Oct-4+/Tenascin C+ neuroblastoma cells serve as progenitors of tumor-derived endothelial cells

E2F1-regulated USP5 contributes to the tumorigenic capacity of glioma stem cells through the maintenance of OCT4 stability

Mesenchymal glioma stem cells (MES GSCs) are a subpopulation of cells in glioblastoma (GBM) that contribute to a worse prognosis owing to their highly aggressive nature and resistance to radiation therapy. Here, OCT4 is characterized as a critical factor in sustaining the stemness phenotype of MES GSC. We find that OCT4 is expressed intensively in MES GSC and is intimately associated with poor prognosis, moreover, OCT4 depletion leads to diminished invasive capacity and impairment of the stem phenotype in MES GSC. Subsequently, we demonstrated that USP5 is a deubiquitinating enzyme which directly interacts with OCT4 and preserves OCT4 stability through its deubiquitination. USP5 was additionally proven to be aberrantly over-expressed in MES GSCs, and its depletion resulted in a noticeable diminution of OCT4 and consequently a reduced self-renewal and tumorigenic capacity of MES GSCs, which can be substantially restored by ectopic expression of OCT4. In addition, we detected the dominant molecule that regulates USP5 transcription, E2F1, with dual luciferase reporter gene analysis. In combination, targeting the E2F1-USP5-OCT4 axis is a potentially emerging strategy for the therapy of GBM.

Identification of GB3 as a Novel Biomarker of Tumor-Derived Vasculature in Neuroblastoma Using a Stiffness-Based Model

Neuroblastoma (NB) is a childhood cancer in sympathetic nervous system cells. NB exhibits cellular heterogeneity, with adrenergic and mesenchymal states displaying distinct tumorigenic potentials. NB is highly vascularized, and blood vessels can form through various mechanisms, including endothelial transdifferentiation, leading to the development of tumor-derived endothelial cells (TECs) associated with chemoresistance. We lack specific biomarkers for TECs. Therefore, identifying new TEC biomarkers is vital for effective NB therapies. A stiffness-based platform simulating human arterial and venous stiffness was developed to study NB TECs in vitro. Adrenergic cells cultured on arterial-like stiffness transdifferentiated into TECs, while mesenchymal state cells did not. The TECs derived from adrenergic cells served as a model to explore new biomarkers, with a particular focus on GB3, a glycosphingolipid receptor implicated in angiogenesis, metastasis, and drug resistance. Notably, the TECs unequivocally expressed GB3, validating its novelty as a marker. To explore targeted therapeutic interventions, nanoparticles functionalized with the non-toxic subunit B of the Shiga toxin were generated, because they demonstrated a robust affinity for GB3-positive cells. Our results demonstrate the value of the stiffness-based platform as a predictive tool for assessing NB aggressiveness, the discovery of new biomarkers, and the evaluation of the effectiveness of targeted therapeutic strategies.

Inhibition of OCT4 binding at the MYCN locus induces neuroblastoma cell death accompanied by downregulation of transcripts with high-open reading frame dominance

Amplification of MYCN is observed in high-risk neuroblastomas (NBs) and is associated with a poor prognosis. MYCN expression is directly regulated by multiple transcription factors, including OCT4, MYCN, CTCF, and p53 in NB. Our previous study showed that inhibition of p53 binding at the MYCN locus induces NB cell death. However, it remains unclear whether inhibition of alternative transcription factor induces NB cell death. In this study, we revealed that the inhibition of OCT4 binding at the MYCN locus, a critical site for the human-specific OCT4-MYCN positive feedback loop, induces caspase-2-mediated cell death in MYCN-amplified NB. We used the CRISPR/deactivated Cas9 (dCas9) technology to specifically inhibit transcription factors from binding to the MYCN locus in the MYCN-amplified NB cell lines CHP134 and IMR32. In both cell lines, the inhibition of OCT4 binding at the MYCN locus reduced MYCN expression, thereby suppressing MYCN-target genes. After inhibition of OCT4 binding, differentially downregulated transcripts were associated with high-open reading frame (ORF) dominance score, which is associated with the translation efficiency of transcripts. These transcripts were enriched in splicing factors, including MYCN-target genes such as HNRNPA1 and PTBP1. Furthermore, transcripts with a high-ORF dominance score were significantly associated with genes whose high expression is associated with a poor prognosis in NB. Because the ORF dominance score correlates with the translation efficiency of transcripts, our findings suggest that MYCN maintains the expression of transcripts with high translation efficiency, contributing to a poor prognosis in NB. In conclusion, the inhibition of OCT4 binding at the MYCN locus resulted in reduced MYCN activity, which in turn led to the downregulation of high-ORF dominance transcripts and subsequently induced caspase-2-mediated cell death in MYCN-amplified NB cells. Therefore, disruption of the OCT4 binding at the MYCN locus may serve as an effective therapeutic strategy for MYCN-amplified NB.

Vasculogenic Mimicry Occurs at Low Levels in Primary and Recurrent Glioblastoma

Vasculogenic mimicry (VM), the ability of tumour cells to form functional microvasculature without an endothelial lining, may contribute to anti-angiogenic treatment resistance in glioblastoma. We aimed to assess the extent of VM formation in primary and recurrent glioblastomas and to determine whether VM vessels also express prostate-specific membrane antigen (PSMA), a pathological vessel marker. Formalin-fixed paraffin-embedded tissue from 35 matched pairs of primary and recurrent glioblastoma was immunohistochemically labelled for PSMA and CD34 and stained with periodic acid-Schiff (PAS). Vascular structures were categorised as endothelial vessels (CD34+/PAS+) or VM (CD34-/PAS+). Most blood vessels in both primary and recurrent tumours were endothelial vessels, and these significantly decreased in recurrent tumours (p < 0.001). PSMA was expressed by endothelial vessels, and its expression was also decreased in recurrent tumours (p = 0.027). VM was observed in 42.86% of primary tumours and 28.57% of recurrent tumours. VM accounted for only a small proportion of the tumour vasculature and VM density did not differ between primary and recurrent tumours (p = 0.266). The functional contribution of VM and its potential as a treatment target in glioblastoma require further investigation.

Cancer Stem Cells in Tumours of the Central Nervous System in Children: A Comprehensive Review

Cancer stem cells (CSCs) are a subgroup of cells found in various kinds of tumours with stem cell characteristics, such as self-renewal, induced differentiation, and tumourigenicity. The existence of CSCs is regarded as a major source of tumour recurrence, metastasis, and resistance to conventional chemotherapy and radiation treatment. Tumours of the central nervous system (CNS) are the most common solid tumours in children, which have many different types including highly malignant embryonal tumours and midline gliomas, and low-grade gliomas with favourable prognoses. Stem cells from the CNS tumours have been largely found and reported by researchers in the last decade and their roles in tumour biology have been deeply studied. However, the cross-talk of CSCs among different CNS tumour types and their clinical impacts have been rarely discussed. This article comprehensively reviews the achievements in research on CSCs in paediatric CNS tumours. Biological functions, diagnostic values, and therapeutic perspectives are reviewed in detail. Further investigations into CSCs are warranted to improve the clinical practice in treating children with CNS tumours.

Crosstalk between Noncoding RNAs and the Epigenetics Machinery in Pediatric Tumors and Their Microenvironment

According to the World Health Organization, every year, an estimated 400,000+ new cancer cases affect children under the age of 20 worldwide. Unlike adult cancers, pediatric cancers develop very early in life due to alterations in signaling pathways that regulate embryonic development, and environmental factors do not contribute much to cancer development. The highly organized complex microenvironment controlled by synchronized gene expression patterns plays an essential role in the embryonic stages of development. Dysregulated development can lead to tumor initiation and growth. The low mutational burden in pediatric tumors suggests the predominant role of epigenetic changes in driving the cancer phenotype. However, one more upstream layer of regulation driven by ncRNAs regulates gene expression and signaling pathways involved in the development. Deregulation of ncRNAs can alter the epigenetic machinery of a cell, affecting the transcription and translation profiles of gene regulatory networks required for cellular proliferation and differentiation during embryonic development. Therefore, it is essential to understand the role of ncRNAs in pediatric tumor development to accelerate translational research to discover new treatments for childhood cancers. This review focuses on the role of ncRNA in regulating the epigenetics of pediatric tumors and their tumor microenvironment, the impact of their deregulation on driving pediatric tumor progress, and their potential as effective therapeutic targets.

Advances on the roles of tenascin-C in cancer

The roles of the extracellular matrix molecule tenascin-C (TNC) in health and disease have been extensively reviewed since its discovery over 40 years ago. Here, we will describe recent insights into the roles of TNC in tumorigenesis, angiogenesis, immunity and metastasis. In addition to high levels of expression in tumors, and during chronic inflammation, and bacterial and viral infection, TNC is also expressed in lymphoid organs. This supports potential roles for TNC in immunity control. Advances using murine models with engineered TNC levels were instrumental in the discovery of important functions of TNC as a danger-associated molecular pattern (DAMP) molecule in tissue repair and revealed multiple TNC actions in tumor progression. TNC acts through distinct mechanisms on many different cell types with immune cells coming into focus as important targets of TNC in cancer. We will describe how this knowledge could be exploited for cancer disease management, in particular for immune (checkpoint) therapies.

RNA N6-Methyladenine Modification, Cellular Reprogramming, and Cancer Stemness

N⁶-Methyladenosine (m⁶A) is the most abundant modification on eukaryote messenger RNA and plays a key role in posttranscriptional regulation of RNA metabolism including splicing, intracellular transport, degradation, and translation. m⁶A is dynamically regulated by methyltransferases (writers), RNA-binding proteins (readers), and demethylases (erasers). Recent studies demonstrate that perturbation of m⁶A regulators remarkably influences cell fate transitions through rewiring various biological processes, such as growth, differentiation, and survival. Moreover, aberrant m⁶A modification is implicated in a variety of diseases, in particular cancer. In this review, we describe the functional linkage of m⁶A modifications to cellular reprogramming and cancer stemness properties.

Immune Remodeling of the Extracellular Matrix Drives Loss of Cancer Stem Cells and Tumor Rejection

The nature of the tumor microenvironment (TME) influences the ability of tumor-specific T cells to control tumor growth. In this study, we performed an unbiased comparison of the TME of regulatory T-cell (Treg)-replete and Treg-depleted carcinogen-induced tumors, including Treg-depleted responding (regressing) and non-responding (growing) tumors. This analysis revealed an inverse relationship between extracellular matrix (ECM) and T-cell infiltrates where responding tumors were T-cell rich and ECM poor, whereas the converse was observed in non-responder tumors. For this reason, we hypothesized that the ECM acted as a barrier to successful T-cell infiltration and tumor rejection. However, further experiments revealed that this was not the case but instead showed that an effective T-cell response dramatically altered the density of ECM in the TME. Along with loss of ECM and high numbers of infiltrating T cells, responder tumors were distinguished by the development of lymphatic and blood vessel networks with specialized immune function. ECM-rich tumors exhibited a stem cell-like gene expression profile and superior tumor-initiating capacity, whereas such features were absent in responder tumors. Overall, these findings define an extended role for an effective immune response, not just in direct killing of tumor cells but in widescale remodeling of the TME to favor loss of ECM, elimination of cancer stem cells, and propagation of adaptive immunity.

Oct4 Regulates the Transition of Cancer Stem-Like Cells to Tumor Endothelial-Like Cells in Human Liver Cancer

Octamer-binding transcription factor 4 (Oct4) has been recently implicated as a proangiogenic regulator in several induced pluripotent stem cells (iPSCs), however, its role in cancer stem-like cells (CSCs) remain unclear. We report here that Oct4 participates in tumor vasculogenesis in liver CSCs (LCSCs). We identify that LCSCs possess the potential of endothelial trans-differentiation under endothelial induction, present endothelial specific markers and their functions in vitro, and participate in neovasculogenesis in vivo. The knockdown of the Oct4A by short hairpin RNA (shRNA) in LCSCs represses endothelial trans-differentiation potential, but induces endothelial lineage-restricted differentiation, the latter is positively regulated by Oct4B1. Furthermore, Oct4 regulates vasculogenesis in LCSCs may be via the AKT-NF-κB-p65 signaling pathway. This work reveals Oct4, which is a crucial regulator, plays a critical role in tumor endothelial-like cells transition of LCSCs through Oct4A and Oct4B1 by different ways. The simultaneous inhibition of both the isoforms of Oct4 is hence expected to help regress neovascularization derived from CSCs. Our findings may provide insights to the possible new mechanisms of tumor vasculogenesis for primary liver cancer.

De novo evolved gene product NCYM in the pathogenesis and clinical outcome of human neuroblastomas and other cancers

NCYM is an antisense transcript of MYCN oncogene and promotes tumor progression. NCYM encodes a de novo protein whose open reading frame evolved from noncoding genomic regions in the ancestor of Homininae. Because of its topology, NCYM is always co-amplified with MYCN oncogene, and the mutual regulations between NCYM and MYCN maintain their expressions at high levels in MYCN-amplified tumors. NCYM stabilizes MYCN by inhibiting GSK3β, whereas MYCN stimulates transcription of both NCYM and MYCN. NCYM mRNA and its noncoding transcript variants MYCNOS have been shown to stimulate MYCN expression via direct binding to MYCN promoter, indicating that both coding and noncoding transcripts of NCYM induce MYCN expression. In contrast to the noncoding functions of NCYM, NCYM protein also promotes calpain-mediated cleavage of c-MYC. The cleaved product called Myc-nick inhibits cell death and promotes cancer cell migration. Furthermore, NCYM-mediated inhibition of GSK3β results in the stabilization of β-catenin, which promotes aggressiveness of bladder cancers. These MYCN-independent functions of NCYM showed their clinical significance in MYCN-non-amplified tumors, including adult tumors. This year is the 30th anniversary of the identification of NCYM/MYCNOS gene. On this special occasion, we summarize the current understanding of molecular functions and the clinical significance of NCYM and discuss future directions to achieve therapeutic strategies targeting NCYM.

Biological evaluation of pyrazolyl-urea and dihydro-imidazo-pyrazolyl-urea derivatives as potential anti-angiogenetic agents in the treatment of neuroblastoma

Pyrazolyl-urea and dihydro-imidazo-pyrazolyl-urea compounds (STIRUR 13, STIRUR 41 and BUR 12) have been demonstrated to exert a strong inhibitory effect on interleukin 8 or N-formyl-methionyl-leucyl-phenylalanine-induced chemotaxis of human neutrophils. Since the migration of cancer cells is comparable to that of neutrophils, the purpose of this study is to evaluate the biological effect of STIRUR 13, STIRUR 41 and BUR 12 on ACN and HTLA-230, two neuroblastoma (NB) cell lines with different degree of malignancy. HTLA-230 cells, stage-IV NB cells, have high plasticity and can serve as progenitors of endothelial cells. The results herein reported show that the three tested compounds were not cytotoxic for both NB cells and did not alter their clonogenic potential. However, all compounds were able to inhibit the ability of HTLA-230 to form vascular-like structures. On the basis of these findings, pyrazolyl-urea and dihydro-imidazo-pyrazolyl-urea derivatives could be proposed as agents potentially effective in counteracting NB malignancy by inhibiting cell migration and tumor angiogenesis which represent important hallmarks responsible for cancer survival and progression.

Interplay between MycN and c-Myc regulates radioresistance and cancer stem cell phenotype in neuroblastoma upon glutamine deprivation

Targeting glutamine metabolism has emerged as a potential therapeutic strategy for Myc overexpressing cancer cells. Myc proteins contribute to an aggressive neuroblastoma phenotype. Radiotherapy is one of the treatment modalities for high-risk neuroblastoma patients. Herein, we investigated the effect of glutamine deprivation in combination with irradiation in neuroblastoma cells representative of high-risk disease and studied the role of Myc member interplay in regulating neuroblastoma cell radioresistance. Methods: Cell proliferation and viability assays were used to establish the effect of glutamine deprivation in neuroblastoma cells expressing c-Myc or MycN. Gene silencing and overexpression were used to modulate the expression of Myc genes to determine their role in neuroblastoma radioresistance. qPCR and western blot investigated interplay between expression of Myc members. The impact of glutamine deprivation on cell response following irradiation was explored using a radiobiological 3D colony assay. DNA repair gene pathways as well as CSC-related genes were studied by qPCR array. Reactive Oxygen Species (ROS) and glutathione (GSH) levels were detected by fluorescence and luminescence probes respectively. Cancer-stem cell (CSC) properties were investigated by sphere-forming assay and flow cytometry to quantify CSC markers. Expression of DNA repair genes and CSC-related genes was analysed by mining publicly available patient datasets. Results: Our results showed that glutamine deprivation decreased neuroblastoma cell proliferation and viability and modulated Myc member expression. We then demonstrated for the first time that combined glutamine deprivation with irradiation led to a selective radioresistance of MYCN-amplified neuroblastoma cells. By exploring the underlying mechanism of neuroblastoma radioresistance properties, our results highlight interplay between c-Myc and MycN expression suggesting compensatory mechanisms in Myc proteins leading to radioresistance in MYCN-amplified cells. This result was associated with the ability of MYCN-amplified cells to dysregulate the DNA repair gene pathway, maintain GSH and ROS levels and to increase the CSC-like population and properties. Conversely, glutamine deprivation led to radiosensitization in non-MYCN amplified cell lines through a disruption of the cell redox balance and a trend to decrease in the CSC-like populations. Mining publicly available gene expression dataset obtained from pediatric neuroblastoma patients, we identified a correlation pattern between Myc members and CSC-related genes as well as a specific group of DNA repair gene pathways. Conclusions: This study demonstrated that MycN and c-Myc tightly cooperate in regulation of the neuroblastoma CSC phenotypes and radioresistance upon glutamine deprivation. Pharmacologically, strategies targeting glutamine metabolism may prove beneficial in Myc-driven tumors. Consideration of MycN/c-Myc status in selecting neuroblastoma patients for glutamine metabolism treatment will be important to avoid potential radioresistance.

Targeting cancer stem cell pathways for cancer therapy

Since cancer stem cells (CSCs) were first identified in leukemia in 1994, they have been considered promising therapeutic targets for cancer therapy. These cells have self-renewal capacity and differentiation potential and contribute to multiple tumor malignancies, such as recurrence, metastasis, heterogeneity, multidrug resistance, and radiation resistance. The biological activities of CSCs are regulated by several pluripotent transcription factors, such as OCT4, Sox2, Nanog, KLF4, and MYC. In addition, many intracellular signaling pathways, such as Wnt, NF-κB (nuclear factor-κB), Notch, Hedgehog, JAK-STAT (Janus kinase/signal transducers and activators of transcription), PI3K/AKT/mTOR (phosphoinositide 3-kinase/AKT/mammalian target of rapamycin), TGF (transforming growth factor)/SMAD, and PPAR (peroxisome proliferator-activated receptor), as well as extracellular factors, such as vascular niches, hypoxia, tumor-associated macrophages, cancer-associated fibroblasts, cancer-associated mesenchymal stem cells, extracellular matrix, and exosomes, have been shown to be very important regulators of CSCs. Molecules, vaccines, antibodies, and CAR-T (chimeric antigen receptor T cell) cells have been developed to specifically target CSCs, and some of these factors are already undergoing clinical trials. This review summarizes the characterization and identification of CSCs, depicts major factors and pathways that regulate CSC development, and discusses potential targeted therapy for CSCs.

Role of GOLPH3 and TPX2 in Neuroblastoma DNA Damage Response and Cell Resistance to Chemotherapy

Neuroblastoma (NB) is an aggressive, relapse-prone infancy tumor of the sympathetic nervous system and is the leading cause of death among preschool age diseases, so the search for novel therapeutic targets is crucial. Golgi phosphoprotein 3 (GOLPH3) has been reported to be involved in the development, and in the DNA damage response, of various human cancers. Golgi dispersal is a common feature of DNA damage response in mammalian cells. Understanding how cells react to DNA damage is essential in order to recognize the systems used to escape from elimination. We induced DNA damage in two human neuroblastoma cell lines by curcumin. The exposure of neuroblastoma cells to curcumin induced: (a) up-regulation of GOLPH3⁺ cells; (b) augmentation of double-strand breaks; (c) Golgi fragmentation and dispersal throughout the cytoplasm; (d) increase of apoptosis and autophagy; (e) increased expression of TPX2 oncoprotein, able to repair DNA damage. Primary neuroblastoma samples analysis confirmed these observations. Our findings suggest that GOLPH3 expression levels may represent a clinical marker of neuroblastoma patients’ responsiveness to DNA damaging therapies—and of possible resistance to them. Novel molecules able to interfere with GOLPH3 and TPX2 pathways may have therapeutic benefits when used in combination with standard DNA damaging therapeutic agents in neuroblastoma

Tenascin-C increases lung metastasis by impacting blood vessel invasions

Metastasis is a major cause of death in cancer patients. The extracellular matrix molecule tenascin-C is a known promoter of metastasis, however the underlying mechanisms are not well understood. To further analyze the impact of tenascin-C on cancer progression we generated MMTV-NeuNT mice that develop spontaneous mammary tumors, on a tenascin-C knockout background. We also developed a syngeneic orthotopic model in which tumor cells derived from a MMTV-NeuNT tumor. Tumor cells were transfected with control shRNA or with shRNA to knockdown tenascin-C expression and, were grafted into the mammary gland of immune competent, wildtype or tenascin-C knockout mice. We show that stromal-derived tenascin-C increases metastasis by reducing apoptosis and inducing the cellular plasticity of cancer cells located in pulmonary blood vessels invasions (BVI), before extravasation. We characterized BVI as organized structures of tightly packed aggregates of proliferating tumor cells with epithelial characteristics, surrounded by Fsp1+ cells, internally located platelets and, a luminal monolayer of endothelial cells. We found extracellular matrix, in particular, tenascin-C, between the stromal cells and the tumor cell cluster. In mice lacking stromal-derived tenascin-C, the organization of pulmonary BVI was significantly affected, revealing novel functions of host-derived tenascin-C in supporting the integrity of the endothelial cell coat, increasing platelet abundance, tumor cell survival, epithelial plasticity, thereby promoting overall lung metastasis. Many effects of tenascin-C observed in BVI including enhancement of cellular plasticity, survival and migration, could be explained by activation of TGF-β signaling. Finally, in several human cancers, we also observed BVI to be surrounded by an endothelial monolayer and to express tenascin-C. Expression of tenascin-C is specific to BVI and is not observed in lymphatic vascular invasions frequent in breast cancer, which lack an endothelial lining. Given that BVI have prognostic significance for many tumor types, such as shorter cancer patient survival, increased metastasis, vessel occlusion, and organ failure, our data revealing a novel mechanism by which stromal tenascin-C promotes metastasis in human cancer, may have potential for diagnosis and therapy.

The Role of the Extracellular Matrix in Cancer Stemness

As our understanding of cancer cell biology progresses, it has become clear that tumors are a heterogenous mixture of different cell populations, some of which contain so called "cancer stem cells" (CSCs). Hallmarks of CSCs include self-renewing capability, tumor-initiating capacity and chemoresistance. The extracellular matrix (ECM), a major structural component of the tumor microenvironment, is a highly dynamic structure and increasing evidence suggests that ECM proteins establish a physical and biochemical niche for CSCs. In cancer, abnormal ECM dynamics occur due to disrupted balance between ECM synthesis and secretion and altered expression of matrix-remodeling enzymes. Tumor-derived ECM is biochemically distinct in its composition and is stiffer compared to normal ECM. In this review, we will provide a brief overview of how different components of the ECM modulate CSC properties then discuss how physical, mechanical, and biochemical cues from the ECM drive cancer stemness. Given the fact that current CSC targeting therapies face many challenges, a better understanding of CSC-ECM interactions will be crucial to identify more effective therapeutic strategies to eliminate CSCs.

Quantitative proteomic profiling of tumor-associated vascular endothelial cells in colorectal cancer

To investigate the global proteomic profiles of vascular endothelial cells (VECs) in the tumor microenvironment and antiangiogenic therapy for colorectal cancer (CRC), matched pairs of normal (NVECs) and tumor-associated VECs (TVECs) were purified from CRC tissues by laser capture microdissection and subjected to iTRAQ-based quantitative proteomics analysis. Here, 216 differentially expressed proteins (DEPs) were identified and used for bioinformatics analysis. Interestingly, these proteins were implicated in epithelial mesenchymal transition (EMT), ECM-receptor interaction, focal adhesion, PI3K-Akt signaling pathway, angiogenesis and HIF-1 signaling pathway, which may play important roles in CRC angiogenesis. Among these DEPs we found that Tenascin-C (TNC) was upregulated in TVECs of CRC and correlated with CRC multistage carcinogenesis and metastasis. Furthermore, the reduction of tumor-derived TNC could attenuate human umbilical vein endothelial cell (HUVEC) proliferation, migration and tube formation through ITGB3/FAK/Akt signaling pathway. Based on the present work, we provided a large-scale proteomic profiling of VECs in CRC with quantitative information, a certain number of potential antiangiogenic targets and a novel vision in the angiogenesis bio-mechanism of CRC.

Summary: We provided large-scale proteomic profiling of vascular endothelial cells in colorectal cancer with quantitative information, a number of potential antiangiogenic targets and a novel vision in the angiogenesis bio-mechanism of CRC.

Association of Single-Nucleotide Polymorphism REX1 rs6815391, OCT4 rs13409 or rs3130932, and CTBP2 rs3740535 with Primary Lung Cancer Susceptibility: A Case-Control Study in a Chinese Population

The purpose of the current study is to explore the contribution of single-nucleotide polymorphisms (SNPs) of REX1 rs6815391, OCT4 rs13409 or rs3130932, and CTBP2 rs3740535 to the risk of lung cancer. A questionnaire survey was used to obtain basic information of the included subjects. A case control study was performed in 1121 patients and 1121 controls. All subjects were subjected to blood sampling for genomic DNA extraction and genotyping of the cancer stem cell-associated gene SNPs, including REX1 rs6815391, OCT4 rs13409 or rs3130932, and CTBP2 rs3740535 by real-time PCR. The association with the risk of primary lung cancer and interaction with environmental factors were assessed using unconditional logistic regression for the odds ratios and corresponding 95% confidence intervals. The genotype frequency distribution of OCT4 rs13409 loci was statistically significant, but there was no significant difference in the rest of the loci between lung cancer patients and healthy controls. The OCT4 gene was also related with lung cancer susceptibility in the genetic model after adjusting for lung cancer-related factors. Despite the presence of the dominant or recessive model, the four loci polymorphisms were associated with pollution near the place of residence, house type, worse ventilation situation, smoking, passive smoking, cooking oil fumes (COF), and family history of cancer, which increased the risk of lung cancer. Nonmarried status, 18.5≤BMI, COF, smoking, passive smoking, family history of cancer, and history of lung disease were independent risk factors of lung cancer susceptibility. Additionally, college degree or above, no pollution near the place of residence, protective genotype 1 or 2, and well ventilation can reduce the occurrence of lung cancer. There is an interaction between the four loci and environmental factors, and OCT4 rs13409 is a risk factor of primary lung cancer.

The carotid body: a physiologically relevant germinal niche in the adult peripheral nervous system

Oxygen constitutes a vital element for the survival of every single cell in multicellular aerobic organisms like mammals. A complex homeostatic oxygen-sensing system has evolved in these organisms, including detectors and effectors, to guarantee a proper supply of the element to every cell. The carotid body represents the most important peripheral arterial chemoreceptor organ in mammals and informs about hypoxemic situations to the effectors at the brainstem cardiorespiratory centers. To optimize organismal adaptation to maintained hypoxemic situations, the carotid body has evolved containing a niche of adult tissue-specific stem cells with the capacity to differentiate into both neuronal and vascular cell types in response to hypoxia. These neurogenic and angiogenic processes are finely regulated by the niche and by hypoxia itself. Our recent data on the cellular and molecular mechanisms underlying the functioning of this niche might help to comprehend a variety of different diseases coursing with carotid body failure, and might also improve our capacity to use these stem cells for the treatment of neurological disease. Herein, we review those data about the recent characterization of the carotid body niche, focusing on the study of the phenotype and behavior of multipotent stem cells within the organ, comparing them with other well-documented neural stem cells within the adult nervous system.

High Oct4 expression: implications in the pathogenesis of neuroblastic tumours

BACKGROUND

Neuroblastic tumours (NBTs) are paediatric solid tumours derived from embryonic neural crest cells which harbour their own cancer stem cells (CSC). There is evidence indicating that CSC may be responsible for tumour progression, chemotherapy resistance and recurrence in NBTs. Oct4 is a transcription factor which plays a key role in mammal embryonic development and stem cell fate regulation. The aim of the study is to elucidate the clinical significance of Oct4 in NBTs.

METHODS

We studied Oct4 expression in 563 primary NBTs using digital image quantification. Chi-square test was applied to analyse the correlation between histopathology and the Oct4+ cell percentage. Survival analysis was carried out with Kaplan-Meier curves and log-rank test. Additionally, a multivariate Cox regression analysis with the stepwise backwards (Wald) method was undertaken to calculate the impact of Oct4 expression level on survival.

RESULTS

We found that tumours with a high proportion of cells expressing Oct4 correlated statistically with undifferentiated and poorly differentiated neuroblastoma / nodular ganglioneuroblastoma, and that Oct4 expression was not present in ganglioneuroma (p < 0.05). Statistical analysis also indicated a relationship between high Oct4 expression levels, high-risk patients according to the International Neuroblastoma Risk Group pre-treatment classification parameters, larger blood vessels and low survival rates.

CONCLUSIONS

These results suggest that the Oct4 gene may regulate NBT pathogenic differentiation pathways, and should thus be considered as a target for knockdown when developing novel therapies for high-risk NBT patients.

Emerging roles of Myc in stem cell biology and novel tumor therapies

The pathophysiological roles and the therapeutic potentials of Myc family are reviewed in this article. The physiological functions and molecular machineries in stem cells, including embryonic stem (ES) cells and induced pluripotent stem (iPS) cells, are clearly described. The c-Myc/Max complex inhibits the ectopic differentiation of both types of artificial stem cells. Whereas c-Myc plays a fundamental role as a "double-edged sword" promoting both iPS cells generation and malignant transformation, L-Myc contributes to the nuclear reprogramming with the significant down-regulation of differentiation-associated genetic expression. Furthermore, given the therapeutic resistance of neuroendocrine tumors such as small-cell lung cancer and neuroblastoma, the roles of N-Myc in difficult-to-treat tumors are discussed. N-Myc and p53 exhibit the co-localization in the nucleus and alter p53-dependent transcriptional responses which are necessary for DNA repair, anti-apoptosis, and lipid metabolic reprogramming. NCYM protein stabilizes N-Myc, resulting in the stimulation of Oct4 expression, while Oct4 induces both N-Myc and NCYM via direct transcriptional activation of N-Myc, [corrected] thereby leading to the enhanced metastatic potential. Importantly enough, accumulating evidence strongly suggests that c-Myc can be a promising therapeutic target molecule among Myc family in terms of the biological characteristics of cancer stem-like cells (CSCs). The presence of CSCs leads to the intra-tumoral heterogeneity, which is mainly responsible for the therapeutic resistance. Mechanistically, it has been shown that Myc-induced epigenetic reprogramming enhances the CSC phenotypes. In this review article, the author describes two major therapeutic strategies of CSCs by targeting c-Myc; Firstly, Myc-dependent metabolic reprogramming is closely related to CD44 variant-dependent redox stress regulation in CSCs. It has been shown that c-Myc increases NADPH production via enhanced glutaminolysis with a finely-regulated mechanism. Secondly, the dormancy of CSCs due to FBW7-depedent c-Myc degradation pathway is also responsible for the therapeutic resistance to the conventional anti-tumor agents, the action points of which are largely dependent on the operation of the cell cycle. That is why the loss-of-functional mutations of FBW7 gene are expected to trigger "awakening" of dormant CSCs in the niche with c-Myc up-regulation. Collectively, although the further research is warranted to develop the effective anti-tumor therapeutic strategy targeting Myc family, we cancer researchers should always catch up with the current advances in the complex functions of Myc family in highly-malignant and heterogeneous tumor cells to realize the precision medicine.

CHL1 gene acts as a tumor suppressor in human neuroblastoma

Neuroblastoma is an aggressive, relapse-prone childhood tumor of the sympathetic nervous system that accounts for 15% of pediatric cancer deaths. A distal portion of human chromosome 3p is often deleted in neuroblastoma, this region may contain one or more putative tumor suppressor genes. A 2.54 Mb region at 3p26.3 encompassing the smallest region of deletion pinpointed CHL1 gene, the locus for neuronal cell adhesion molecule close homolog of L1. We found that low CHL1 expression predicted poor outcome in neuroblastoma patients. Here we have used two inducible cell models to analyze the impact of CHL1 on neuroblastoma biology. Over-expression of CHL1 induced neurite-like outgrowth and markers of neuronal differentiation in neuroblastoma cells, halted tumor progression, inhibited anchorage-independent colony formation, and suppressed the growth of human tumor xenografts. Conversely, knock-down of CHL1 induced neurite retraction and activation of Rho GTPases, enhanced cell proliferation and migration, triggered colony formation and anchorage-independent growth, accelerated growth in orthotopic xenografts mouse model. Our findings demonstrate unambiguously that CHL1 acts as a regulator of proliferation and differentiation of neuroblastoma cells through inhibition of the MAPKs and Akt pathways. CHL1 is a novel candidate tumor suppressor in neuroblastoma, and its associated pathways may represent a promising target for future therapeutic interventions.

Isolation and characterization of renal cancer stem cells from patient-derived xenografts

As rapidly developing patient-derived xenografts (PDX) could represent potential sources of cancer stem cells (CSC), we selected and characterized non-cultured PDX cell suspensions from four different renal carcinomas (RCC). Only the cell suspensions from the serial xenografts (PDX-1 and PDX-2) of an undifferentiated RCC (RCC-41) adapted to the selective CSC medium. The cell suspension derived from the original tumor specimen (RCC-41-P-0) did not adapt to the selective medium and strongly expressed CSC-like markers (CD133 and CD105) together with the non-CSC tumor marker E-cadherin. In comparison, PDX-1 and PDX-2 cells exhibited evolution in their phenotype since PDX-1 cells were CD133^high/CD105-/Ecad^low and PDX-2 cells were CD133^low/CD105-/Ecad-. Both PDX subsets expressed additional stem cell markers (CD146/CD29/OCT4/NANOG/Nestin) but still contained non-CSC tumor cells. Therefore, using different cell sorting strategies, we characterized 3 different putative CSC subsets (RCC-41-PDX-1/CD132+, RCC-41-PDX-2/CD133-/EpCAM^low and RCC-41-PDX-2/CD133⁺/EpCAM^bright). In addition, transcriptomic analysis showed that RCC-41-PDX-2/CD133⁻ over-expressed the pluripotency gene ERBB4, while RCC-41-PDX-2/CD133⁺ over-expressed several tumor suppressor genes. These three CSC subsets displayed ALDH activity, formed serial spheroids and developed serial tumors in SCID mice, although RCC-41-PDX-1/CD132⁺ and RCC-41-PDX-2/CD133⁺ displayed less efficiently the above CSC properties. RCC-41-PDX-1/CD132⁺ tumors showed vessels of human origin with CSC displaying peri-vascular distribution. By contrast, RCC-41-PDX-2 originated tumors exhibiting only vessels of mouse origin without CSC peri-vascular distribution.

Altogether, our results indicate that PDX murine microenvironment promotes a continuous redesign of CSC phenotype, unmasking CSC subsets potentially present in a single RCC or generating ex novo different CSC-like subsets.

Collateral Damage Intended-Cancer-Associated Fibroblasts and Vasculature Are Potential Targets in Cancer Therapy

After oncogenic transformation, tumor cells rewire their metabolism to obtain sufficient energy and biochemical building blocks for cell proliferation, even under hypoxic conditions. Glucose and glutamine become their major limiting nutritional demands. Instead of being autonomous, tumor cells change their immediate environment not only by their metabolites but also by mediators, such as juxtacrine cell contacts, chemokines and other cytokines. Thus, the tumor cells shape their microenvironment as well as induce resident cells, such as fibroblasts and endothelial cells (ECs), to support them. Fibroblasts differentiate into cancer-associated fibroblasts (CAFs), which produce a qualitatively and quantitatively different extracellular matrix (ECM). By their contractile power, they exert tensile forces onto this ECM, leading to increased intratumoral pressure. Moreover, along with enhanced cross-linkage of the ECM components, CAFs thus stiffen the ECM. Attracted by tumor cell- and CAF-secreted vascular endothelial growth factor (VEGF), ECs sprout from pre-existing blood vessels during tumor-induced angiogenesis. Tumor vessels are distinct from EC-lined vessels, because tumor cells integrate into the endothelium or even mimic and replace it in vasculogenic mimicry (VM) vessels. Not only the VM vessels but also the characteristically malformed EC-lined tumor vessels are typical for tumor tissue and may represent promising targets in cancer therapy.

Physiological Plasticity of Neural-Crest-Derived Stem Cells in the Adult Mammalian Carotid Body

Adult stem cell plasticity, or the ability of somatic stem cells to cross boundaries and differentiate into unrelated cell types, has been a matter of debate in the last decade. Neural-crest-derived stem cells (NCSCs) display a remarkable plasticity during development. Whether adult populations of NCSCs retain this plasticity is largely unknown. Herein, we describe that neural-crest-derived adult carotid body stem cells (CBSCs) are able to undergo endothelial differentiation in addition to their reported role in neurogenesis, contributing to both neurogenic and angiogenic processes taking place in the organ during acclimatization to hypoxia. Moreover, CBSC conversion into vascular cell types is hypoxia inducible factor (HIF) dependent and sensitive to hypoxia-released vascular cytokines such as erythropoietin. Our data highlight a remarkable physiological plasticity in an adult population of tissue-specific stem cells and could have impact on the use of these cells for cell therapy.

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Adult carotid body stem cells display multipotency during organ adaptation to hypoxia

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Neural-crest-derived stem cells contribute to angiogenesis in the adult carotid body

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Endothelial differentiation from carotid body stem cells is HIF2α and EPO dependent

Cigarette smoke extracts induce overexpression of the proto-oncogenic gene interleukin-13 receptor α2 through activation of the PKA-CREB signaling pathway to trigger malignant transformation of lung vascular endothelial cells and angiogenesis

Cigarette smoking is a major cause of lung cancer. Tumor-associated endothelial cells (TAECs) play important roles in tumor angiogenesis and metastasis. However, whether cigarette smoking can trigger genesis of lung TAECs has not been reported yet. In the current study, we used lung endothelial cell (EC) lines as a model to study the pathological effect of cigarette smoke extracts (CSEs) on human lung ECs, and found that a lower dose of 4% CSEs obviously caused abnormal morphological changes in ECs, increased the permeability of endothelial monolayer, while a higher concentration of 8% CSEs caused EC apoptosis. Strikingly, CSEs induced a 117-fold overexpression of a pro-tumorigenic interleukin-13 receptor α2 gene (IL-13Rα2, also named as CT-19) through activation of the protein kinase A (PKA) and cAMP response element-binding protein (CREB) signaling pathway. A PKA specific inhibitor H89 completely abolished CSEs-induced IL-13Rα2 overexpression. The overexpression of IL-13Rα2 in lung ECs significantly increased the tumorigenic, migratory, and angiogenic capabilities of the cells, suggesting that IL-13Rα2 promotes genesis of lung TAECs. Together, our data show that CSEs activate the PKA, CREB, and IL-13Rα2 axis in lung ECs, and IL-13Rα2 promotes the malignant transformation of lung ECs and genesis of TAECs with robust angiogenic and oncogenic capabilities. Our study provides new insight into the mechanism of CSEs-triggered lung cancer angiogenesis and tumorigenesis, suggesting that the PKA-CREB-IL-13Rα2 axis is a potential target for novel anti-lung tumor angiogenesis and anti-lung cancer drug discovery.

Tenascin-C secreted by transdifferentiated retinal pigment epithelial cells promotes choroidal neovascularization via integrin αV

Tenascin-C is expressed in choroidal neovascular (CNV) membranes in eyes with age-related macular degeneration (AMD). However, its role in the pathogenesis of CNV remains to be elucidated. Here we investigated the role of tenascin-C in CNV formation. In immunofluorescence analyses, tenascin-C co-stained with α-SMA, pan-cytokeratin, CD31, CD34, and integrin α_V in the CNV membranes of patients with AMD and a mouse model of laser-induced CNV. A marked increase in the expression of tenascin-C mRNA and protein was observed 3 days after laser photocoagulation in the mouse CNV model. Tenascin-C was also shown to promote proliferation and inhibit adhesion of human retinal pigment epithelial (hRPE) cells in vitro. Moreover, tenascin-C promoted proliferation, adhesion, migration, and tube formation in human microvascular endothelial cells (HMVECs); these functions were, however, blocked by cilengitide, an integrin α_V inhibitor. Exposure to TGF-β2 increased tenascin-C expression in hRPE cells. Conditioned media harvested from TGF-β2-treated hRPE cell cultures enhanced HMVEC proliferation and tube formation, which were inhibited by pretreatment with tenascin-C siRNA. The CNV volume was significantly reduced in tenascin-C knockout mice and tenascin-C siRNA-injected mice. These findings suggest that tenascin-C is secreted by transdifferentiated RPE cells and promotes the development of CNV via integrin α_V in a paracrine manner. Therefore, tenascin-C could be a potential therapeutic target for the inhibition of CNV development associated with AMD.

Linking Pluripotency Reprogramming and Cancer

Tumor development and the generation of induced pluripotent stem cells are highly comparable processes with striking similarities. Cellular plasticity is inherent to tumor evolution, rendering cells that acquire a stem cell-like phenotype, for which Sox2 activation has proved instrumental for the plastic acquisition of stemness properties in tumor cells. Understanding the molecular mechanisms underlying both events might uncover novel approaches for the development of anticancer therapeutics and constitute model systems for understanding tumor generation and ensuring the biosafety of cell-based therapies. Stem Cells Translational Medicine 2017;6:335-339.

Valproic Acid Increases CD133 Positive Cells that Show Low Sensitivity to Cytostatics in Neuroblastoma

Valproic acid (VPA) is a well-known antiepileptic drug that exhibits antitumor activities through its action as a histone deacetylase inhibitor. CD133 is considered to be a cancer stem cell marker in several tumors including neuroblastoma. CD133 transcription is strictly regulated by epigenetic modifications. We evaluated the epigenetic effects of treatment with 1mM VPA and its influence on the expression of CD133 in four human neuroblastoma cell lines. Chemoresistance and cell cycle of CD133+ and CD133- populations were examined by flow cytometry. We performed bisulfite conversion followed by methylation-sensitive high resolution melting analysis to assess the methylation status of CD133 promoters P1 and P3. Our results revealed that VPA induced CD133 expression that was associated with increased acetylation of histones H3 and H4. On treatment with VPA and cytostatics, CD133+ cells were mainly detected in the S and G2/M phases of the cell cycle and they showed less activated caspase-3 compared to CD133- cells. UKF-NB-3 neuroblastoma cells which express CD133 displayed higher colony and neurosphere formation capacities when treated with VPA, unlike IMR-32 which lacks for CD133 protein. Induction of CD133 in UKF-NB-3 was associated with increased expression of phosphorylated Akt and pluripotency transcription factors Nanog, Oct-4 and Sox2. VPA did not induce CD133 expression in cell lines with methylated P1 and P3 promoters, where the CD133 protein was not detected. Applying the demethylating agent 5-aza-2'-deoxycytidine to the cell lines with methylated promoters resulted in CD133 re-expression that was associated with a drop in P1 and P3 methylation level. In conclusion, CD133 expression in neuroblastoma can be regulated by histone acetylation and/or methylation of its CpG promoters. VPA can induce CD133+ cells which display high proliferation potential and low sensitivity to cytostatics in neuroblastoma. These results give new insight into the possible limitations to use VPA in cancer therapy.

A Promyelocytic Leukemia Protein-Thrombospondin-2 Axis and the Risk of Relapse in Neuroblastoma

PURPOSE

Neuroblastoma is a childhood malignancy originating from the sympathetic nervous system with a complex biology, prone to metastasize and relapse. High-risk, metastatic cases are explained in part by amplification or mutation of oncogenes, such as MYCN and ALK, and loss of tumor suppressor genes in chromosome band 1p. However, it is fundamental to identify other pathways responsible for the large portion of neuroblastomas with no obvious molecular alterations.

EXPERIMENTAL DESIGN

Neuroblastoma cell lines were used for the assessment of tumor growth in vivo and in vitro Protein expression in tissues and cells was assessed using immunofluorescence and IHC. The association of promyelocytic leukemia (PML) expression with neuroblastoma outcome and relapse was calculated using log-rank and Mann-Whitney tests, respectively. Gene expression was assessed using chip microarrays.

RESULTS

PML is detected in the developing and adult sympathetic nervous system, whereas it is not expressed or is low in metastatic neuroblastoma tumors. Reduced PML expression in patients with low-risk cancers, that is, localized and negative for the MYCN proto-oncogene, is strongly associated with tumor recurrence. PML-I, but not PML-IV, isoform suppresses angiogenesis via upregulation of thrombospondin-2 (TSP2), a key inhibitor of angiogenesis. Finally, PML-I and TSP2 expression inversely correlates with tumor angiogenesis and recurrence in localized neuroblastomas.

CONCLUSIONS

Our work reveals a novel PML-I-TSP2 axis for the regulation of angiogenesis and cancer relapse, which could be used to identify patients with low-risk, localized tumors that might benefit from chemotherapy. Clin Cancer Res; 22(13); 3398-409. ©2016 AACR.

Tenascin-C promotes angiogenesis in fibrovascular membranes in eyes with proliferative diabetic retinopathy

PURPOSE

We previously demonstrated that tenascin-C was highly expressed in the fibrovascular membranes (FVMs) of patients with proliferative diabetic retinopathy (PDR). However, its role in the pathogenesis of FVMs has not been determined. The purpose of this study was to investigate what role tenascin-C plays in the formation and angiogenesis of FVMs.

METHODS

The level of tenascin-C was determined by sandwich enzyme-linked immunosorbent assay in the vitreous samples collected from patients with PDR and with a macular hole as control. The locations of tenascin-C, α- smooth muscle actin (SMA), CD34, glial fibrillary acidic protein (GFAP), and integrin αV in the FVMs from PDR patients were determined by immunohistochemistry. We also measured the in vitro expression of the mRNA and protein of tenascin-C in vascular smooth muscle cells (VSMCs) stimulated by interleukin (IL)-13. The effects of tenascin-C on cell proliferation, migration, and tube formation were determined in human retinal endothelial cells (HRECs) in culture.

RESULTS

The mean vitreous levels of tenascin-C were significantly higher in patients with PDR than in patients with a macular hole (p<0.001). Double immunofluorescence analyses of FVMs from PDR patients showed that tenascin-C co-stained FVMs with α-SMA, CD34, and integrin αV but not with GFAP. In addition, IL-13 treatment increased both the expression and secretion of tenascin-C by VSMCs in a dose-dependent manner. Tenascin-C exposure promoted proliferation, migration, and tube formation in HRECs. Tenascin-C neutralizing antibody significantly blocked the tube formation by HRECs exposed to VSMC-IL-13-conditioned medium.

CONCLUSIONS

Our findings suggest that tenascin-C is secreted from VSMCs and promotes angiogenesis in the FVMs associated with PDR.

Sunitinib but not VEGF blockade inhibits cancer stem cell endothelial differentiation

Different mechanisms of angiogenesis and vasculogenesis are involved in the development of the tumor vasculature. Among them, cancer stem cells are known to contribute to tumor vasculogenesis through their direct endothelial differentiation. Here, we investigated the effect of anti-angiogenic therapy on vasculogenesis of cancer stem cells derived from breast and renal carcinomas. We found that all the anti-angiogenic approaches impaired proliferation and survival of cancer stem cells once differentiated into endothelial cells in vitro and reduced murine angiogenesis in vivo. At variance, only VEGF-receptor inhibition using the non-specific tyrosine kinase inhibitor Sunitinib or the anti-VEGF-receptor 2 neutralizing antibody, but not VEGF blockade using Bevacizumab, impaired the process of endothelial differentiation in vitro, suggesting a VEGF-independent mechanism. In addition, tyrosine kinase inhibition by Sunitinib but not VEGF blockade using the soluble VEGF trap sFlk1 inhibited the cancer stem cell-induced vasculogenesis in vivo. Accordingly, Sunitinib but not Bevacizumab inhibited the induction of hypoxia-inducible factor pathway occurring during endothelial differentiation under hypoxia. The present results highlight a differential effect of VEGF-receptor blockade versus VEGF inhibition in tumor vascularization. VEGFR blockade inhibits the process of tumor vasculogenesis occurring during tumor hypoxia whereas the effect of VEGF inhibition appears restricted to differentiated endothelial cells.

Involvement of HMGB1 in Resistance to Tumor Vessel-Targeted, Monoclonal Antibody-Based Immunotherapy

High mobility group box 1 (HMGB1) is a member of the “danger associated molecular patterns” (DAMPs) than can localize in various compartments of the cell (from the nucleus to the cell surface) and subserve different functions accordingly. HMGB1 is implicated in maintenance of genomic stability, autophagy, immune regulation, and tumor growth. HMGB1-induced autophagy promotes tumor resistance to chemotherapy, as shown in different models of malignancy, for example, osteosarcoma, leukemia, and gastric cancer. To the best of our knowledge, there is virtually no information on the relationships between HMGB1 and resistance to immunotherapy. A recent study from our group has shed new light on this latter issue. We have demonstrated that targeting of tumor-derived endothelial cells with an anti-human CD31 monoclonal antibody in a human neuroblastoma model was unsuccessful due to a complex chain of events involving the participation of HMGB1. These results are discussed in detail since they provide the first evidence for a role of HMGB1 in resistance of tumor cells to monoclonal antibody-based immunotherapy.

Tenascin-C at a glance

Tenascin-C (TNC) is a hexameric, multimodular extracellular matrix protein with several molecular forms that are created through alternative splicing and protein modifications. It is highly conserved amongst vertebrates, and molecular phylogeny indicates that it evolved before fibronectin. Tenascin-C has many extracellular binding partners, including matrix components, soluble factors and pathogens; it also influences cell phenotype directly through interactions with cell surface receptors. Tenascin-C protein synthesis is tightly regulated, with widespread protein distribution in embryonic tissues, but restricted distribution of tenascin-C in adult tissues. Tenascin-C is also expressed de novo during wound healing or in pathological conditions, including chronic inflammation and cancer. First described as a modulator of cell adhesion, tenascin-C also directs a plethora of cell signaling and gene expression programs by shaping mechanical and biochemical cues within the cellular microenvironment. Exploitment of the pathological expression and function of tenascin-C is emerging as a promising strategy to develop new diagnostic, therapeutic and bioengineering tools. In this Cell Science at a Glance article and the accompanying poster we provide a succinct and comprehensive overview of the structural and functional features of tenascin-C and its potential roles in developing embryos and under pathological conditions.

Sendai virus-mediated expression of reprogramming factors promotes plasticity of human neuroblastoma cells

Neuroblastoma (NB) is the most common extracranial solid tumor that originates from multipotent neural crest cells. NB cell populations that express embryonic stem cell-associated genes have been identified and shown to retain a multipotent phenotype. However, whether somatic reprogramming of NB cells can produce similar stem-cell like populations is unknown. Here, we sought to reprogram NB cell lines using an integration-free Sendai virus vector system. Of four NB cell lines examined, only SH-IN cells formed induced pluripotent stem cell-like colonies (SH-IN 4F colonies) at approximately 6 weeks following transduction. These SH-IN 4F colonies were alkaline phosphatase-positive. Array comparative genomic hybridization analysis indicated identical genomic aberrations in the SH-IN 4F cells as in the parental cells. SH-IN 4F cells had the ability to differentiate into the three embryonic germ layers in vitro, but rather formed NBs in vivo. Furthermore, SH-IN 4F cells exhibited resistance to cisplatin treatment and differentiated into endothelial-like cells expressing CD31 in the presence of vascular endothelial growth factor. These results suggest that SH-IN 4F cells are partially reprogrammed NB cells, and could be a suitable model for investigating the plasticity of aggressive tumors.

Failure of anti tumor-derived endothelial cell immunotherapy depends on augmentation of tumor hypoxia

We have previously demonstrated that Tenascin-C (TNC)⁺ human neuroblastoma (NB) cells transdifferentiate into tumor-derived endothelial cells (TDEC), which have been detected both in primary tumors and in tumors formed by human NB cell lines in immunodeficient mice. TDEC are genetically unstable and may favor tumor progression, suggesting that their elimination could reduce tumor growth and dissemination. So far, TDEC have never been targeted by antibody-mediated immunotherapy in any of the tumor models investigated.

To address this issue, immunodeficient mice carrying orthotopic NB formed by the HTLA-230 human cell line were treated with TDEC-targeting cytotoxic human (h)CD31, that spares host-derived endothelial cells, or isotype-matched mAbs. hCD31 mAb treatment did not affect survival of NB-bearing mice, but increased significantly hypoxia in tumor microenvironment, where apoptotic and proliferating TDEC coexisted, indicating the occurrence of vascular remodeling.

Tumor cells from hCD31 mAb treated mice showed i) up-regulation of epithelial-mesenchymal transition (EMT)-related and vascular mimicry (VM)-related gene expression, ii) expression of endothelial (i.e. CD31 and VE-cadherin) and EMT-associated (i.e. Twist-1, N-cadherin and TNC) immunophenotypic markers, and iii) up-regulation of high mobility group box-1 (HMGB-1) expression. In vitro experiments with two NB cell lines showed that hypoxia was the common driver of all the above phenomena and that human recombinant HMGB-1 amplified EMT and TDEC trans-differentiation.

In conclusion, TDEC targeting with hCD31 mAb increases tumor hypoxia, setting the stage for the occurrence of EMT and of new waves of TDEC trans-differentiation. These adaptive responses to the changes induced by immunotherapy in the tumor microenvironment allow tumor cells to escape from the effects of hCD31 mAb.

Functional interplay between MYCN, NCYM, and OCT4 promotes aggressiveness of human neuroblastomas

Neuroblastoma is a pediatric solid tumor that originates from embryonic neural crest cells. The MYCN gene locus is frequently amplified in unfavorable neuroblastomas, and the gene product promotes the progression of neuroblastomas. However, the molecular mechanisms by which MYCN amplification contributes to stem cell-like states of neuroblastoma remain elusive. In this study, we show that MYCN and its cis-antisense gene, NCYM, form a positive feedback loop with OCT4, a core regulatory gene maintaining a multipotent state of neural stem cells. We previously reported that NCYM is co-amplified with the MYCN gene in primary human neuroblastomas and that the gene product promotes aggressiveness of neuroblastoma by stabilization of MYCN. In 36 MYCN-amplified primary human neuroblastomas, OCT4 mRNA expression was associated with unfavorable prognosis and was correlated with that of NCYM. The OCT4 protein induced both NCYM and MYCN in human neuroblastoma cells, whereas NCYM stabilized MYCN to induce OCT4 and stem cell-related genes, including NANOG, SOX2, and LIN28. In sharp contrast to MYCN, enforced expression of c-MYC did not enhance OCT4 expression in human neuroblastoma cells. All-trans retinoic acid treatment reduced MYCN, NCYM, and OCT4 expression, accompanied by the decreased amount of OCT4 recruited onto the intron 1 region of MYCN. Knockdown of NCYM or OCT4 inhibited formation of spheres of neuroblastoma cells and promoted asymmetric cell division in MYCN-amplified human neuroblastoma cells. These results suggest that the functional interplay between MYCN, NCYM, and OCT4 contributes to aggressiveness of MYCN-amplified human neuroblastomas.

Tenascin-C: a novel candidate marker for cancer stem cells in glioblastoma identified by tissue microarrays

Glioblastoma multiforme (GBM) is a highly aggressive brain tumor, with dismal survival outcomes. Recently, cancer stem cells (CSCs) have been demonstrated to play a role in therapeutic resistance and are considered to be the most likely cause of cancer relapse. The identification of CSCs is an important step toward finding new and effective ways to treat GBM. Tenascin-C (TNC) protein has been identified as a potential marker for CSCs in gliomas based on previous work. Here, we have investigated the expression of TNC in tissue microarrays including 17 GBMs, 18 WHO grade III astrocytomas, 15 WHO grade II astrocytomas, 4 WHO grade I astrocytomas, and 7 normal brain tissue samples by immunohistochemical staining. TNC expression was found to be highly associated with the grade of astrocytoma. It has a high expression level in most of the grade III astrocytomas and GBMs analyzed and a very low expression in most grade II astrocytomas, whereas it is undetectable in grade I astrocytomas and normal brain tissues. Double-immunofluorescence staining for TNC and CD133 in GBM tissues revealed that there was a high overlap between theses two positive populations. The results were further confirmed by flow cytometry analysis of TNC and CD133 in GBM-derived stem-like neurospheres in vitro. A limiting dilution assay demonstrated that the sphere formation ability of CD133⁺/TNC⁺ and CD133^–/TNC⁺ cell populations is much higher than that of the CD133⁺/TNC^– and CD133^–/TNC^– populations. These results suggest that TNC is not only a potential prognostic marker for GBM but also a potential marker for glioma CSCs, where the TNC⁺ population is identified as a CSC population overlapping with part of the CD133^– cell population.

The Activation of the Sox2 RR2 Pluripotency Transcriptional Reporter in Human Breast Cancer Cell Lines is Dynamic and Labels Cells with Higher Tumorigenic Potential

The striking similarity displayed at the mechanistic level between tumorigenesis and the generation of induced pluripotent stem cells and the fact that genes and pathways relevant for embryonic development are reactivated during tumor progression highlights the link between pluripotency and cancer. Based on these observations, we tested whether it is possible to use a pluripotency-associated transcriptional reporter, whose activation is driven by the SRR2 enhancer from the Sox2 gene promoter (named S4+ reporter), to isolate cancer stem cells (CSCs) from breast cancer cell lines. The S4+ pluripotency transcriptional reporter allows the isolation of cells with enhanced tumorigenic potential and its activation was switched on and off in the cell lines studied, reflecting a plastic cellular process. Microarray analysis comparing the populations in which the reporter construct is active versus inactive showed that positive cells expressed higher mRNA levels of cytokines (IL-8, IL-6, TNF) and genes (such as ATF3, SNAI2, and KLF6) previously related with the CSC phenotype in breast cancer.

Priming cancer cells for drug resistance: role of the fibroblast niche

Conventional and targeted chemotherapies remain integral strategies to treat solid tumors. Despite the large number of anti-cancer drugs available, chemotherapy does not completely eradicate disease. Disease recurrence and the growth of drug resistant tumors remain significant problems in anti-cancer treatment. To develop more effective treatment strategies, it is important to understand the underlying cellular and molecular mechanisms of drug resistance. It is generally accepted that cancer cells do not function alone, but evolve through interactions with the surrounding tumor microenvironment. As key cellular components of the tumor microenvironment, fibroblasts regulate the growth and progression of many solid tumors. Emerging studies demonstrate that fibroblasts secrete a multitude of factors that enable cancer cells to become drug resistant. This review will explore how fibroblast secretion of soluble factors act on cancer cells to enhance cancer cell survival and cancer stem cell renewal, contributing to the development of drug resistant cancer.

Immunosuppressive microenvironment in neuroblastoma

According to the cancer immunoediting model, the interplay between tumor cells and the host immune system is crucial for the control of tumor growth. NB is a pediatric tumor that presents with metastatic disease at diagnosis in about 50% of the cases, the majority of which have poor prognosis. In this Review article, immune escape pathways adopted by human neuroblastoma (NB) cells are reviewed. These include intrinsic defects of tumor cells such impaired expression of the HLA class I related antigen processing machinery and functional alterations of the tumor microenvironment (TM) induced by NB cell-derived immunosuppressive molecules as MICA and HLA-G. Finally, examples of therapeutic interventions targeting the TM are discussed to emphasize the concept that successful cancer treatment may be achieved using this strategy.

p38MAPK inhibition: a new combined approach to reduce neuroblastoma resistance under etoposide treatment

Neuroblastoma (NB) is the second most common solid pediatric tumor and is characterized by clinical and biological heterogeneity, and stage-IV of the disease represents 50% of all cases. Considering the limited success of present chemotherapy treatment, it has become necessary to find new and effective therapies. In this context, our approach consists of identifying and targeting key molecular pathways associated with NB chemoresistance. This study has been carried out on three stage-IV NB cell lines with different status of MYCN amplification. Cells were exposed to a standard chemotherapy agent, namely etoposide, either alone or in combination with particular drugs, which target intracellular signaling pathways. Etoposide alone induced a concentration-dependent reduction of cell viability and, at very high doses, totally counteracted cell tumorigenicity and neurosphere formation. In addition, etoposide activated p38 mitogen-activated protein kinase (MAPK), AKT and c-Jun N-terminal kinase. Pre-treatment with SB203580, a p38MAPK inhibitor, dramatically sensibilized NB cells to etoposide, strongly reducing the dosage needed to inhibit tumorigenicity and neurosphere formation. Importantly, SB203580–etoposide cotreatment also reduced cell migration and invasion by affecting cyclooxygenase-2, intercellular adhesion molecule-1, C–X–C chemokine receptor-4 and matrix metalloprotease-9. Collectively, our results suggest that p38MAPK inhibition, in combination with standard chemotherapy, could represent an effective strategy to counteract NB resistance in stage-IV patients.

Downregulation of OCT4 promotes differentiation and inhibits growth of BE (2)-C human neuroblastoma I-type cells

In in vitro continuous culture, N (neuroblastic)-, S (substrate adherent)- and I (intermediate)-type cells were identified in human neuroblastoma (NB), where I-type is recognized as a stem cell type. Octamer-binding protein 4 (OCT4) is a cell marker used to identify the stemness of cells, whose roles in regulating I-type NB cells have yet to be fully elucidated. In the present study, we assessed the differentiation regulation role of OCT4 in BE (2)-C of I-type cells. We demonstrated that downregulation of OCT4 expression in BE (2)-C was associated with reduced cell proliferation and loss of colony formation ability on soft agar, and prompted BE (2)-C cells to differentiate to S-type cells. By contrast, overexpression of OCT4 increased cell proliferation and colony formation ratio, but no obvious differentiation promotion was observed. Furthermore, induced differentiation of BE (2)-C cells to S-type by 5-bromo-2'-deoxyuridine (BrdUrd) was accompanied by reduced expression of OCT4.

MYCN: from oncoprotein to tumor-associated antigen

MYCN is a well-known oncogene over-expressed in different human malignancies including neuroblastoma (NB), rhabdomyosarcoma, medulloblastoma, astrocytoma, Wilms' tumor, and small cell lung cancer. In the case of NB, MYCN amplification is an established biomarker of poor-prognosis. MYCN belongs to a family of transcription factors (the most important of which is C-MYC) that show a high degree of homology. Down-regulation of MYC protein expression leads to tumor regression in animal models, indicating that MYC proteins represent interesting therapeutic targets. Pre-requisites for a candidate tumor-associated antigen (TAA) to be targeted by immunotherapeutic approaches are the following, (i) expression should be tumor-restricted, (ii) the putative TAA should be up-regulated in cancer cells, and (iii) protein should be processed into immunogenic peptides capable of associating to major histocompatibility complex molecules with high affinity. Indeed, the MYCN protein is not expressed in human adult tissues and up-regulated variably in NB cells, and MYCN peptides capable of associating to HLA-A1 or HLA-A2 molecules with high affinity have been identified. Thus the MYCN protein qualifies as putative TAA in NB. Additional issues that determine the feasibility of targeting a putative TAA with cytotoxic T lymphocytes (CTLs) and will be here discussed are the following, (i) the inadequacy of tumor cells per se to act as antigen-presenting cells witnessed, in the case of NB cells, by the low to absent expression of HLA class I molecules, the lack of co-stimulatory molecules and multiple defects in the HLA class I related antigen processing machinery, and (ii) the immune evasion mechanisms operated by cancer cells to fool the host immune system, such as up-regulation of soluble immunosuppressive molecules (e.g., soluble MICA and HLA-G in the case of NB) or generation of immunosuppressive cells in the tumor microenvironment. A final issue that deserves consideration is the strategy used to generate CTL.

Frizzled receptor 6 marks rare, highly tumourigenic stem-like cells in mouse and human neuroblastomas

Wnt signalling is an important component of vertebrate development, required for specification of the neural crest. Ten Wnt receptors [Frizzled receptor 1-10 (Fzd1-10)] have been identified so far, some of which are expressed in the developing nervous system and the neural crest. Here we show that expression of one such receptors, Fzd6, predicts poor survival in neuroblastoma patients and marks rare, HIF1/2 α-positive cells in tumour hypoxic areas. Fzd6 positive neuroblastoma cells form neurospheres with high efficiency, are resistant to doxorubicin killing and express high levels of mesenchymal markers such as Twist1 and Notch1. Expression of Fzd6 is required for the expression of genes of the non-canonical Wnt pathway and the spheres forming activity. When transplanted into immunodeficient mice, neuroblastoma cells expressing the Fzd6 marker grow more aggressively than their Fzd6 negative counterparts. We conclude that Fzd6 is a new surface marker of aggressive neuroblastoma cells with stem cell-like features.