Frizzled2 signaling regulates growth of high-risk neuroblastomas by interfering with β-catenin-dependent and β-catenin-independent signaling pathways

Precision Oncology in Pediatric Cancer Surgery

Pediatric precision oncology has provided a greater understanding of the wide range of molecular alterations in difficult-to-treat or rare tumors with the aims of increasing survival as well as decreasing toxicity and morbidity from current cytotoxic therapies. In this article, the authors discuss the current state of pediatric precision oncology which has increased access to novel targeted therapies while also providing a framework for clinical implementation in this unique population. The authors evaluate the targetable mutations currently under investigation-with a focus on pediatric solid tumors-and discuss the key surgical implications associated with novel targeted therapies.

HSV1 microRNAs in glioblastoma development: an in silico study

Glioblastoma multiforme (GBM) is a highly aggressive primary brain tumor. Recent findings highlighted the significance of viral microRNAs (miRs) in regulating post-transcriptional mRNA expression in various human conditions. Although HSV1 encodes viral miRs and affects the central nervous system, no study investigated the roles of HSV1-encoding miRs in GBM development. This study applied in silico approaches to investigate whether HSV1-encoding miRs are involved in GBM development and, if so, how they regulate tumor-suppressive/oncogenes expression in GBM. This study leveraged bioinformatics approaches to identify the potential effect of HSV1 miRs in GBM development. The GSE158284, GSE153679, and GSE182109 datasets were analyzed to identify differentially expressed genes in GBM tissues and cell lines using the limma package in the R software. The GSE182109 dataset was analyzed to determine gene expression at the single-cell levels using the Seurat package in the R software. The TCGA-GTEX, GDSC, CTRP, immunogenetic, and enrichment analyses were performed to study the impact of identified viral HSV1 miRs targets in GBM development. hsv1-miR-H6-3p is upregulated in GBM and can be responsible for EPB41L1 and SH3PXD2A downregulation in GBM tissues. Also, hsv1-miR-H1-5p is upregulated in GBM and can decrease the expression of MELK, FZD2, NOVA1, TMEM97, PTPRZ1, and PDGFC in GBM development. The single-cell RNA sequencing analyses have demonstrated that MELK, FZD2, NOVA1, TMEM97, PTPRZ1, and PDGFC are expressed in astrocytes residing in the GBM microenvironment. This study provides novel insights into the potential roles of HSV1 miRs in GBM pathogenesis and offers a reference for further studies on the significance of HSV1 miRs in GBM development.

Neural crest cells development and neuroblastoma progression: Role of Wnt signaling

Neuroblastoma (NB) is one of the most common heterogeneous extracranial cancers in infancy that arises from neural crest (NC) cells of the sympathetic nervous system. The Wnt signaling pathway, both canonical and noncanonical pathway, is a highly conserved signaling pathway that regulates the development and differentiation of the NC cells during embryogenesis. Reports suggest that aberrant activation of Wnt ligands/receptors in Wnt signaling pathways promote progression and relapse of NB. Wnt signaling pathways regulate NC induction and migration in a similar manner; it regulates proliferation and metastasis of NB. Inhibiting the Wnt signaling pathway or its ligands/receptors induces apoptosis and abrogates proliferation and tumorigenicity in all major types of NB cells. Here, we comprehensively discuss the Wnt signaling pathway and its mechanisms in regulating the development of NC and NB pathogenesis. This review highlights the implications of aberrant Wnt signaling in the context of etiology, progression, and relapse of NB. We have also described emerging strategies for Wnt-based therapies against the progression of NB that will provide new insights into the development of Wnt-based therapeutic strategies for NB.

Serine-Threonine Kinase Receptor-Associated Protein (STRAP) Knockout Decreases the Malignant Phenotype in Neuroblastoma Cell Lines

Background: Serine-threonine kinase receptor-associated protein (STRAP) plays an important role in neural development but also in tumor growth. Neuroblastoma, a tumor of neural crest origin, is the most common extracranial solid malignancy of childhood and it continues to carry a poor prognosis. The recent discovery of the role of STRAP in another pediatric solid tumor, osteosarcoma, and the known function of STRAP in neural development, led us to investigate the role of STRAP in neuroblastoma tumorigenesis. Methods: STRAP protein expression was abrogated in two human neuroblastoma cell lines, SK-N-AS and SK-N-BE(2), using transient knockdown with siRNA, stable knockdown with shRNA lentiviral transfection, and CRISPR-Cas9 genetic knockout. STRAP knockdown and knockout cells were examined for phenotypic alterations in vitro and tumor growth in vivo. Results: Cell proliferation, motility, and growth were significantly decreased in STRAP knockout compared to wild-type cells. Indicators of stemness, including mRNA abundance of common stem cell markers Oct4, Nanog, and Nestin, the percentage of cells expressing CD133 on their surface, and the ability to form tumorspheres were significantly decreased in the STRAP KO cells. In vivo, STRAP knockout cells formed tumors less readily than wild-type tumor cells. Conclusion: These novel findings demonstrated that STRAP plays a role in tumorigenesis and maintenance of neuroblastoma stemness.

Wnt5A modulates integrin expression in a receptor-dependent manner in ovarian cancer cells

Wnt5A signals through various receptors that confer versatile biological functions. Here, we used Wnt5A overexpressing human ovarian SKOV-3 and OVCAR-3 stable clones for assessing integrin expression, cell proliferation, migration, invasion, and the ability of multicellular aggregates (MCAs) formation. We found here, that Wnt5A regulates differently the expression of its receptors in the stable Wnt5A overexpressing clones. The expression levels of Frizzled (FZD)-2 and -5, were increased in different clones. However ROR-1, -2 expression levels were differently regulated in clones. Wnt5A overexpressing clones showed increased cell proliferation, migration, and clonogenicity. Moreover, Wnt5A overexpressing SKOV-3 clone showed increased MCAs formation ability. Cell invasion had been increased in OVCAR-3-derived clones, while this was decreased in SKOV-3-derived clone. Importantly, αv integrin expression levels were increased in all assessed clones, accompanied by increased cell attachment to fibronectin and focal adhesion kinase activity. Moreover, the treatment of clones with Box5 as a Wnt5A/FZD5 antagonist abrogates ITGAV increase, cell proliferation, migration, and their attachment to fibronectin. Accordingly, we observed significantly higher expression levels of ITGAV and ITGB3 in human high-grade serous ovarian cancer specimens and ITGAV correlated positively with Wnt5A in metastatic serous type ovarian cancer. In summary, we hypothesize here, that Wnt5A/FZD-5 signaling modulate αv integrin expression levels that could be associated with ovarian cancer cell proliferation, migration, and fibronectin attachment.

Molecular targeting therapies for neuroblastoma: Progress and challenges

There is an urgent need to identify novel therapies for childhood cancers. Neuroblastoma is the most common pediatric solid tumor, and accounts for ~15% of childhood cancer‐related mortality. Neuroblastomas exhibit genetic, morphological and clinical heterogeneity, which limits the efficacy of existing treatment modalities. Gaining detailed knowledge of the molecular signatures and genetic variations involved in the pathogenesis of neuroblastoma is necessary to develop safer and more effective treatments for this devastating disease. Recent studies with advanced high‐throughput “omics” techniques have revealed numerous genetic/genomic alterations and dysfunctional pathways that drive the onset, growth, progression, and resistance of neuroblastoma to therapy. A variety of molecular signatures are being evaluated to better understand the disease, with many of them being used as targets to develop new treatments for neuroblastoma patients. In this review, we have summarized the contemporary understanding of the molecular pathways and genetic aberrations, such as those in MYCN, BIRC5, PHOX2B, and LIN28B, involved in the pathogenesis of neuroblastoma, and provide a comprehensive overview of the molecular targeted therapies under preclinical and clinical investigations, particularly those targeting ALK signaling, MDM2, PI3K/Akt/mTOR and RAS‐MAPK pathways, as well as epigenetic regulators. We also give insights on the use of combination therapies involving novel agents that target various pathways. Further, we discuss the future directions that would help identify novel targets and therapeutics and improve the currently available therapies, enhancing the treatment outcomes and survival of patients with neuroblastoma.

Pan-cancer analysis of the developmental pathways reveals non-canonical wnt signaling as a driver of mesenchymal-type tumors

The processes of angiogenesis, cell proliferation, invasion, and migration, and the signaling pathways that drive these events, are activated in both cancer and during embryonic development. Here, we systematically assessed how the activity of major developmental signaling pathways, represented by the expression of genes encoding components of the pathways, correlated with patient survival in ∼8000 patients across 17 cancer types. We also compared the expressed genes enriched in developmental pathways with those associated with epithelial-mesenchymal transition (EMT) both in a cancer cohort and in mice during embryonic development. We found that EMT and gene expression profiles consistent with high activity of several developmental pathways, including the TGFβ, Notch, and non-canonical Wnt pathways, significantly correlated with poor patient survival in multiple cancer types. We investigated individual components of these pathways and found that expression of the gene encoding the non-canonical Wnt receptor, frizzled 2 (FZD2), is highly correlated with both poor patient survival and gene expression indicating EMT in the tumors. Further mechanistic studies and pathway analyses revealed that FZD2-regulated genes in cancer cells in culture or FZD2-regulated gene sets from the TCGA data or FZD2-regulated genes involved in mouse organogenesis converged in EMT-associated biological processes, suggesting that FZD2 is a key driver of mesenchymal-like cell state and thus, a contributor to cancer progression and metastasis.

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.

WNT2-Mediated FZD2 Stabilization Regulates Esophageal Cancer Metastasis via STAT3 Signaling

Esophageal cancer micro environment factor WNT2 was critical in cancer metastasis. However, very little is known about WNT2 receptors and their role in the malignant progression of ESCC. The clinical significance and underlying molecular mechanisms of FZD2, one of the receptors of WNT2, was further investigated in ESCC. We found that FZD2 expression was positively correlated with WNT2 levels in clinical ESCC specimens through database analysis. Upregulated FZD2 expression was detected in 69% (69/100) of the primary ESCC cases examined, and increased FZD2 expression was significantly correlated with poor prognosis (P < 0.05). Mechanistically, FZD2 induced the migration and invasion of ESCC cells by regulating the FZD2/STAT3 signaling. In vivo xenograft experiments further revealed the metastasis-promoting role of FZD2 in ESCC. Moreover, we found that the WNT2 ligand could stabilize and phosphorylate the FZD2 receptor by attenuating FZD2 ubiquitination, leading to the activation of STAT3 signaling and the initiation of ESCC cell metastasis. Collectively, our data revealed that a novel non-canonical WNT2/FZD2/STAT3 signaling axis is critical for ESCC progression. Strategies targeting this specific signaling axis might be developed to treat patients with ESCC.

A Wnt-BMP4 Signaling Axis Induces MSX and NOTCH Proteins and Promotes Growth Suppression and Differentiation in Neuroblastoma

The Wnt and bone morphogenetic protein (BMP) signaling pathways are known to be crucial in the development of neural crest lineages, including the sympathetic nervous system. Surprisingly, their role in paediatric neuroblastoma, the prototypic tumor arising from this lineage, remains relatively uncharacterised. We previously demonstrated that Wnt/b-catenin signaling can have cell-type-specific effects on neuroblastoma phenotypes, including growth inhibition and differentiation, and that BMP4 mRNA and protein were induced by Wnt3a/Rspo2. In this study, we characterised the phenotypic effects of BMP4 on neuroblastoma cells, demonstrating convergent induction of MSX homeobox transcription factors by Wnt and BMP4 signaling and BMP4-induced growth suppression and differentiation. An immunohistochemical analysis of BMP4 expression in primary neuroblastomas confirms a striking absence of BMP4 in poorly differentiated tumors, in contrast to a high expression in ganglion cells. These results are consistent with a tumor suppressive role for BMP4 in neuroblastoma. RNA sequencing following BMP4 treatment revealed induction of Notch signaling, verified by increases of Notch3 and Hes1 proteins. Together, our data demonstrate, for the first time, Wnt-BMP-Notch signaling crosstalk associated with growth suppression of neuroblastoma.

Developing preclinical models of neuroblastoma: driving therapeutic testing

Despite advances in cancer therapeutics, particularly in the area of immuno-oncology, successful treatment of neuroblastoma (NB) remains a challenge. NB is the most common cancer in infants under 1 year of age, and accounts for approximately 10% of all pediatric cancers. Currently, children with high-risk NB exhibit a survival rate of 40–50%. The heterogeneous nature of NB makes development of effective therapeutic strategies challenging. Many preclinical models attempt to mimic the tumor phenotype and tumor microenvironment. In vivo mouse models, in the form of genetic, syngeneic, and xenograft mice, are advantageous as they replicated the complex tumor-stroma interactions and represent the gold standard for preclinical therapeutic testing. Traditional in vitro models, while high throughput, exhibit many limitations. The emergence of new tissue engineered models has the potential to bridge the gap between in vitro and in vivo models for therapeutic testing. Therapeutics continue to evolve from traditional cytotoxic chemotherapies to biologically targeted therapies. These therapeutics act on both the tumor cells and other cells within the tumor microenvironment, making development of preclinical models that accurately reflect tumor heterogeneity more important than ever. In this review, we will discuss current in vitro and in vivo preclinical testing models, and their potential applications to therapeutic development.

FZD2 regulates cell proliferation and invasion in tongue squamous cell carcinoma

Many studies have shown that FZD2 is significantly associated with tumor development and tumor metastasis. The purpose of the present study was to gain insight into the role of FZD2 in the cell proliferation and invasion of tongue squamous cell carcinoma. According to TCGA-HNSC dataset, among the 10 Frizzled receptors, FZD2 exhibited the highest degree of differential expression between cancer tissues and normal tissues, and the overall survival of patients with higher FZD2 levels was shown to be significantly shorter compared with those with lower FZD2 levels. The upregulation of FZD2 in clinical tongue cancer tissues was validated by real-time PCR. Knockdown of FZD2 inhibited the proliferation, migration and invasion of CAL-27 and TCA-8113 cells, whereas overexpression of FZD2 led to the opposite results. Further analysis revealed that FZD2 is positively correlated with WNT3A, WNT5B, WNT7A and WNT2 and is negatively correlated with WNT4. These results indicated that FZD2 may act as an oncogene in tongue squamous cell carcinoma. Therefore, FZD2 may be a target for the diagnosis, prognosis and gene therapy of tongue cancer.

Perfluorooctanoic acid-induced toxicities in chicken embryo primary cardiomyocytes: Roles of PPAR alpha and Wnt5a/Frizzled2

Perfluorooctanoic acid (PFOA) is a widespread persistent organic pollutant and may induce developmental toxicities, including developmental cardiotoxicity. To explore the potential mechanism of developmental cardiotoxicity induced by PFOA exposure, chicken embryo primary cardiomyocytes were extracted either from chicken embryos pretreated with PFOA (2 mg/kg), or from untreated embryos and then directly exposed cells to PFOA (1, 10, 30 or 100 μg/ml) in culture. Additionally, peroxisome proliferator activated receptor alpha (PPAR alpha) silencing lentivirus was applied to the embryos on embryonic day (ED2). Cell viability was measured with CCK-8 kit, morphology was assessed with hematoxylin and eosin staining, and intracellular Ca²⁺ concentrations were determined with Fluo-4 AM probe. Western blotting was utilized to confirm PPAR alpha silencing efficiency and the protein abundance of Wnt5a and Frizzled2. The results indicated that both PFOA pretreatment and direct exposure decreased primary cardiomyocyte viability, altered cell morphology and increased intracellular Ca²⁺ concentrations. While l-carnitine co-treatment effectively abolished such changes, PPAR alpha silencing only abolished most of the changes in PFOA pretreatment group, but not in cells directly exposed to relatively high doses of PFOA. The protein abundance of Wnt5a and Frizzled2 was increased by PFOA pretreatment, while direct exposure to PFOA increased Frizzled2 abundance but decreased Wnt5a abundance. PPAR alpha silencing resulted in over 50% decrease of PPAR alpha expression level, which abolished the Wnt5a/Frizzled2 expression alterations following PFOA exposure. In conclusion, PFOA-induced primary cardiomyocyte toxicity is associated with PPAR alpha and Wnt5a/Frizzled2, in which PPAR alpha seems to play regulatory roles towards Wnt5a/Frizzled2.

WNT Signaling in Neuroblastoma

The term WNT (wingless-type MMTV integration site family) signaling comprises a complex molecular pathway consisting of ligands, receptors, coreceptors, signal transducers and transcriptional modulators with crucial functions during embryonic development, including all aspects of proliferation, morphogenesis and differentiation. Its involvement in cancer biology is well documented. Even though WNT signaling has been divided into mainly three distinct branches in the past, increasing evidence shows that some molecular hubs can act in various branches by exchanging interaction partners. Here we discuss developmental and clinical aspects of WNT signaling in neuroblastoma (NB), an embryonic tumor with an extremely broad clinical spectrum, ranging from spontaneous differentiation to fatal outcome. We discuss implications of WNT molecules in NB onset, progression, and relapse due to chemoresistance. In the light of the still too high number of NB deaths, new pathways must be considered.

The role of β-catenin and paired-like homeobox 2B (PHOX2B) expression in neuroblastoma patients; predictive and prognostic value

BACKGROUND

The expression of β-catenin and paired-like homeobox 2B (PHOX2B) expression were assessed in Neuroblastoma (NB) patients as a diagnostic, prognostic and/or predictive markers.

METHODS

Bone marrow (BM) samples of 52 NB patients were assessed for the expression of β-catenin by immunohistochemistry (IHC), and PHOX2B by real time PCR (RT-PCR), compared to 12 healthy normal controls (NC). The data were correlated to the clinic-pathological features of the patients, response to treatment and disease relapse.

RESULTS

β-catenin was expressed in 40 (76.92%) patients (P < .001). While PHOX2B was expressed in 32/52 (61.5%) patients, with a fold change of 0.29 (0.01-40.0, P = .096). β-catenin expression associated significantly with advanced tumor stage, high risk, positive results by MIBG and bone scan (P = .002, P < .001, P = .006, P = .013; respectively). Also it associated significantly with synaptophysin expression in the BM biopsy (P < .001), with a significant concordance (K = 0.519, P < .001). The expression of β-catenin associated significantly with PHOX2B gene expression [28/32 (87.5%), P = .04], and its fold change (P = .027), with a significant measure of agreement (K = 0.297, P = .022). The fold change of PHOX2B gene expression associated significantly with the high risk of the patients (P = .04). Poor response to treatment associated significantly with the expression of neuron specific enolase (NSE), β-catenin and PHOX2B in NB patients (P = .021, P = .019 and P = .040; respectively). The sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV) of synaptophysin for the diagnosis of BM metastasis in NB patients were (69%, 65.2%, 71.4%, 62.5%; respectively, P = .024). While with β-catenin (93.1%, 43.5%, 67.5%, 83.3%; respectively, P = .003), and PHOX2B expression (65.5%, 34.5%, 59.4%, 50%; respectively, P = .574).

CONCLUSION

β-Catenin could be used as a sensitive and reliable marker for detection of BM metastasis and also a good predictor for resistance to treatment in NB patients. While, PHOX2B gene expression in BM aspirate could be a marker for high risk patients and poor response to treatment.

Wnt Signaling Is a Major Determinant of Neuroblastoma Cell Lineages

The neural crest (NC), which has been referred to as the fourth germ layer, comprises a multipotent cell population which will specify diverse cells and tissues, including craniofacial cartilage and bones, melanocytes, the adrenal medulla and the peripheral nervous system. These cell fates are known to be determined by gene regulatory networks (GRNs) acting at various stages of NC development, such as induction, specification, and migration. Although transcription factor hierarchies and some of their interplay with morphogenetic signaling pathways have been characterized, the full complexity of activities required for regulated development remains uncharted. Deregulation of these pathways may contribute to tumorigenesis, as in the case of neuroblastoma, a frequently lethal embryonic cancer thought to arise from the sympathoadrenal lineage of the NC. In this “Hypothesis and Theory” article, we utilize the next generation sequencing data from neuroblastoma cells and tumors to evaluate the possible influences of Wnt signaling on NC GRNs and on neuroblastoma cell lineages. We propose that Wnt signaling is a major determinant of regulatory networks that underlie mesenchymal/neural crest cell (NCC)-like cell identities through PRRX1 and YAP/TAZ transcription factors. Furthermore, Wnt may also co-operate with Hedgehog signaling in driving proneural differentiation programmes along the adrenergic (ADRN) lineage. Elucidation of Signaling Regulatory Networks can augment and complement GRNs in characterizing cell identities, which may in turn contribute to the design of improved therapeutics tailored to primary and relapsing neuroblastoma.

Remote ischemic perconditioning attenuates adverse cardiac remodeling and preserves left ventricular function in a rat model of reperfused myocardial infarction

AIMS

Remote ischemic conditioning (RIC) is considered a potential clinical approach to reduce myocardial infarct size and ameliorate adverse post-infarct left ventricular (LV) remodeling, however the mechanisms are unknown. The aim was to clarify the impact of RIC on Neuregulin-1 (NRG-1)/ErbBs expression, inflammation and LV hemodynamic function.

METHODS AND RESULTS

Male Sprague-Dawley rats were subjected to 30 min occlusion of the left coronary artery (LCA) followed by 2 weeks of reperfusion and separated into three groups: (1) sham operated (without LCA occlusion); (2) Myocardial ischemia/reperfusion (MIR) and (3) remote ischemic perconditioning group (MIR + RIPerc). Cardiac structural and functional changes were evaluated by echocardiography and on the isolated working heart system. The level of H3K4me3 at the NRG-1 promoter, and both plasma and LV tissue levels of NRG-1 were assessed. The expression of pro-inflammatory cytokines, ECM components and ErbB receptors were assessed by RT-qPCR. MIR resulted in a significant decrease in LV function and enlargement of LV chamber. This was accompanied with a decrease in the level of H3K4me3 at the NRG-1 promoter. Consequently NRG-1 protein levels were reduced in the infarcted myocardium. Subsequently, an upregulated influx of CD68+ macrophages, high expression of MMP-2 and -9 as well as an increase of IL-1β, TLR-4, TNF-α, TNC expression were observed. In contrast, RIPerc significantly decreased inflammation and improved LV function in association with the enhancement of NRG-1 levels and ErbB3 expression.

CONCLUSIONS

These findings may reveal a novel anti-remodeling and anti-inflammatory effect of RIPerc, involving activation of NRG-1/ErbB3 signaling.

Frizzled Receptors as Potential Therapeutic Targets in Human Cancers

Frizzled receptors (FZDs) are a family of seven-span transmembrane receptors with hallmarks of G protein-coupled receptors (GPCRs) that serve as receptors for secreted Wingless-type (WNT) ligands in the WNT signaling pathway. Functionally, FZDs play crucial roles in regulating cell polarity, embryonic development, cell proliferation, formation of neural synapses, and many other processes in developing and adult organisms. In this review, we will introduce the basic structural features and review the biological function and mechanism of FZDs in the progression of human cancers, followed by an analysis of clinical relevance and therapeutic potential of FZDs. We will focus on the development of antibody-based and small molecule inhibitor-based therapeutic strategies by targeting FZDs for human cancers.

Differential prognostic impact of interleukin-34 mRNA expression and infiltrating immune cell composition in intrinsic breast cancer subtypes

Interleukin-34 (IL-34) is a ligand for the CSF-1R and has also two additional receptors, PTPRZ1 and syndecan-1. IL-34 plays a role in innate immunity, inflammation, and cancer. However, the role of IL-34 in breast cancer is still ill-defined. We analyzed IL-34 mRNA expression in breast cancer cell lines and breast cancer patients and applied established computational approaches (CIBERSORT, ESTIMATE, TIMER, TCIA), to analyze gene expression data from The Cancer Genome Atlas (TCGA). Expression of IL-34 was associated with a favorable prognosis in luminal and HER2 but not basal breast cancer patients. Gene expression of CSF-1 and CSF-1R was strongly associated with myeloid cell infiltration, while we found no or only weak correlations between IL-34, PTPRZ1, syndecan-1 and myeloid cells. In vitro experiments showed that tyrosine phosphorylation of CSF-1R, ERK, and FAK and cell migration are differentially regulated by IL-34 and CSF-1 in breast cancer cell lines. Collectively, our data suggest that correlation of IL-34 gene expression with survival is dependent on the molecular breast cancer subtype. Furthermore, IL-34 is not associated with myeloid cell infiltration and directly regulates breast cancer cell migration and signaling.

Wnt Signalling Drives Context-Dependent Differentiation or Proliferation in Neuroblastoma

Neuroblastoma is one of the commonest and deadliest solid tumours of childhood, and is thought to result from disrupted differentiation of the developing sympathoadrenergic lineage of the neural crest. Neuroblastoma exhibits intra- and intertumoural heterogeneity, with high risk tumours characterised by poor differentiation, which can be attributable to MYCN-mediated repression of genes involved in neuronal differentiation. MYCN is known to co-operate with oncogenic signalling pathways such as Alk, Akt and MEK/ERK signalling, and, together with c-MYC has been shown to be activated by Wnt signalling in various tissues. However, our previous work demonstrated that Wnt3a/Rspo2 treatment of some neuroblastoma cell lines can, paradoxically, decrease c-MYC and MYCN proteins. This prompted us to define the neuroblastoma-specific Wnt3a/Rspo2-driven transcriptome using RNA sequencing, and characterise the accompanying changes in cell biology. Here we report the identification of ninety Wnt target genes, and show that Wnt signalling is upstream of numerous transcription factors and signalling pathways in neuroblastoma. Using live-cell imaging, we show that Wnt signalling can drive differentiation of SK-N-BE(2)-C and SH-SY5Y cell-lines, but, conversely, proliferation of SK-N-AS cells. We show that cell-lines that differentiate show induction of pro-differentiation BMP4 and EPAS1 proteins, which is not apparent in the SK-N-AS cells. In contrast, SK-N-AS cells show increased CCND1, phosphorylated RB and E2F1 in response to Wnt3a/Rspo2, consistent with their proliferative response, and these proteins are not increased in differentiating lines. By meta-analysis of the expression of our 90 genes in primary tumour gene expression databases, we demonstrate discrete expression patterns of our Wnt genes in patient cohorts with different prognosis. Furthermore our analysis reveals interconnectivity within subsets of our Wnt genes, with one subset comprised of novel putative drivers of neuronal differentiation repressed by MYCN. Assessment of β-catenin immunohistochemistry shows high levels of β-catenin in tumours with better differentiation, further supporting a role for canonical Wnt signalling in neuroblastoma differentiation.

WNT signaling, the development of the sympathoadrenal-paraganglionic system and neuroblastoma

Neuroblastoma (NB) is a tumor of the sympathoadrenal system arising in children under 15 years of age. In Germany, NB accounts for 7% of childhood cancer cases, but 11% of cancer deaths. It originates from highly migratory progenitor cells that leave the dorsal neural tube and contribute neurons and glial cells to sympathetic ganglia, and chromaffin and supportive cells to the adrenal medulla and paraganglia. Clinically, histologically and molecularly, NBs present as extremely heterogeneous, ranging from very good to very poor prognosis. The etiology of NB still remains unclear and needs to be elucidated, however, aberrant auto- and paracrine embryonic cell communications seem to be likely candidates to initiate or facilitate the emergence, progression and regression of NB. The wingless-type MMTV integration site (WNT) family of proteins represents an evolutionary highly conserved signaling system that orchestrates embryogenesis. At least 19 ligands in the human, numerous receptors and co-receptors are known, which control not only proliferation, but also cell polarity, migration and differentiation. Here we seek to interconnect aspects of WNT signaling with sympathoadrenal and paraganglionic development to define new WNT signaling cues in the etiology and progression of NB.

Neural crest and cancer: Divergent travelers on similar paths

Neural crest cells are multipotent progenitors that dynamically interpret diverse microenvironments to migrate significant distances as a loosely associated collective and contribute to many tissues in the developing vertebrate embryo. Uncovering details of neural crest migration has helped to inform a general understanding of collective cell migration, including that which occurs during cancer metastasis. Here, we discuss several commonalities and differences of neural crest and cancer cell migration and behavior. First, we focus on some of the molecular pathways required for the initial specification and potency of neural crest cells and the roles of many of these pathways in cancer progression. We also describe epithelial-to-mesenchymal transition, which plays a critical role in initiating both neural crest migration and cancer metastasis. Finally, we evaluate studies that demonstrate myriad forms of cell-cell and cell-environment communication during neural crest and cancer collective migration to highlight the remarkable similarities in their molecular and cell biological regulation.

Frizzled 8 promotes the cell proliferation and metastasis of renal cell carcinoma

Recent reports have shown a rapid rise in the incidence of renal cell carcinoma (RCC), and Wnt (Wingless-related integration site) signaling pathway is important in RCC. Frizzled 8 (FZD8) is a member of Frizzled (FZD) receptor family which could activate canonical or non-canonical Wnt/β-catenin pathways. Nevertheless, the role of FZD8 in RCC is poorly investigated. The immunohistochemical analysis showed high expression of FZD8 in RCC tissues compared with peri-tumor tissues. FZD8 knockdown decreased the ability of proliferation and metastasis of RCC cells. Research revealed that the FZD8 regulated the transcription of Cyclin D1, c-Myc, and could promote the epithelial to mesenchymal transition (EMT) by mediating Vimentin and Snail through the Wnt/β-catenin signaling pathway. In addition, the results of our experiment revealed that FZD8 is involved in the regulation of non-canonical Wnt signaling pathway. These data suggested that the expression of FZD8 may play an important role in the proliferation and metastasis of RCC, and serve as a putative promising drug target for human RCC therapy.

PlGF and VEGF-A Regulate Growth of High-Risk MYCN-Single Copy Neuroblastoma Xenografts via Different Mechanisms

Neuroblastoma (NB) is the most common extracranial solid tumor of childhood and is a rapidly growing, highly-vascularized cancer. NBs frequently express angiogenic factors and high tumor angiogenesis has been associated with poor outcomes. Placental growth factor (PlGF) is an angiogenic protein belonging to the vascular endothelial growth factor (VEGF) family and is up-regulated mainly in pathologic conditions. Recently, PlGF was identified as a member of a gene expression signature characterizing highly malignant NB stem cells drawing attention as a potential therapeutic target in NB. In the present study, we sought to investigate the expression of PlGF in NB patients and the effect of PlGF inhibition on high-risk MYCN-non-amplified SK-N-AS NB xenografts. Human SK-N-AS cells, which are poorly differentiated and express PlGF and VEGF-A, were implanted subcutaneously in athymic nude mice. Treatment was done by intratumoral injection of replication-incompetent adenoviruses (Ad) expressing PlGF- or VEGF-specific short hairpin (sh)RNA, or soluble (s)VEGF receptor 2 (VEGFR2). The effect on tumor growth and angiogenesis was analyzed. High PlGF expression levels were observed in human advanced-stage NBs. Down-regulating PlGF significantly reduced NB growth in established NB xenografts by reducing cancer cell proliferation but did not suppress angiogenesis. In contrast, blocking VEGF by administration of Ad(sh)VEGF and Ad(s)VEGFR2 reduced tumor growth associated with decreased tumor vasculature. These findings suggest that PlGF and VEGF-A modulate MYCN-non-amplified NB tumors by different mechanisms and support a role for PlGF in NB biology.