Novel integrated workflow allows production and in-depth quality assessment of multifactorial reprogrammed skeletal muscle cells from human stem cells.

Skeletal muscle tissue engineering aims at generating biological substitutes that restore, maintain or improve normal muscle function; however, the quality of cells produced by current protocols remains insufficient. Here, we developed a multifactor-based protocol that combines adenovector (AdV)-mediated MYOD expression, small molecule inhibitor and growth factor treatment, and electrical pulse stimulation (EPS) to efficiently reprogram different types of human-derived multipotent stem cells into physiologically functional skeletal muscle cells (SMCs). The protocol was complemented through a novel in silico workflow that allows for in-depth estimation and potentially optimization of the quality of generated muscle tissue, based on the transcriptomes of transdifferentiated cells. We additionally patch-clamped phenotypic SMCs to associate their bioelectrical characteristics with their transcriptome reprogramming. Overall, we set up a comprehensive and dynamic approach at the nexus of viral vector-based technology, bioinformatics, and electrophysiology that facilitates production of high-quality skeletal muscle cells and can guide iterative cycles to improve myo-differentiation protocols.

Drug Repurposing at the Interface of Melanoma Immunotherapy and Autoimmune Disease.

Cancer cells have a remarkable ability to evade recognition and destruction by the immune system. At the same time, cancer has been associated with chronic inflammation, while certain autoimmune diseases predispose to the development of neoplasia. Although cancer immunotherapy has revolutionized antitumor treatment, immune-related toxicities and adverse events detract from the clinical utility of even the most advanced drugs, especially in patients with both, metastatic cancer and pre-existing autoimmune diseases. Here, the combination of multi-omics, data-driven computational approaches with the application of network concepts enables in-depth analyses of the dynamic links between cancer, autoimmune diseases, and drugs. In this review, we focus on molecular and epigenetic metastasis-related processes within cancer cells and the immune microenvironment. With melanoma as a model, we uncover vulnerabilities for drug development to control cancer progression and immune responses. Thereby, drug repurposing allows taking advantage of existing safety profiles and established pharmacokinetic properties of approved agents. These procedures promise faster access and optimal management for cancer treatment. Together, these approaches provide new disease-based and data-driven opportunities for the prediction and application of targeted and clinically used drugs at the interface of immune-mediated diseases and cancer towards next-generation immunotherapies.

Mechanisms of Functional Pleiotropy of p73 in Cancer and Beyond.

The transcription factor p73 is a structural and functional homolog of TP53, the most famous and frequently mutated tumor-suppressor gene. The TP73 gene can synthesize an overwhelming number of isoforms via splicing events in 5' and 3' ends and alternative promoter usage. Although it originally came into the spotlight due to the potential of several of these isoforms to mimic p53 functions, it is now clear that TP73 has its own unique identity as a master regulator of multifaceted processes in embryonic development, tissue homeostasis, and cancer. This remarkable functional pleiotropy is supported by a high degree of mechanistic heterogeneity, which extends far-beyond the typical mode of action by transactivation and largely relies on the ability of p73 isoforms to form protein-protein interactions (PPIs) with a variety of nuclear and cytoplasmic proteins. Importantly, each p73 isoform carries a unique combination of functional domains and residues that facilitates the establishment of PPIs in a highly selective manner. Herein, we summarize the expanding functional repertoire of TP73 in physiological and oncogenic processes. We emphasize how TP73's ability to control neurodevelopment and neurodifferentiation is co-opted in cancer cells toward neoneurogenesis, an emerging cancer hallmark, whereby tumors promote their own innervation. By further exploring the canonical and non-canonical mechanistic patterns of p73, we apprehend its functional diversity as the result of a sophisticated and coordinated interplay of: (a) the type of p73 isoforms (b) the presence of p73 interaction partners in the cell milieu, and (c) the architecture of target gene promoters. We suppose that dysregulation of one or more of these parameters in tumors may lead to cancer initiation and progression by reactivating p73 isoforms and/or p73-regulated differentiation programs thereof in a spatiotemporally inappropriate manner. A thorough understanding of the mechanisms supporting p73 functional diversity is of paramount importance for the efficient and precise p73 targeting not only in cancer, but also in other pathological conditions where TP73 dysregulation is causally involved.

LncRNA-SLC16A1-AS1 induces metabolic reprogramming during Bladder Cancer progression as target and co-activator of E2F1.

Long non-coding RNAs (lncRNAs) have emerged as integral components of E2F1-regulated gene regulatory networks (GRNs), but their implication in advanced or treatment-refractory malignancy is unknown. Methods: We combined high-throughput transcriptomic approaches with bioinformatics and structure modeling to search for lncRNAs that participate in E2F1-activated prometastatic GRNs and their phenotypic targets in the highly-relevant case of E2F1-driven aggressive bladder cancer (BC). RNA immunoprecipitation was performed to verify RNA-protein interactions. Functional analyses including qRT-PCR, immunoblotting, luciferase assays and measurement of extracellular fluxes were conducted to validate expression and target gene regulation. Results: We identified E2F1-responsive lncRNA-SLC16A1-AS1 and its associated neighboring protein-coding gene, SLC16A1/MCT1, which both promote cancer invasiveness. Mechanistically, upon E2F1-mediated co-transactivation of the gene pair, SLC16A1-AS1 associates with E2F1 in a structure-dependent manner and forms an RNA-protein complex that enhances SLC16A1/MCT1 expression through binding to a composite SLC16A1-AS1:E2F1-responsive promoter element. Moreover, SLC16A1-AS1 increases aerobic glycolysis and mitochondrial respiration and fuels ATP production by fatty acid ß-oxidation. These metabolic changes are accompanied by alterations in the expression of the SLC16A1-AS1:E2F1-responsive gene PPARA, a key mediator of fatty acid ß-oxidation. Conclusions: Our results unveil a new gene regulatory program by which E2F1-induced lncRNA-SLC16A1-AS1 forms a complex with its transcription factor that promotes cancer metabolic reprogramming towards the acquisition of a hybrid oxidative phosphorylation/glycolysis cell phenotype favoring BC invasiveness.

Adenoviral mediated expression of anti-inflammatory progranulin by placental explants modulates endothelial cell activation by decrease of ICAM-1 expression.

INTRODUCTION: Functional disorders of the villous trophoblast may result in preeclampsia through the release of endothelial activating substances. Progranulin is an anti-inflammatory, pro-angiogenic cytokine with TNF-α antagonizing activity. The trophoblastic expression of progranulin is increased during preeclampsia. The aim of the study was to investigate the impact of placental progranulin synthesis on endothelial cell activation. METHODS: Placental progranulin expression was modified by transduction of an adenoviral vector. Primary isolated human umbilical venous endothelial cells (HUVECs) were incubated with conditioned medium of first trimester placental explants. Functional studies on HUVECs included assays for proliferation, viability, cytotoxicity and analyzes of Intercellular adhesion molecule-1 (ICAM-1) and E-selectin expression. RESULTS: Placental progranulin expression was more than 10-fold higher by using an adenoviral-mediated overexpression system (Ad.PGRN) compared to control vector (Ad.CTRL) and untreated controls. Incubation of HUVECs with conditioned placental medium revealed a dose-dependent increase of cytotoxicity, reduced cell proliferation and viability and resulted in an increase of ICAM-1 and E-selectin expression. Overexpression of progranulin (Ad.PGRN) antagonized the ICAM-1 expression induced by conditioned medium. However progranulin did not influence the effects on cell proliferation, viability, cytotoxicity and E-selectin expression in HUVECs. DISCUSSION: Regulation of gene expression in human placental explants is possible by usage of an adenoviral vector system. The increase of endothelial ICAM-1 expression following the incubation with placental conditioned medium was partly reversed by overexpression of placental progranulin. It is suggested that up-regulation of the placental progranulin expression is an endogenous anti-inflammatory mechanism that partially antagonizes the endothelial cell activation during preeclampsia.

Rewiring E2F1 with classical NHEJ via APLF suppression promotes bladder cancer invasiveness.

BACKGROUND: Bladder cancer progression has been associated with dysfunctional repair of double-strand breaks (DSB), a deleterious type of DNA lesions that fuel genomic instability. Accurate DSB repair relies on two distinct pathways, homologous recombination (HR) and classical non-homologous end-joining (c-NHEJ). The transcription factor E2F1 supports HR-mediated DSB repair and protects genomic stability. However, invasive bladder cancers (BC) display, in contrast to non-invasive stages, genomic instability despite their high E2F1 levels. Hence, E2F1 is either inefficient in controlling DSB repair in this setting, or rewires the repair apparatus towards alternative, error-prone DSB processing pathways. METHODS: RT-PCR and immunoblotting, in combination with bioinformatics tools were applied to monitor c-NHEJ factors status in high-E2F1-expressing, invasive BC versus low-E2F1-expressing, non-invasive BC. In vivo binding of E2F1 on target gene promoters was demonstrated by ChIP assays and E2F1 CRISPR-Cas9 knockdown. MIR888-dependent inhibition of APLF by E2F1 was demonstrated using overexpression and knockdown experiments, in combination with luciferase assays. Methylation status of MIR888 promoter was monitored by methylation-specific PCR. The changes in invasion potential and the DSB repair efficiency were estimated by Boyden chamber assays and pulse field electrophoresis, correspondingly. RESULTS: Herein, we show that E2F1 directly transactivates the c-NHEJ core factors Artemis, DNA-PKcs, ligase IV, NHEJ1, Ku70/Ku80 and XRCC4, but indirectly inhibits APLF, a chromatin modifier regulating c-NHEJ. Inhibition is achieved by miR-888-5p, a testis-specific, X-linked miRNA which, in normal tissues, is often silenced via promoter methylation. Upon hypomethylation in invasive BC cells, MIR888 is transactivated by E2F1 and represses APLF. Consequently, E2F1/miR-888/APLF rewiring is established, generating conditions of APLF scarcity that compromise proper c-NHEJ function. Perturbation of the E2F1/miR-888/APLF axis restores c-NHEJ and ameliorates cell invasiveness. Depletion of miR-888 can establish a 'high E2F1/APLF/DCLRE1C' signature, which was found to be particularly favorable for BC patient survival. CONCLUSION: Suppression of the 'out-of-context' activity of miR-888 improves DSB repair and impedes invasiveness by restoring APLF.

Drug Repositioning Inferred from E2F1-Coregulator Interactions Studies for the Prevention and Treatment of Metastatic Cancers.

Metastasis management remains a long-standing challenge. High abundance of E2F1 triggers tumor progression by developing protein-protein interactions (PPI) with coregulators that enhance its potential to activate a network of prometastatic transcriptional targets. Methods: To identify E2F1-coregulators, we integrated high-throughput Co-immunoprecipitation (IP)/mass spectometry, GST-pull-down assays, and structure modeling. Potential inhibitors of PPI discovered were found by bioinformatics-based pharmacophore modeling, and transcriptome profiling was conducted to screen for coregulated downstream targets. Expression and target gene regulation was validated using qRT-PCR, immunoblotting, chromatin IP, and luciferase assays. Finally, the impact of the E2F1-coregulator complex and its inhibiting drug on metastasis was investigated in vitro in different cancer entities and two mouse metastasis models. Results: We unveiled that E2F1 forms coactivator complexes with metastasis-associated protein 1 (MTA1) which, in turn, is directly upregulated by E2F1. The E2F1:MTA1 complex potentiates hyaluronan synthase 2 (HAS2) expression, increases hyaluronan production and promotes cell motility. Disruption of this prometastatic E2F1:MTA1 interaction reduces hyaluronan synthesis and infiltration of tumor-associated macrophages in the tumor microenvironment, thereby suppressing metastasis. We further demonstrate that E2F1:MTA1 assembly is abrogated by small-molecule, FDA-approved drugs. Treatment of E2F1/MTA1-positive, highly aggressive, circulating melanoma cells and orthotopic pancreatic tumors with argatroban prevents metastasis and cancer relapses in vivo through perturbation of the E2F1:MTA1/HAS2 axis. Conclusion: Our results propose argatroban as an innovative, E2F-coregulator-based, antimetastatic drug. Cancer patients with the infaust E2F1/MTA1/HAS2 signature will likely benefit from drug repositioning.

DNp73-induced degradation of tyrosinase links depigmentation with EMT-driven melanoma progression.

Melanoma is an aggressive cancer with poor prognosis, requiring personalized management of advanced stages and establishment of molecular markers. Melanomas derive from melanocytes, which specifically express tyrosinase, the rate-limiting enzyme of melanin-synthesis. We demonstrate that melanomas with high levels of DNp73, a cancer-specific variant of the p53 family member p73 and driver of melanoma progression show, in contrast to their less-aggressive low-DNp73 counterparts, hypopigmentation in vivo. Mechanistically, reduced melanin-synthesis is mediated by a DNp73-activated IGF1R/PI3K/AKT axis leading to tyrosinase ER-arrest and proteasomal degradation. Tyrosinase loss triggers reactivation of the EMT signaling cascade, a mesenchymal-like cell phenotype and increased invasiveness. DNp73-induced depigmentation, Slug increase and changes in cell motility are recapitulated in neural crest-derived melanophores of Xenopus embryos, underscoring a previously unnoticed physiological role of tyrosinase as EMT inhibitor. This data provides a mechanism of hypopigmentation accompanying cancer progression, which can be exploited in precision diagnosis of patients with melanoma-associated hypopigmentation (MAH), currently seen as a favorable prognostic factor. The DNp73/IGF1R/Slug signature in colorless lesions might aid to clinically discriminate between patients with MAH-associated metastatic disease and those, where MAH is indeed a sign of regression.

Emerging functional markers for cancer stem cell-based therapies: Understanding signaling networks for targeting metastasis.

Metastasis is one of the most challenging issues in cancer patient management, and effective therapies to specifically target disease progression are missing, emphasizing the urgent need for developing novel anti-metastatic therapeutics. Cancer stem cells (CSCs) gained fast attention as a minor population of highly malignant cells within liquid and solid tumors that are responsible for tumor onset, self-renewal, resistance to radio- and chemotherapies, and evasion of immune surveillance accelerating recurrence and metastasis. Recent progress in the identification of their phenotypic and molecular characteristics and interactions with the tumor microenvironment provides great potential for the development of CSC-based targeted therapies and radical improvement in metastasis prevention and cancer patient prognosis. Here, we report on newly uncovered signaling mechanisms controlling CSC's aggressiveness and treatment resistance, and CSC-specific agents and molecular therapeutics, some of which are currently under investigation in clinical trials, gearing towards decisive functional CSC intrinsic or surface markers. One special research focus rests upon subverted regulatory pathways such as insulin-like growth factor 1 receptor signaling and its interactors in metastasis-initiating cell populations directly related to the gain of stem cell- and EMT-associated properties, as well as key components of the E2F transcription factor network regulating metastatic progression, microenvironmental changes, and chemoresistance. In addition, the study provides insight into systems biology tools to establish complex molecular relationships behind the emergence of aggressive phenotypes from high-throughput data that rely on network-based analysis and their use to investigate immune escape mechanisms or predict clinical outcome-relevant CSC receptor signaling signatures. We further propose that customized vector technologies could drastically enhance systemic drug delivery to target sites, and summarize recent progress and remaining challenges. This review integrates available knowledge on CSC biology, computational modeling approaches, molecular targeting strategies, and delivery techniques to envision future clinical therapies designed to conquer metastasis-initiating cells.

MiR-205-5p and miR-342-3p cooperate in the repression of the E2F1 transcription factor in the context of anticancer chemotherapy resistance.

High rates of lethal outcome in tumour metastasis are associated with the acquisition of invasiveness and chemoresistance. Several clinical studies indicate that E2F1 overexpression across high-grade tumours culminates in unfavourable prognosis and chemoresistance in patients. Thus, fine-tuning the expression of E2F1 could be a promising approach for treating patients showing chemoresistance. Methods: We integrated bioinformatics, structural and kinetic modelling, and experiments to study cooperative regulation of E2F1 by microRNA (miRNA) pairs in the context of anticancer chemotherapy resistance. Results: We showed that an enhanced E2F1 repression efficiency can be achieved in chemoresistant tumour cells through two cooperating miRNAs. Sequence and structural information were used to identify potential miRNA pairs that can form tertiary structures with E2F1 mRNA. We then employed molecular dynamics simulations to show that among the identified triplexes, miR-205-5p and miR-342-3p can form the most stable triplex with E2F1 mRNA. A mathematical model simulating the E2F1 regulation by the cooperative miRNAs predicted enhanced E2F1 repression, a feature that was verified by in vitro experiments. Finally, we integrated this cooperative miRNA regulation into a more comprehensive network to account for E2F1-related chemoresistance in tumour cells. The network model simulations and experimental data indicate the ability of enhanced expression of both miR-205-5p and miR-342-3p to decrease tumour chemoresistance by cooperatively repressing E2F1. Conclusions: Our results suggest that pairs of cooperating miRNAs could be used as potential RNA therapeutics to reduce E2F1-related chemoresistance.

Unraveling a tumor type-specific regulatory core underlying E2F1-mediated epithelial-mesenchymal transition to predict receptor protein signatures.

Cancer is a disease of subverted regulatory pathways. In this paper, we reconstruct the regulatory network around E2F, a family of transcription factors whose deregulation has been associated to cancer progression, chemoresistance, invasiveness, and metastasis. We integrate gene expression profiles of cancer cell lines from two E2F1-driven highly aggressive bladder and breast tumors, and use network analysis methods to identify the tumor type-specific core of the network. By combining logic-based network modeling, in vitro experimentation, and gene expression profiles from patient cohorts displaying tumor aggressiveness, we identify and experimentally validate distinctive, tumor type-specific signatures of receptor proteins associated to epithelial-mesenchymal transition in bladder and breast cancer. Our integrative network-based methodology, exemplified in the case of E2F1-induced aggressive tumors, has the potential to support the design of cohort- as well as tumor type-specific treatments and ultimately, to fight metastasis and therapy resistance.Deregulation of E2F family transcription factors is associated with cancer progression and metastasis. Here, the authors construct a map of the regulatory network around the E2F family, and using gene expression profiles, identify tumour type-specific regulatory cores and receptor expression signatures associated with epithelial-mesenchymal transition in bladder and breast cancer.

MiR-182 promotes cancer invasion by linking RET oncogene activated NF-κB to loss of the HES1/Notch1 regulatory circuit.

BACKGROUND: Dominant-activating mutations in the RET proto-oncogene, a receptor tyrosine kinase, are responsible for the development of medullary thyroid carcinoma (MTC) and causative for multiple endocrine neoplasia (MEN) type 2A and 2B. These tumors are highly aggressive with a high propensity for early metastasis and chemoresistance. This attribute makes this neoplasia an excellent model for probing mechanisms underlying cancer progression. METHODS: The expression level of miR-182 was measured in MTC tumor specimens and in TT cells by real-time RT-PCR. TT cells and modified NThy-ori 3.1 that stably express RETM918T were used to investigate RET-dependent regulation of miR-182. Identification and validation of miR-182 targets and pathways was accomplished with luciferase assays, qRT-PCR, Western blotting and immunofluorescence. In vitro, overexpression and knockdown experiments were carried out to examine the impact of miR-182 and HES1 on invasion and migration. RESULTS: We found that miR-182 expression is significantly upregulated in MTC patient samples and tumor-derived cell lines harboring mutated RET. Inhibition of RET oncogenic signaling through a dominant-negative RET∆TK mutant in TT cells reduces miR-182, whereas overexpression of RETM918T in NThy-ori 3.1 cells increases miR-182 levels. We further show that overexpression of this miRNA in NThy.miR-182 cells promotes the invasive and migratory properties without affecting cell proliferation. MiR-182 is upregulated after RET induced NF-κB translocation into the nucleus via binding of NF-κB to the miR-182 promoter. Database analysis revealed that HES1, a repressor of the Notch pathway, is a target of miR-182, whose upregulation correlates with loss of HES1 transcription in MTC tissue samples and mutant RET cell lines. Moreover, we demonstrated that the 3'UTR of the HES1 mRNA bearing the targeting sequence for miR-182 clearly reduced luciferase reporter activity in cells expressing miR-182. Decreased expression of HES1 promotes migration by upregulating Notch1 inhibitor Deltex1 and consequent repression of Notch1. CONCLUSION: We demonstrate a novel mechanism for MTC aggressiveness in which mutated RET/NF-κB-driven expression of miR-182 impedes HES1 activation in a negative feedback loop. This observation might open new possibilities to treat RET oncogene associated metastatic cancer.

Integrated Loss of miR-1/miR-101/miR-204 Discriminates Metastatic from Nonmetastatic Penile Carcinomas and Can Predict Patient Outcome.

PURPOSE: Penile squamous cell carcinoma is a rare but aggressive cancer. Little is known about pivotal events in tumor pathogenesis and metastasis. Lymph node metastasis is the prevailing prognostic factor while clinical detection in patients remains difficult. Our aim was to identify distinct miRNAs that are differentially expressed in metastatic vs nonmetastatic penile carcinoma, which may serve as diagnostic biomarkers for disease progression. MATERIALS AND METHODS: TaqMan® arrays and quantitative polymerase chain reaction were applied to analyze miRNA profiles in penile squamous cell carcinoma specimens and glans tissue from 24 patients. The prognostic value of deregulated miRNAs was analyzed using the Kaplan-Meier method. The Spearman test was applied to determine a potential linkage between distinctive miRNAs in individual patients. RESULTS: Loss of miR-1 (p = 0.0048), miR-101 (p = 0.0001) and miR-204 (p = 0.0004) in metastasizing tumors and associated metastases (p = 0.0151, 0.0019 and 0.0003, respectively) distinguished patients with metastatic and nonmetastatic penile squamous cell carcinoma. These 3 miRNAs showed a coherent expression pattern. Consistently, patients with low levels of all 3 miRNAs had worse survival (p = 0.03). We identified a coordinately regulated miRNA target hub that is over expressed in penile squamous cell carcinoma and associated with lymphovascular invasion. CONCLUSIONS: Our results provide evidence of a novel multiple miRNA based signature associated with lymph node metastasis and unfavorable prognosis of penile squamous cell carcinoma. The integrated loss of miR-1, miR-101 and miR-204 may predict the formation of metastases in penile cancer at an early stage.

Immune responses to WT1 in patients with AML or MDS after chemotherapy and allogeneic stem cell transplantation.

Wilms' tumor gene 1 (WT1) is overexpressed in leukemia and WT1-derived CD8(+) T-cell epitopes for immunotherapies targeting WT1 have been defined. Here, we analyzed expression of WT1 in 226 peripheral blood and bone marrow samples from patients with acute myeloid leukemia or myelodysplastic syndrome (AML/MDS) before and after allogeneic stem cell transplantation (SCT). Transcripts were assessed by quantitative polymerase chain reaction, and WT1-specific CD8+ cytotoxic T cells (CTL) were monitored by tetramer staining and enzyme-linked immunospot (ELISPOT) assays. Reduction of WT1 levels correlated with a longer survival (p < 0.01). Increment of WT1 transcripts eventually resulted in relapse and subsequent death of the patients. In patients with longer survival and continuous complete remission (cCR) after SCT, higher and enduring frequencies of WT1-specific CTL than in patients developing a relapse were detected. These cells were effector T cells secreting interferon gamma and granzyme B. In summary, WT1 is a suitable marker for the detection of minimal residual disease after SCT or chemotherapy. A rising WT1 signal correlated with a dismal prognosis of the patients. WT1-specific CD8(+) T cells might contribute to the maintenance of a cCR. Targeting WT-1 by peptide/protein vaccination as well as adoptive transfer of genetically modified T cells are future options in the individualized therapy for AML/MDS patients.

Epigenetic factor EPC1 is a master regulator of DNA damage response by interacting with E2F1 to silence death and activate metastasis-related gene signatures.

Transcription factor E2F1 is a key regulator of cell proliferation and apoptosis. Recently, it has been shown that aberrant E2F1 expression often detectable in advanced cancers contributes essentially to cancer cell propagation and characterizes the aggressive potential of a tumor. Conceptually, this requires a subset of malignant cells capable of evading apoptotic death through anticancer drugs. The molecular mechanism by which the pro-apoptotic activity of E2F1 is antagonized is widely unclear. Here we report a novel function for EPC1 (enhancer of polycomb homolog 1) in DNA damage protection. Depletion of EPC1 potentiates E2F1-mediated apoptosis in response to genotoxic treatment and abolishes tumor cell motility. We found that E2F1 directly binds to the EPC1 promoter and EPC1 vice versa physically interacts with bifunctional E2F1 to modulate its transcriptional activity in a target gene-specific manner. Remarkably, nuclear-colocalized EPC1 activates E2F1 to upregulate the expression of anti-apoptotic survival genes such as BCL-2 or Survivin/BIRC5 and inhibits death-inducing targets. The uncovered cooperativity between EPC1 and E2F1 triggers a metastasis-related gene signature in advanced cancers that predicts poor patient survival. These findings unveil a novel oncogenic function of EPC1 for inducing the switch into tumor progression-relevant gene expression that may help to set novel therapies.

Association of RHAMM with E2F1 promotes tumour cell extravasation by transcriptional up-regulation of fibronectin.

Dissemination of cancer cells from primary to distant sites is a complex process; little is known about the genesis of metastatic changes during disease development. Here we show that the metastatic potential of E2F1-dependent circulating tumour cells (CTCs) relies on a novel function of the hyaluronan-mediated motility receptor RHAMM. E2F1 directly up-regulates RHAMM, which in turn acts as a co-activator of E2F1 to stimulate expression of the extracellular matrix protein fibronectin. Enhanced fibronectin secretion links E2F1/RHAMM transcriptional activity to integrin-ß1-FAK signalling associated with cytoskeletal remodelling and enhanced tumour cell motility. RHAMM depletion abolishes fibronectin expression and cell transmigration across the endothelial layer in E2F1-activated cells. In a xenograft model, knock-down of E2F1 or RHAMM in metastatic cells protects the liver parenchyma of mice against extravasation of CTCs, whereas the number of transmigrated cells increases in response to E2F1 induction. Expression data from clinical tissue samples reveals high E2F1 and RHAMM levels that closely correlate with malignant progression. These findings suggest a requirement for RHAMM in late-stage metastasis by a mechanism involving cooperative stimulation of fibronectin, with a resultant tumourigenic microenvironment important for enhanced extravasation and distant organ colonization. Therefore, stimulation of the E2F1-RHAMM axis in aggressive cancer cells is of high clinical significance. Targeting RHAMM may represent a promising approach to avoid E2F1-mediated metastatic dissemination.

DNp73 exerts function in metastasis initiation by disconnecting the inhibitory role of EPLIN on IGF1R-AKT/STAT3 signaling.

Dissemination of cancer cells from primary tumors is the key event in metastasis, but specific determinants are widely unknown. Here, we show that DNp73, an inhibitor of the p53 tumor suppressor family, drives migration and invasion of nonmetastatic melanoma cells. Knockdown of endogenous DNp73 reduces this behavior in highly metastatic cell lines. Tumor xenografts expressing DNp73 show a higher ability to invade and metastasize, while growth remains unaffected. DNp73 facilitates an EMT-like phenotype with loss of E-cadherin and Slug upregulation. We provide mechanistic insight toward regulation of LIMA1/EPLIN by p73/DNp73 and demonstrate a direct link between the DNp73-EPLIN axis and IGF1R-AKT/STAT3 activation. These findings establish initiation of the invasion-metastasis cascade via EPLIN-dependent IGF1R regulation as major activity of DNp73.

E2F1 promotes angiogenesis through the VEGF-C/VEGFR-3 axis in a feedback loop for cooperative induction of PDGF-B.

Angiogenesis is essential for primary tumor growth and metastatic dissemination. E2F1, frequently upregulated in advanced cancers, was recently shown to drive malignant progression. In an attempt to decipher the molecular events underlying this behavior, we demonstrate that the tumor cell-associated vascular endothelial growth factor-C/receptor-3 (VEGF-C/VEGFR-3) axis is controlled by E2F1. Activation or forced expression of E2F1 in cancer cells leads to the upregulation of VEGFR-3 and its ligand VEGF-C, whereas E2F1 depletion prevents their expression. E2F1-dependent receptor induction is crucial for tumor cells to enhance formation of capillary tubes and neovascularization in mice. We further provide evidence for a positive feedback loop between E2F1 and VEGFR-3 signaling to stimulate pro-angiogenic platelet-derived growth factor B (PDGF-B). E2F1 or VEGFR-3 knockdown results in reduced PDGF-B levels, while the coexpression synergistically upregulates promoter activity and endogenous protein expression of PDGF-B. Our findings delineate an as yet unrecognized function of E2F1 as enhancer of angiogenesis via regulation of VEGF-C/VEGFR-3 signaling in tumors to cooperatively activate PDGF-B expression. Targeting this pathway might be reasonable to complement standard anti-angiogenic treatment of cancers with deregulated E2F1.

Germline RET sequence variation I852M and occult medullary thyroid cancer: harmless polymorphism or causative mutation?

OBJECTIVE: Rearranged during transfection (RET) gene analysis, widely used to identify carriers at risk of medullary thyroid cancer (MTC), occasionally uncovers novel sequence 'variants of unknown clinical significance' including RET I852M. This study aimed to clarify whether RET I852M represents a harmless polymorphism or a pathogenic mutation. DESIGN: Clinical investigation supported by functional characterization of I852M mutant cells in vitro. PATIENTS AND MEASUREMENTS: Genotype-phenotype correlation including five kindreds from a three-generational Caucasian I852M RET family. RESULTS: A node-negative occult MTC was found in the 64-year-old index patient who had increased basal and stimulated peak calcitonin levels of 190 and 13 307 ng/l, respectively. Her 4-year-old grandson had no histopathological evidence of C-cell disease although his serum calcitonin levels had increased within 5 months from 3·2 to 6·3 ng/l basally and from 17·2 to 24·5 ng/l after pentagastrin stimulation. His mother and two 11- and 1·5-year-old siblings, also carrying the gene, had normal basal and stimulated calcitonin levels and hence did not undergo surgery. Functional characterization of transfected NIH3T3 cells in vitro (cell proliferation rate; cell viability; anchorage-independent cell growth; cell migration; and invasion) indicated that I852M mutant cells have transforming and migratory activities similar to American Thyroid Association (ATA) class A V804M mutants. I852M mutants demonstrated a weaker proliferative potential than fast-proliferating ATA class C C634R mutants and revealed a weaker migratory activity compared with aggressively growing ATA class D A883F mutants. CONCLUSIONS: I852M sequence variations represent genuine RET mutations, falling into ATA class A of weakly activating RET germline mutations.