Urokinase-type plasminogen activator receptor (uPAR)-mediated regulation of WNT/β-catenin signaling is enhanced in irradiated medulloblastoma cells

Basic mechanism of mobilizing cell movement during invasion of glioblastoma and target selection of targeted therapy

BACKGROUND

Glioblastoma (GBM), also known as glioblastoma multiforme, is a rapidly growing and highly invasive malignant tumor. Due to the inability to clearly distinguish between glioblastoma and normal tissue, surgery cannot achieve safe resection, often leading to poor patient prognosis and inevitable tumor recurrence. According to previous studies, GBM invasion is related to intercellular adhesion, matrix degradation, extracellular matrix and its related adhesion molecules, as well as the molecular matrix of protein hydrolases in the microenvironment of GBM cells and stromal cells.

AIM OF REVIEW

The aim is to enhance our understanding of the molecular mechanisms underlying GBM invasion and to advance research on targeted therapies for inhibiting GBM invasion.

KEY SCIENTIFIC CONCEPTS OF REVIEW

This article describes the protein hydrolases that may affect GBM cell invasion, changes in the cytoskeleton during motility, and the regulatory mechanisms of intracellular signaling pathways in GBM invasion. In addition, we also explored the possibility of targeted therapy against invasion related molecules in GBM.

Cancer stem cells: advances in knowledge and implications for cancer therapy

Cancer stem cells (CSCs), a small subset of cells in tumors that are characterized by self-renewal and continuous proliferation, lead to tumorigenesis, metastasis, and maintain tumor heterogeneity. Cancer continues to be a significant global disease burden. In the past, surgery, radiotherapy, and chemotherapy were the main cancer treatments. The technology of cancer treatments continues to develop and advance, and the emergence of targeted therapy, and immunotherapy provides more options for patients to a certain extent. However, the limitations of efficacy and treatment resistance are still inevitable. Our review begins with a brief introduction of the historical discoveries, original hypotheses, and pathways that regulate CSCs, such as WNT/β-Catenin, hedgehog, Notch, NF-κB, JAK/STAT, TGF-β, PI3K/AKT, PPAR pathway, and their crosstalk. We focus on the role of CSCs in various therapeutic outcomes and resistance, including how the treatments affect the content of CSCs and the alteration of related molecules, CSCs-mediated therapeutic resistance, and the clinical value of targeting CSCs in patients with refractory, progressed or advanced tumors. In summary, CSCs affect therapeutic efficacy, and the treatment method of targeting CSCs is still difficult to determine. Clarifying regulatory mechanisms and targeting biomarkers of CSCs is currently the mainstream idea.

Therapeutic Approaches of Dual-targeted Nanomedicines for Tumor Multidrug Resistance

Currently, the main cause of cancer chemotherapy failure is multi-drug resistance (MDR), which involves a variety of complex mechanisms. Compared with traditional small-molecule chemotherapy, targeted nanomedicines offer promising alternative strategies as an emerging form of therapy, especially active targeted nanomedicines. However, although single-targeted nanomedicines have made some progress in tumor therapy, the complexity of tumor microenvironment and tumor heterogeneity limits their efficacy. Dual-targeted nanomedicines can simultaneously target two tumor-specific factors that cause tumor MDR, which have the potential in overcoming tumor MDR superior to single-targeted nanomedicines by further enhancing cell uptake and cytotoxicity in new forms, as well as the effectiveness of tumor-targeted delivery. This review discusses tumor MDR mechanisms and the latest achievements applied to dual-targeted nanomedicines in tumor MDR.

Leukocyte cell-derived chemotaxin 2 regulates epithelial-mesenchymal transition and cancer stemness in hepatocellular carcinoma

Leukocyte cell-derived chemotaxin 2 (LECT2) acts as a tumor suppressor in hepatocellular carcinoma (HCC). However, the antineoplastic mechanism of LECT2, especially its influence on hepatic cancer stem cells (CSCs), remains largely unknown. In The Cancer Genome Atlas cohort, LECT2 mRNA expression was shown to be associated with stage, grade, recurrence, and overall survival in human HCC patients, and LECT2 expression was downregulated in hepatoma tissues compared with the adjacent nontumoral liver. Here, we show by immunofluorescence and immunoblot analyses that LECT2 was expressed at lower levels in tumors and in poorly differentiated HCC cell lines. Using functional assays, we also found LECT2 was capable of suppressing oncogenic behaviors such as cell proliferation, anchorage-independent growth, migration, invasiveness, and epithelial-mesenchymal transition in hepatoma cells. Moreover, we show exogenous LECT2 treatment inhibited CSC functions such as tumor sphere formation and drug efflux. Simultaneously, hepatic CSC marker expression was also downregulated, including expression of CD133 and CD44. This was supported by infection with adenovirus encoding LECT2 (Ad-LECT2) in HCC cells. Furthermore, in animal experiments, Ad-LECT2 gene therapy showed potent efficacy in treating HCC. We demonstrate LECT2 overexpression significantly promoted cell apoptosis and reduced neovascularization/CSC expansion in rat hepatoma tissues. Mechanistically, we showed using immunoblot and immunofluorescence analyses that LECT2 inhibited β-catenin signaling via the suppression of the hepatocyte growth factor/c-MET axis to diminish CSC properties in HCC cells. In summary, we reveal novel functions of LECT2 in the suppression of hepatic CSCs, suggesting a potential alternative strategy for HCC therapy.

Modulation of Cellular Function by the Urokinase Receptor Signalling: A Mechanistic View

Urokinase-type plasminogen activator receptor (uPAR or CD87) is a glycosyl-phosphatidyl-inositol anchored (GPI) membrane protein. The uPAR primary ligand is the serine protease urokinase (uPA), converting plasminogen into plasmin, a broad spectrum protease, active on most extracellular matrix components. Besides uPA, the uPAR binds specifically also to the matrix protein vitronectin and, therefore, is regarded also as an adhesion receptor. Complex formation of the uPAR with diverse transmembrane proteins, including integrins, formyl peptide receptors, G protein-coupled receptors and epidermal growth factor receptor results in intracellular signalling. Thus, the uPAR is a multifunctional receptor coordinating surface-associated pericellular proteolysis and signal transduction, thereby affecting physiological and pathological mechanisms. The uPAR-initiated signalling leads to remarkable cellular effects, that include increased cell migration, adhesion, survival, proliferation and invasion. Although this is beyond the scope of this review, the uPA/uPAR system is of great interest to cancer research, as it is associated to aggressive cancers and poor patient survival. Increasing evidence links the uPA/uPAR axis to epithelial to mesenchymal transition, a highly dynamic process, by which epithelial cells can convert into a mesenchymal phenotype. Furthermore, many reports indicate that the uPAR is involved in the maintenance of the stem-like phenotype and in the differentiation process of different cell types. Moreover, the levels of anchor-less, soluble form of uPAR, respond to a variety of inflammatory stimuli, including tumorigenesis and viral infections. Finally, the role of uPAR in virus infection has received increasing attention, in view of the Covid-19 pandemics and new information is becoming available. In this review, we provide a mechanistic perspective, via the detailed examination of consolidated and recent studies on the cellular responses to the multiple uPAR activities.

SMYD3 Promotes Cell Cycle Progression by Inducing Cyclin D3 Transcription and Stabilizing the Cyclin D1 Protein in Medulloblastoma

Simple Summary

Medulloblastoma is the most common malignant pediatric brain tumor and is classified into four molecular subgroups: Wnt, Shh, Group 3, and Group 4. Of these subgroups, patients with Myc+ Group 3 MB have the worst prognosis. Using an RNAi functional genomic screen, we identified the lysine methyltransferase SMYD3 as a crucial epigenetic regulator responsible for promoting Group 3 MB cell growth. We demonstrated that SMYD3 drives MB cell cycle progression by inducing cyclin D3 transcription and preventing cyclin D1 ubiquitination. Using in vitro and ex vivo studies, we showed that SMYD3 suppression by shRNA and BCI-121 significantly impaired proliferation, resulting in the downregulation of cyclin D3, cyclin D1, and pRBSer795. Moreover, we are the first to show that SMYD3 methylates the cyclin D1 protein, indicating that the SMYD3 stabilizes cyclin D1 through post-translational modification. Collectively, our studies position SMYD3 as a promising treatment option for Group 3 Myc+ MB patients.

Abstract

Medulloblastoma (MB) is the most common malignant pediatric brain tumor. Maximum safe resection, postoperative craniospinal irradiation, and chemotherapy are the standard of care for MB patients. MB is classified into four subgroups: Shh, Wnt, Group 3, and Group 4. Of these subgroups, patients with Myc+ Group 3 MB have the worst prognosis, necessitating alternative therapies. There is increasing interest in targeting epigenetic modifiers for treating pediatric cancers, including MB. Using an RNAi functional genomic screen, we identified the lysine methyltransferase SMYD3, as a crucial epigenetic regulator that drives the growth of Group 3 Myc+ MB cells. We demonstrated that SMYD3 directly binds to the cyclin D3 promoter to activate its transcription. Further, SMYD3 depletion significantly reduced MB cell proliferation and led to the downregulation of cyclin D3, cyclin D1, pRBSer795, with concomitant upregulations in RB in vitro. Similar results were obtained following pharmacological inhibition of SMYD3 using BCI-121 ex vivo. SMYD3 knockdown also promoted cyclin D1 ubiquitination, indicating that SMYD3 plays a vital role in stabilizing the cyclin D1 protein. Collectively, our studies demonstrate that SMYD3 drives cell cycle progression in Group 3 Myc+ MB cells and that targeting SMYD3 has the potential to improve clinical outcomes for high-risk patients.

Role, molecular mechanism and the potential target of breast cancer stem cells in breast cancer development

Breast cancer (BC) is one of the most common malignant tumors in women globally, and its occurrence has surpassed lung cancer and become the biggest threat for women. At present, breast cancer treatment includes surgical resection or postoperative chemotherapy and radiotherapy. However, tumor relapse and metastasis usually lead to current therapy failure thanks to breast cancer stem cells (BCSCs)-mediated tumorigenicity and drug resistance. Drug resistance is mainly due to the long-term quiescent G0 phase, strong DNA repairability, and high expression of ABC transporter, and the tumorigenicity is reflected in the activation of various proliferation pathways related to BCSCs. Therefore, understanding the characteristics of BCSCs and their intracellular and extracellular molecular mechanisms is crucial for the development of targeted drugs for BCSCs. To this end, we discussed the latest developments in BCSCs research, focusing on the analysis of specific markers, critical signaling pathways that maintain the stemness of BCSCs，such as NOTCH, Wnt/β-catenin, STAT3, Hedgehog, and Hippo-YAP signaling, immunomicroenviroment and summarizes targeting therapy strategies for stemness maintenance and differentiation, which provides a theoretical basis for further exploration of treating breast cancer and preventing relapse derived from BCSCs.

A Novel miR-98 Negatively Regulates the Resistance of Endometrial Cancer Cells to Paclitaxel by Suppressing ABCC10/MRP-7

Endometrial cancer (EC) is one of the most frequent gynecological tumors, and chemoresistance is a major obstacle to improving the prognosis of EC patients. MicroRNAs (miRNAs) and long non-coding RNAs (lncRNAs) have recently emerged as crucial chemoresistance regulators that alter the levels of downstream target genes. Multidrug Resistance Protein 7 (MRP-7/ABCC10) is an ATP-binding cassette transporter that causes the resistance to anti-cancer drugs. The purpose of this research is to determine whether MRP-7 has a role in mediating the sensitivity of EC cells to paclitaxel and whether the expression of MRP-7 is regulated by miR-98 and lncRNA NEAT1. We reported that the levels of MRP-7 were significantly increased in EC tissues and associated with an unfavorable prognosis. Downregulation of MRP-7 in EC cells sensitized these cells to paclitaxel and reduced cell invasion. PLAUR serves as a downstream molecule of MRP-7 and facilitates paclitaxel resistance and EC cell invasiveness. Moreover, miR-98 serves as a tumor suppressor to inhibit MRP-7 expression, leading to the repression of paclitaxel resistance. Furthermore, a novel lncRNA, NEAT1, was identified as a suppressor of miR-98, and NEAT1 could upregulate MRP-7 levels by reducing the expression of miR-98. Taken together, these findings demonstrate that upregulation of MRP-7 and NEAT1, and downregulation of miR-98 have important roles in conferring paclitaxel resistance to EC cells. The modulation of these molecules may help overcome the chemoresistance against paclitaxel in EC cells.

Adipose-PAS interactions in the context of its localised bio-engineering potential (Review)

Adipocytes are a known source of stem cells. They are easy to harvest, and are a suitable candidate for autogenous grafts. Adipose derived stem cells (ADSCs) have multiple target tissues which they can differentiate into, including bone and cartilage. In adipose tissue, ADSCs are able to differentiate, as well as providing energy and a supply of cytokines/hormones to manage the hypoxic and lipid/hormone saturated adipose environment. The plasminogen activation system (PAS) controls the majority of proteolytic activities in both adipose and wound healing environments, allowing for rapid cellular migration and tissue remodelling. While the primary activation pathway for PAS occurs through the urokinase plasminogen activator (uPA), which is highly expressed by endothelial cells, its function is not limited to enabling revascularisation. Proteolytic activity is dependent on protease activation, localisation, recycling mechanisms and substrate availability. uPA and uPA activated plasminogen allows pluripotent cells to arrive to new local environments and fulfil the niche demands. However, overstimulation, the acquisition of a migratory phenotype and constant protein turnover can be unconducive to the formation of structured hard and soft tissues. To maintain a suitable healing pattern, the proteolytic activity stimulated by uPA is modulated by plasminogen activator inhibitor 1. Depending on the physiological settings, different parts of the remodelling mechanism are activated with varying results. Utilising the differences within each microenvironment to recreate a desired niche is a valid therapeutic bio-engineering approach. By controlling the rate of protein turnover combined with a receptive stem cell lineage, such as ADSC, a novel avenue on the therapeutic opportunities may be identified, which can overcome limitations, such as scarcity of stem cells, low angiogenic potential or poor host tissue adaptation.

Urokinase-type plasminogen activator-mediated crosstalk between N-cadherin and β-catenin promotes wound healing

Urokinase-type plasminogen activator (uPA; encoded by Plau) is a serine proteinase that, in the central nervous system, induces astrocytic activation. β-Catenin is a protein that links the cytoplasmic tail of cadherins to the actin cytoskeleton, thus securing the formation of cadherin-mediated cell adhesion complexes. Disruption of cell-cell contacts leads to the detachment of β-catenin from cadherins, and β-catenin is then degraded by the proteasome following its phosphorylation by GSK3β. Here, we show that astrocytes release uPA following a scratch injury, and that this uPA promotes wound healing via a plasminogen-independent mechanism. We found that uPA induces the detachment of β-catenin from the cytoplasmic tail of N-cadherin (NCAD; also known as CDH2) by triggering its phosphorylation at Tyr654. Surprisingly, this is not followed by degradation of β-catenin because uPA also induces the phosphorylation of the low density lipoprotein receptor-related protein 6 (LRP6) at Ser1490, which then blocks the kinase activity of GSK3β. Our work indicates that the ensuing cytoplasmic accumulation of β-catenin is followed by its nuclear translocation and β-catenin-triggered transcription of the receptor for uPA (Plaur), which in turn is required for uPA to induce astrocytic wound healing.

CRISPR/Cas9 uPAR Gene Knockout Results in Tumor Growth Inhibition, EGFR Downregulation and Induction of Stemness Markers in Melanoma and Colon Carcinoma Cell Lines

uPAR is a globular protein, tethered to the cell membrane by a GPI-anchor involved in several cancer-related properties and its overexpression commonly correlates with poor prognosis and metastasis. We investigated the consequences of uPAR irreversible loss in human melanoma and colon cancer cell lines, knocking out its expression by CRISPR/Cas9. We analyzed through flow cytometry, western blotting and qPCR, the modulation of the most known cancer stem cells-associated genes and the EGFR while we observed the proliferation rate exploiting 2D and 3D cellular models. We also generated uPAR “rescue” expression cell lines as well as we promoted the expression of only its 3’UTR to demonstrate the involvement of uPAR mRNA in tumor progression. Knocking out PLAUR, uPAR-encoding gene, we observed an inhibited growth ratio unexpectedly coupled with a significant percentage of cells acquiring a stem-like phenotype. In vivo experiments demonstrated that uPAR loss completely abrogates tumorigenesis despite the gained stem-like profile. Nonetheless, we proved that the reintroduction of the 3’UTR of PLAUR gene was sufficient to restore the wild-type status validating the hypothesis that such a region may act as a “molecular sponge”. In particular miR146a, by binding PLAUR 3’ UTR region might be responsible for uPAR-dependent inhibition of EGFR expression.

Medulloblastoma cancer stem cells: molecular signatures and therapeutic targets

Medulloblastoma (MB) is the most common malignant primary intracranial neoplasm diagnosed in childhood. Although numerous efforts have been made during the past few years to exploit novel targeted therapies for this aggressive neoplasm, there still exist substantial hitches hindering successful management of MB. Lately, progress in cancer biology has shown evidence that a subpopulation of cells within the tumour, namely cancer stem cells (CSCs), are thought to be responsible for the resistance to most chemotherapeutic agents and radiation therapy, accounting for cancer recurrence. Hence, it is crucial to identify the molecular signatures and genetic aberrations that characterise those CSCs and develop therapies that specifically target them. In this review, we aim to give an overview of the main genetic and molecular cues that depict MB-CSCs and provide a synopsis of the novel therapeutic approaches that specifically target this population of cells to attain enhanced antitumorous effects and therefore overcome resistance to therapy.

Wnt Signaling in Ovarian Cancer Stemness, EMT, and Therapy Resistance

Ovarian cancers represent the deadliest among gynecologic malignancies and are characterized by a hierarchical structure with cancer stem cells (CSCs) endowed with self-renewal and the capacity to differentiate. The Wnt/β-catenin signaling pathway, known to regulate stemness in a broad spectrum of stem cell niches including the ovary, is thought to play an important role in ovarian cancer. Importantly, Wnt activity was shown to correlate with grade, epithelial to mesenchymal transition, chemotherapy resistance, and poor prognosis in ovarian cancer. This review will discuss the current knowledge of the role of Wnt signaling in ovarian cancer stemness, epithelial to mesenchymal transition (EMT), and therapy resistance. In addition, the alleged role of exosomes in the paracrine activation of Wnt signaling and pre-metastatic niche formation will be reviewed. Finally, novel potential treatment options based on Wnt inhibition will be highlighted.

The uPAR System as a Potential Therapeutic Target in the Diseased Eye

Dysregulation of vascular networks is characteristic of eye diseases associated with retinal cell degeneration and visual loss. Visual impairment is also the consequence of photoreceptor degeneration in inherited eye diseases with a major inflammatory component, but without angiogenic profile. Among the pathways with high impact on vascular/degenerative diseases of the eye, a central role is played by a system formed by the ligand urokinase-type plasminogen activator (uPA) and its receptor uPAR. The uPAR system, although extensively investigated in tumors, still remains a key issue in vascular diseases of the eye and even less studied in inherited retinal pathologies such as retinitis pigmantosa (RP). Its spectrum of action has been extended far beyond a classical pro-angiogenic function and has emerged as a central actor in inflammation. Preclinical studies in more prevalent eye diseases characterized by neovascular formation, as in retinopathy of prematurity, wet macular degeneration and rubeosis iridis or vasopermeability excess as in diabetic retinopathy, suggest a critical role of increased uPAR signaling indicating the potentiality of its modulation to counteract neovessel formation and microvascular dysfunction. The additional observation that the uPAR system plays a major role in RP by limiting the inflammatory cascade triggered by rod degeneration rises further questions about its role in the diseased eye.

Role of MYC-miR-29-B7-H3 in Medulloblastoma Growth and Angiogenesis

Medulloblastoma (MB) is the most common embryonal neuroepithelial tumor, with poor patient outcomes and secondary complications. In this study, we investigated the role of the B7 family of immune checkpoint homolog 3 (B7-H3) expression in MB angiogenesis. B7-H3, a co-inhibitory immune checkpoint, is highly expressed and is associated with lower overall survival in MYC⁺ MB's. Evidence for a direct transcriptional role of MYC on the B7-H3 gene promoter was confirmed by MYC inhibition and anti-MYC antibody ChIP analysis. Interestingly, MYC inhibition not only downregulated the B7-H3 protein expression, but also rescued miR-29 expression, thus indicating a triangular regulatory relationship between MYC, miR-29, and B7-H3 in Group 3 MB cells. From RNA seq and IPAD assay, we observed a negative feedback loop between miR-29 and MYC that may control B7-H3 expression levels in MB cells. Our studies show that B7-H3 expression levels play a crucial role in promoting MB angiogenesis which can be inhibited by miR-29 overexpression via miR-29-mediated B7-H3 downregulation. The tumor suppressor role of miR-29 is mediated by the activation of JAK/STAT1 signaling that further plays a role in MYC-B7-H3 downregulation in MB. This study highlights B7-H3 as a viable target in MB angiogenesis, and that the expression of miR-29 can inhibit B7-H3 and sensitize MB cells to treatment with MYC-inhibiting drugs.

Nucleolin Is a Functional Binding Protein for Salinomycin in Neuroblastoma Stem Cells

The aim of this study is to illuminate a novel therapeutic approach by identifying a functional binding target of salinomycin, an emerging anticancer stem cell (CSC) agent, and to help dissect the underlying action mechanisms. By utilizing integrated strategies, we identify that nucleolin (NCL) is likely a salinomycin-binding target and a critical regulator involved in human neuroblastoma (NB) CSC activity. Salinomycin markedly suppresses NB CD34 expression and reduces CD34+ cell population in an NCL-dependent manner via disruption of the interaction of NCL with CD34 promoter. The elevated levels of NCL expression in NB tumors are associated with poor patient survival. Altogether, these results indicate that NCL is likely a novel functional salinomycin-binding target that exhibits the potential to be a prognostic marker for NB therapy.

The Use of Normal Stem Cells and Cancer Stem Cells for Potential Anti-Cancer Therapeutic Strategy

BACKGROUND

Despite recent advance in conventional cancer therapies including surgery, radiotherapy, chemotherapy, and immunotherapy to reduce tumor size, unfortunately cancer mortality and metastatic cancer incidence remain high. Along with a deeper understanding of stem cell biology, cancer stem cell (CSC) is important in targeted cancer therapy. Herein, we review representative patents using not only normal stem cells as therapeutics themselves or delivery vehicles, but also CSCs as targets for anti-cancer strategy.

METHODS

Relevant patent literatures published between 2005 and 2017 are discussed to present developmental status and experimental results on using normal stem cells and CSCs for cancer therapy and explore potential future directions in this field.

RESULTS

Stem cells have been considered as important element of regenerative therapy by promoting tissue regeneration. Particularly, there is a growing trend to use stem cells as a target drug-delivery system to reduce undesirable side effects in non-target tissues. Noteworthy, studies on CSC-specific markers for distinguishing CSCs from normal stem cells and mature cancer cells have been conducted as a selective anti-cancer therapy with few side effects. Many researchers have also reported the development of various substances with anticancer effects by targeting CSCs from cancer tissues.

CONCLUSION

There has been a continuing increase in the number of studies on therapeutic stem cells and CSC-specific markers for selective diagnosis and therapy of cancer. This review focuses on the current status in the use of normal stem cells and CSCs for targeted cancer therapy. Future direction is also proposed.

Diversity and functional evolution of the plasminogen activator system

The urokinase plasminogen activator system is a family of serine proteases which consists of uPA (urokinase plasminogen activator), uPAR (urokinase type plasminogen activator receptor) and PAI-1 (plasminogen activator inhibitor 1). In addition to their significant roles in activation, these proteases act as key regulators of the tumor microenvironment and are involved in the metastatic process in many cancers. High levels of uPA system proteases in many human cancer predicts poor patient prognosis and strongly indicated a key role of uPA system in cancer metastasis. Individual components of uPA system are found to be differentially expressed in cancer cells compared to normal cells and therefore are potential therapeutic targets. In this review, we present the molecular and cellular mechanisms underlying the role of uPA system in cancer progression. Epithelial to mesenchymal transitions (EMT) is the main cause of the cancer cell metastasis. We have also attempted to relate the role of uPA signaling in EMT of cancer cells.

Dual-targeting Wnt and uPA receptors using peptide conjugated ultra-small nanoparticle drug carriers inhibited cancer stem-cell phenotype in chemo-resistant breast cancer

Heterogeneous tumor cells, high incidence of tumor recurrence, and decrease in overall survival are the major challenges for the treatment of chemo-resistant breast cancer. Results of our study showed differential chemotherapeutic responses among breast cancer patient derived xenograft (PDX) tumors established from the same patients. All doxorubicin (Dox)-resistant tumors expressed higher levels of cancer stem-like cell biomarkers, including CD44, Wnt and its receptor LRP5/6, relative to Dox-sensitive tumors. To effectively treat resistant tumors, we developed an ultra-small magnetic iron oxide nanoparticle (IONP) drug carrier conjugated with peptides that are dually targeted to Wnt/LRP5/6 and urokinase plasminogen activator receptor (uPAR). Our results showed that simultaneous binding to LRP5/6 and uPAR by the dual receptor targeted IONPs was required to inhibit breast cancer cell invasion. Molecular analysis revealed that the dual receptor targeted IONPs significantly inhibited Wnt/β-catenin signaling and cancer stem-like phenotype of tumor cells, with marked reduction of Wnt ligand, CD44 and uPAR. Systemic administration of the dual targeted IONPs led to nanoparticle-drug delivery into PDX tumors, resulting in stronger tumor growth inhibition compared to non-targeted or single-targeted IONP-Dox in a human breast cancer PDX model. Therefore, co-targeting Wnt/LRP and uPAR using IONP drug carriers is a promising therapeutic approach for effective drug delivery to chemo-resistant breast cancer.

High-throughput proteome analysis reveals targeted TRPM8 degradation in prostate cancer

The Ca²⁺-permeable ion channel TRPM8 is a hallmark of the prostate epithelium. We recently discovered that TRPM8 is an ionotropic testosterone receptor. This finding suggested that testosterone-induced TRPM8 activity regulates Ca²⁺ homeostasis in the prostate epithelium. Since androgens are significantly implicated in prostate cancer development, the role of the novel testosterone receptor TRPM8 in cancer was assessed in our study. Although TRPM8 mRNA levels increase at the early prostate cancer stages, we found that it is not proportionally translated into TRPM8 protein levels. High-throughput proteome analysis revealed that TRPM8 degradation is enhanced in human prostate cancer cells. This degradation is executed via a dual degradation mechanism with the involvement of both lysosomal and proteasomal proteolytic pathways. The evaluation of the TRPM8 expression pattern in prostate cancer patients further confirmed the incidence of TRPM8 removal from the plasma membrane and its internalization pattern coincided with the severity of the tumor. Together, our results indicate that enhanced TRPM8 hydrolysis in prostate cancer could present an adaptation mechanism, sustained via bypassing testosterone-induced rapid Ca²⁺ uptake through TRPM8, thus, diminishing the rates of apoptosis. In this light, recovery of TRPM8 may pose a novel therapeutic strategy for an anti-tumor defense mechanism.

Combined EphB2 receptor knockdown with radiation decreases cell viability and invasion in medulloblastoma

Background

Medulloblastoma is one of the most common types of pediatric brain tumor characterized by the subpopulation of cells that exhibit high invasive potential and radioresistant properties. In addition, dysregulated function and signaling by Eph family of receptors have been shown to impart pro-tumorigenic characteristics in this brain malignancy. In the current study, we investigated whether EphB2 knockdown in combination with radiation can alter invasiveness and decrease medulloblastoma tumor growth or viability in vitro.

Methods

The expression of EphB2 receptor was analyzed by immunohistochemistry and Western blotting. Microarray analysis and mRNA analysis was performed on medulloblastoma patient datasets and compared to the normal cerebellum. The radiosensitization effect following EphB2 knockdown was determined by clonogenic assay in human medulloblastoma cells. Effects of EphB2-siRNA in absence or presence of radiation on cell cycle distribution, cell viability, and invasion were analyzed by flow cytometry, MTT assay, trypan blue exclusion assay, xcelligence system, and Western blotting.

Results

We observed that EphB2 is expressed in both medulloblastoma cell lines and patient samples and its downregulation sensitized these cells to radiation as evident by decreased clonogenic survival fractions. EphB2 expression was also high across different medulloblastoma subgroups compared to normal cerebellum. The radiosensitization effect observed following EphB2 knockdown was in part mediated by enhanced G2/M cell cycle arrest. We also found that the combined approach of EphB2 knockdown and radiation exposure significantly reduced overall cell viability in medulloblastoma cells compared to control groups. Similar results were obtained in the xcelligence-based invasion assay. Western blot analysis also demonstrated changes in the protein expression of cell proliferation, cell survival, and invasion molecules in the combination group versus others.

Conclusions

Overall, our findings indicate that specific targeting of EphB2 receptor in combination with radiation may serve as an effective therapeutic strategy in medulloblastoma. Future studies are warranted to test the efficacy of this approach in in vivo preclinical models.

Electronic supplementary material

The online version of this article (doi:10.1186/s12935-017-0409-7) contains supplementary material, which is available to authorized users.

Upregulation of CFTR in patients with endometriosis and its involvement in NFκB-uPAR dependent cell migration

Endometriotic tissues exhibit high migration ability with the underlying mechanisms remain elusive. Our previous studies have demonstrated that cystic fibrosis transmembrane conductance regulator (CFTR) acts as a tumor suppressor regulating cell migration. In the present study, we explored whether CFTR plays a role in the development of human endometriosis. We found that both mRNA and protein expression levels of CFTR and urokinase-type plasminogen activator receptor (uPAR) were significantly increased in ectopic endometrial tissues from patients with endometriosis compared to normal endometrial tissues from women without endometriosis and positively correlated. In human endometrial Ishikawa (ISK) cells, overexpression of CFTR stimulated cell migration with upregulated NFκB p65 and uPAR. Knockdown of CFTR inhibited cell migration. Furthermore, inhibition of NFκB with its inhibitors (curcumin or Bay) significantly reduced the expression of uPAR and cell migration in the CFTR-overexpressing ISK cells. Collectively, the present results suggest that the CFTR-NFκB-uPAR signaling may contribute to the progression of human endometriosis, and indicate potential targets for diagnosis and treatment.

TRPM8 channel as a novel molecular target in androgen-regulated prostate cancer cells

The cold and menthol receptor TRPM8 is highly expressed in prostate and prostate cancer (PC). Recently, we identified that TRPM8 is as an ionotropic testosterone receptor. The TRPM8 mRNA is expressed in early prostate tumors with high androgen levels, while anti-androgen therapy greatly reduces its expression. Here, from the chromatin-immunoprecipitation (ChIP) analysis, we found that an androgen response element (ARE) mediates androgen regulation of trpm8. Furthermore, using immunofluorescence, calcium-imaging and planar lipid bilayers, we identified that TRPM8 channel is functionally regulated by androgens in the prostate. Although TRPM8 mRNA is expressed at high levels, we found that the TRPM8 protein undergoes ubiquitination and degradation in PC cells. The mass-spectrometry analysis of TRPM8, immunoprecipitated from LNCaP cells identified ubiquitin-like modifier-activating enzyme 1 (UBA1). PYR-41, a potent inhibitor of initial enzyme in the ubiquitination cascade, UBA1, increased TRPM8 activity on the plasma membrane (PM) of LNCaP cells. Furthermore, PYR-41-mediated _PMTRPM8 activity was accompanied by enhanced activation of p53 and Caspase-9. Interestingly, we found that the trpm8 promoter possesses putative binding sites for p53 and that the overexpression of p53 increased the TRPM8 mRNA levels. In addition to the genomic regulation of TRPM8 by AR and p53, our findings indicate that the testosterone-induced _PMTRPM8 activity elicits Ca²⁺ uptake, subsequently causing apoptotic cell death. These findings support the strategy of rescuing _PMTRPM8 expression as a new therapeutic application through the regulation of PC cell growth and proliferation.

Immunohistochemical Detection of Urokinase Plasminogen Activator and Urokinase Plasminogen Activator Receptor in Canine Vascular Endothelial Tumours

Immunohistochemistry was used to assess the expression of urokinase plasminogen activator (uPA) and uPA receptor (uPAR) in 57 canine primary haemangiosarcomas (HSAs), 26 canine cutaneous haemangiomas (HAs) and in control sections of canine cutaneous granulation tissue. The correlation between uPA/uPAR expression and the Ki67 labelling index (LI) was estimated in the HSA and HA tissues. uPA was expressed by 73.2% and 75.0% of splenic HSAs and non-splenic HSAs, respectively. All HSA tissues tested expressed uPAR. Expression of both molecules was significantly higher in HSAs than in cutaneous HAs (3.8% for uPA and 30.7% for uPAR). The average Ki67 LI of the uPA(+)/uPAR(+) HSAs was significantly higher than that of uPA(-)/uPAR(+) HSAs and HA tissues (mean ± SDs 32.8 ± 15.3, 15.2 ± 7.2 and 2.1 ± 0.7, respectively; P <0.05). These results suggest that uPA and uPAR play a significant role in the malignant proliferation of canine HSA, regardless of the primary origin of the tumour.

The HSP90 Inhibitor Ganetespib Radiosensitizes Human Lung Adenocarcinoma Cells

The molecular chaperone HSP90 is involved in stabilization and function of multiple client proteins, many of which represent important oncogenic drivers in NSCLC. Utilization of HSP90 inhibitors as radiosensitizing agents is a promising approach. The antitumor activity of ganetespib, HSP90 inhibitor, was evaluated in human lung adenocarcinoma (AC) cells for its ability to potentiate the effects of IR treatment in both in vitro and in vivo. The cytotoxic effects of ganetespib included; G2/M cell cycle arrest, inhibition of DNA repair, apoptosis induction, and promotion of senescence. All of these antitumor effects were both concentration- and time-dependent. Both pretreatment and post-radiation treatment with ganetespib at low nanomolar concentrations induced radiosensitization in lung AC cells in vitro. Ganetespib may impart radiosensitization through multiple mechanisms: such as down regulation of the PI3K/Akt pathway; diminished DNA repair capacity and promotion of cellular senescence. In vivo, ganetespib reduced growth of T2821 tumor xenografts in mice and sensitized tumors to IR. Tumor irradiation led to dramatic upregulation of β-catenin expression in tumor tissues, an effect that was mitigated in T2821 xenografts when ganetespib was combined with IR treatments. These data highlight the promise of combining ganetespib with IR therapies in the treatment of AC lung tumors.

Radiation-induced motility alterations in medulloblastoma cells

Photon irradiation has been repeatedly suspected of increasing tumor cell motility and promoting locoregional recurrence of disease. This study was set up to analyse possible mechanisms underlying the potentially radiation-altered motility in medulloblastoma cells. Medulloblastoma cell lines D425 and Med8A were analyzed in migration and adhesion experiments with and without photon and carbon ion irradiation. Expression of integrins was determined by quantitative FACS analysis. Matrix metalloproteinase concentrations within cell culture supernatants were investigated by enzyme-linked immunosorbent assay (ELISA). Statistical analysis was performed using Student's t-test. Both photon and carbon ion irradiation significantly reduced chemotactic medulloblastoma cell transmigration through 8-μm pore size membranes, while simultaneously increasing adherence to fibronectin- and collagen I- and IV-coated surfaces. Correspondingly, both photon and carbon ion irradiation downregulate soluble MMP9 concentrations, while upregulating cell surface expression of proadhesive extracellular matrix protein-binding integrin α5. The observed phenotype of radiation-altered motility is more pronounced following carbon ion than photon irradiation. Both photon and (even more so) carbon ion irradiation are effective in inhibiting medulloblastoma cell migration through downregulation of matrix metalloproteinase 9 and upregulation of proadhesive cell surface integrin α5, which lead to increased cell adherence to extracellular matrix proteins.

Melanoma cell therapy: Endothelial progenitor cells as shuttle of the MMP12 uPAR-degrading enzyme

The receptor for the urokinase-type plasminogen activator (uPAR) accounts for many features of cancer progression, and is therefore considered a target for anti-tumoral therapy. Only full length uPAR mediates tumor progression. Matrix-metallo-proteinase-12 (MMP12)-dependent uPAR cleavage results into the loss of invasion properties and angiogenesis. MMP12 can be employed in the field of “targeted therapies” as a biological drug to be delivered directly in patient's tumor mass. Endothelial Progenitor Cells (EPCs) are selectively recruited within the tumor and could be used as cellular vehicles for delivering anti-cancer molecules. The aim of our study is to inhibit cancer progression by engeneering ECFCs, a subset of EPC, with a lentivirus encoding the anti-tumor uPAR-degrading enzyme MMP12. Ex vivo manipulated ECFCs lost the capacity to perform capillary morphogenesis and acquired the anti-tumor and anti-angiogenetic activity. In vivo MMP12-engineered ECFCs cleaved uPAR within the tumor mass and strongly inhibited tumor growth, tumor angiogenesis and development of lung metastasis.

The possibility to exploit tumor homing and activity of autologous MMP12-engineered ECFCs represents a novel way to combat melanoma by a “personalized therapy”, without rejection risk.

The i.v. injection of radiolabelled MMP12-ECFCs can thus provide a new theranostic approach to control melanoma progression and metastasis.

Biflavone Ginkgetin, a Novel Wnt Inhibitor, Suppresses the Growth of Medulloblastoma

Medulloblastoma (MB) is a form of malignant brain tumor that predominantly arises in infants and children, of which approximately 25 % is due to upregulation of canonical Wnt pathway with mainly mutations in CTNNB1. Therefore, Wnt inhibitors could offer rational therapeutic strategies and chemoprevention for this malignant cancer. In our present study, we undertook a screening for antagonists of Wnt signaling from 600 natural compounds, and identified Ginkgetin, a biflavone isolated from Cephalotaxus fortunei var. alpina. Ginkgetin inhibited Wnt pathway with an IC50 value around 5.92 μM and structure-activity relationship analysis suggested the methoxy group in Ginkgetin as a functional group. Biflavone Ginkgetin showed obvious cytotoxicity in Daoy and D283 MB cells. Cell cycle analysis by flow cytometry showed that Ginkgetin induced efficiently G2/M phase arrest in Daoy cells. Further mechanism studies showed that Ginkgetin reduced the expression of Wnt target genes, including Axin2, cyclinD1 and survivin in MB cells. The phosphorylation level of β-catenin also decreased in a time- and concentration-dependent manner. Collectively, our data suggest that Ginkgetin is a novel inhibitor of Wnt signaling, and as such warrants further exploration as a promising anti-medulloblastoma candidate.

Aldehyde Dehydrogenase Is Regulated by β-Catenin/TCF and Promotes Radioresistance in Prostate Cancer Progenitor Cells

Radiotherapy is a curative treatment option in prostate cancer. Nevertheless, patients with high-risk prostate cancer are prone to relapse. Identification of the predictive biomarkers and molecular mechanisms of radioresistance bears promise to improve cancer therapies. In this study, we show that aldehyde dehydrogenase (ALDH) activity is indicative of radioresistant prostate progenitor cells with an enhanced DNA repair capacity and activation of epithelial-mesenchymal transition (EMT). Gene expression profiling of prostate cancer cells, their radioresistant derivatives, ALDH(+) and ALDH(-) cell populations revealed the mechanisms, which link tumor progenitors to radioresistance, including activation of the WNT/β-catenin signaling pathway. We found that expression of the ALDH1A1 gene is regulated by the WNT signaling pathway and co-occurs with expression of β-catenin in prostate tumor specimens. Inhibition of the WNT pathway led to a decrease in ALDH(+) tumor progenitor population and to radiosensitization of cancer cells. Taken together, our results indicate that ALDH(+) cells contribute to tumor radioresistance and their molecular targeting may enhance the effectiveness of radiotherapy.

Antrodin C inhibits epithelial-to-mesenchymal transition and metastasis of breast cancer cells via suppression of Smad2/3 and β-catenin signaling pathways

Epithelial-to-mesenchymal transition (EMT) is a crucial event involved metastasis of certain tumors. Thus, identifying chemical agents that can block EMT is highly warranted for the development of anti-cancer chemoprevention/chemotherapies. In this study, we found that Antrodin C (ADC), a maleimide derivative isolated from Antrodia cinnamomea health food product inhibits TGF-β1-induced EMT and breast cancer cell metastasis in vitro. Pretreatment of MCF-7 cells with ADC significantly blocked TGF-β1-induced phenotypic changes and actin cytoskeleton remodeling. In addition, ADC was able to up-regulate epithelial markers such as E-cadherin and occludin, whereas mesenchymal markers including N-cadherin and vimentin were significantly inhibited, possibly through the modulation of transcriptional regulators Smad/Smad3. ADC blocked TGF-β1-induced migration and invasion of MCF-7 cells through the down-regulation of matrix-metalloproteinases (MMP-2, -9) and urokinase plasminogen activator (uPA). The inhibition of MMPs and uPA activity by ADC was reasoned by suppression of its corresponding transcription factor β-catenin. Taken together, our data suggested that ADC attenuates the TGF-β1-induced EMT, migration and invasion of human breast carcinoma through the suppression of Smad2/3 and β-catenin signaling pathways.

The Ser/Thr kinase MAP4K4 drives c-Met-induced motility and invasiveness in a cell-based model of SHH medulloblastoma

Medulloblastoma (MB) comprises four molecularly and genetically distinct subgroups of embryonal brain tumors that develop in the cerebellum. MB mostly affects infants and children and is difficult to treat because of frequent dissemination of tumor cells within the leptomeningeal space. A potential promoter of cell dissemination is the c-Met proto-oncogene receptor tyrosine kinase, which is aberrantly expressed in many human tumors including MB. Database analysis showed that c-Met is highly expressed in the sonic hedgehog (SHH) subgroup and in a small subset of Group 3 and Group 4 MB tumors. Using a cell-based three-dimensional cell motility assay combined with live-cell imaging, we investigated whether the c-Met ligand HGF could drive dissemination of MB cells expressing high levels of c-Met, and determined downstream effector mechanisms of this process. We detected variable c-Met expression in different established human MB cell lines, and we found that in lines expressing high c-Met levels, HGF promoted cell dissemination and invasiveness. Specifically, HGF-induced c-Met activation enhanced the capability of the individual cells to migrate in a JNK-dependent manner. Additionally, we identified the Ser/Thr kinase MAP4K4 as a novel driver of c-Met-induced invasive cell dissemination. This increased invasive motility was due to MAP4K4 control of F-actin dynamics in structures required for migration and invasion. Thus, MAP4K4 couples growth factor signaling to actin cytoskeleton regulation in tumor cells, suggesting that MAP4K4 could present a promising novel target to be evaluated for treating growth factor-induced dissemination of MB tumors of different subgroups and of other human cancers.

The TRPM8 protein is a testosterone receptor: I. Biochemical evidence for direct TRPM8-testosterone interactions

The transient receptor potential ion channel of the melastatin subfamily, TRPM8, is a major cold receptor in the peripheral nervous system. Along with the sensory neurons, the TRPM8 protein is highly expressed in the prostate epithelial cells, and this expression is regulated by androgens. Here we investigated the expression and intracellular localization of the TRPM8 channel in relationship to androgens. We performed experiments using human prostate tissues obtained from healthy individuals and patients with prostate cancer at various stages of the disease as well as in cultured cells. Using an immunohistochemistry approach, we detected an intensive colocalization pattern of the TRPM8 protein with endogenous androgens in all tissues tested, suggesting possible interactions. Co-immunoprecipitation experiments performed using cultured prostate epithelial cells, prostate cancer cells, and HEK-293 cells stably expressing TRPM8 further confirmed direct binding of the steroid hormone, testosterone, to the TRPM8 protein. Applications of picomolar concentrations of testosterone to the primary human prostate cells, endogenously expressing TRPM8, elicited Ca(2+) responses and channel currents, and those were inhibited in the presence of TRPM8 antagonist, N-(2-aminoethyl)-N-(4-(benzyloxy)-3-methoxybenzyl)thiophene-2-carboxamide hydrochloride. These results indicate that the TRPM8 channel is physically associated with testosterone and suggest that, in addition to a genomic role, testosterone plays a role in direct regulation of the TRPM8 channel function.

c-Met signaling in the development of tumorigenesis and chemoresistance: Potential applications in pancreatic cancer

Pancreatic ductal adenocarcinoma is the 4^th leading cause of cancer deaths in the United States. The majority of patients are candidates only for palliative chemotherapy, which has proven largely ineffective in halting tumor progression. One proposed mechanism of chemoresistance involves signaling via the mesenchymal-epithelial transition factor protein (MET), a previously established pathway critical to cell proliferation and migration. Here, we review the literature to characterize the role of MET in the development of tumorigenesis, metastasis and chemoresistance, highlighting the potential of MET as a therapeutic target in pancreatic cancer. In this review, we characterize the role of c-Met in the development of tumorigenesis, metastasis and chemoresistance, highlighting the potential of c-Met as a therapeutic target in pancreatic cancer.

Loss of urokinase receptor sensitizes cells to DNA damage and delays DNA repair

DNA damage induced by numerous exogenous or endogenous factors may have irreversible consequences on the cell leading to cell cycle arrest, senescence and cell death. The DNA damage response (DDR) is powerful signaling machinery triggered in response to DNA damage, to provide DNA damage recognition, signaling and repair. Most anticancer drugs induce DNA damage, and DNA repair in turn attenuates therapeutic efficiency of those drugs. Approaches delaying DNA repair are often used to increase efficiency of treatment. Recent data show that ubiquitin-proteasome system is essential for signaling and repair of DNA damage. However, mechanisms providing regulation of proteasome intracellular localization, activity, and recruitment to DNA damage sites are elusive. Even less investigated are the roles of extranuclear signaling proteins in these processes. In this study, we report the involvement of the serine protease urokinase-type plasminogen activator receptor (uPAR) in DDR-associated regulation of proteasome. We show that in vascular smooth muscle cells (VSMC) uPAR activates DNA single strand break repair signaling pathway. We provide evidence that uPAR is essential for functional assembly of the 26S proteasome. We further demonstrate that uPAR mediates DNA damage-induced phosphorylation, nuclear import, and recruitment of the regulatory subunit PSMD6 to proteasome. We found that deficiency of uPAR and PSMD6 delays DNA repair and leads to decreased cell survival. These data may offer new therapeutic approaches for diseases such as cancer, cardiovascular and neurodegenerative disorders.

Dysregulation of ubiquitin homeostasis and β-catenin signaling promote spinal muscular atrophy

The autosomal recessive neurodegenerative disease spinal muscular atrophy (SMA) results from low levels of survival motor neuron (SMN) protein; however, it is unclear how reduced SMN promotes SMA development. Here, we determined that ubiquitin-dependent pathways regulate neuromuscular pathology in SMA. Using mouse models of SMA, we observed widespread perturbations in ubiquitin homeostasis, including reduced levels of ubiquitin-like modifier activating enzyme 1 (UBA1). SMN physically interacted with UBA1 in neurons, and disruption of Uba1 mRNA splicing was observed in the spinal cords of SMA mice exhibiting disease symptoms. Pharmacological or genetic suppression of UBA1 was sufficient to recapitulate an SMA-like neuromuscular pathology in zebrafish, suggesting that UBA1 directly contributes to disease pathogenesis. Dysregulation of UBA1 and subsequent ubiquitination pathways led to β-catenin accumulation, and pharmacological inhibition of β-catenin robustly ameliorated neuromuscular pathology in zebrafish, Drosophila, and mouse models of SMA. UBA1-associated disruption of β-catenin was restricted to the neuromuscular system in SMA mice; therefore, pharmacological inhibition of β-catenin in these animals failed to prevent systemic pathology in peripheral tissues and organs, indicating fundamental molecular differences between neuromuscular and systemic SMA pathology. Our data indicate that SMA-associated reduction of UBA1 contributes to neuromuscular pathogenesis through disruption of ubiquitin homeostasis and subsequent β-catenin signaling, highlighting ubiquitin homeostasis and β-catenin as potential therapeutic targets for SMA.

The expressions of Wnt/β-catenin pathway-related components in brainstem gliomas

BACKGROUND

The overall prognosis of brainstem gliomas is very poor, and the current treatment cannot significantly prolong the overall survival of these patients; therefore, studying the molecular biological mechanisms of the occurrence and development of brainstem gliomas has important significance for their treatment. The Wnt/β-catenin signaling pathway is closely associated with the occurrence and development of tumors, but its relationship with brainstem gliomas remains unclear.

METHODS

This study used Western blot and immunohistochemistry methods to detect the expressions of Wnt/β-catenin signaling pathway-related components such as Wnt-1, Wnt-2, β-catenin and C-myc in six cases of normal brain tissues and 24 cases of brainstem gliomas and analyzed the relationship between their expressions and clinicopathological characteristics.

RESULTS

Wnt-1 had no obvious expression in normal brain tissues and did not show any significant difference between high- and low-grade brainstem gliomas; the expressions of Wnt-2, β-catenin and C-myc in high-grade brainstem gliomas were significantly higher than that in low-grade brainstem gliomas and normal brain tissues and were positively correlated with the expression of Ki-67. Moreover, the expressions of Wnt-2 and C-myc were significantly associated with the prognosis of brainstem glioma patients; additionally, there was a trend toward increased β-catenin expression with shorter survival, but there was no statistical difference.

CONCLUSIONS

Wnt/β-catenin signaling pathway might be abnormally activated and plays an important role in the occurrence and development of brainstem gliomas. Wnt-2, β-catenin and C-myc may be potential targets for brainstem glioma treatment.

uPAR-controlled oncolytic adenoviruses eliminate cancer stem cells in human pancreatic tumors

Pancreatic tumors contain cancer stem cells highly resistant to chemotherapy. The identification of therapies that can eliminate this population of cells might provide with more effective treatments. In the current work we evaluated the potential of oncolytic adenoviruses to act against pancreatic cancer stem cells (PCSC). PCSC from two patient-derived xenograft models were isolated from orthotopic pancreatic tumors treated with saline, or with the chemotherapeutic agent gemcitabine. An enrichment in the number of PCSC expressing the cell surface marker CD133 and a marked enhancement on tumorsphere formation was observed in gemcitabine treated tumors. No significant increase in the CD44, CD24, and epithelial-specific antigen (ESA) positive cells was observed. Neoplastic sphere-forming cells were susceptible to adenoviral infection and exposure to oncolytic adenoviruses resulted in elevated cytotoxicity with both Adwt and the tumor specific AduPARE1A adenovirus. In vivo, intravenous administration of a single dose of AduPARE1A in human-derived pancreatic xenografts led to a remarkable anti-tumor effect. In contrast to gemcitabine AduPARE1A treatment did not result in PCSC enrichment. No enrichment on tumorspheres neither on the CD133(+) population was detected. Therefore our data provide evidences of the relevance of uPAR-controlled oncolytic adenoviruses for the elimination of pancreatic cancer stem cells.

Epigenetic regulation of miRNA-211 by MMP-9 governs glioma cell apoptosis, chemosensitivity and radiosensitivity

Glioblastoma multiforme (GBM) is the most aggressive brain cancer, and to date, no curative treatment has been developed. In this study, we report that miR-211, a microRNA predicted to target MMP-9, is suppressed in grade IV GBM specimens. Furthermore, we found that miR-211 suppression in GBM involves aberrant methylation-mediated epigenetic silencing of the miR-211 promoter. Indeed, we observed a highly significant inverse correlation between miR-211 expression and MMP-9 protein levels, which is indicative of post-transcriptional control of gene expression. Additionally, shRNA specific for MMP-9 (pM) promoted miR-211 expression via demethylation of miR-211 promoter-associated CpG islands (-140 to +56). In independent experiments, we confirmed that miR-211 overexpression and pM treatments led to the activation of the intrinsic mitochondrial/Caspase-9/3-mediated apoptotic pathway in both glioma cells and cancer stem cells (CSC). We also investigated whether miR-211 is involved in the regulation of MMP-9 and thus plays a functional role in GBM. We found an acute inhibitory effect of miR-211 on glioma cell invasion and migration via suppression of MMP-9. Given the insensitivity of some GBMs to radiation and chemotherapy (temozolomide) along with the hypothesis that glioma CSC cause resistance to therapy, our study indicates that miR-211 or pM in combination with ionizing radiation (IR) and temozolomide significantly induces apoptosis and DNA fragmentation. Of note, miR-211- and pM-treated CSC demonstrated increased drug retention capacity, as observed by MDR1/P-gp mediated-Rhodamine 123 drug efflux activity assay. These results suggest that either rescuing miR-211 expression or downregulation of MMP-9 may have a new therapeutic application for GBM patients in the future.

tPA regulates neurite outgrowth by phosphorylation of LRP5/6 in neural progenitor cells

Despite the important role of tissue plasminogen activator (tPA) as a neuromodulator in neurons, microglia, and astrocytes, its role in neural progenitor cell (NPC) development is not clear yet. We identified that tPA is highly expressed in NPCs compared with neurons. Inhibition of tPA activity or expression using tPA stop, PAI-1, or tPA siRNA inhibited neurite outgrowth from NPCs, while overexpression or addition of exogenous tPA increased neurite outgrowth. The expression of Wnt and β-catenin as well as phosphorylation of LRP5 and LRP6, which has been implicated in Wnt-β-catenin signaling, was rapidly increased after tPA treatment and was decreased by tPA siRNA transfection. Knockdown of β-catenin or LRP5/6 expression by siRNA prevented tPA-induced neurite extension. NPCs obtained from tPA KO mice showed impaired neurite outgrowth compared with WT NPCs. In ischemic rat brains, axon density was higher in the brains transplanted with WT NPCs than in those with tPA KO NPCs, suggesting increased axonal sprouting by NPC-derived tPA. tPA-mediated regulation of neuronal maturation in NPCs may play an important role during development and in regenerative conditions.

Multifunctional roles of urokinase plasminogen activator (uPA) in cancer stemness and chemoresistance of pancreatic cancer

Pancreatic ductal adenocarcinoma (PDAC) is almost always lethal. One of the underlying reasons for this lethality is believed to be the presence of cancer stem cells (CSC), which impart chemoresistance and promote recurrence, but the mechanisms responsible are unclear. Recently the poor prognosis of PDAC has been correlated with increased expression of urokinase plasminogen activator (uPA). In the present study we examine the role of uPA in the generation of PDAC CSC. We observe a subset of cells identifiable as a side population (SP) when sorted by flow cytometry of MIA PaCa-2 and PANC-1 pancreatic cancer cells that possess the properties of CSC. A large fraction of these SP cells are CD44 and CD24 positive, are gemcitabine resistant, possess sphere-forming ability, and exhibit increased tumorigenicity, known characteristics of cancer stemness. Increased tumorigenicity and gemcitabine resistance decrease after suppression of uPA. We observe that uPA interacts directly with transcription factors LIM homeobox-2 (Lhx2), homeobox transcription factor A5 (HOXA5), and Hey to possibly promote cancer stemness. uPA regulates Lhx2 expression by suppressing expression of miR-124 and p53 expression by repressing its promoter by inactivating HOXA5. These results demonstrate that regulation of gene transcription by uPA contributes to cancer stemness and clinical lethality.