues. NPY-specific inhibition resulted in increased cancer apoptosis, decreased motility, and energetic metabolic pathway changes. A comparison of metabolomic response in NPY-inhibited cells with the transcriptome response in human PCa patients treated with Botox showed shared 13 pathways, including the tricarboxylic acid cycle. We identified that NF-κB is a potential NPY downstream mediator. Using in vitro models and tissues derived from a previous human chemical denervation study, we show that Botox specifically, but not exclusively, inhibits NPY in cancer. Quantification of NPY nerves is independently predictive of PCa-specific death. Finally, NPY nerves might be involved in radiation therapy (RT) resistance, as radiation-induced apoptosis is reduced when PCa cells are cocultured with dorsal root ganglia/nerves and NPY positive nerves are increased in prostates of patients that failed RT.

CONCLUSION

These data suggest that targeting the NPY neural microenvironment may represent a therapeutic approach for the treatment of PCa and resistance through the regulation of multiple oncogenic mechanisms.

Hypoxia Regulates DPP4 Expression, Proteolytic Inactivation, and Shedding from Ovarian Cancer Cells

The treatment of ovarian cancer has not significantly changed in decades and it remains one of the most lethal malignancies in women. The serine protease dipeptidyl peptidase 4 (DPP4) plays key roles in metabolism and immunity, and its expression has been associated with either pro- or anti-tumour effects in multiple tumour types. In this study, we provide the first evidence that DPP4 expression and enzyme activity are uncoupled under hypoxic conditions in ovarian cancer cells. Whilst we identified strong up-regulation of DPP4 mRNA expression under hypoxic growth, the specific activity of secreted DPP4 was paradoxically decreased. Further investigation revealed matrix metalloproteinases (MMP)-dependent inactivation and proteolytic shedding of DPP4 from the cell surface, mediated by at least MMP10 and MMP13. This is the first report of uncoupled DPP4 expression and activity in ovarian cancer cells, and suggests a previously unrecognized, cell- and tissue-type-dependent mechanism for the regulation of DPP4 in solid tumours. Further studies are necessary to identify the functional consequences of DPP4 processing and its potential prognostic or therapeutic value.

Murine neuroblastoma cell lines developed by conditional reprogramming preserve heterogeneous phenotypes observed in vivo

Neuroblastoma (NB) is a pediatric tumor of the peripheral nervous system. Treatment of the disease represents an unsolved clinical problem, as survival of patients with aggressive form of NB remains below 50%. Despite recent identification of numerous potential therapeutic targets, clinical trials validating them are challenging due to the rarity of the disease and its high patient-to-patient heterogeneity. Hence, there is a need for the accurate preclinical models that would allow testing novel therapeutic approaches and prioritizing the clinical studies, preferentially in personalized way. Here, we propose using conditional reprogramming (CR) technology for rapid development of primary NB cell cultures that could become a new model for such tests. This newly established method allowed for indefinite propagation of normal and tumor cells of epithelial origin in an undifferentiated state by their culture in the presence of Rho-associated kinase (ROCK) inhibitor, Y-27632, and irradiated mouse feeder cells. Using a modification of this approach, we isolated cell lines from tumors arising in the TH-MYCN murine transgenic model of NB (CR-NB). The cells were positive for neuronal markers, including Phox2B and peripherin and consisted of two distinct populations: mesenchymal and adrenergic expressing corresponding markers of their specific lineage. This heterogeneity of the CR-NB cells mimicked the different tumor cell phenotypes in TH-MYCN tumor tissues. The CR-NB cells preserved anchorage-independent growth capability and were successfully passaged, frozen and biobanked. Further studies are required to determine the utility of this method for isolation of human NB cultures, which can become a novel model for basic, translational, and clinical research, including individualized drug testing.

Neuropeptide Y receptor interactions regulate its mitogenic activity

Neuropeptide Y (NPY) is a multifunctional neurotransmitter acting via G protein-coupled receptors - Y1R, Y2R and Y5R. NPY activities, such as its proliferative effects, are mediated by multiple receptors, which have the ability to dimerize. However, the role of this receptor interplay in NPY functions remains unclear. The goal of the current study was to identify NPY receptor interactions, focusing on the ligand-binding fraction, and determine their impact on the mitogenic activity of the peptide. Y1R, Y2R and Y5R expressed in CHO-K1 cells formed homodimers detectable on the cell surface by cross-linking. Moreover, Y1R and Y5R heterodimerized, while no Y2R/Y5R heterodimers were detected. Nevertheless, Y5R failed to block internalization of its cognate receptor in both Y1R/Y5R and Y2R/Y5R transfectants, indicating Y5R transactivation upon stimulation of the co-expressed receptor. These receptor interactions correlated with an augmented mitogenic response to NPY. In Y1R/Y5R and Y2R/Y5R transfectants, the proliferative response started at picomolar NPY concentrations, while nanomolar concentrations were needed to trigger proliferation in cells transfected with single receptors. Thus, our data identify direct and indirect heterotypic NPY receptor interactions as the mechanism amplifying its activity. Understanding these processes is crucial for the design of treatments targeting the NPY system.

Established Models and New Paradigms for Hypoxia-Driven Cancer-Associated Bone Disease

The five-year survival rate for primary bone cancers is ~ 70% while almost all cases of secondary metastatic bone cancer are terminal. Hypoxia, the deficiency of oxygen which occurs as the rate of tumour growth exceeds the supply of vascularisation, is a key promoter of tumour progression. Hypoxia-driven effects in the primary tumour are wide ranging including changes in gene expression, dysregulation of signalling pathways, resistance to chemotherapy, neovascularisation, increased tumour cell proliferation and migration. Paget's seed and soil theory states that for a metastasising tumour cell 'the seed' it requires the correct microenvironment 'soil' to colonise. Why and how metastasising tumour cells colonise the bone is a complex and intriguing problem. However, once present tumour cells are able to disrupt bone homeostasis through increasing osteoclast activity and downregulating osteoblast function. Osteoclast resorption releases growth factors from the bone matrix that subsequently contribute to the proliferation of invasive tumour cells creating the vicious cycle of bone loss and metastatic cancer progression. Recently, we have shown that hypoxia increases expression and release of lysyl oxidase (LOX) from primary mammary tumours, which in turn disrupts bone homeostasis to favour osteolytic degradation to create pre-metastatic niches in the bone microenvironment. We also demonstrated how treatment with bisphosphonates could block this cancer-induced bone remodelling and reduce secondary bone metastases. This review describes the roles of hypoxia in primary tumour progression to metastasis, with a focus on key signalling pathways and treatment options to reduce patient morbidity and increase survival.

Dipeptidyl Peptidase-IV Inhibition for the Treatment of Cardiovascular Disease - Recent Insights Focusing on Angiogenesis and Neovascularization

Dipeptidyl peptidase IV (DPP-IV) is a complex enzyme that acts as a membrane-anchored cell surface exopeptidase and transmits intracellular signals through a small intracellular tail. DPP-IV exists in human blood in a soluble form, and truncates a large number of peptide hormones, chemokines, cytokines, and growth factors in vitro and in vivo. DPP-IV has gained considerable interest as a therapeutic target, and a variety of DPP-IV inhibitors that prolong the insulinotropic effects of glucagon-like peptide-1 (GLP-1) are widely used in clinical settings as antidiabetic drugs. Indeed, DPP-IV is upregulated in proinflammatory states, including obesity and cardiovascular disease with and without diabetes mellitus. Consistent with this maladaptive role, DPP-IV inhibitors seem to exert a protective role in cardiovascular disease. In addition to their GLP-1-dependent vascular protective actions, DPP-IV inhibitors exhibit GLP-1-independent beneficial effects on angiogenesis/neovascularization via several signaling pathways (e.g., stromal cell-derived factor-1α/C-X-C chemokine receptor type-4, vascular endothelial growth factor-A/endothelial nitric oxide synthase, etc.). This review focuses on recent findings in this field, highlighting the role of DPP-IV in therapeutic angiogenesis/neovascularization in ischemic heart disease and peripheral artery disease.

Neuropeptide Y (NPY) promotes inflammation-induced tumorigenesis by enhancing epithelial cell proliferation

We have demonstrated that neuropeptide Y (NPY), abundantly produced by enteric neurons, is an important regulator of intestinal inflammation. However, the role of NPY in the progression of chronic inflammation to tumorigenesis is unknown. We investigated whether NPY could modulate epithelial cell proliferation and apoptosis, and thus regulate tumorigenesis. Repeated cycles of dextran sodium sulfate (DSS) were used to model inflammation-induced tumorigenesis in wild-type (WT) and NPY knockout (NPY^-/-) mice. Intestinal epithelial cell lines (T84) were used to assess the effects of NPY (0.1 µM) on epithelial proliferation and apoptosis in vitro. DSS-WT mice exhibited enhanced intestinal inflammation, polyp size, and polyp number (7.5 ± 0.8) compared with DSS-NPY^-/- mice (4 ± 0.5, P < 0.01). Accordingly, DSS-WT mice also showed increased colonic epithelial proliferation (PCNA, Ki67) and reduced apoptosis (TUNEL) compared with DSS-NPY^-/- mice. The apoptosis regulating microRNA, miR-375, was significantly downregulated in the colon of DSS-WT (2-fold, P < 0.01) compared with DSS-NPY^-/--mice. In vitro studies indicated that NPY promotes cell proliferation (increase in PCNA and β-catenin, P < 0.05) via phosphatidyl-inositol-3-kinase (PI3-K)-β-catenin signaling, suppressed miR-375 expression, and reduced apoptosis (increase in phospho-Bad). NPY-treated cells also displayed increased c-Myc and cyclin D1, and reduction in p21 (P < 0.05). Addition of miR-375 inhibitor to cells already treated with NPY did not further enhance the effects induced by NPY alone. Our findings demonstrate a novel regulation of inflammation-induced tumorigenesis by NPY-epithelial cross talk as mediated by activation of PI3-K signaling and downregulation of miR-375.

NEW & NOTEWORTHY

Our work exemplifies a novel role of neuropeptide Y (NPY) in regulating inflammation-induced tumorigenesis via two modalities: first by enhanced proliferation (PI3-K/pAkt), and second by downregulation of microRNA-375 (miR-375)-dependent apoptosis in intestinal epithelial cells. Our data establish the existence of a microRNA-mediated cross talk between enteric neurons producing NPY and intestinal epithelial cells, and the potential of neuropeptide-regulated miRNAs as potential therapeutic molecules for the management of inflammation-associated tumors in the gut.

In Vivo Model for Testing Effect of Hypoxia on Tumor Metastasis

Hypoxia has been implicated in the metastasis of Ewing sarcoma (ES) by clinical observations and in vitro data, yet direct evidence for its pro-metastatic effect is lacking and the exact mechanisms of its action are unclear. Here, we report an animal model that allows for direct testing of the effects of tumor hypoxia on ES dissemination and investigation into the underlying pathways involved. This approach combines two well-established experimental strategies, orthotopic xenografting of ES cells and femoral artery ligation (FAL), which induces hindlimb ischemia. Human ES cells were injected into the gastrocnemius muscles of SCID/beige mice and the primary tumors were allowed to grow to a size of 250 mm³. At this stage either the tumors were excised (control group) or the animals were subjected to FAL to create tumor hypoxia, followed by tumor excision 3 days later. The efficiency of FAL was confirmed by a significant increase in binding of hypoxyprobe-1 in the tumor tissue, severe tumor necrosis and complete inhibition of primary tumor growth. Importantly, despite these direct effects of ischemia, an enhanced dissemination of tumor cells from the hypoxic tumors was observed. This experimental strategy enables comparative analysis of the metastatic properties of primary tumors of the same size, yet significantly different levels of hypoxia. It also provides a new platform to further assess the mechanistic basis for the hypoxia-induced alterations that occur during metastatic tumor progression in vivo. In addition, while this model was established using ES cells, we anticipate that this experimental strategy can be used to test the effect of hypoxia in other sarcomas, as well as tumors orthotopically implanted in sites with a well-defined blood supply route.

Neuropeptide Y as a Biomarker and Therapeutic Target for Neuroblastoma

Neuroblastoma (NB) is a pediatric malignant neoplasm of sympathoadrenal origin. Challenges in its management include stratification of this heterogeneous disease and a lack of both adequate treatments for high-risk patients and noninvasive biomarkers of disease progression. Our previous studies have identified neuropeptide Y (NPY), a sympathetic neurotransmitter expressed in NB, as a potential therapeutic target for these tumors by virtue of its Y5 receptor (Y5R)-mediated chemoresistance and Y2 receptor (Y2R)-mediated proliferative and angiogenic activities. The goal of this study was to determine the clinical relevance and utility of these findings. Expression of NPY and its receptors was evaluated in corresponding samples of tumor RNA, tissues, and sera from 87 patients with neuroblastic tumors and in tumor tissues from the TH-MYCN NB mouse model. Elevated serum NPY levels correlated with an adverse clinical presentation, poor survival, metastasis, and relapse, whereas strong Y5R immunoreactivity was a marker of angioinvasive tumor cells. In NB tissues from TH-MYCN mice, high immunoreactivity of both NPY and Y5R marked angioinvasive NB cells. Y2R was uniformly expressed in undifferentiated tumor cells, which supports its previously reported role in NB cell proliferation. Our findings validate NPY as a therapeutic target for advanced NB and implicate the NPY/Y5R axis in disease dissemination. The correlation between elevated systemic NPY and NB progression identifies serum NPY as a novel NB biomarker.

Suppression of CD26 inhibits growth and metastasis of pancreatic cancer

CD26/DPPIV is a glycosylated transmembrane type II protein and has a multitude of biological functions, while its impact on the malignant phenotypes of cancer cells has not been fully understood. This study aimed to investigate the effect of CD26 on growth and metastasis of pancreatic cancer cells in vitro and in vivo. We found in this study that CD26 expression was higher in cell lines that derived from the metastatic sites than those from the primary tumor sites. In specimens of pancreatic cancer patients, CD26 expression was higher in cancerous tissues than in paired normal tissues. In in vitro experiments, knockdown of CD26 expression inhibited cell growth, migration, invasion, colony formation, and increased cell apoptosis of pancreatic cancer cells. Knockdown of CD26 also decreased tumor growth and liver metastasis in vivo by using xenograft animal models. Suppression of CD26 could inhibit expression of epithelial-mesenchymal transition (EMT) regulatory genes. Our results indicated that CD26 may represent a new therapeutic target for pancreatic cancer.

Identification of Mithramycin Analogues with Improved Targeting of the EWS-FLI1 Transcription Factor

PURPOSE

The goal of this study was to identify second-generation mithramycin analogues that better target the EWS-FLI1 transcription factor for Ewing sarcoma. We previously established mithramycin as an EWS-FLI1 inhibitor, but the compound's toxicity prevented its use at effective concentrations in patients.

EXPERIMENTAL DESIGN

We screened a panel of mithralogs to establish their ability to inhibit EWS-FLI1 in Ewing sarcoma. We compared the IC50 with the MTD established in mice to determine the relationship between efficacy and toxicity. We confirmed the suppression of EWS-FLI1 at the promoter, mRNA, gene signature, and protein levels. We established an improved therapeutic window by using time-lapse microscopy to model the effects on cellular proliferation in Ewing sarcoma cells relative to HepG2 control cells. Finally, we established an improved therapeutic window using a xenograft model of Ewing sarcoma.

RESULTS

EC-8105 was found to be the most potent analogue and was able to suppress EWS-FLI1 activity at concentrations nontoxic to other cell types. EC-8042 was substantially less toxic than mithramycin in multiple species but maintained suppression of EWS-FLI1 at similar concentrations. Both compounds markedly suppressed Ewing sarcoma xenograft growth and inhibited EWS-FLI1 in vivo

CONCLUSIONS

These results provide a basis for the continued development of EC-8042 and EC-8105 as EWS-FLI1 inhibitors for the clinic. Clin Cancer Res; 22(16); 4105-18. ©2016 AACR.

Regulation of Dipeptidyl Peptidase IV in the Post-stroke Rat Brain and In Vitro Ischemia: Implications for Chemokine-Mediated Neural Progenitor Cell Migration and Angiogenesis

Cerebral ischemia evokes abnormal release of proteases in the brain microenvironment that spatiotemporally impact angio-neurogenesis. Dipeptidyl peptidase IV (DPPIV), a cell surface and secreted protease, has been implicated in extracellular matrix remodeling by regulating cell adhesion, migration, and angiogenesis through modifying the functions of the major chemokine stromal-derived factor, SDF1. To elucidate the possible association of DPPIV in ischemic brain, we examined the expression of DPPIV in the post-stroke rat brain and under in vitro ischemia by oxygen glucose deprivation (OGD). We further investigated the effects of DPPIV on SDF1 mediated in vitro chemotactic and angiogenic functions. DPPIV protein and mRNA levels were significantly upregulated during repair phase in the ischemic cortex of the rat brain, specifically in neurons, astrocytes, and endothelial cells. In vitro exposure of Neuro-2a neuronal cells and rat brain endothelial cells to OGD resulted in upregulation of DPPIV. In vitro functional analysis showed that DPPIV decreases the SDF1-mediated angiogenic potential of rat brain endothelial cells and inhibits the migration of Neuro-2a and neural progenitor cells. Western blot analyses revealed decreased levels of phosphorylated ERK1/2 and AKT in the presence of DPPIV. DPPIV inhibitor restored the effects of SDF1. Proteome profile array screening further revealed that DPPIV decreases matrix metalloproteinase-9, a key downstream effector of ERK-AKT signaling pathways. Overall, delayed induction of DPPIV in response to ischemia/reperfusion suggests that DPPIV may play an important role in endogenous brain tissue remodeling and repair processes. This may be mediated through modulation of SDF1-mediated cell migration and angiogenesis.

Neuropeptide Y (NPY) in tumor growth and progression: Lessons learned from pediatric oncology

Neuropeptide Y (NPY) is a sympathetic neurotransmitter with pleiotropic actions, many of which are highly relevant to tumor biology. Consequently, the peptide has been implicated as a factor regulating the growth of a variety of tumors. Among them, two pediatric malignancies with high endogenous NPY synthesis and release - neuroblastoma and Ewing sarcoma - became excellent models to investigate the role of NPY in tumor growth and progression. The stimulatory effect on tumor cell proliferation, survival, and migration, as well as angiogenesis in these tumors, is mediated by two NPY receptors, Y2R and Y5R, which are expressed in either a constitutive or inducible manner. Of particular importance are interactions of the NPY system with the tumor microenvironment, as hypoxic conditions commonly occurring in solid tumors strongly activate the NPY/Y2R/Y5R axis. This activation is triggered by hypoxia-induced up-regulation of Y2R/Y5R expression and stimulation of dipeptidyl peptidase IV (DPPIV), which converts NPY to a selective Y2R/Y5R agonist, NPY(3-36). While previous studies focused mainly on the effects of NPY on tumor growth and vascularization, they also provided insight into the potential role of the peptide in tumor progression into a metastatic and chemoresistant phenotype. This review summarizes our current knowledge of the role of NPY in neuroblastoma and Ewing sarcoma and its interactions with the tumor microenvironment in the context of findings in other malignancies, as well as discusses future directions and potential clinical implications of these discoveries.

High neuropeptide Y release associates with Ewing sarcoma bone dissemination - in vivo model of site-specific metastases

Ewing sarcoma (ES) develops in bones or soft tissues of children and adolescents. The presence of bone metastases is one of the most adverse prognostic factors, yet the mechanisms governing their formation remain unclear. As a transcriptional target of EWS-FLI1, the fusion protein driving ES transformation, neuropeptide Y (NPY) is highly expressed and released from ES tumors. Hypoxia up-regulates NPY and activates its pro-metastatic functions. To test the impact of NPY on ES metastatic pattern, ES cell lines, SK-ES1 and TC71, with high and low peptide release, respectively, were used in an orthotopic xenograft model. ES cells were injected into gastrocnemius muscles of SCID/beige mice, the primary tumors excised, and mice monitored for the presence of metastases. SK-ES1 xenografts resulted in thoracic extra-osseous metastases (67%) and dissemination to bone (50%) and brain (25%), while TC71 tumors metastasized to the lungs (70%). Bone dissemination in SK-ES1 xenografts associated with increased NPY expression in bone metastases and its accumulation in bone invasion areas. The genetic silencing of NPY in SK-ES1 cells reduced bone degradation. Our study supports the role for NPY in ES bone invasion and provides new models for identifying pathways driving ES metastases to specific niches and testing anti-metastatic therapeutics.

Neuropeptide Y is a physiological substrate of fibroblast activation protein: Enzyme kinetics in blood plasma and expression of Y2R and Y5R in human liver cirrhosis and hepatocellular carcinoma

Fibroblast activation protein (FAP) is a dipeptidyl peptidase (DPP) and endopeptidase that is weakly expressed in normal adult human tissues but is greatly up-regulated in activated mesenchymal cells of tumors and chronically injured tissue. The identities and locations of target substrates of FAP are poorly defined, in contrast to the related protease DPP4. This study is the first to characterize the physiological substrate repertoire of the DPP activity of endogenous FAP present in plasma. Four substrates, neuropeptide Y (NPY), peptide YY, B-type natriuretic peptide and substance P, were analyzed by mass spectrometry following proteolysis in human or mouse plasma, and by in vivo localization in human liver tissues with cirrhosis and hepatocellular carcinoma (HCC). NPY was the most efficiently cleaved substrate of both human and mouse FAP, whereas all four peptides were efficiently cleaved by endogenous DPP4, indicating that the in vivo degradomes of FAP and DPP4 differ. All detectable DPP-specific proteolysis and C-terminal processing of these neuropeptides was attributable to FAP and DPP4, and plasma kallikrein, respectively, highlighting their combined physiological significance in the regulation of these neuropeptides. In cirrhotic liver and HCC, NPY and its receptor Y2R, but not Y5R, were increased in hepatocytes near the parenchymal-stromal interface where there is an opportunity to interact with FAP expressed on nearby activated mesenchymal cells in the stroma. These novel findings provide insights into the substrate specificity of FAP, which differs greatly from DPP4, and reveal a potential function for FAP in neuropeptide regulation within liver and cancer biology.

Modeling the initiation of Ewing sarcoma tumorigenesis in differentiating human embryonic stem cells

Oncogenic transformation in Ewing sarcoma tumors is driven by the fusion oncogene EWS-FLI1. However, despite the well-established role of EWS-FLI1 in tumor initiation, the development of models of Ewing sarcoma in human cells with defined genetic elements has been challenging. Here, we report a novel approach to model the initiation of Ewing sarcoma tumorigenesis that exploits the developmental and pluripotent potential of human embryonic stem cells. The inducible expression of EWS-FLI1 in embryoid bodies, or collections of differentiating stem cells, generates cells with properties of Ewing sarcoma tumors, including characteristics of transformation. These cell lines exhibit anchorage-independent growth, a lack of contact inhibition and a strong Ewing sarcoma gene expression signature. Furthermore, these cells also demonstrate a requirement for the persistent expression of EWS-FLI1 for cell survival and growth, which is a hallmark Ewing sarcoma tumors.

CD26 a cancer stem cell marker and therapeutic target

Cancer stem cells (CSCs) comprise a tumor subpopulation responsible for tumor maintenance, resistance to chemotherapy, recurrence and metastasis. The identification of this cell group is very important, but there is still no consensus on its characterization. Several CSC markers have been described, like CD133, CD24, CD44 and ALDH1, but more research to identify new markers to facilitate the identification of CSC in a heterogeneous tumoral mass is required. Thus, this article describes the CD26 expression as a CSC marker and the role that it plays in different types of cancer. CD26 expression correlates with some characteristics of CSCs, like the formation of spheres in vitro, formation of new tumors, and resistance to chemotherapy. CD26 is therefore suggested as an auxiliary marker for CSC in different types of cancer, and as a potential therapeutic target.

WT1 regulates angiogenesis in Ewing Sarcoma

Angiogenesis is required for tumor growth. WT1, a protein that affects both mRNA transcription and splicing, has recently been shown to regulate expression of vascular endothelial growth factor (VEGF), one of the major mediators of angiogenesis. In the present study, we tested the hypothesis that WT1 is a key regulator of tumor angiogenesis in Ewing sarcoma. We expressed exogenous WT1 in the WT1-null Ewing sarcoma cell line, SK-ES-1, and we suppressed WT1 expression using shRNA in the WT1-positive Ewing sarcoma cell line, MHH-ES. Suppression of WT1 in MHH-ES cells impairs angiogenesis, while expression of WT1 in SK-ES-1 cells causes increased angiogenesis. Different WT1 isoforms result in vessels with distinct morphologies, and this correlates with preferential upregulation of particular VEGF isoforms. WT1-expressing tumors show increased expression of pro-angiogenic molecules such as VEGF, MMP9, Ang-1, and Tie-2, supporting the hypothesis that WT1 is a global regulator of angiogenesis. We also demonstrate that WT1 regulates the expression of a panel of pro-angiogenic molecules in Ewing sarcoma cell lines. Finally, we found that WT1 expression is correlated with VEGF expression, MMP9 expression, and microvessel density in samples of primary Ewing sarcoma. Thus, our results demonstrate that WT1 expression directly regulates tumor angiogenesis by controlling the expression of a panel of pro-angiogenic genes.

Structure-function based molecular relationships in Ewing's sarcoma

Ewing's Sarcoma Oncogene (ews) on chromosome 22q12 is encoding a ubiquitously expressed RNA-binding protein (EWS) with unknown function that is target of tumor-specific chromosomal translocations in Ewing's sarcoma family of tumors. A model of transcription complex was proposed in which the heterodimer Rpb4/7 binds to EAD, connecting it to Core RNA Pol II. The DNA-binding domain, provided by EFP, is bound to the promoter. Rpb4/7 binds RNA, stabilizing the transcription complex. The complex Rpb4/7 can stabilize the preinitiation complexes by converting the conformation of RNA Pol II. EWS may change its conformation, so that NTD becomes accessible. Two different mechanisms of interaction between EWS and RNA Pol II are proposed: (I) an intermolecular EWS-EWS interaction between two molecules, pushing conformation from “closed” to “open” state, or (II) an intramolecular interaction inside the molecule of EWS, pushing conformation of the molecule from “closed” to “open” state. The modified forms of EWS may interact with Pol II subunits hsRpb5 and hsRpb7. The EWS and EFPs binding partners are described schematically in a model, an attempt to link the transcription with the splicing. The proposed model helps to understand the functional molecular interactions in cancer, to find new partners and ways to treat cancer.

Systemic levels of neuropeptide Y and dipeptidyl peptidase activity in patients with Ewing sarcoma--associations with tumor phenotype and survival

BACKGROUND

Ewing sarcoma (ES) is driven by fusion of the Ewing sarcoma breakpoint region 1 gene (EWSR1) with an E26 transformation-specific (ETS) transcription factor (EWS-ETS), most often the Friend leukemia integration 1 transcription factor (FLI1). Neuropeptide Y (NPY) is an EWS-FLI1 transcriptional target; it is highly expressed in ES and exerts opposing effects, ranging from ES cell death to angiogenesis and cancer stem cell propagation. The functions of NPY are regulated by dipeptidyl peptidase IV (DPPIV), a hypoxia-inducible enzyme that cleaves the peptide and activates its growth-promoting actions. The objective of this study was to determine the clinically relevant functions of NPY by identifying the associations between patients' ES phenotype and their NPY concentrations and DPP activity.

METHODS

NPY concentrations and DPP activity were measured in serum samples from 223 patients with localized ES and 9 patients with metastatic ES provided by the Children's Oncology Group.

RESULTS

Serum NPY levels were elevated in ES patients compared with the levels in a healthy control group and an osteosarcoma patient population, and the elevated levels were independent of EWS-ETS translocation type. Significantly higher NPY concentrations were detected in patients with ES who had tumors of pelvic and bone origin. A similar trend was observed in patients with metastatic ES. There was no effect of NPY on survival in patients with localized ES. DPP activity in sera from patients with ES did not differ significantly from that in healthy controls and patients with osteosarcoma. However, high DPP levels were associated with improved survival.

CONCLUSIONS

Systemic NPY levels are elevated in patients with ES, and these high levels are associated with unfavorable disease features. DPPIV in serum samples from patients with ES is derived from nontumor sources, and its high activity is correlated with improved survival.

Neuropeptide Y receptor Y5 as an inducible pro-survival factor in neuroblastoma: implications for tumor chemoresistance

Neuroblastoma (NB) is a pediatric tumor of neural crest origin with heterogeneous phenotypes. While low stage tumors carry a favorable prognosis, over 50% of high risk NB relapses after treatment with a fatal outcome. Thus, developing therapies targeting refractory NB remains an unsolved clinical problem. Brain-derived neurotrophic factor (BDNF) and its TrkB receptor are known to protect NB cells from chemotherapy-induced cell death, while neuropeptide Y (NPY), acting via its Y2 receptor (Y2R), is an autocrine proliferative and angiogenic factor crucial for maintaining NB tumor growth. Here, we show that in NB cells, BDNF stimulates the synthesis of NPY and induces expression of another one of its receptors, Y5R. In human NB tissues, the expression of NPY and Y5R positively correlated with the expression of BDNF and TrkB. Functionally, BDNF triggered Y5R internalization in NB cells, while Y5R antagonist inhibited BDNF-induced p44/42-MAPK activation and its pro-survival activity. These observations suggested TrkB-Y5R transactivation that resulted in cross-talk between their signaling pathways. Additionally, NPY and Y5R were up-regulated in a BDNF-independent manner in NB cells under pro-apoptotic conditions, such as serum deprivation and chemotherapy, as well as in cell lines and tissues derived from post-treatment NB tumors. Blocking Y5R in chemoresistant NB cells rich in this receptor sensitized them to chemotherapy-induced apoptosis and inhibited their growth in vivo by augmenting cell death. In summary, the NPY/Y5R axis is an inducible survival pathway activated in NB by BDNF or cellular stress. Upon such activation, Y5R augments the pro-survival effect of BDNF via its interactions with TrkB receptor and exerts an additional BDNF-independent anti-apoptotic effect, both of which contribute to NB chemoresistance. Therefore, the NPY/Y5R pathway may become a novel therapeutic target for patients with refractory NB, thus far an incurable form of this disease.