A cadherin switch underlies malignancy in high-grade gliomas

Retroelement co-option disrupts the cancer transcriptional programme

BACKGROUND

Transcriptional activation of otherwise repressed retrotransposable elements (RTEs) is a hallmark of cancer, shaping tumour progression and immunogenicity by multifaceted, yet incompletely understood, mechanisms.

METHODS

We used an extended pan-cancer transcriptome assembly to identify potential effects of RTEs on the genes within which they have integrated or those in proximity. These were subsequently verified in test cases by further analysis of transcriptional profiles in cancer patient data, and by in vitro studies involving restoration of gene activity, and proliferation and migration assays in cancer cell lines.

RESULTS

We report that cancer-specific transcriptional activation of RTEs causes frequent reduction or loss of gene function. Exonisation and alternative splicing of RTEs creates non-functional RNA and protein isoforms and derepressed RTE promoter activity initiates antisense transcription, both at the expense of the canonical isoforms. Contrary to theoretical expectation, transcriptionally activated RTEs affect genes with established tumour-promoting functions, including the common essential RNGTT and the lung cancer-promoting CHRNA5 genes. Furthermore, the disruptive effect of RTE activation on adjacent tumour-promoting genes is associated with slower disease progression in clinical data, whereas experimental restoration of gene activity enhances tumour cell growth and invasiveness in vitro.

CONCLUSIONS

These findings underscore the gene-disruptive potential of seemingly innocuous germline RTE integrations, unleashed only by their transcriptional utilisation in cancer. They further suggest that such metastable RTE integrations are co-opted as sensors of the epigenetic and transcriptional changes occurring during cellular transformation and as executors that disrupt the function of tumour-promoting genes.

Plasma-Derived Exosomal i-tRF-LeuCAA as Biomarker for Glioma Diagnosis and Promoter of Epithelial-Mesenchymal Transition via TPM4 Regulation

AIMS

This study aimed to discover plasma-derived exosomal tsRNAs that serve as novel diagnostic biomarkers for glioma and to investigate the mechanism by which tsRNAs regulate glioma development.

METHODS

Differentially expressed tsRNAs in the plasma exosomes of glioma patients were identified using small RNA array sequencing. Bioinformatics analyses were used to predict the biological function of tsRNAs. The changes in the phenotypes of glioma cells treated with a tsRNA mimic and inhibitor were detected. The diagnostic and prognostic characteristics of potential target genes and their related functions in gliomas were further analyzed. The cell and animal experiments were used to analyze the molecular mechanisms.

RESULTS

Among the 453 differentially expressed tsRNAs identified in the plasma-derived exosomes of glioma patients using small RNA sequencing, i-tRF-LeuCAA was associated with the prognosis and molecular diagnostic characteristics of glioma patients and promoted the migration, invasion, and proliferation of glioma cells and inhibited their apoptosis. In addition, TPM4 is a potential target of i-tRF-LeuCAA and is related to epithelial-mesenchymal transition in gliomas.

CONCLUSIONS

i-tRF-LeuCAA could be served as a non-invasive biomarker in the diagnosis and prognosis of glioma. i-tRF-LeuCAA may indirectly regulate TPM4 expression and influence epithelial-mesenchymal transition, which may promote glioma progression.

MYH9 promotes malignant progression of glioma cells through regulating β-catenin stability via epithelial-mesenchymal transition signaling pathway

Epithelial‒mesenchymal transition (EMT) is a process in which polar epithelial cells transform into active mesenchymal cells and acquire invasion and migration capabilities (Cano CE, Motoo Y, Iovanna JL in Sci World J 10, 2010). EMT is involved in multiple physiological and pathological processes in the human body. The occurrence of EMT involves many signal transduction pathways and complex molecular mechanisms related to calnexin, growth factors, transcription factors, and the microenvironment. EMT is closely related to the invasion and metastasis of tumour cells. The MYH9 gene is closely associated with tumour progression. However, the function and regulatory mechanism of MYH9 in tumour occurrence and development remain unclear. Herein, we revealed for the first time that the migration, invasion, and metastatic abilities of glioma cells decreased significantly after MYH9 expression was downregulated. Moreover, our results suggested that MYH9 regulated the epithelial‒mesenchymal transition (EMT) process in glioma cells via β-catenin. In this mechanism, MYH9 was shown to bind to β-catenin and to increase its protein level by recruiting the deubiquitinase USP2 to form a complex. This complex suppressed β-catenin protein degradation, ultimately enhancing EMT signal transduction. This MYH9/β-catenin/EMT pathway represents a new molecular mechanism involved in the invasion promotion in gliomas. Our findings also demonstrated that MYH9 was crucial for inducing glioma cell migration. In summary, we suggest that MYH9 is a potential molecular marker for predicting tumour progression and prognosis and highlight its role in a new molecular mechanism of tumour metastasis.

Cadherin Expression Profiles Define Glioblastoma Differentiation and Patient Prognosis

Cadherins are cell-cell adhesion proteins which have been strongly implicated in cancer invasion, dissemination and metastasis capacity; thus, they are key players in the epithelial-to-mesenchymal transition (EMT) program. However, their role in glioblastoma (GBM), a primary central nervous system aggressive tumor, remains to be clarified. N-, E- and P-cadherin expression was analyzed on a large series of GBMs, characterized with clinical, imaging and neuropathological parameters, as well as with patients' survival data. In addition, cadherins' expression was studied in match-recurrent cases. Using TCGA data, cadherin expression profiles were also evaluated according to GBM transcription subtypes. N-cadherin expression was observed in 81.5% of GBM, followed by E-cadherin in 31% and P-cadherin in 20.8%. Upon tumor recurrence, P-cadherin was the only significantly upregulated cadherin compared with the primary tumor, being positive in 65.8% of the cases. Actually, P-cadherin gain was observed in 51.4% of matched primary-recurrent cases. Cadherins' co-expression was also explored. Interestingly, E- and N-cadherin co-expression identified a GBM subgroup with frequent epithelial differentiation and a significant survival benefit. On the other hand, subgroups with P-cadherin expression carried the worse prognosis. P- and N-cadherin co-expression correlated with the presence of a mesenchymal phenotype. Expressions of isolated P-cadherin or E- and P-cadherin co-expression were associated with imaging characteristics of aggressiveness, to highly heterogeneous tumors, an d to worse patient survival. Classical cadherins co-expression subgroups present consistent clinical, imaging, neuropathological and survival differences, which probably reflect different states of an EMT-like program in GBM.

Cytosolic Cadherin 4 promotes angiogenesis and metastasis in papillary thyroid cancer by suppressing the ubiquitination/degradation of β-catenin

BACKGROUND

Although the long-term prognosis of papillary thyroid cancer (PTC) is favorable, distant metastasis significantly compromises the prognosis and quality of life for patients with PTC. The Cadherin family plays a pivotal role in tumor metastasis; however, the involvement of Cadherin 4 (CDH4) in the metastatic cascade remains elusive.

METHODS

The expression and subcellular localization of CDH4 were determined through immunohistochemistry, immunofluorescence, and western blot analyses. The impact of CDH4 on cell migration, invasion, angiogenesis, and metastasis was assessed using transwell assays, tube formation assays, and animal experiments. Immunoprecipitation assay and mass spectrometry were employed to examine protein associations. The influence of CDH4 on the subcellular expression of β-catenin and active β-catenin was investigated via western blotting and immunofluorescence. Protein stability and ubiquitination assay were employed to verify the impact of CDH4 on β-catenin degradation. Rescue experiments were performed to ensure the significance of CDH4 in regulating nuclear β-catenin signaling.

RESULTS

CDH4 was found to be significantly overexpressed in PTC tissues and predominantly localized in the cytoplasm. Furthermore, the overexpression of CDH4 in tumor tissues is associated with lymph node metastasis in PTC patients. Cytosolic CDH4 promoted the migration, invasion, and lung metastasis of PTC cells and stimulated the angiogenesis and tumorigenesis of PTC; however, this effect could be reversed by Tegavivint, an antagonist of β-catenin. Mechanistically, cytosolic CDH4 disrupted the interaction between β-catenin and β-TrCP1, consequently impeding the ubiquitination process of β-catenin and activating the nuclear β-catenin signaling.

CONCLUSIONS

CDH4 induces PTC angiogenesis and metastasis via the inhibition of β-TrCP1-dependent ubiquitination of β-Catenin.

Early clonal extinction in glioblastoma progression revealed by genetic barcoding

Glioblastoma progression in its early stages remains poorly understood. Here, we transfer PDGFB and genetic barcodes in mouse brain to initiate gliomagenesis and enable direct tracing of glioblastoma evolution from its earliest possible stage. Unexpectedly, we observe a high incidence of clonal extinction events and progressive divergence in clonal sizes, even after the acquisition of malignant phenotype. Computational modeling suggests these dynamics result from clonal-based cell-cell competition. Through bulk and single-cell transcriptome analyses, coupled with lineage tracing, we reveal that Myc transcriptional targets have the strongest correlation with clonal size imbalances. Moreover, we show that the downregulation of Myc expression is sufficient to drive competitive dynamics in intracranially transplanted gliomas. Our findings provide insights into glioblastoma evolution that are inaccessible using conventional retrospective approaches, highlighting the potential of combining clonal tracing and transcriptomic analyses in this field.

3D Chromatin Architecture Re-Wiring at the CDH3/CDH1 Loci Contributes to E-Cadherin to P-Cadherin Expression Switch in Gastric Cancer

Cadherins are cell-cell adhesion molecules, fundamental for cell architecture and polarity. E-cadherin to P-cadherin switch can rescue adherens junctions in epithelial tumours. Herein, we disclose a mechanism for E-cadherin to P-cadherin switch in gastric cancers. CDH1 and CDH3 mRNA expression was obtained from 42 gastric tumours' RNA-seq data. CRISPR-Cas9 was used to knock out CDH1 and a putative regulatory element. CDH1-depleted and parental cells were submitted to proteomics and enrichment GO terms analysis; ATAC-seq/4C-seq with a CDH1 promoter viewpoint to assess chromatin accessibility and conformation; and RT-PCR/flow cytometry to assess CDH1/E-cadherin and CDH3/P-cadherin expression. In 42% of gastric tumours analysed, CDH1 to CDH3 switch was observed. CDH1 knockout triggered CDH1/E-cadherin complete loss and CDH3/P-cadherin expression increase at plasma membrane. This switch, likely rescuing adherens junctions, increased cell migration/proliferation, commonly observed in aggressive tumours. E- to P-cadherin switch accompanied increased CDH1 promoter interactions with CDH3-eQTL, absent in normal stomach and parental cells. CDH3-eQTL deletion promotes CDH3/CDH1 reduced expression. These data provide evidence that loss of CDH1/E-cadherin expression alters the CDH3 locus chromatin conformation, allowing a CDH1 promoter interaction with a CDH3-eQTL, and promoting CDH3/P-cadherin expression. These data highlight a novel mechanism triggering E- to P-cadherin switch in gastric cancer.

Cadherin‐3 is a novel oncogenic biomarker with prognostic value in glioblastoma

Glioblastoma (GBM) is the most common and malignant primary brain tumor in adults. The prognosis of patients is very poor, with a median overall survival of ~ 15 months after diagnosis. Cadherin‐3 (also known as P‐cadherin), a cell–cell adhesion molecule encoded by the CDH3 gene, is deregulated in several cancer types, but its relevance in GBM is unknown. In this study, we investigated the functional roles, the associated molecular signatures, and the prognostic value of CDH3/P‐cadherin in this highly malignant brain tumor. CDH3/P‐cadherin mRNA and protein levels were evaluated in human glioma samples. Knockdown and overexpression models of P‐cadherin in GBM were used to evaluate its functional role in vitro and in vivo. CDH3‐associated gene signatures were identified by enrichment analyses and correlations. The impact of CDH3 in the survival of GBM patients was assessed in independent cohorts using both univariable and multivariable models. We found that P‐cadherin protein is expressed in a subset of gliomas, with an increased percentage of positive samples in grade IV tumors. Concordantly, CDH3 mRNA levels in glioma samples from The Cancer Genome Atlas (TCGA) database are increased in high‐grade gliomas. P‐cadherin displays oncogenic functions in multiple knockdown and overexpression GBM cell models by affecting cell viability, cell cycle, cell invasion, migration, and neurosphere formation capacity. Genes that were positively correlated with CDH3 are enriched for oncogenic pathways commonly activated in GBM. In vivo, GBM cells expressing high levels of P‐cadherin generate larger subcutaneous tumors and cause shorter survival of mice in an orthotopic intracranial model. Concomitantly, high CDH3 expression is predictive of shorter overall survival of GBM patients in independent cohorts. Together, our results show that CDH3/P‐cadherin expression is associated with aggressiveness features of GBM and poor patient prognosis, suggesting that it may be a novel therapeutic target for this deadly brain tumor.

Cadherin Expression and EMT: A Focus on Gliomas

Cadherins are calcium-binding proteins with a pivotal role in cell adhesion and tissue homeostasis. The cadherin-dependent mechanisms of cell adhesion and migration are exploited by cancer cells, contributing to tumor invasiveness and dissemination. In particular, cadherin switch is a hallmark of epithelial to mesenchymal transition, a complex development process vastly described in the progression of most epithelial cancers. This is characterized by drastic changes in cell polarity, adhesion, and motility, which lead from an E-cadherin positive differentiated epithelial state into a dedifferentiated mesenchymal-like state, prone to metastization and defined by N-cadherin expression. Although vastly explored in epithelial cancers, how these mechanisms contribute to the pathogenesis of other non-epithelial tumor types is poorly understood. Herein, the current knowledge on cadherin expression in normal development in parallel to tumor pathogenesis is reviewed, focusing on epithelial to mesenchymal transition. Emphasis is taken in the unascertained cadherin expression in CNS tumors, particularly in gliomas, where the potential contribution of an epithelial-to-mesenchymal-like process to glioma genesis and how this may be associated with changes in cadherin expression is discussed.

Therapeutic targeting of membrane-associated proteins in central nervous system tumors

The activity of the most complex system, the central nervous system (CNS) is profoundly regulated by a huge number of membrane-associated proteins (MAP). A minor change stimulates immense chemical changes and the elicited response is organized by MAP, which acts as a receptor of that chemical or channel enabling the flow of ions. Slight changes in the activity or expression of these MAPs lead to severe consequences such as cognitive disorders, memory loss, or cancer. CNS tumors are heterogeneous in nature and hard-to-treat due to random mutations in MAPs; like as overexpression of EGFRvIII/TGFβR/VEGFR, change in adhesion molecules α5β3 integrin/SEMA3A, imbalance in ion channel proteins, etc. Extensive research is under process for developing new therapeutic approaches using these proteins such as targeted cytotoxic radiotherapy, drug-delivery, and prodrug activation, blocking of receptors like GluA1, developing viral vector against cell surface receptor. The combinatorial approach of these strategies along with the conventional one might be more potential. Henceforth, our review focuses on in-depth analysis regarding MAPs aiming for a better understanding for developing an efficient therapeutic approach for targeting CNS tumors.

Correlation between the Expression of Interleukin-6, STAT3, E-Cadherin and N-Cadherin Protein and Invasiveness in Nonfunctional Pituitary Adenomas

Objective  This study aimed to investigate the expression of interleukin (IL)-6, signal transducer and activator of transcription 3 (STAT3), epithelial-cadherin (E- cadherin) and neural-cadherin (N-cadherin) proteins in nonfunctional pituitary adenomas, and their correlation with invasiveness. Methods  Thirty cases of nonfunctional pituitary adenoma pathological wax specimens were selected from our hospital, including 20 cases of invasive nonfunctional pituitary adenoma (INFPA) and 10 noninvasive nonfunctional pituitary adenomas (NNFPAs). Envision was used to detect IL-6, STAT3, E-cadherin , and N-cadherin in specimens. Statistical methods were used to analyze the correlation between the four proteins and the Knosp classification of nonfunctional pituitary adenomas. Result  IL-6 and STAT3 were highly expressed in INFPAs but poorly expressed in NNFPAs. E-cadherin expression in INFPAs was lower than that in NNFPAs. N-cadherin was positive or strongly positive in both groups. Spearman's correlation analysis showed that the expression of IL-6 and STAT3 was positively correlated with Knosp's classification, whereas the expression of E-cadherin was negatively correlated with Knosp classification. Meanwhile, the expression of N-cadherin was not correlated with Knosp's classification. Conclusion  The expression of the IL-6, STAT3, E-cadherin proteins were associated nonfunctional pituitary adenomas. However, the expression of N-cadherin was not correlated with nonfunctional pituitary adenomas.

Long noncoding RNA FER1L4 promotes the malignant processes of papillary thyroid cancer by targeting the miR-612/ Cadherin 4 axis

BACKGROUND

Long noncoding RNAs (lncRNAs) have emerged as crucial regulators in various cancers. However, the functional roles of most lncRNA in papillary thyroid cancer (PTC) are not detailly understood. This study aims to investigate the biological function and molecular mechanism of lncRNA Fer-1 like family member 4 (FER1L4) in PTC.

METHODS

The expression of FER1L4 in PTC was determined via operating quantitative real-time PCR assays. Meanwhile, the clinical significance of FER1L4 in patients with PTC was described. The biological functions of FER1L4 on PTC cells were evaluated by gain and loss of function experiments. Moreover, animal experiments were performed to reveal the effect on tumor growth. Subcellular distribution of FER1L4 was determined by fluorescence in situ hybridization and subcellular localization assays. Luciferase reporter assay and RNA immunoprecipitation assay were applied to define the relationship between FER1L4, miR-612, and Cadherin 4 (CDH4).

RESULTS

Upregulated expression of FER1L4 in PTC tissues was positively correlated with lymph node metastasis (P = 0.020), extrathyroidal extension (P = 0.013) and advanced TNM stages (P = 0.013). In addition, knockdown of FER1L4 suppressed PTC cell proliferation, migration, and invasion, whereas ectopic expression of FER1L4 inversely promoted these processes. Mechanistically, FER1L4 could competitively bind with miR-612 to prevent the degradation of its target gene CDH4. This condition was further confirmed in the rescue assays.

CONCLUSIONS

This study first demonstrates FER1L4 plays an oncogenic role in PTC via a FER1L4-miR-612-CDH4 axis and may provide new therapeutic and diagnostic targets for PTC.

Design, synthesis and biological evaluation of N-anthraniloyl tryptamine derivatives as pleiotropic molecules for the therapy of malignant glioma

COX-2 and STAT3 are two key culprits in the glioma microenvironment. Herein, to inhibit COX-2 and block STAT3 signaling, we disclosed 27 N-anthraniloyl tryptamine compounds based on the combination of melatonin derivatives and N-substituted anthranilic acid derivatives. Among them, NP16 showed the best antiproliferative activity and moderate COX-2 inhibition. Of note, NP16 decreased the level of p-JAK2 and p-STAT3, and blocked the nuclear translocation of STAT3 in GBM cell lines. Moreover, NP16 downregulated the MMP-9 expression of BV2 cells in a co-culture system of BV2 and C6 glioma cells, abrogated the proliferative/invasive/migratory abilities of GBM cells, induced apoptosis by ROS and the Bcl-2-regulated apoptotic pathway, and induced obvious G₂/M arrest in glioma cells in vitro. Furthermore, NP16 displayed favorable pharmacokinetic profiles covering long half-life (11.43 ± 0.43 h) and high blood-brain barrier permeability. Finally, NP16 effectively inhibited tumor growth, promoted the survival rate, increased the expression of E-cadherin and reduced overproduction of PGE₂, MMP-9, VEGF-A and the level of p-STAT3 in tumor tissue, and improved the anxiety-like behavior in C6 glioma model. All these evidences demonstrated N-anthraniloyl tryptamine derivatives as multifunctional anti-glioma agents with high potency could drain the swamp to beat glioma.

Overexpressed P75CUX1 promotes EMT in glioma infiltration by activating β-catenin

The homeobox protein cut-like 1 (CUX1) comprises three isoforms and has been shown to be involved in the development of various types of malignancies. However, the expression and role of the CUX1 isoforms in glioma remain unclear. Herein, we first identified that P75CUX1 isoform exhibited consistent expression among three isoforms in glioma with specifically designed antibodies to identify all CUX1 isoforms. Moreover, a significantly higher expression of P75CUX1 was found in glioma compared with non-tumor brain (NB) tissues, analyzed with western blot and immunohistochemistry, and the expression level of P75CUX1 was positively associated with tumor grade. In addition, Kaplan-Meier survival analysis indicated that P75CUX1 could serve as an independent prognostic indicator to identify glioma patients with poor overall survival. Furthermore, CUX1 knockdown suppressed migration and invasion of glioma cells both in vitro and in vivo. Mechanistically, this study found that P75CUX1 regulated epithelial-mesenchymal transition (EMT) process mediated via β-catenin, and CUX1/β-catenin/EMT is a novel signaling cascade mediating the infiltration of glioma. Besides, CUX1 was verified to promote the progression of glioma via multiple other signaling pathways, such as Hippo and PI3K/AKT. In conclusion, we suggested that P75CUX1 could serve as a potential prognostic indicator as well as a novel treatment target in malignant glioma.

Expression and Prognostic Significance of Cadherin 4 (CDH4) in Renal Cell Carcinoma

Background

Aberrant expression of cadherin family members and their possible biological function have been widely studied in renal cell carcinoma (RCC). However, the expression of cadherin 4 (CDH4) and its value in RCC diagnosis and prognosis remains elusive.

Material/Methods

The TCGA database was used to analyze the expression of CDH4 and its clinical parameters and prognosis in 891 RCC patients. In addition, real-time PCR was used to verify the transcription of CDH4 in renal clear cell carcinoma tissue, and the distribution of protein was observed by immunohistochemical staining.

Results

We found that the mRNA level of CDH4 was elevated in primary RCC in contrast with normal kidney samples using bioinformatics analysis based on the TCGA database. Among the 3 main subtypes of RCC, transcriptional CDH4 was significantly increased in KIRC and KIRP, while it was downregulated in KICH. Interestingly, CDH4 mRNA gradually decreased with the progression of KIRC and KIRP. The transcription of CDH4 in the primary tumor of KIRP patients at T3–T4 stages and KIRC patients with lymph node and distant metastasis were decreased significantly. Overall survival (OS) showed that KIRC and KICH patients with lower expression of CDH4 had worse outcomes.

Conclusions

The transcriptional level of CDH4 may serve as an effective diagnostic and prognostic biomarker for RCC patients.

Gold Nanoparticles in Glioma Theranostics

Despite many endeavors to treat malignant gliomas in the last decades, the median survival of patients has not significantly improved. The infiltrative nature of high-grade gliomas and the impermeability of the blood-brain barrier to the most therapeutic agents remain major hurdles, impeding an efficacious treatment. Theranostic platforms bridging diagnosis and therapeutic modalities aim to surmount the current limitations in diagnosis and therapy of glioma. Gold nanoparticles (AuNPs) due to their biocompatibility and tunable optical properties have widely been utilized for an assortment of theranostic purposes. In this Review, applications of AuNPs as imaging probes, drug/gene delivery systems, radiosensitizers, photothermal transducers, and multimodal theranostic agents in malignant gliomas are discussed. This Review also aims to provide a perspective on cancer theranostic applications of AuNPs in future clinical trials.

IGFBP5 increases cell invasion and inhibits cell proliferation by EMT and Akt signaling pathway in Glioblastoma multiforme cells

Background

Recurrence of Glioblastoma multiforme (GBM) seems to be the rule despite combination therapies. Cell invasion and cell proliferation are major reasons for recurrence of GBM. And insulin-like growth factor binding protein 5 (IGFBP5) is the most conserved of the IGFBPs and is frequently dysregulated in cancers and metastatic tissues.

Results

By studying the human glioma tissues, we find that IGFBP5 expression associate to the histopathological classification and highly expressed in GBM. Using IGFBP5 mutants we demonstrate that knockdown of IGFBP5 inhibited cell invasion, whereas promoting cell proliferation in GBM cells. Mechanistically, we observed that promoting GBM cell proliferation by inhibiting IGFBP5 was associated with stimulating Akt (Protein kinase B) phosphorylation. However, IGFBP5 promote GBM cell invasion was related to the epithelial-to-mesenchymal transition (EMT). Furthermore, the Chinese Glioma Genome Altas (CGGA) database show that IGFBP5 is significantly increased in recurrent glioma and it predicted worse survival.

Conclusions

The obtained results indicate that IGFBP5 has two sides in GBM—inhibiting cell proliferation but promoting cell invasion.

Glioblastoma models driven by different mutations converge to the proneural subtype

The need of reliable syngeneic animal models for gliomas has been addressed in the last decades by reproducing genetic alterations typical of human glioblastoma in the mouse. Since different alterations underlie different molecular glioblastoma subtypes it is commonly expected that tumors induced by specific alterations represent models of the corresponding subtypes. We tested this assumption by a multilevel analysis ranging from a detailed histopathological analysis to a genome-wide expression profiling by microarray and RNA-seq on gliomas induced by two distinct molecular alterations: the overstimulation of the PDGF- and the EGF- pathways. These alterations are landmarks of proneural and classical glioblastoma subtypes respectively. However, our results consistently showed a strong similarity between the two glioma models. The expression profiles of both models converged toward a signature typical of oligodendrocyte progenitor cells, regardless the wide differentiative potential of the cell of origin. A classification based on similarity with human gliomas profiles revealed that both models belong to the proneural subtype. Our results highlight that reproducing a molecular alteration specific of a glioblastoma subtype not necessarily generates a tumor model recapitulating such subtype.

Cdh4 Down-Regulation Impairs in Vivo Infiltration and Malignancy in Patients Derived Glioblastoma Cells

The high invasive phenotype of glioblastoma is one of the main causes of therapy inefficacy and tumor relapse. Cell adhesion molecules of the cadherin family are involved in cell migration and are known as master regulators of epithelial tumor invasiveness, but their role in glioblastoma is less understood. In particular, we recently demonstrated, in the syngeneic murine model, the occurrence of a previously undescribed cadherin switch between Cdh2 and Cdh4 during gliomagenesis, which is necessary for the acquisition of the highly infiltrative and tumorigenic phenotype of these cells. In the present study, we tested the role of Cdh4 in human gliomas. Our results on patient-derived glioma cells demonstrate a positive correlation between Cdh4 expression levels and the loss of cell-cell contact inhibition of proliferation controls that allows cells to proliferate over confluence. Moreover, the silencing of Cdh4 by artificial microRNAs induced a decrease in the infiltrative ability of human glioma cells both in vitro and in vivo. More strikingly, Cdh4 silencing induced an impairment of the tumorigenic potential of these cells after orthotopic transplantation in immunodeficient mice. Overall, we conclude that in human glioblastoma, Cdh4 can also actively contribute in regulating cell invasiveness and malignancy.

PDGF-B: The missing piece in the mosaic of PDGF family role in craniofacial development

BACKGROUND

The platelet-derived growth factor (PDGF) family consists of four ligands (PDGF-A, PDGF-B, PDGF-C, PDGF-D) and two tyrosine kinase receptors (PDGFR-α and PDGFR-β). In vertebrates, PDGF signaling influences cell proliferation, migration, and matrix deposition, and its up-regulation is implicated in cancer progression. Despite this evidence, the role of each family member during embryogenesis is still incomplete and partially controversial. In particular, study of the role of pdgf signaling during craniofacial development has been focused on pdgf-a, while the role of pdgf-b is almost unknown due to the lethal phenotypes of pdgf-b-null mice.

RESULTS

By using a pdgf-b splice-blocking morpholino approach, we highlighted impairment of neural crest cell (NCC) migration in Xenopus laevis morphants, leading to alteration of NCC derivatives formation, such as cranial nerves and cartilages. We also uncovered a possible link between pdgf-b and the expression of cadherin superfamily members cdh6 and cdh11, which mediate cell-cell adhesion promoting NCC migration.

CONCLUSIONS

Our results suggested that pdgf-b signaling is involved in cranial NCC migration and it is required for proper formation of craniofacial NCC derivatives. Taken together, these data unveiled a new role for pdgf-b during vertebrate development, contributing to complete the picture of pdgf signaling role in craniofacial development.

EMT Regulation by Autophagy: A New Perspective in Glioblastoma Biology

Epithelial-to-mesenchymal transition (EMT) and its reverse process MET naturally occur during development and in tissue repair in vertebrates. EMT is also recognized as the crucial event by which cancer cells acquire an invasive phenotype through the activation of specific transcription factors and signalling pathways. Even though glial cells have a mesenchymal phenotype, an EMT-like process tends to exacerbate it during gliomagenesis and progression to more aggressive stages of the disease. Autophagy is an evolutionary conserved degradative process that cells use in order to maintain a proper homeostasis, and defects in autophagy have been associated to several pathologies including cancer. Besides modulating cell resistance or sensitivity to therapy, autophagy also affects the migration and invasion capabilities of tumor cells. Despite this evidence, few papers are present in literature about the involvement of autophagy in EMT-like processes in glioblastoma (GBM) so far. This review summarizes the current understanding of the interplay between autophagy and EMT in cancer, with special regard to GBM model. As the invasive behaviour is a hallmark of GBM aggressiveness, defining a new link between autophagy and EMT can open a novel scenario for targeting these processes in future therapeutical approaches.

The Attenuation of Trophoblast Invasion Caused by the Downregulation of EZH2 Is Involved in the Pathogenesis of Human Recurrent Miscarriage

Recurrent miscarriage (RM) is currently defined as two or more losses of a clinically established intrauterine pregnancy. Despite years of research, RM continues to be a clinically frustrating challenge for patients and physicians, and its etiology remains poorly understood. Accumulating evidence has suggested that epigenetic modifications are involved in early embryogenesis, and defects in epigenetic patterning contribute to the development of RM. Here, we studied the role of enhancer of zeste homolog 2 (EZH2) in the pathogenesis of RM and found that the EZH2 expression was significantly decreased in the villi from women with RM compared with that in control villi. EZH2 promoted the invasion of trophoblast cells. Moreover, EZH2 could promote epithelial-mesenchymal transition by epigenetically silencing CDX1. Both chromatin immunoprecipitation (ChIP)-PCR and dual-luciferase report assays demonstrated that EZH2 repressed CDX1 transcription via direct binding to its promoter region and then trimethylating Histone3-Lysine27. Furthermore, we discovered that progesterone, which is used extensively in the treatment of miscarriage and RM, increased the expression of EZH2 via the extracellular signaling-regulated kinase (ERK1/2) pathway. These findings revealed that EZH2 may regulate trophoblast invasion as an epigenetic factor, suggesting that EZH2 might be a potential therapeutic target for RM.

Autophagy induction impairs Wnt/β-catenin signalling through β-catenin relocalisation in glioblastoma cells

Autophagy is an evolutionary conserved process mediating lysosomal degradation of cytoplasmic material. Its involvement in cancer progression is highly controversial, due to its dual role in both limiting tumoural transformation and in protecting established tumoral cells from unfavorable conditions. Little is known about the cross-talk between autophagy and intracellular signalling pathways, as well as about autophagy impact on signalling molecules turnover. An aberrantly activated Wnt/β-catenin signalling is responsible for tumour proliferation, invasion, and stemness maintenance. Here we show that autophagy negatively regulates Wnt/β-catenin signalling in glioblastoma multiforme (GBM) cells, through Dishevelled degradation. We also provide the first evidence that autophagy promotes β-catenin relocalisation within the cell, by inducing a decrease of the nuclear protein fraction. In particular, upon autophagy induction, β-catenin appears mainly localized in sub-membrane areas where it associates with N-cadherin to form epithelial-like cell-cell adhesion structures. Our data indicate, for the first time, that autophagy induction results in Wnt signalling attenuation and in β-catenin relocalisation within the GBM cell. These findings further support the idea that autophagy modulation could represent a potential therapeutical strategy to contrast GBM progression.

Signaling pathways and mesenchymal transition in pediatric high-grade glioma

Pediatric high-grade gliomas (pHGG), including diffuse intrinsic pontine gliomas (DIPG), are the most lethal types of cancer in children. In recent years, it has become evident that these tumors are driven by epigenetic events, mainly mutations involving genes encoding Histone 3, setting them apart from their adult counterparts. These tumors are exceptionally resistant to chemotherapy and respond only temporarily to radiotherapy. Moreover, their delicate location and diffuse growth pattern make complete surgical resection impossible. In many other forms of cancer, chemo- and radioresistance, in combination with a diffuse, invasive phenotype, are associated with a transcriptional program termed the epithelial-to-mesenchymal transition (EMT). Activation of this program allows cancer cells to survive individually, invade surrounding tissues and metastasize. It also enables them to survive exposure to cytotoxic therapy, including chemotherapeutic drugs and radiation. We here suggest that EMT plays an important, yet poorly understood role in the biology and therapy resistance of pHGG and DIPG. This review summarizes the current knowledge on the major signal transduction pathways and transcription factors involved in the epithelial-to-mesenchymal transition in cancer in general and in pediatric HGG and DIPG in particular. Despite the fact that the mesenchymal transition has not yet been specifically studied in pHGG and DIPG, activation of pathways and high levels of transcription factors involved in EMT have been described. We conclude that the mesenchymal transition is likely to be an important element of the biology of pHGG and DIPG and warrants further investigation for the development of novel therapeutics.

Blocking hepatic metastases of colon cancer cells using an shRNA against Rac1 delivered by activatable cell-penetrating peptide

Hepatic metastasis is one of the critical progressions of colon cancer. Blocking this process is key to prolonging survival time in cancer patients. Studies on activatable cell-penetrating peptides (dtACPPs) have demonstrated their potential as gene carriers. It showed high tumor cell-targeting specificity and transfection efficiency and low cytotoxicity in the in vitro settings of drug delivery. However, using this system to silence target genes to inhibit metastasis in colorectal cancer cells has not been widely reported and requires further investigation. In this study, we observed that expression of Rac1, a key molecule for cytoskeletal reorganization, was higher in hepatic metastatic tumor tissue compared with prime colon cancer tissue and that patients with high Rac1-expressing colon cancer showed shorter survival time. Base on these findings, we created dtACPP-PEG-DGL (dtACPPD)/shRac1 nanoparticles and demonstrated that they downregulated Rac1 expression in colon cancer cells. Moreover, we observed inhibitory effects on migration, invasion and adhesion in HCT116 colorectal cancer cells in vitro, and our results showed that Rac1 regulated colon cancer cell matrix adhesion through the regulation of cytofilament dynamics. Moreover, mechanically, repression of Rac1 inhibiting cells migration and invasion by enhancing cell to cell adhesion and reducing cell to extracellular matrix adhesion. Furthermore, when atCDPPD/shRac1 nanoparticles were administered intravenously to a HCT116 xenograft model, significant tumor metastasis to the liver was inhibited. Our results suggest that atCDPP/shRac1 nanoparticles may enable the blockade of hepatic metastasis in colon cancer.

Nicotinic acid inhibits glioma invasion by facilitating Snail1 degradation

Malignant glioma is a formidable disease that commonly leads to death, mainly due to the invasion of tumor cells into neighboring tissues. Therefore, inhibition of tumor cell invasion may provide an effective therapy for malignant glioma. Here we report that nicotinic acid (NA), an essential vitamin, inhibits glioma cell invasion in vitro and in vivo. Treatment of the U251 glioma cells with NA in vitro results in reduced invasion, which is accompanied by a loss of mesenchymal phenotype and an increase in cell-cell adhesion. At the molecular level, transcription of the adherens junction protein E-cadherin is upregulated, leading to accumulation of E-cadherin protein at the cell-cell boundary. This can be attributed to NA's ability to facilitate the ubiquitination and degradation of Snail1, a transcription factor that represses E-cadherin expression. Similarly, NA transiently inhibits neural crest migration in Xenopus embryos in a Snail1-dependent manner, indicating that the mechanism of action for NA in cell migration is evolutionarily conserved. We further show that NA injection blocks the infiltration of tumor cells into the adjacent brain tissues and improves animal survival in a rat model of glioma. These results suggest that NA treatment may be developed into a potential therapy for malignant glioma.

Density-Dependent Regulation of Glioma Cell Proliferation and Invasion Mediated by miR-9

The phenotypic axis of invasion and proliferation in malignant glioma cells is a well-documented phenomenon. Invasive glioma cells exhibit a decreased proliferation rate and a resistance to apoptosis, and invasive tumor cells dispersed in brain subsequently revert to proliferation and contribute to secondary tumor formation. One miRNA can affect dozens of mRNAs, and some miRNAs are potent oncogenes. Multiple miRNAs are implicated in glioma malignancy, and several of which have been identified to regulate tumor cell motility and division. Using rat 9 L gliosarcoma and human U87 glioblastoma cell lines, we investigated miRNAs associated with the switch between glioma cell invasion and proliferation. Using micro-dissection of 9 L glioma tumor xenografts in rat brain, we identified disparate expression of miR-9 between cells within the periphery of the primary tumor, and those comprising tumor islets within the invasive zone. Modifying miR-9 expression in in vitro assays, we report that miR-9 controls the axis of glioma cell invasion/proliferation, and that its contribution to invasion or proliferation is biphasic and dependent upon local tumor cell density. In addition, immunohistochemistry revealed elevated hypoxia inducible factor 1 alpha (HIF-1α) in the invasive zone as compared to the primary tumor periphery. We also found that hypoxia promotes miR-9 expression in glioma cells. Based upon these findings, we propose a hypothesis for the contribution of miR-9 to the dynamics glioma invasion and satellite tumor formation in brain adjacent to tumor.

Noninvasive Monitoring of Glioma Growth in the Mouse

Malignant gliomas are the most common and deadly primary malignant brain tumors. In vivo orthotopic models could doubtless represent an appropriate tool to test novel treatment for gliomas. However, methods commonly used to monitor the growth of glioma inside the mouse brain are time consuming and invasive. We tested the reliability of a minimally invasive procedure, based on a secreted luciferase (Gaussia luciferase), to frequently monitor the changes of glioma size.

Gluc activity was evaluated from blood samples collected from the tail tip of mice twice a week, allowing to make a growth curve for the tumors. We validated the correlation between Gluc activity and tumor size by analysing the tumor after brain dissection. We found that this method is reliable for monitoring human glioma transplanted in immunodeficient mice, but it has strong limitation in immunocompetent models, where an immune response against the luciferase is developed during the first weeks after transplant.

Whole-genome bisulfite sequencing of cell-free DNA identifies signature associated with metastatic breast cancer

Background

A number of clinico-pathological criteria and molecular profiles have been used to stratify patients into high- and low-risk groups. Currently, there are still no effective methods to determine which patients harbor micrometastatic disease after standard breast cancer therapy and who will eventually develop local or distant recurrence. The purpose of our study was to identify circulating DNA methylation changes that can be used for prediction of metastatic breast cancer (MBC).

Results

Differential methylation analysis revealed ~5.0 × 10⁶ differentially methylated CpG loci in MBC compared with healthy individuals (H) or disease-free survivors (DFS). In contrast, there was a strong degree of similarity between H and DFS. Overall, MBC demonstrated global hypomethylation and focal CpG island (CPGI) hypermethylation. Data analysis identified 21 novel hotspots, within CpG islands, that differed most dramatically in MBC compared with H or DFS.

Conclusions

This unbiased analysis of cell-free (cf) DNA identified 21 DNA hypermethylation hotspots associated with MBC and demonstrated the ability to distinguish tumor-specific changes from normal-derived signals at the whole-genome level. This signature is a potential blood-based biomarker that could be advantageous at the time of surgery and/or after the completion of chemotherapy to indicate patients with micrometastatic disease who are at a high risk of recurrence and who could benefit from additional therapy.

Electronic supplementary material

The online version of this article (doi:10.1186/s13148-015-0135-8) contains supplementary material, which is available to authorized users.