Rictor regulates MMP-9 activity and invasion through Raf-1-MEK-ERK signaling pathway in glioma cells

Current Status of Research on Targeted Therapy Against Central Nervous System Tumors in Low- and Lower-Middle-Income Countries

OBJECTIVE

In recent decades, a significant body of research has focused on targeted therapies for the treatment of central nervous system (CNS) tumors to enhance the effectiveness of management strategies. However, most of these efforts have been centered in high-income countries, which renders the generalizability of their results to low- and middle-income countries questionable. Therefore, in this review, we systematically investigated the status of research conducted on targeted therapy for CNS tumors in low- and lower-middle-income countries to elucidate the contribution of these countries in advancing neuro-oncology.

METHODS

A systematic search of 3 databases was performed using a predefined search strategy. After screening the articles based on our inclusion/exclusion criteria, the data were extracted to a predesigned Excel worksheet.

RESULTS

A review of 44 included studies showed that India, Iran, and Lebanon were the only countries with a contribution to this field. All included studies were laboratory or animal experiments, and there were no clinical studies in this field. The most investigated CNS tumor was malignant glioma, and gene-targeted therapy was the most investigated category of targeted therapies in these countries.

CONCLUSIONS

Low- and lower-middle-income countries comprise more than half of the world population, but they are deprived of targeted therapies against CNS tumors. Although there are basic experiments performed on this subject, they originate in a limited number of these countries. Therefore, targeted therapy is in its preliminary stage in these countries.

mTORC2 interactome and localization determine aggressiveness of high-grade glioma cells through association with gelsolin

mTOR complex 2 (mTORC2) has been implicated as a key regulator of glioblastoma cell migration. However, the roles of mTORC2 in the migrational control process have not been entirely elucidated. Here, we elaborate that active mTORC2 is crucial for GBM cell motility. Inhibition of mTORC2 impaired cell movement and negatively affected microfilament and microtubule functions. We also aimed to characterize important players involved in the regulation of cell migration and other mTORC2-mediated cellular processes in GBM cells. Therefore, we quantitatively characterized the alteration of the mTORC2 interactome under selective conditions using affinity purification-mass spectrometry in glioblastoma. We demonstrated that changes in cell migration ability specifically altered mTORC2-associated proteins. GSN was identified as one of the most dynamic proteins. The mTORC2-GSN linkage was mostly highlighted in high-grade glioma cells, connecting functional mTORC2 to multiple proteins responsible for directional cell movement in GBM. Loss of GSN disconnected mTORC2 from numerous cytoskeletal proteins and affected the membrane localization of mTORC2. In addition, we reported 86 stable mTORC2-interacting proteins involved in diverse molecular functions, predominantly cytoskeletal remodeling, in GBM. Our findings might help expand future opportunities for predicting the highly migratory phenotype of brain cancers in clinical investigations.

The Extracellular Matrix in Glioblastomas: A Glance at Its Structural Modifications in Shaping the Tumoral Microenvironment-A Systematic Review

BACKGROUND AND AIM

While many components of the ECM have been isolated and characterized, its modifications in the specific setting of GBMs have only been recently explored in the literature. The aim of this paper is to provide a systematic review on the topic and to assess the ECM's role in shaping tumoral development.

METHODS

An online literature search was launched on PubMed/Medline and Scopus using the research string "((Extracellular matrix OR ECM OR matrix receptor OR matrix proteome) AND (glioblastoma OR GBM) AND (tumor invasion OR tumor infiltration))", and a systematic review was conducted in accordance with the PRISMA-P guidelines.

RESULTS

The search of the literature yielded a total of 693 results. The duplicate records were then removed (n = 13), and the records were excluded via a title and abstract screening; 137 studies were found to be relevant to our research question and were assessed for eligibility. Upon a full-text review, 59 articles were finally included and were summarized as follows based on their focus: (1) proteoglycans; (2) fibrillary proteins, which were further subdivided into the three subcategories of collagen, fibronectin, and laminins; (3) glycoproteins; (4) degradative enzymes; (5) physical forces; (6) and glioma cell and microglia migratory and infiltrative patterns.

CONCLUSIONS

Our systematic review demonstrates that the ECM should not be regarded anymore as a passive scaffold statically contributing to mechanical support in normal and pathological brain tissue but as an active player in tumor-related activity.

mTORC1/C2 regulate spermatogenesis in Eriocheir sinensis via alterations in the actin filament network and cell junctions

Spermatogenesis is a finely regulated process of germ cell proliferation and differentiation that leads to the production of sperm in seminiferous tubules. Although the mammalian target of rapamycin (mTOR) signaling pathway is crucial for spermatogenesis in mammals, its functions and molecular mechanisms in spermatogenesis remain largely unknown in nonmammalian species, particularly in Crustacea. In this study, we first identified es-Raptor (the core component of mTOR complex 1) and es-Rictor (the core component of mTOR complex 2) from the testis of Eriocheir sinensis. Dynamic localization of es-Raptor and es-Rictor implied that these proteins were indispensable for the spermatogenesis of E. sinensis. Furthermore, es-Raptor and es-Rictor knockdown results showed that the mature sperm failed to be released, causing almost empty lumens in the testis. We investigated the reasons for these effects and found that the actin-based cytoskeleton was disrupted in the knockdown groups. In addition, the integrity of the testis barrier (similar to the blood-testis barrier in mammals) was impaired and affected the expression of cell junction proteins. Further study revealed that es-Raptor and es-Rictor may regulate spermatogenesis via both mTORC1- and mTORC2-dependent mechanisms that involve es-rpS6 and es-Akt/es-PKC, respectively. Moreover, to explore the testis barrier in E. sinensis, we established a cadmium chloride (CdCl₂)-induced testis barrier damage model as a positive control. Morphological and immunofluorescence results were similar to those of the es-Raptor and es-Rictor knockdown groups. Altogether, es-Raptor and es-Rictor were important for spermatogenesis through maintenance of the actin filament network and cell junctions in E. sinensis.

The Metalloprotease-Disintegrin ADAM8 Alters the Tumor Suppressor miR-181a-5p Expression Profile in Glioblastoma Thereby Contributing to Its Aggressiveness

Glioblastoma (GBM) as the most common and aggressive brain tumor is characterized by genetic heterogeneity, invasiveness, radio-/chemoresistance, and occurrence of GBM stem-like cells. The metalloprotease-disintegrin ADAM8 is highly expressed in GBM tumor and immune cells and correlates with poor survival. In GBM, ADAM8 affects intracellular kinase signaling and increases expression levels of osteopontin/SPP1 and matrix metalloproteinase 9 (MMP9) by an unknown mechanism. Here we explored whether microRNA (miRNA) expression levels could be regulators of MMP9 expression in GBM cells expressing ADAM8. Initially, we identified several miRNAs as dysregulated in ADAM8-deficient U87 GBM cells. Among these, the tumor suppressor miR-181a-5p was significantly upregulated in ADAM8 knockout clones. By inhibiting kinase signaling, we found that ADAM8 downregulates expression of miR-181a-5p via activation of signal transducer and activator of transcription 3 (STAT3) and mitogen-activated protein kinase (MAPK) signaling suggesting an ADAM8-dependent silencing of miR-181a-5p. In turn, mimic miR-181a-5p transfection caused decreased cell proliferation and lower MMP9 expression in GBM cells. Furthermore, miR-181a-5p was detected in GBM cell-derived extracellular vesicles (EVs) as well as patient serum-derived EVs. We identified miR-181a-5p downregulating MMP9 expression via targeting the MAPK pathway. Analysis of patient tissue samples (n=22) revealed that in GBM, miR-181a-5p is strongly downregulated compared to ADAM8 and MMP9 mRNA expression, even in localized tumor areas. Taken together, we provide evidence for a functional axis involving ADAM8/miR-181a-5p/MAPK/MMP9 in GBM tumor cells.

Mechanisms involved in the anti-tumor effects of Toosendanin in glioma cells

BACKGROUND

Toosendanin (TSN) is a triterpenoid compound mainly used as an ascaris repellant. Recent studies have shown that it possesses antitumor effects in many types of tumor cells. However, the effects of TSN on glioma cells have rarely been reported.

METHODS

Different assays were performed to investigate the effects of TSN on the different glioma cell lines including U87MG and LN18. The assays included colony formation, wound healing, and transwell assays. Furthermore, Hoechst 33342 staining, flow cytometry, and western blotting analysis were performed to investigate the apoptotic activities of TSN. Finally, the results were confirmed using a xenograft tumor model that comprised of nude mice.

RESULTS

In vitro, the CCK-8 and colony formation assays showed that TSN effectively inhibited glioma cell proliferation. Moreover, the inhibitory effects on glioma cell migration and invasion were demonstrated through the wound healing and transwell assays, respectively. Hoechst 33342 staining, flow cytometry, and western blotting assays demonstrated the significant effect of TSN in the apoptosis induction of glioma cells. Furthermore, the anti-glioma effect of TSN was exerted through the inhibition of the PI3K/Akt/mTOR signaling pathways as demonstrated by western blotting analysis. In addition, the effects of TSN on glioma cell viability, apoptosis, cell cycle arrest, migration, and invasion were reversed by 740Y-P, a PI3K activator. Finally, the mouse xenograft model confirmed the suppressive effect of TSN on tumor growth in vivo.

CONCLUSION

Our results suggest that TSN is a promising chemotherapeutic drug for patients with glioma.

Tumor Associated Macrophages, as the Dominant Immune Cells, Are an Indispensable Target for Immunologically Cold Tumor-Glioma Therapy?

Tumor microenvironment (TME) is the cornerstone of the occurrence, development, invasion and diffusion of the malignant central nerve system (CNS) tumor, glioma. As the largest number of inflammatory cells in glioma TME, tumor associated macrophages (TAMs) and their secreted factors are indispensable to the progression of glioma, which is a well-known immunologically “cold” tumor, including the growth of tumor cells, invasion, migration, angiogenesis, cancer immunosuppression and metabolism. TAMs intimately interface with the treatment failure and poor prognosis of glioma patients, and their density increases with increasing glioma grade. Recently, great progress has been made in TAM-targeting for anti-tumor therapy. According to TAMs’ function in tumorigenesis and progression, the major anti-tumor treatment strategies targeting TAMs are to hinder macrophage recruitment in TME, reduce TAMs viability or remodel TAMs phenotype from M2 to M1. Different approaches offer unique and effective anti-tumor effect by regulating the phagocytosis, polarization and pro-tumor behaviors of macrophages in the therapy of glioma. The present review summarizes the significant characteristics and related mechanisms of TAMs and addresses the related research progress on targeting TAMs in glioma.

Lack of GD3 synthase (St8sia1) attenuates malignant properties of gliomas in genetically engineered mouse model

High expression of gangliosides GD3 and GD2 is observed in human gliomas. The functions of GD3 and GD2 in malignant properties have been reported in glioma cells in vitro, but those functions have not yet been investigated in vivo. In this study, we showed that deficiency of GD3 synthase (GD3S, St8sia1) attenuated glioma progression and clinical and pathological features in a platelet-derived growth factor B-driven murine glioma model. Lack of GD3S resulted in the prolonged lifespan of glioma-bearing mice and low-grade pathology in generated gliomas. Correspondingly, they showed reduced phosphorylation levels of Akt, Erks, and Src family kinases in glioma tissues. A DNA microarray study revealed marked alteration in the expression of various genes, particularly in MMP family genes, in GD3S-deficient gliomas. Re-expression of GD3S restored expression of MMP9 in primary-cultured glioma cells. We also identified a transcription factor, Ap2α, expressed in parallel with GD3S expression, and showed that Ap2α was critical for the induction of MMP9 by transfection of its cDNA and luciferase reporter genes, and a ChIP assay. These findings suggest that GD3S enhances the progression of gliomas by enhancement of the Ap2α-MMP9 axis. This is the first report to describe the tumor-enhancing functions of GD3S in vivo.

AGAP2-AS1 May Promote the Occurrence and Development of Glioblastoma by Sponging miR-9-5p: Evidence From a ceRNA Network

Glioblastoma (GBM), the primary malignant brain tumor, is typically associated with a poor prognosis and poor quality of life, mainly due to the lack of early diagnostic biomarkers and therapeutic targets. However, gene sequencing technologies and bioinformatics analysis are currently being actively utilized to explore potential targets for the diagnosis and management of malignancy. Herein, based on a variety of bioinformatics tools for the reverse prediction of target genes associated with the prognosis of GBM, a ceRNA network of AGAP2-AS1-miR-9-5p-MMP2/MMP9 was constructed, and a potential therapeutic target for GBM was identified. Enrichment analysis predicted that the ceRNA regulatory network participates in the processes of cell proliferation, differentiation, and migration.

Novel insights into astrocyte-mediated signaling of proliferation, invasion and tumor immune microenvironment in glioblastoma

Glioblastoma (GBM) continues to be the most aggressive cancer of the brain. The dismal prognosis is largely attributed to the microenvironment surrounding tumor cells. Astrocytes, the main component of the GBM microenvironment, play several fundamental physiological roles in the central nervous system. During the development of GBM, tumor-associated astrocytes (TAAs) directly contact GBM cells, which activate astrocytes to form reactive astrocytes, facilitating tumor progression, proliferation and migration through multiple well-understood signaling pathways. Notably, TAAs also influence GBM cell behaviors via suppressing immune responses and enhancing the chemoradiotherapy resistance of tumor cells. These new activities are closely linked with the treatment and prognosis of GBM. In this review, we discuss recent advances regarding new functions of reactive astrocytes, including TAA-cancer cell interactions, mechanisms involved in immunosuppressive regulation, and chemoradiotherapy resistance. It is expected that these updated experimental or clinical studies of TAAs may provide a promising approach for GBM treatment in the near future.

TNF-α mediated MEK-ERK signaling in invasion with putative network involving NF-κB and STAT-6: a new perspective in glioma

Glioblastoma is the most common malignant primary brain tumor with poor prognosis. Invasion involves pro-inflammatory cytokines and major signaling hubs. Tumor necrosis factor-α (TNF-α) acts as a master switch in establishing an intricate link between inflammation and cancer. The present study attempted to explore the possible implication of MAPK extracellular signaling-regulated kinase kinase (MEK)-extracellular signaling-regulated kinase (ERK) signaling pathway and expression of nuclear factor-κB (NF-κB), signal transducers and activators of transcription-6 (STAT-6), ERK, and phosphorylated-ERK (p-ERK) signaling proteins in TNF-α microenvironment. U0126 and PD98059 were used to inhibit the MEK-ERK1/2 pathway. TNF-α stimulation enhanced invasion in U87MG, U251MG and patient-derived primary glioma cells, whereas cell viability was not altered. Matrix metalloproteinase-2 (MMP-2) activity was increased only in U251MG glioma cells. These data suggest that TNF-α microenvironment plays an important role in the invasion of U251MG, U87MG, and patient-derived primary glioma cells, without any cytotoxic effect. The MMP-2 activity is differentially regulated by TNF-α stimulation in these cells. TNF-α stimulation upregulated the protein expression of ERK-1, ERK-2 and also increased the level of p-ERK1/2. TNF-α stimulation further upregulated the expression of NF-κB1, STAT-6 in tandem with Ras-MEK signaling system in U87MG cells, which emphasized the possible involvement of these signaling hubs in the glioma microenvironment. MEK-ERK inhibitors significantly attenuated the invasion of U87MG cells mediated by the TNF-α stimulation, probably through their inhibitory impact on p-ERK1/2 and ERK-2. This study provides the possible rationale of invasion by glioma cells in a TNF-α-induced pro-inflammatory milieu, which involves direct role of MEK-ERK signaling, with possible implication of NF-κB and STAT-6.

Epidermal Growth Factor Receptor Extracellular Domain Mutations in Glioblastoma Present Opportunities for Clinical Imaging and Therapeutic Development

We explored the clinical and pathological impact of epidermal growth factor receptor (EGFR) extracellular domain missense mutations. Retrospective assessment of 260 de novo glioblastoma patients revealed a significant reduction in overall survival of patients having tumors with EGFR mutations at alanine 289 (EGFR^A289D/T/V). Quantitative multi-parametric magnetic resonance imaging analyses indicated increased tumor invasion for EGFR^A289D/T/V mutants, corroborated in mice bearing intracranial tumors expressing EGFR^A289V and dependent on ERK-mediated expression of matrix metalloproteinase-1. EGFR^A289V tumor growth was attenuated with an antibody against a cryptic epitope, based on in silico simulation. The findings of this study indicate a highly invasive phenotype associated with the EGFR^A289V mutation in glioblastoma, postulating EGFR^A289V as a molecular marker for responsiveness to therapy with EGFR-targeting antibodies.

Sinomenine Hydrochloride Inhibits the Metastasis of Human Glioblastoma Cells by Suppressing the Expression of Matrix Metalloproteinase-2/-9 and Reversing the Endogenous and Exogenous Epithelial-Mesenchymal Transition

As shown in our previous study, sinomenine hydrochloride (SH), the major bioactive alkaloid isolated from Sinomenium acutum Rehd. et Wils. (Fam. Menispermaceae), initiates the autophagy-mediated death of human glioblastoma cells by generating reactive oxygen species and activating the autophagy-lysosome pathway. However, its effects on the migration and invasion of human glioblastoma cells have not yet been elucidated. Therefore, human glioblastoma U87 and SF767 cells were treated with SH (0.125 and 0.25 mM) for 24 h, and cell migration and invasion were assessed using scratch wound healing, migration and invasion assays. SH promoted G0/G1 phase arrest, inhibited the migration and invasion of the two cell lines, suppressed the activation of nuclear factor kappa B (NFκB) and the expression of matrix metalloproteinase (MMP)-2/-9, triggered endoplasmic reticulum (ER) stress, reversed the exogenous epithelial-mesenchymal transition (EMT) induced by the inflammatory microenvironment and the endogenous EMT. Additionally, NFκB p65 overexpression blocked the SH-mediated inhibitory effects on MMP-2/-9 expression and cell invasion. SH-induced autophagy was reduced in CCAAT/enhancer binding protein (C/EBP) homologous protein (CHOP) or autophagy-related 5 (ATG5)-silenced human glioblastoma cells and cells treated with 4-phenylbutyric acid (4-PBA) or 3-methyladenine (3-MA), as shown by the decreased levels of the microtubule-associated protein light chain 3B (LC3B)-II and autophagic vacuoles (AVs) stained with monodansylcadaverine (MDC), respectively. Moreover, knockdown of CHOP or ATG5 and treatment with 4-PBA or 3-MA abolished the SH-mediated inhibition of mesenchymal markers (vimentin, Snail and Slug) expression and cell invasion, respectively. Importantly, SH also regulated the above related pathways in nude mice. Based on these findings, SH inhibited cell proliferation by inducing cell cycle arrest, and attenuated the metastasis of U87 and SF767 cells by suppressing MMP-2/-9 expression and reversing the endogenous and exogenous EMT in vitro and/or in vivo. Thus, SH might be a new potential anti-metastasis agent for the treatment of human glioblastoma.

Targeted delivery of nano-PTX to the brain tumor-associated macrophages

Nanoparticles containing mixed lipid monolayer shell, biodegradable polymer core and rabies virus glycoprotein (RVG) peptide as brain targeting ligand, were developed for brain targeted delivery of paclitaxel (PTX) to treat malignant glioma. RVG conjugated PTX loaded NPs (RVG-PTX-NPs) had the desirable size (~140 nm), narrow size distribution and spherical shape. RVG-PTX-NPs showed poor uptake by neurons and selective targeting to the brain tumor associated macrophages (TAMs) with controlled release and tumor specific toxicity. In vivo studies revealed that RVG-PTX-NPs were significant to cross the blood-brain barrier (BBB) and had specific targeting to the brain. Most importantly, RVG-PTX-NPs showed effectiveness for anti-glioma therapy on human glioma of mice model. We concluded that RVG-PTX-NPs provided an effective approach for brain-TAMs targeted delivery for the treatment of glioma.

Molecular and Genetic Determinants of Glioma Cell Invasion

A diffusely invasive nature is a major obstacle in treating a malignant brain tumor, "diffuse glioma", which prevents neurooncologists from surgically removing the tumor cells even in combination with chemotherapy and radiation. Recently updated classification of diffuse gliomas based on distinct genetic and epigenetic features has culminated in a multilayered diagnostic approach to combine histologic phenotypes and molecular genotypes in an integrated diagnosis. However, it is still a work in progress to decipher how the genetic aberrations contribute to the aggressive nature of gliomas including their highly invasive capacity. Here we depict a set of recent discoveries involving molecular genetic determinants of the infiltrating nature of glioma cells, especially focusing on genetic mutations in receptor tyrosine kinase pathways and metabolic reprogramming downstream of common cancer mutations. The specific biology of glioma cell invasion provides an opportunity to explore the genotype-phenotype correlation in cancer and develop novel glioma-specific therapeutic strategies for this devastating disease.

Eya2 overexpression promotes the invasion of human astrocytoma through the regulation of ERK/MMP9 signaling

The overexpression of eyes absent (Eya) 2 has been found in several human cancers. However, its biological roles and clinical significance in human astrocytoma have not yet been explored. This study investigated the clinical significance and biological roles of Eya2 in human astrocytoma tissues and cell lines. Using immunohistochemistry, we found Eya2 overexpression in 33 out of 90 (36.7%) astrocytoma specimens. The rate of Eya2 overexpression was higher in grade III-IV (48.1%) than in grade Ⅰ+Ⅱ astrocytomas (21.1%). Transfection with an Eya2 expression plasmid was performed in A172 cells with a low endogenous expression of Eya2 and the knockdown of Eya2 was carried out in U251 cells with a high endogenous expression using siRNA. Eya2 overexpression induced A172 cell proliferation and invasion, while the knockdown of Eya2 using siRNA decreased the proliferation and invasion of U251 cells. In addition, we found that transfection with the Eya2 expression plasmid facilitated cell cycle progression, and that the knockdown of Eya2 inhibited cell cycle progression, accompanied by a change in the expression of cell cycle-related proteins, including cyclin D1 and cyclin E. Eya2 also positively regulated extracellular signal-regulated kinase (ERK) activity and matrix metalloproteinase (MMP)9 expression. The blockade of ERK signaling using an inhibitor abolished the effects of Eya2 on A172 cell invasion and MMP9 production. In addition, we found that there was a positive correlation between Eya2 and Six1 in the astrocytoma cell lines. Immunoprecipitation revealed that Eya2 interacted with Six1 protein in the U251 cell line, which exhibited a high expression of both proteins. Eya2 failed to upregulate MMP expression in the A172 cells in which Six1 was silenced. On the whole, our data indicate that Eya2 may serve as a potential oncoprotein in human astrocytoma. Eya2 regulates astrocytoma cell proliferation and invasion, possibly through the regulation of ERK signaling.

Rab5a is overexpressed in oral cancer and promotes invasion through ERK/MMP signaling

Ras-related protein Rab-5A (Rab5a) has been identified to be overexpressed in several types of human cancer. However, its clinical significance and biological roles in oral cancer remain unclear. In the present study, the protein expression of Rab5a was examined in 79 cases of oral squamous cell carcinoma samples using immunohistochemistry. It was demonstrated that Rab5a protein was upregulated in 49.3% (39/79) of cancer samples. Small interfering RNA knockdown was performed on Detroit 562 cells with high endogenous expression. Rab5a transfection was performed in FaDu cells with low endogenous levels. Rab5a depletion was revealed to inhibit cell growth, invasion and colony formation while its overexpression facilitated cell growth, invasion, and colony formation. In addition, Rab5a facilitated cell cycle progression and cell migration. It was also demonstrated that Rab5a depletion downregulated and its overexpression upregulated the expression levels of various cell cycle-associated proteins, and matrix metalloproteinase-2 (MMP-2). Furthermore, Rab5a positively regulated the extracellular signal-regulated kinase (ERK) signaling pathway and promoted epithelial-mesenchymal transition (EMT). ERK inhibitor PD98059 partially inhibited the role of Rab5a on MMP-2, cyclin D1, cell proliferation and invasion. The results of the present study suggest that Rab5a is overexpressed in oral cancer tissue samples and promotes the malignant phenotype through EMT and the ERK/MMP-2 signaling pathway.

Derlin-1 overexpression confers poor prognosis in muscle invasive bladder cancer and contributes to chemoresistance and invasion through PI3K/AKT and ERK/MMP signaling

Derlin-1 has been found to be overexpressed in several human cancers. However, its clinical significance and biological roles in bladder cancer remain unexplored. Here, we found that Derlin-1 was upregulated in 38.6% (58/150) cases of cancer samples. The rate of Derlin-1 overexpression was higher in muscle invasive bladder cancer (MIBC) than non-muscle invasive bladder cancer (NMIBC) (p=0.0079). Derlin-1 was a predicting factor for poor patient prognosis. Derlin-1 depletion inhibited while its overexpression facilitated cell invasion and colony formation. In addition, Derlin-1 overexpression induced cisplatin resistance while its depletion sensitized cancer cells to cisplatin. Further analysis demonstrated that Derlin-1 activated AKT phosphorylation and upregulated Bcl-2 expression. Blockage of AKT signaling by LY294005 abolished the effects of Derlin-1 on Bcl-2 and cisplatin resistance. Immunoprecipitation indicated Derlin-1 interacted with p110α subunit of PI3K. In addition, we showed that Derlin-1 depletion downregulated and its overexpression upregulated cell MMP-2/9 expression and ERK phosphorylation. Derlin-1 mediated upregulation of MMP-2/9 could be blocked by ERK inhibitor. In conclusion, our study demonstrated that Derlin-1 is overexpressed in bladder cancer and promotes malignant phenotype through ERK/MMP and PI3K/AKT/Bcl-2 signaling pathway.

Molecular differences between cerebral blood volume and vessel size in glioblastoma multiforme

The purpose of this study was to investigate the molecular background of cerebral blood volume (CBV) and vessel size (VS) of capillaries in glioblastoma multiforme (GBM). Both parameters are derived from extended perfusion MR imaging.A prospective case study including 21 patients (median age 66 years, 10 females) was performed. Before operation, CBV and VS of contrast enhancing tumor were assessed. Tissue was sampled from the assessed areas under neuronavigation control. After RNA extraction, transcriptional data was analyzed by Weighted Gene Co-Expression Network Analysis (WGCNA) and split into modules based on its network affiliations. Gene Set Enrichment Analysis (GSEA) identified biological functions or pathways of the genetic modules. These were applied on 484 GBM samples of the TCGA database.Ten modules were highly correlated to CBV and VS. One module was exclusively associated to VS and highly correlated to hypoxia, another one exclusively to CBV showing strong enrichments in the Epithelial Growth Factor (EGF) pathway and Epithelial-to-Mesenchymal-Transition (EMT). Moreover, patients with increased CBV and VS predominantly showed a mesenchymal gene-expression, a finding that could be corroborated by TCGA data.In conclusion, CBV and VS mirror different genetic pathways and reflect certain molecular subclasses of GBM.

Evaluation of Akt and RICTOR Expression Levels in Astrocytomas of All Grades

The mammalian target of rapamycin (mTOR) binds to several protein partners and forms two complexes, termed mTOR complexes 1 and 2 (mTORC1/2), that differ in components, substrates, and regulation. mTORC2 contains the protein Rapamycin-insensitive companion of mTOR (RICTOR); phosphorylates kinases of the AGC family, such as Akt; and controls the cytoskeleton. Even though the regulation of mTORC2 activity remains poorly understood, the hyperactivation of this signaling pathway has been shown to contribute to the oncogenic properties of gliomas in experimental models. In this work, we evaluated expression and phosphorylation of Akt, and expression of RICTOR and Ki-67 in 195 human astrocytomas of different grades (38 cases of grade I, 49 grade II, 15 grade III, and 93 grade IV) and 30 normal brains. Expression and phosphorylation of Akt increased with histological grade and correlated with a worse overall survival in glioblastomas (GBMs). RICTOR was overexpressed in grade I and II astrocytomas and demonstrated a shift to nuclear localization in GBMs. Nuclear RICTOR was associated to increased proliferation in GBMs. Our results point to an increase in total and phosphorylated Akt in high-grade gliomas and to a possible role of RICTOR in proliferations of high-grade GBM cells.

RICTOR polymorphisms affect efficiency of platinum-based chemotherapy in Chinese non-small-cell lung cancer patients

AIM

We investigated the association between RICTOR polymorphisms and clinical outcomes of platinum-based chemotherapy for Chinese non-small-cell lung cancer patients.

MATERIALS & METHODS

Ten tag SNPs were genotyped in 1004 patients to assess their association with clinical benefit, overall survival, progression-free survival, gastrointestinal toxicity, neutropenia, anemia and thrombocytopenia.

RESULTS

rs6878291 was significantly associated with clinical benefit (odds ratio: 2.037; p = 0.001) and reduced progression-free survival (hazard ratio: 1.461; p = 0.001). Stratified analysis showed that their most significant interaction was in nonsmokers. No association was observed between SNPs and other clinical outcomes.

CONCLUSION

The study showed evidences for RICTOR polymorphisms' role in platinum-based chemotherapy efficiency, which could provide new insight to lung cancer management.

Suppression of the invasive potential of Glioblastoma cells by mTOR inhibitors involves modulation of NFκB and PKC-α signaling

Glioblastoma (GBM) is the most aggressive type of brain tumors in adults with survival period <1.5 years of patients. The role of mTOR pathway is documented in invasion and migration, the features associated with aggressive phenotype in human GBM. However, most of the preclinical and clinical studies with mTOR inhibitors are focused on antiproliferative and cytotoxic activity in GBM. In this study, we demonstrate that mTOR inhibitors-rapamycin (RAP), temisirolimus (TEM), torin-1 (TOR) and PP242 suppress invasion and migration induced by Tumor Necrosis Factor-α (TNFα) and tumor promoter, Phorbol 12-myristate 13-acetate (PMA) and also reduce the expression of the TNFα and IL1β suggesting their potential to regulate factors in microenvironment that support tumor progression. The mTOR inhibitors significantly decreased MMP-2 and MMP-9 mRNA, protein and activity that was enhanced by TNFα and PMA. The effect was mediated through reduction of Protein kinase C alpha (PKC-α) activity and downregulation of NFκB. TNFα- induced transcripts of NFκB targets -VEGF, pentraxin-3, cathepsin-B and paxillin, crucial in invasion were restored to basal level by these inhibitors. With limited therapeutic interventions currently available for GBM, our findings are significant and suggest that mTOR inhibitors may be explored as anti-invasive drugs for GBM treatment.

miR-139 Functions as An Antioncomir to Repress Glioma Progression Through Targeting IGF-1 R, AMY-1, and PGC-1β

Gliomas are the most common primary malignant brain tumor with poor prognosis, characterized by a highly heterogeneous cell population, extensive proliferation, and migration. A lot of molecular mechanisms regulate gliomas development and invasion, including abnormal expression of oncogenes and variation of epigenetic modification. MicroRNAs could affect cell growth and functions. Several reports have demonstrated that miR-139 plays multifunctions in kinds of solid tumors through different pathways. However, the antitumor mechanisms of this miR-139 are not unveiled in detail. In this study, we not only validated the low expression level of miR-139 in glioma tissues and cell lines but also detected the effect of miR-139 on modulating gliomas proliferation and invasion both in vitro and in vivo. We identified insulin-like growth factor 1 receptor, associate of Myc 1, and peroxisome proliferator-activated receptor γ coactivator 1β as direct targets of miR-139 and the levels of them were all inversely correlated with miR-139 in gliomas. Insulin like growth factor 1 receptor promoted gliomas invasion through Akt signaling and increased proliferation in the peroxisome proliferator-activated receptor γ coactivator 1β-dependent way. Associate of Myc 1 also facilitated gliomas progression by activating c-Myc pathway. Overexpression of the target genes could retrieve the antitumor function of miR-139, respectively, in different degrees. The nude mice transplantation tumor experiment displayed that glioma cells stably expressed miR-139 growth much slower in vivo than the negative control cells. Taken together, these findings suggested miR-139 acted as a favorable factor against gliomas progression and uncovered a novel regulatory mechanism, which may provide a new evidenced prognostic marker and therapeutic target for gliomas.

Serum-Induced Differentiation of Glioblastoma Neurospheres Leads to Enhanced Migration/Invasion Capacity That Is Associated with Increased MMP9

Glioblastoma (GBM) is a highly infiltrative brain tumor in which cells with properties of stem cells, called glioblastoma stem cells (GSCs), have been identified. In general, the dominant view is that GSCs are responsible for the initiation, progression, invasion and recurrence of this tumor. In this study, we addressed the question whether the differentiation status of GBM cells is associated with their invasive capacity. For this, several primary GBM cell lines were used, cultured either as neurospheres known to enrich for GSCs or in medium supplemented with 10% FCS that promotes differentiation. The differentiation state of the cells was confirmed by determining the expression of stem cell and differentiation markers. The migration/invasion potential of these cells was tested using in vitro assays and intracranial mouse models. Interestingly, we found that serum-induced differentiation enhanced the invasive potential of GBM cells, which was associated with enhanced MMP9 expression. Chemical inhibition of MMP9 significantly reduced the invasive potential of differentiated cells in vitro. Furthermore, the serum-differentiated cells could revert back to an undifferentiated/stem cell state that were able to form neurospheres, although with a reduced efficiency as compared to non-differentiated counterparts. We propose a model in which activation of the differentiation program in GBM cells enhances their infiltrative potential and that depending on microenvironmental cues a significant portion of these cells are able to revert back to an undifferentiated state with enhanced tumorigenic potential. Thus, effective therapy should target both GSCs and differentiated offspring and targeting of differentiation-associated pathways may offer therapeutic opportunities to reduce invasive growth of GBM.

MMP2 and MMP7 at the invasive front of gastric cancer are not associated with mTOR expression

Background

Regulation of MMP expression by activation of mTOR signalling has been demonstrated for several tumor types, but has thus far not been confirmed in gastric cancer.

Findings

The study compromised 128 patients who underwent gastric resection for cancer (66.4 % male; 86 intestinal, 42 diffuse type). Immunohistochemical staining of MMPs was performed to analyse the topographical pattern of MMP expression at the tumor center and the invasive front, respectively. MMP2 showed higher expression at the invasive front compared to the tumor center, whereas MMP7 staining scores were higher in the tumor center, and there was no difference for MMP9. The expression of p-mTOR was higher in the tumor center than at the invasive front, with a similar trend for mTOR. For intestinal type gastric cancer there was a weak correlation of MMP9 with expression of mTOR in the tumor center. Otherwise, there was no correlation of the MMPs with mTOR. By treatment of MKN45 gastric cancer cells with rapamycin, a reduction of p-mTOR in the Western blot was achieved; however, expression of MMPs remained unaffected.

Conclusions

Expression of MMP2 and MMP7 in gastric cancer is not associated with mTOR, MMP9 expression might be related to mTOR signalling in a subset of tumors.

Electronic supplementary material

The online version of this article (doi:10.1186/s13000-015-0449-z) contains supplementary material, which is available to authorized users.

CCL15/CCR1 axis is involved in hepatocellular carcinoma cells migration and invasion

The identification of new biomarkers for the early detection of hepatocellular carcinoma is critical in the development of tumor-targeted therapy, which is possibly advantageous on the prognosis of this disease. Results from our previous study indicated that CCL15 can be a specific proteomic biomarker of hepatocellular carcinoma, which plays an important role in tumorigenesis and tumor invasion. In this study, we found that CCL15 can induce hepatocellular carcinoma cell migration and invasion. Furthermore, CCR1, the receptor of CCL15, was demonstrated to play a critical role in metastatic hepatocellular carcinoma. CCR1 short hairpin RNA significantly inhibited CCL15-induced chemotaxis and invasion of HepG2 cells. Moreover, CCR1 knockdown significantly limited the activity and expression of matrix metalloproteinase-2 (MMP-2) and MMP-9. These findings suggest that CCR1 plays critical roles in hepatocellular carcinoma metastasis, which indicates that CCR1 may be a potential molecular target in hepatocellular carcinoma therapy.

Activation of sonic hedgehog signaling enhances cell migration and invasion by induction of matrix metalloproteinase-2 and -9 via the phosphoinositide-3 kinase/AKT signaling pathway in glioblastoma

Aberrant hedgehog signaling contributes to the development of various malignancies, including glioblastoma (GBM). However, the potential mechanism of hedgehog signaling in GBM migration and invasion has remained to be elucidated. The present study showed that enhanced hedgehog signaling by recombinant human sonic hedgehog N-terminal peptide (rhSHH) promoted the adhesion, invasion and migration of GBM cells, accompanied by increases in mRNA and protein levels of matrix metalloproteinase-2 (MMP-2) and MMP-9. However, inhibition of hedgehog signaling with cyclopamine suppressed the adhesion, invasion and migration of GBM cells, accompanied by decreases in mRNA and protein levels of MMP-2 and -9. Furthermore, it was found that MMP-2- and MMP-9-neutralizing antibodies or GAM6001 reversed the inductive effects of rhSHH on cell migration and invasion. In addition, enhanced hedgehog signaling by rhSHH increased AKT phosphorylation, whereas blockade of hedgehog signaling decreased AKT phosphorylations. Further experiments showed that LY294002, an inhibitor of phosphoinositide-3 kinase (PI3K), decreased rhSHH-induced upregulation of MMP-2 and -9. Finally, the protein expression of glioblastoma-associated oncogene 1 was positively correlated with levels of phosphorylated AKT as well as protein expressions of MMP-2 and -9 in GBM tissue samples. In conclusion, the present study indicated that the hedgehog pathway regulates GBM-cell migration and invasion by increasing MMP-2 and MMP-9 production via the PI3K/AKT pathway.

Autocrine IL-8 promotes F-actin polymerization and mediate mesenchymal transition via ELMO1-NF-κB-Snail signaling in glioma

Glioma is the most common form of primary malignant brain cancers. Tumor cell invasiveness is a critical challenge in the clinical management of glioma patients. The invasive biological feature of glioma cell is stimulated by both autocrine and paracrine factors including chemokine IL-8. In this study, we report that the production of IL-8 is higher in glioma tissues and cells than adjacent nontumor tissues (ANT) and normal glial cells. Autocrine IL-8 can increase the invasive ability of glioma cells by binding to CXCR1. In addition, high expression of IL-8 indicates poor prognosis of glioma patients. Furthermore, IL-8 is capable of modulating cell migration and invasion by regulating the activation of RAC1 which resulted in cytoskeletal reorganisation in an ELMO1 dependent manner. Finally, we found that IL-8 could enhance mesenchymal transition(MT) of glioma cells by activating ELMO1-NF-κB-Snail signaling. Our data indicate that IL-8 autocrine is responsible for the invasive phenotype of glioma and IL-8 may be a useful prognostic marker for glioma and novel therapeutic target for glioma invasion intervention.

Integrin α3β1 signaling through MEK/ERK determines alternative polyadenylation of the MMP-9 mRNA transcript in immortalized mouse keratinocytes

Integrin α3β1 is highly expressed in both normal and tumorigenic epidermal keratinocytes where it regulates genes that control cellular function and extracellular matrix remodeling during normal and pathological tissue remodeling processes, including wound healing and development of squamous cell carcinoma (SCC). Previous studies identified a role for α3β1 in immortalized and transformed keratinocytes in the regulation of genes that promote tumorigenesis, invasion, and pro-angiogenic crosstalk to endothelial cells. One such gene, matrix metalloproteinase-9 (MMP-9), is induced by α3β1 through a post-transcriptional mechanism of enhanced mRNA stability. In the current study, we sought to investigate the mechanism through which α3β1 controls MMP-9 mRNA stability. First, we utilized a luciferase reporter assay to show that AU-rich elements (AREs) residing within the 3’-untranslated region (3’-UTR) of the MMP-9 mRNA renders the transcript unstable in a manner that is independent of α3β1. Next, we cloned a truncated variant of the MMP-9 mRNA which is generated through usage of an alternative, upstream polyadenylation signal and lacks the 3’-UTR region containing the destabilizing AREs. Using an RNase protection assay to distinguish “long” (full-length 3’-UTR) and “short” (truncated 3’-UTR) MMP-9 mRNA variants, we demonstrated that the shorter, more stable mRNA that lacks 3’-UTR AREs was preferentially generated in α3β1-expressing keratinocytes compared with α3β1-deficient (i.e., α3-null) keratinocytes. Moreover, we determined that α3β1-dependent alternative polyadenylation was acquired by immortalized keratinocytes, as primary neonatal keratinocytes did not display α3β1-dependent differences in the long and short transcripts. Finally, pharmacological inhibition of the extracellular signal-regulated kinase (ERK)/mitogen-activated protein kinase (MAPK) pathway in α3β1-expressing keratinocytes caused a shift towards long variant expression, while Raf-1-mediated activation of ERK in α3-null keratinocytes dramatically enhanced short variant expression, indicating a role for ERK/MAPK signaling in α3β1-mediated selection of the proximal polyadenylation site. These findings identify a novel mode of integrin α3β1-mediated gene regulation through alternative polyadenylation.

MiR-204 inhibits human NSCLC metastasis through suppression of NUAK1

BACKGROUND

Lung cancer is a leading cause of cancer-related mortality worldwide and non-small-cell lung carcinoma (NSCLC) is responsible for almost 80% of lung cancer-related deaths. Identifying novel molecules that can repress the invasiveness and metastasis of lung cancer will facilitate the development of new antilung cancer strategies. The aim of this study is to determine the roles of NUAK1 (a downstream of Akt) and miR-204 in the invasiveness and metastasis of NSCLC and to reveal the correlation between NUAK1 and miR-204.

METHODS

The expression of NUAK1 in primary human NSCLC tissues was evaluated by immunohistochemistry. Real-time PCR was employed to measure the expression level of miR-204. The effect of NUAK1 and miR204 on the prognosis of NSCLC patients was evaluated by log-rank test. The siRNA transfection was used to manipulate the expression levels of NUAK1 and miR204 in cancer cells. Chemotaxis assay, Scratch assay, and Matrigel invasion assay were performed to evaluate the migration and invasion of cells. Cellular F-actin measurement was used to measure F-actin polymerisation in lung cancer cells. Western blot was used to detect the expression levels of corresponding proteins. The Luciferase assay and RNA immunoprecipitation were used to confirm the actual binding site of miR-204 to 3'UTR of NUAK1.

RESULTS

Increased expression of NUAK1 is correlated with the invasiveness and metastasis of human NSCLC. Knockdown of NUAK1 inhibited cell migration and invasion. In addition, this study showed that NUAK1 influenced mTOR phosphorylation and induced the phosphorylation of p70S6K1 and eukaryotic initiation factor 4E-binding protein1 (4E-BP1), two downstream targets of mTOR in NSCLC cells. At the same time, decreased expression of miR-204 promoted NSCLC progression and, contrarily, manipulated upregulation of miR-204-inhibited cell migration and invasion. There is clinical relevance between miR-204 downregulation and NUAK1 upregulation in human NSCLC. Furthermore, we found that miR-204 inhibited NSCLC tumour invasion by directly targeting and downregulating NUAK1 expression. Finally, our data suggested that the downregulation of miR-204 was due to hypermethylation of its promoter region.

CONCLUSIONS

Our results indicate that NUAK1 is excessively expressed in NSCLC and plays important roles in NSCLC invasion. The miR-204 acts as a tumour suppressor by inhibiting NUAK1 expression in NSCLC. Both NUAK1 and miR-204 may serve as potential targets of NSCLC therapy.

rpS6 regulates blood-testis barrier dynamics through Akt-mediated effects on MMP-9

Mammalian target of rapamycin complex 1 (mTORC1) is an emerging regulator of blood-tissue barriers that utilizes ribosomal protein S6 (rpS6) as the downstream signaling molecule. To explore the role of rpS6 in blood-testis barrier (BTB) function, a constitutively active quadruple rpS6 phosphomimetic mutant was constructed in mammalian expression vector and overexpressed in Sertoli cells cultured in vitro that mimicked the BTB in vivo. Using this quadruple phosphomimetic mutant, phosphorylated (p)-rpS6 was shown to disrupt IGF-1/insulin signaling, thereby abolishing Akt phosphorylation, which led to an induction of MMP-9. This increase in MMP-9 secretion perturbed the Sertoli cell tight junction permeability barrier by proteolysis-mediated downregulation of tight junction proteins at the BTB. These findings were confirmed by the use of a specific MMP-9 inhibitor that blocked the disruption of the tight junction permeability barrier by the rpS6 mutant. Additionally, RNA interference (RNAi)-mediated Akt silencing was able to mimic the results of rpS6 mutant overexpression in Sertoli cells, further confirming this p-rpS6-Akt-MMP-9 signaling pathway. In conclusion, these data support a new concept of mTORC1-mediated BTB regulation, that is possibly also applicable to other blood-tissue barriers.

The mTOR kinase inhibitors polarize glioma-activated microglia to express a M1 phenotype

BACKGROUND

Increased activation of mammalian target of rapamycin (mTOR) is observed in numerous human cancers. Recent studies on the glioma kinome have identified several deregulated pathways that converge and activate mTOR. The available evidence on the role of microglia in CNS cancers would suggest a dual role, a tumoricidal role and -on the contrary- a role favoring tumor growth.

METHODS

In the present paper, we have compared the effects of μM concentrations of rapamycin (RAPA) and its analog, RAD001 (RAD), on activated microglia; the latter was obtained by exposing cells to conditioned medium harvested either from inflammatory activated glioma cells (LI-CM) or from glioma cells kept under basal conditions (C-CM).

RESULTS

Here we show that the inhibition of mTOR polarizes glioma-activated microglial cells towards the M1 phenotype, with cytotoxic activities, preventing the induction of the M2 status that promotes tumor growth. In fact RAPA and RAD significantly increased iNOS expression and activity, while on the same time significantly reducing IL-10 gene expression induced by C-CM, thus suggesting that the drugs prevent the acquisition of a M2 phenotype in response to glioma factors promoting a classic M1 activation. Similar results were obtained using the conditioned media obtained after glioma stimulation with LPS-IFNγ (LI-CM), which was found to induce a mixture of M1 and M2a/b polarization phenotypes. In these conditions, the inhibition of mTOR led to a significant up-regulation of iNOS, and in parallel to the down-regulation of both ARG and IL-10 gene expression.

CONCLUSIONS

These data suggest that mTOR inhibition may prevent glioma induced M2 polarization of microglial cells and increase their cytotoxic potential, possibly resulting in antitumor actions.

Tumor suppressive miRNA-34a suppresses cell proliferation and tumor growth of glioma stem cells by targeting Akt and Wnt signaling pathways

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miR-34a was decreased in both glioma and glioma stem cell-lines as compared to normal brain tissues.

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Glioma stem cell-lines HNGC-2 and NSG-K16 possess the mesenchymal glioblastoma phenotype.

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miR-34a over-expression in these cell lines decreased their proliferative and migratory potential, and induced apoptosis.

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Rictor, a part of the mTORC2 complex, is a novel target for miR-34a in glioma stem cells.

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The tumor suppressive function of miR-34a is mediated via Rictor and affects the AKT/mTOR pathway and Wnt signaling.

MiRNA-34a is considered as a potential prognostic marker for glioma, as studies suggest that its expression negatively correlates with patient survival in grade III and IV glial tumors. Here, we show that expression of miR-34a was decreased in a graded manner in glioma and glioma stem cell-lines as compared to normal brain tissues. Ectopic expression of miR-34a in glioma stem cell-lines HNGC-2 and NSG-K16 decreased the proliferative and migratory potential of these cells, induced cell cycle arrest and caused apoptosis. Notably, the miR-34a glioma cells formed significantly smaller xenografts in immuno-deficient mice as compared with control glioma stem cell-lines. Here, using a bioinformatics approach and various biological assays, we identify Rictor, as a novel target for miR-34a in glioma stem cells. Rictor, a defining component of mTORC2 complex, is involved in cell survival signaling. mTORC2 lays downstream of Akt, and thus is a direct activator of Akt. Our earlier studies have elaborated on role of Rictor in glioma invasion (Das et al., 2011). Here, we demonstrate that miR34a over-expression in glioma stem cells profoundly decreased levels of p-AKT (Ser473), increased GSK-3β levels and targeted for degradation β-catenin, an important mediator of Wnt signaling pathway. This led to diminished levels of the Wnt effectors cyclin D1 and c-myc. Collectively, we show that the tumor suppressive function of miR-34a in glioblastoma is mediated via Rictor, which through its effects on AKT/mTOR pathway and Wnt signaling causes pronounced effects on glioma malignancy.

Role of Akt in human malignant glioma: from oncogenesis to tumor aggressiveness

Gathering evidence has revealed that Akt signaling pathway plays an important role in glioma progression and aggressiveness. Among Akt kinases the most studied, Akt1, has been involved in many cellular processes that are in favor of cell malignancy. More recently, the actions of the two other isoforms, Akt2 and Akt3 have emerged in glioma. After a description of Akt pathway activation, we will explore the role of each isoform in malignant glioma that strengthens the current preclinical and clinical studies evaluating the impact of Akt pathway targeting in glioblastomas.

Regulation of matrix metalloproteinase-1, -3, and -9 in Mycobacterium tuberculosis-dependent respiratory networks by the rapamycin-sensitive PI3K/p70(S6K) cascade

This study was designed to investigate the role of the phosphatidyl inositol 3-kinase (PI3K)/AKT/p70(S6K) signaling path on regulation of primary normal human bronchial epithelial cell-derived matrix metalloproteinase (MMP)-1, -3, and -9 expression in tuberculosis (TB). These MMPs are key in pathological extracellular matrix degradation in TB. Normal human bronchial epithelials were stimulated with conditioned medium from monocytes infected with virulent TB (CoMTb) and components of the PI3K/AKT signaling pathway blocked using specific chemical inhibitors and siRNA. MMP gene expression was measured by RT-PCR and secretion by ELISA, luminex, or zymography. Phospho-p70 S6K was detected by Western blot analysis and activity blocked by rapamycin. Chemical blockade of the proximal catalytic PI3K p110 subunit augmented MMP-1 and MMP-9 in a dose-dependent manner (all P<0.001) but suppressed MMP-3 (P<0.01). Targeted siRNA studies identified the p110α isoform as key causing 5-fold increase in TB network-dependent MMP-1 secretion to 4900 ± 1100 pg/ml. Specific inhibition of the AKT node suppressed all 3 MMPs. Phospho-p70(S6K) was identified in the cellular model, and rapamycin, a p70(S6K) inhibitor, inhibited MMP-1 (P<0.001) and MMP-3 (P<0.01) but not MMP-9. Controls were epithelial cells that were unstimulated or exposed to conditioned medium from monocytes not exposed to TB. In summary, blockade of the proximal PI3K catalytic subunit increases MMP-1 and MMP-9, whereas rapamycin decreased both MMP-1 and MMP-3. The regulation of the PI3K path in TB is complex, MMP specific, and a potential immunotherapeutic target in diseases characterized by tissue destruction.

Regulation of blood-testis barrier (BTB) dynamics during spermatogenesis via the "Yin" and "Yang" effects of mammalian target of rapamycin complex 1 (mTORC1) and mTORC2

In mammalian testes, haploid spermatozoa are formed from diploid spermatogonia during spermatogenesis, which is a complicated cellular process. While these cellular events were reported in the 1960s and 1970s, the underlying molecular mechanism(s) that regulates these events remained unexplored until the past ∼10 years. For instance, adhesion proteins were shown to be integrated components at the Sertoli cell-cell interface and/or the Sertoli-spermatid interface in the late 1980s. But only until recently, studies have demonstrated that some of the adhesion proteins serve as the platform for signal transduction that regulates cell adhesion. In this chapter, a brief summary and critical discussion are provided on the latest findings regarding these cell-adhesion proteins in the testis and their relationship to spermatogenesis. Moreover, antagonistic effects of two mammalian target of rapamycin (mTOR) complexes, known as mTORC1 and mTORC2, on cell-adhesion function in the testis are discussed. Finally, a hypothetic model is presented to depict how these two mTOR-signaling complexes having the "yin" and "yang" antagonistic effects on the Sertoli cell tight junction (TJ)-permeability barrier can maintain the blood-testis barrier (BTB) integrity during the epithelial cycle while preleptotene spermatocytes are crossing the BTB.

Combined RNAi-mediated suppression of Rictor and EGFR resulted in complete tumor regression in an orthotopic glioblastoma tumor model

The PI3K/AKT/mTOR pathway is commonly over activated in glioblastoma (GBM), and Rictor was shown to be an important regulator downstream of this pathway. EGFR overexpression is also frequently found in GBM tumors, and both EGFR and Rictor are associated with increased proliferation, invasion, metastasis and poor prognosis. This research evaluated in vitro and in vivo whether the combined silencing of EGFR and Rictor would result in therapeutic benefits. The therapeutic potential of targeting these proteins in combination with conventional agents with proven activity in GBM patients was also assessed. In vitro validation studies were carried out using siRNA-based gene silencing methods in a panel of three commercially available human GBM cell lines, including two PTEN mutant lines (U251MG and U118MG) and one PTEN-wild type line (LN229). The impact of EGFR and/or Rictor silencing on cell migration and sensitivity to chemotherapeutic drugs in vitro was determined. In vivo validation of these studies was focused on EGFR and/or Rictor silencing achieved using doxycycline-inducible shRNA-expressing U251MG cells implanted orthotopically in Rag2M mice brains. Target silencing, tumor size and tumor cell proliferation were assessed by quantification of immunohistofluorescence-stained markers. siRNA-mediated silencing of EGFR and Rictor reduced U251MG cell migration and increased sensitivity of the cells to irinotecan, temozolomide and vincristine. In LN229, co-silencing of EGFR and Rictor resulted in reduced cell migration, and increased sensitivity to vincristine and temozolomide. In U118MG, silencing of Rictor alone was sufficient to increase this line’s sensitivity to vincristine and temozolomide. In vivo, while the silencing of EGFR or Rictor alone had no significant effect on U251MG tumor growth, silencing of EGFR and Rictor together resulted in a complete eradication of tumors. These data suggest that the combined silencing of EGFR and Rictor should be an effective means of treating GBM.

Derlin-1 is overexpressed in non-small cell lung cancer and promotes cancer cell invasion via EGFR-ERK-mediated up-regulation of MMP-2 and MMP-9

Previous studies indicated a role of Derlin-1 in human cancers; however, its expression pattern in non-small cell lung cancer (NSCLC) and the molecular mechanism of Derlin-1 on cancer progression have not been characterized. In the present study, Derlin-1 expression was examined in lung cancer cell lines and human tissues. Derlin-1 overexpression correlated with pTNM stage, lymph node metastasis, and poor overall survival. siRNA knockdown of Derlin-1 impaired anchorage-dependent and anchorage-independent cell growth and invasion in A549 and H1299 cell lines, and its overexpression promoted proliferation and invasion in HBE and LTE cell lines. Derlin-1 depletion decreased matrix metalloproteinase (MMP)-2/9 at both protein and mRNA levels, with decreased MAP kinase/extracellular signal-regulated kinase (ERK)/ERK phosphorylation. Derlin-1 overexpression up-regulated MMP-2/9 expression and ERK phosphorylation, which could be reversed by MAP kinase/ERK kinase inhibitor, PD98059. The effect of Derlin-1 on MMP-2/9 up-regulation was abolished in ERK1/2 siRNA-treated cells. Further analysis showed that Derlin-1 overexpression induced EGFR phosphorylation. EGFR inhibitor blocked Derlin-1-mediated up-regulation of EGFR and ERK phosphorylation. MMP-2/9 and p-ERK up-regulation by Derlin-1 was partly blocked in EGFR-depleted cells with siRNA treatment. Immunoprecipitation confirmed the association between Derlin-1 and EGFR. In summary, our results showed that Derlin-1 is overexpressed in NSCLC and promotes invasion by EGFR-ERK-mediated up-regulation of MMP-2 and MMP-9. Derlin-1 may serve as a therapeutic target for NSCLC.

Rictor/mTORC2 regulates blood-testis barrier dynamics via its effects on gap junction communications and actin filament network

In the mammalian testis, coexisting tight junctions (TJs), basal ectoplasmic specializations, and gap junctions (GJs), together with desmosomes near the basement membrane, constitute the blood-testis barrier (BTB). The most notable feature of the BTB, however, is the extensive network of actin filament bundles, which makes it one of the tightest blood-tissue barriers. The BTB undergoes restructuring to facilitate the transit of preleptotene spermatocytes at stage VIII-IX of the epithelial cycle. Thus, the F-actin network at the BTB undergoes cyclic reorganization via a yet-to-be explored mechanism. Rictor, the key component of mTORC2 that is known to regulate actin cytoskeleton, was shown to express stage-specifically at the BTB in the seminiferous epithelium. Its expression was down-regulated at the BTB in stage VIII-IX tubules, coinciding with BTB restructuring at these stages. Using an in vivo model, a down-regulation of rictor at the BTB was also detected during adjudin-induced BTB disruption, illustrating rictor expression is positively correlated with the status of the BTB integrity. Indeed, the knockdown of rictor by RNAi was found to perturb the Sertoli cell TJ-barrier function in vitro and the BTB integrity in vivo. This loss of barrier function was accompanied by changes in F-actin organization at the Sertoli cell BTB in vitro and in vivo, associated with a loss of interaction between actin and α-catenin or ZO-1. Rictor knockdown by RNAi was also found to impede Sertoli cell-cell GJ communication, disrupting protein distribution (e.g., occludin, ZO-1) at the BTB, illustrating that rictor is a crucial BTB regulator.

(99m)Tc-MAG3-aptamer for imaging human tumors associated with high level of matrix metalloprotease-9

The human matrix metalloprotease 9 (hMMP-9) is involved in many physiological processes such as tissue remodeling. Its overexpression in tumors promotes the release of cancer cells thus contributing to tumor metastasis. It is a relevant marker of malignant tumors. We selected an RNA aptamer containing 2'-fluoro, pyrimidine ribonucleosides, that exhibits a strong affinity for hMMP-9 (K(d) = 20 nM) and that discriminates other human MMPs: no binding was detected to either hMMP-2 or -7. Investigating the binding properties of different MMP-9 aptamer variants by surface plasmon resonance allowed the determination of recognition elements. As a result, a truncated aptamer, 36 nucleotides long, was made fully resistant to nuclease following the substitution of every purine ribonucleoside residue by 2'-O-methyl analogues and was conjugated to S-acetylmercaptoacetyltriglycine for imaging purposes. The resulting modified aptamer retained the binding properties of the originally selected sequence. Following (99m)Tc labeling, this aptamer was used for ex vivo imaging slices of human brain tumors. We were able to specifically detect the presence of hMMP-9 in such tissues.

Vitamin K1 enhances sorafenib-induced growth inhibition and apoptosis of human malignant glioma cells by blocking the Raf/MEK/ERK pathway

BACKGROUND

The combined effects of anticancer drugs with nutritional factors against tumor cells have been reported previously. This study characterized the efficacy and possible mechanisms of the combination of sorafenib and vitamin K1 (VK1) on glioma cell lines.

METHODS

We examined the effects of sorafenib, VK1 or their combination on the proliferation and apoptosis of human malignant glioma cell lines (BT325 and U251) by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) assay, flow cytometry and 4',6-diamidino-2-phenylindole (DAPI) assay. The signaling pathway changes were detected by western blotting.

RESULTS

Sorafenib, as a single agent, showed antitumor activity in a dose-dependent manner in glioma cells, but the effects were more pronounced when used in combination with VK1 treatment. Sorafenib in combination with VK1 treatment produced marked potentiation of growth inhibition and apoptosis, and reduced expression of phospho-mitogen-activated protein kinase kinase (MEK) and phospho-extracellular signal-regulated kinase (ERK). Furthermore, the expression levels of antiapoptotic proteins Bcl-2 and Mcl-1 were significantly reduced.

CONCLUSIONS

Our findings indicated that VK1 enhanced the cytotoxicity effect of sorafenib through inhibiting the Raf/MEK/ERK signaling pathway in glioma cells, and suggested that sorafenib in combination with VK1 maybe a new therapeutic option for patients with gliomas.

miR-520c and miR-373 upregulate MMP9 expression by targeting mTOR and SIRT1, and activate the Ras/Raf/MEK/Erk signaling pathway and NF-κB factor in human fibrosarcoma cells

MicroRNA 520c and 373 (miR-520c and miR-373) have been characterized as oncogenes and play critical roles in cancer cell metastasis. However, the relationship between these two microRNAs and matrix metalloproteinases (MMPs), which are important in cancer cell metastasis, remains unknown. Here, we report new evidence in which miR-520c and miR-373 effects in human fibrosarcoma HT1080 cells are associated with MMP9 activity, and this upregulation of MMP9 is not only at the activity and protein levels, but also at that of its mRNA. Our experimental data demonstrate that these effects occur not by direct binding to the MMP9 promoter, but by miR-520c and miR-373 directly targeting the 3'-untranslational region (UTR) of mRNAs of mTOR and SIRT1 (negative regulators of expression of MMP9 via inactivating the Ras/Raf/MEK/Erk signaling pathway and transcription factor NF-κB activity); and thus suppressing translation levels of SIRT1 and mTOR. Moreover, inhibition of key kinases of the Ras/Raf/MEK/Erk signaling pathway and Western blots for selected proteins further identified miR-520c and miR-373 as activating this signaling pathway and NF-κB. In conclusion, miR-520c and miR-373 increased the expression of MMP9 by directly targeting the 3'-UTRs of mRNAs of mTOR and SIRT1 and suppressing their translation; resulting in activation of the Ras/Raf/MEK/Erk signaling pathway and NF-κB; and, finally, increasing the mRNA, protein, and activity of MMP9 and enhancing cell migration and cell growth in 3D type I collagen gels.

Review series: TOR kinase complexes and cell migration

Cell migration is a fundamental process in a wide array of biological and pathological responses. It is regulated by complex signal transduction pathways in response to external cues that couple to growth factor and chemokine receptors. In recent years, the target of rapamycin (TOR) kinase, as part of either TOR complex 1 (TORC1) or TOR complex 2 (TORC2), has been shown to be an important signaling component linking external signals to the cytoskeletal machinery in a variety of cell types and organisms. Thus, these complexes have emerged as key regulators of cell migration and chemotaxis.