Pro-invasive gene regulating effect of irradiation and combined temozolomide-radiation treatment on surviving human malignant glioma cells

Invadopodia associated Thrombospondin-1 contributes to a post-therapy pro-invasive response in glioblastoma cells

A critical challenge in the treatment of glioblastoma (GBM) is its highly invasive nature which promotes cell migration throughout the brain and hinders surgical resection and effective drug delivery. GBM cells demonstrate augmented invasive capabilities following exposure to the current gold standard treatment of radiotherapy (RT) and concomitant and adjuvant temozolomide (TMZ), resulting in rapid disease recurrence. Elucidating the mechanisms employed by post-treatment invasive GBM cells is critical to the development of more effective therapies. In this study, we utilized a Nanostring® Cancer Progression gene expression panel to identify candidate genes that may be involved in enhanced GBM cell invasion after treatment with clinically relevant doses of RT/TMZ. Our findings identified thrombospondin-1 (THBS1) as a pro-invasive gene that is upregulated in these cells. Immunofluorescence staining revealed that THBS1 localised within functional matrix-degrading invadopodia that formed on the surface of GBM cells. Furthermore, overexpression of THBS1 resulted in enhanced GBM cell migration and secretion of MMP-2, which was reduced with silencing of THBS1. The preliminary data demonstrates that THBS1 is associated with invadopodia in GBM cells and is likely involved in the invadopodia-mediated invasive process in GBM cells exposed to RT/TMZ treatment. Therapeutic inhibition of THBS1-mediated invadopodia activity, which facilitates GBM cell invasion, should be further investigated as a treatment for GBM.

Repurposing FDA-approved drugs as inhibitors of therapy-induced invadopodia activity in glioblastoma cells

Glioblastoma (GBM) is the most prevalent primary central nervous system tumour in adults. The lethality of GBM lies in its highly invasive, infiltrative, and neurologically destructive nature resulting in treatment failure, tumour recurrence and death. Even with current standard of care treatment with surgery, radiotherapy and chemotherapy, surviving tumour cells invade throughout the brain. We have previously shown that this invasive phenotype is facilitated by actin-rich, membrane-based structures known as invadopodia. The formation and matrix degrading activity of invadopodia is enhanced in GBM cells that survive treatment. Drug repurposing provides a means of identifying new therapeutic applications for existing drugs without the need for discovery or development and the associated time for clinical implementation. We investigate several FDA-approved agents for their ability to act as both cytotoxic agents in reducing cell viability and as 'anti-invadopodia' agents in GBM cell lines. Based on their cytotoxicity profile, three agents were selected, bortezomib, everolimus and fludarabine, to test their effect on GBM cell invasion. All three drugs reduced radiation/temozolomide-induced invadopodia activity, in addition to reducing GBM cell viability. These drugs demonstrate efficacious properties warranting further investigation with the potential to be implemented as part of the treatment regime for GBM.

Small extracellular vesicles promote invadopodia activity in glioblastoma cells in a therapy-dependent manner

PURPOSE

The therapeutic efficacy of radiotherapy/temozolomide treatment for glioblastoma (GBM) is limited by the augmented invasiveness mediated by invadopodia activity of surviving GBM cells. As yet, however the underlying mechanisms remain poorly understood. Due to their ability to transport oncogenic material between cells, small extracellular vesicles (sEVs) have emerged as key mediators of tumour progression. We hypothesize that the sustained growth and invasion of cancer cells depends on bidirectional sEV-mediated cell-cell communication.

METHODS

Invadopodia assays and zymography gels were used to examine the invadopodia activity capacity of GBM cells. Differential ultracentrifugation was utilized to isolate sEVs from conditioned medium and proteomic analyses were conducted on both GBM cell lines and their sEVs to determine the cargo present within the sEVs. In addition, the impact of radiotherapy and temozolomide treatment of GBM cells was studied.

RESULTS

We found that GBM cells form active invadopodia and secrete sEVs containing the matrix metalloproteinase MMP-2. Subsequent proteomic studies revealed the presence of an invadopodia-related protein sEV cargo and that sEVs from highly invadopodia active GBM cells (LN229) increase invadopodia activity in sEV recipient GBM cells. We also found that GBM cells displayed increases in invadopodia activity and sEV secretion post radiation/temozolomide treatment. Together, these data reveal a relationship between invadopodia and sEV composition/secretion/uptake in promoting the invasiveness of GBM cells.

CONCLUSIONS

Our data indicate that sEVs secreted by GBM cells can facilitate tumour invasion by promoting invadopodia activity in recipient cells, which may be enhanced by treatment with radio-chemotherapy. The transfer of pro-invasive cargos may yield important insights into the functional capacity of sEVs in invadopodia.

The PYK2 inhibitor PF-562271 enhances the effect of temozolomide on tumor growth in a C57Bl/6-Gl261 mouse glioma model

BACKGROUND

The development of resistance to temozolomide (TMZ), a standard chemotherapeutic, limits the effective treatment of glioblastoma (GBM). Focal adhesion kinase (FAK) and proline rich tyrosine kinase 2 (Pyk2) regulate proliferation and invasion of GBM cells. We found that TMZ activates FAK and Pyk2 signaling in GBM. We hypothesized that pharmacological inhibitors of Pyk2/FAK together with TMZ can enhance the inhibitory effect of TMZ on tumor growth and dispersal and improve the treatment outcome.

METHODS

Primary human GBM cell cultures and a C57Bl/6-GL261 mouse glioma implantation model were used. Pyk2 (Tyr579/580) and FAK (Tyr925) phosphorylation was analyzed by western blotting. Viability, cell cycle, migration, invasion and invadopodia formation were investigated in vitro. Animal survival, tumor size and invasion, TUNEL apoptotic cell death and the Ki67 proliferation index were evaluated in vivo upon treatment with TMZ (50 mg/kg, once/day, orally) and the Pyk2/FAK inhibitor PF-562271 (once/daily, 50 mg/kg, orally) vs. TMZ monotherapy.

RESULTS

In vitro studies revealed significantly reduced viability, cell cycle progression, invasion and invadopodia with TMZ (100 µM) + PF-562271 (16 nM) compared with TMZ alone. In vivo studies demonstrated that combinatorial treatment led to prominent reductions in tumor size and invasive margins, extensive signs of apoptosis and a reduced proliferation index, together with a 15% increase in the survival rate in animals, compared with TMZ monotherapy.

CONCLUSION

TMZ + PF-562271 eliminates TMZ-related Pyk2/FAK activation in GBM and improves the treatment efficacy.

Molecular Mechanisms and Clinical Challenges of Glioma Invasion

Glioma is the most common primary brain tumor, and its prognosis is poor. Glioma cells are highly invasive to the brain parenchyma. It is difficult to achieve complete resection due to the nature of the brain tissue, and tumors that invade the parenchyma often recur. The invasiveness of tumor cells has been studied from various aspects, and the related molecular mechanisms are gradually becoming clear. Cell adhesion factors and extracellular matrix factors have a strong influence on glioma invasion. The molecular mechanisms that enhance the invasiveness of glioma stem cells, which have been investigated in recent years, have also been clarified. In addition, it has been discussed from both basic and clinical perspectives that current therapies can alter the invasiveness of tumors, and there is a need to develop therapeutic approaches to glioma invasion in the future. In this review, we will summarize the factors that influence the invasiveness of glioma based on the environment of tumor cells and tissues, and describe the impact of the treatment of glioma on invasion in terms of molecular biology, and the novel therapies for invasion that are currently being developed.

Inhibition of Radiation and Temozolomide-Induced Glioblastoma Invadopodia Activity Using Ion Channel Drugs

Simple Summary

Glioblastoma accounts for approximately 40–50% of all primary brain cancers and is a highly aggressive cancer that rapidly disseminates within the surrounding normal brain. Dynamic actin-rich protrusions known as invadopodia facilitate this invasive process. Ion channels have also been linked to a pro-invasive phenotype and may contribute to facilitating invadopodia activity in cancer cells. The aim of our study was to screen ion channel-targeting drugs for their cytotoxic efficacy and potential anti-invadopodia properties in glioblastoma cells. We demonstrated that the targeting of ion channels in glioblastoma cells can lead to a reduction in invadopodia activity and protease secretion. Importantly, the candidate drugs exhibited a significant reduction in radiation and temozolomide-induced glioblastoma cell invadopodia activity. These findings support the proposed pro-invasive role of ion channels via invadopodia in glioblastoma, which may be ideal therapeutic targets for the treatment of glioblastoma patients.

Abstract

Glioblastoma (GBM) is the most prevalent and malignant type of primary brain cancer. The rapid invasion and dissemination of tumor cells into the surrounding normal brain is a major driver of tumor recurrence, and long-term survival of GBM patients is extremely rare. Actin-rich cell membrane protrusions known as invadopodia can facilitate the highly invasive properties of GBM cells. Ion channels have been proposed to contribute to a pro-invasive phenotype in cancer cells and may also be involved in the invadopodia activity of GBM cells. GBM cell cytotoxicity screening of several ion channel drugs identified three drugs with potent cell killing efficacy: flunarizine dihydrochloride, econazole nitrate, and quinine hydrochloride dihydrate. These drugs demonstrated a reduction in GBM cell invadopodia activity and matrix metalloproteinase-2 (MMP-2) secretion. Importantly, the treatment of GBM cells with these drugs led to a significant reduction in radiation/temozolomide-induced invadopodia activity. The dual cytotoxic and anti-invasive efficacy of these agents merits further research into targeting ion channels to reduce GBM malignancy, with a potential for future clinical translation in combination with the standard therapy.

TMZ regulates GBM stemness via MMP14-DLL4-Notch3 pathway

Glioblastoma (GBM) is one of the most aggressive primary brain tumors with frequent recurrences following the standard methods of treatment-temozolomide (TMZ), ionizing radiation and surgical resection. The objective of our study was to investigate GBM resistance mediated via MMP14 (matrix metalloproteinase 14). We used multiple PDX GBM models and established glioma cell lines to characterize expression and subcellular localization of MMP14 after TMZ treatment. We performed a Kiloplex ELISA-based array to evaluate changes in cellular proteins induced by MMP14 expression and translocation. Lastly, we conducted functional and mechanistic studies to elucidate the role of DLL4 (delta-like canonical notch ligand 4) in regulation of glioma stemness, particularly in the context of its relationship to MMP14. We detected that TMZ treatment promotes nuclear translocation of MMP14 followed by extracellular release of DLL4. DLL4 in turn stimulates cleavage of Notch3, its nuclear translocation and induction of sphering capacity and stemness.

MicroRNA-451 Inhibits Migration of Glioblastoma while Making It More Susceptible to Conventional Therapy

Malignant glioblastoma (GBM, glioma) is the most common and aggressive primary adult brain tumor. The prognosis of GBM patients remains poor, despite surgery, radiation and chemotherapy. The major obstacles for successful remedy are invasiveness and therapy resistance of GBM cells. Invasive glioma cells leave primary tumor core and infiltrate surrounding normal brain leading to inevitable recurrence, even after surgical resection, radiation and chemotherapy. Therapy resistance allowing for selection of more aggressive and resistant sub-populations including GBM stem-like cells (GSCs) upon treatment is another serious impediment to successful treatment. Through their regulation of multiple genes, microRNAs can orchestrate complex programs of gene expression and act as master regulators of cellular processes. MicroRNA-based therapeutics could thus impact broad cellular programs, leading to inhibition of invasion and sensitization to radio/chemotherapy. Our data show that miR-451 attenuates glioma cell migration in vitro and invasion in vivo. In addition, we have found that miR-451 sensitizes glioma cells to conventional chemo- and radio-therapy. Our data also show that miR-451 is regulated in vivo by AMPK pathway and that AMPK/miR-451 loop has the ability to switch between proliferative and migratory pattern of glioma cells behavior. We therefore postulate that AMPK/miR-451 negative reciprocal feedback loop allows GBM cells/GSCs to adapt to tumor “ecosystem” by metabolic and behavioral flexibility, and that disruption of such a loop reduces invasiveness and diminishes therapy resistance.

Radiation Increases Functional KCa3.1 Expression and Invasiveness in Glioblastoma

Glioblastoma (GBM) is a deadly brain tumor, with fast recurrence even after surgical intervention, radio- and chemotherapies. One of the reasons for relapse is the early invasion of surrounding brain parenchyma by GBM, rendering tumor eradication difficult. Recent studies demonstrate that, in addition to eliminate possible residual tumoral cells after surgery, radiation stimulates the infiltrative behavior of GBM cells. The intermediate conductance of Ca²⁺-activated potassium channels (KCa3.1) play an important role in regulating the migration of GBM. Here, we show that high dose radiation of patient-derived GBM cells increases their invasion, and induces the transcription of key genes related to these functions, including the IL-4/IL-4R pair. In addition, we demonstrate that radiation increases the expression of KCa3.1 channels, and that their pharmacological inhibition counteracts the pro-invasive phenotype induced by radiation in tumor cells. Our data describe a possible approach to treat tumor resistance that follows radiation therapy in GBM patients.

Inhibition of Radiation and Temozolomide-Induced Invadopodia Activity in Glioma Cells Using FDA-Approved Drugs

The most common primary central nervous system tumor in adults is the glioblastoma multiforme (GBM). The highly invasive nature of GBM cells is a significant factor resulting in the inevitable tumor recurrence and poor patient prognosis. Tumor cells utilize structures known as invadopodia to faciliate their invasive phenotype. In this study, utilizing an array of techniques, including gelatin matrix degradation assays, we show that GBM cell lines can form functional gelatin matrix degrading invadopodia and secrete matrix metalloproteinase 2 (MMP-2), a known invadopodia-associated matrix-degrading enzyme. Furthermore, these cellular activities were augmented in cells that survived radiotherapy and temozolomide treatment, indicating that surviving cells may possess a more invasive phenotype posttherapy. We performed a screen of FDA-approved agents not previously used for treating GBM patients with the aim of investigating their "anti-invadopodia" and cytotoxic effects in GBM cell lines and identified a number that reduced cell viability, as well as agents which also reduced invadopodia activity. Importantly, two of these, pacilitaxel and vinorelbine tartrate, reduced radiation/temozolomide-induced invadopodia activity. Our data demonstrate the value of testing previously approved drugs (repurposing) as potential adjuvant agents for the treatment of GBM patients to reduce invadopodia activity, inhibit GBM cell invasion, and potentially improve patient outcome.

Bevacizumab and radiotherapy for the treatment of glioblastoma: brothers in arms or unholy alliance?

Glioblastoma (GBM) represents the most frequent primary brain tumor in adults and carries a dismal prognosis despite aggressive, multimodal treatment regimens involving maximal resection, radiochemotherapy, and maintenance chemotherapy. Histologically, GBMs are characterized by a high degree of VEGF-mediated vascular proliferation. In consequence, new targeted anti-angiogenic therapies, such as the monoclonal anti-VEGF-A antibody bevacizumab, have proven effective in attenuating tumor (neo)angiogenesis and were shown to possess therapeutic activity in several phase II trials. However, the role of bevacizumab in the context of multimodal therapy approaches appears to be rather complex. This review will give insights into current concepts, limitations, and controversies regarding the molecular mechanisms and the clinical benefits of bevacizumab treatment in combination with radio(chemo)therapy - particularly in face of the results of recent phase III trials, which failed to demonstrate convincing improvements in overall survival (OS).

The metalloprotease-disintegrin ADAM8 contributes to temozolomide chemoresistance and enhanced invasiveness of human glioblastoma cells

BACKGROUND

Despite multimodal treatment, glioblastoma (GBM) therapy with temozolomide (TMZ) remains inefficient due to chemoresistance. Matrix metalloproteinase (MMP) and a disintegrin and metalloprotease (ADAM), increased in GBM, could contribute to chemoresistance and TMZ-induced recurrence of glioblastoma.

METHODS

TMZ inducibility of metalloproteases was determined in GBM cell lines, primary GBM cells, and tissues from GBM and recurrent GBM. TMZ sensitivity and invasiveness of GBM cells were assessed in the presence of the metalloprotease inhibitors batimastat (BB-94) and marimastat (BB-2516). Metalloprotease-dependent effects of TMZ on mitochondria and pAkt/phosphatidylinositol-3 kinase (PI3K) and phosphorylated extracellular signal-regulated kinase 1/2 (pERK1/2) pathways were analyzed by fluorescence activated cell sorting, morphometry, and immunoblotting. Invasiveness of GBM cells was determined by Matrigel invasion assays. Potential metalloprotease substrates were identified by proteomics and tested for invasion using blocking antibodies.

RESULTS

TMZ induces expression of MMP-1, -9, -14, and ADAM8 in GBM cells and in recurrent GBM tissues. BB-94, but not BB-2516 (ADAM8-sparing) increased TMZ sensitivity of TMZ-resistant and -nonresistant GBM cells with different O(6)-methylguanine-DNA methyltransferase states, suggesting that ADAM8 mediates chemoresistance, which was confirmed by ADAM8 knockdown, ADAM8 overexpression, or pharmacological inhibition of ADAM8. Levels of pAkt and pERK1/2 were increased in GBM cells and correlated with ADAM8 expression, cell survival, and invasiveness. Soluble hepatocyte growth factor (HGF) R/c-met and CD44 were identified as metalloprotease substrates in TMZ-treated GBM cells. Blocking of HGF R/c-met prevented TMZ-induced invasiveness.

CONCLUSIONS

ADAM8 causes TMZ resistance in GBM cells by enhancing pAkt/PI3K, pERK1/2, and cleavage of CD44 and HGF R/c-met. Specific ADAM8 inhibition can optimize TMZ chemotherapy of GBM in order to prevent formation of recurrent GBM in patients.

Effect of Concomitant Radiochemotherapy on Invasion Potential of Glioblastoma

Glioblastoma (GBM) is the most common primary brain tumor in adults with inevitable recurrence after oncotherapy. The insufficient effect of "gold standard" temozolomide-based concomitant radiochemotherapy may be due to the inability to prevent tumor cell invasion. Peritumoral infiltration depends mainly on the interaction between extracellular matrix (ECM) components and cell membrane receptors. Changes in invasive behaviour after oncotherapy can be evaluated at the molecular level by determining the RNA expression and protein levels of the invasion-related ECM components. The expression of nineteen ECM molecules was determined at both RNA and protein levels in thirty-one GBM samples. Fifteen GBM samples originated from the first surgical procedure on patients before oncotherapy, and sixteen GBM samples were collected at the second surgery due to local recurrence after concomitant chemoirradiation. RNA expressions were measured with qRT-PCR, and protein levels were determined by quantitative analysis of Western blots. Only MMP-9 RNA transcript level was reduced (p < 0.05) whereas at protein level, eight molecules showed changes concordant with RNA expression with significant decrease in brevican only. The results suggest that concomitant radiochemotherapy does not have sufficient impact on the expression of invasion-related ECM components of glioblastoma, oncotherapy does not significantly affect its invasive behavior. To avoid the spread of tumors into the brain parenchyma, supplementation of antiproliferative treatment with anti-invasive agents may be worth consideration in oncotherapy for glioblastoma.

MT1-MMP silencing by an shRNA-armed glioma-targeted conditionally replicative adenovirus (CRAd) improves its anti-glioma efficacy in vitro and in vivo

MMP14 (MT1-MMP) is a cell membrane-associated proteinase of the extracellular matrix, whose biological roles vary from angiogenesis to cell proliferation and survival. We recently found a direct correlation between MMP14 expression levels in brain tumors of glioma patients and the disease progression. By using gene silencing as an experimental approach we found that MMP14 knockdown decreases production of pro-angiogenic factors such as VEGF and IL8 and thereby suppresses angiogenesis in glioma tumors. Although the clinical relevance of MMP14 down-regulation and its possible implications for glioma therapy in humans remain unclear, we observed a significant improvement in animal survival upon down-regulation of MMP14 in murine intracranial glioma xenografts infected with MMP14 shRNA-expressing CRAd. We further found that down-regulation of MMP14 in gliomas by combinational treatment with CRAd-S-5/3 and Marimastat, a chemical inhibitor of metalloproteinases, augments suppression of pro-angiogenic factors, caused by the replication-competent adenovirus. We also demonstrated that delivery of MMP14-targeting shRNA by a fiber-modified adenoviral vector to the glioma cells effectively suppresses their proliferation in vitro and in vivo. Thus our data indicate that inhibition of MMP14 expression in tumors in combination with glioma virotherapy could be effectively utilized to suppress angiogenesis and neovascularization of glioma tumors by decreasing production of pro-angiogenic factors.

The serotonin transporter gene polymorphism is associated with the susceptibility and the pain severity in idiopathic trigeminal neuralgia patients

BACKGROUND

To investigate the possible association between the serotonin transporter gene (5-HTTLPR) and rs 25531 polymorphism and the susceptibility and the pain severity in Trigeminal Neuralgia patients.

METHODS

A total of 244 TN patients and 280 age and sex matched healthy volunteer were recruited. 5-HTTLPR and rs 25531 genotyping were performed. All patients received the carbamazepine treatment and the treatment response was evaluated at 6 months.

RESULTS

The genotype distribution of 5-HTTLPR between TN patients and controls were significantly different. The TN Patients had a higher prevalence of short-short genotype than controls. The short-short genotype carriers are also significantly associated with higher pain severity and poorer carbamazepine treatment response compared to the long-long genotype carriers. In contrast, the rs 25531 polymorphism was not associated with the susceptibility to TN, neither with the pain severity and the treat response to carbamazepine.

CONCLUSION

The 5-HTTLPR polymorphism is associated with the susceptibility to TN and pain severity of TN.

Downregulation of ROCK2 through nanocomplex sensitizes the cytotoxic effect of temozolomide in U251 glioma cells

OBJECTIVE

Rho-associated coiled-coil kinase 2 (ROCK2) is an attractive therapeutic target because it is overexpressed in many malignancies, including glioma. Therefore, we designed the current study to determine whether the downregulation of ROCK2 would sensitize the cytotoxic effect of temozolomide (TMZ) in U251 cells.

METHODS

Glycol-polyethyleneimine (PEG-PEI) was used to deliver siROCK2 to U251 cells, and the physical characteristics of the PEG-PEI/siROCK2 complex (referred to as the siROCK2 complex) were investigated. The transfection efficiency and cell uptake were determined by flow cytometry (FCM) and confocal laser microscopy (CLSM), respectively. U251 cells were then treated with 100 μM TMZ, siROCK2 complexes or their combination. The apoptosis rate and cell migration were measured by FCM and wound-healing assay, respectively. The levels of Bax, Bcl-2, cleaved caspase-3, MMP-2, and MMP-9 were detected to analyze the degrees of apoptosis and migration.

RESULTS

Our results revealed that the characteristics of the siROCK2 complexes depended closely on the N/P ratios. PEG-PEI served as a good vector for siROCK2 and exhibited low cytotoxicity toward U251 cells. The CLSM assay showed that the siROCK2 complexes were successfully uptaken and that both the protein and mRNA levels of ROCK2 were significantly suppressed. Furthermore, the combination treatment induced a higher apoptosis rate and markedly increased the gap distance of U251 cells in the wound-healing assay. Levels of the proapoptotic proteins Bax and cleaved caspase-3 were significantly increased, whereas levels of the antiapoptotic protein Bcl-2 and the migration-related proteins MMP-2 and MMP-9 were significantly reduced by the combination treatment compared with either treatment alone.

CONCLUSIONS

In conclusion, our results demonstrate that the combination of TMZ and siROCK2 effectively induces apoptosis and inhibits the migration of U251 cells. Therefore, the combination of TMZ and siROCK2 complex is a potential therapeutic approach for human glioma.

Invasion as target for therapy of glioblastoma multiforme

The survival of cancer patients suffering from glioblastoma multiforme is limited to just a few months even after treatment with the most advanced techniques. The indefinable borders of glioblastoma cell infiltration into the surrounding healthy tissue prevent complete surgical removal. In addition, genetic mutations, epigenetic modifications and microenvironmental heterogeneity cause resistance to radio- and chemotherapy altogether resulting in a hardly to overcome therapeutic scenario. Therefore, the development of efficient therapeutic strategies to combat these tumors requires a better knowledge of genetic and proteomic alterations as well as the infiltrative behavior of glioblastoma cells and how this can be targeted. Among many cell surface receptors, members of the integrin family are known to regulate glioblastoma cell invasion in concert with extracellular matrix degrading proteases. While preclinical and early clinical trials suggested specific integrin targeting as a promising therapeutic approach, clinical trials failed to deliver improved cure rates up to now. Little is known about glioblastoma cell motility, but switches in invasion modes and adaption to specific microenvironmental cues as a consequence of treatment may maintain tumor cell resistance to therapy. Thus, understanding the molecular basis of integrin and protease function for glioblastoma cell invasion in the context of radiochemotherapy is a pressing issue and may be beneficial for the design of efficient therapeutic approaches. This review article summarizes the latest findings on integrins and extracellular matrix in glioblastoma and adds some perspective thoughts on how this knowledge might be exploited for optimized multimodal therapy approaches.

Inhibition of MMP14 potentiates the therapeutic effect of temozolomide and radiation in gliomas

Metalloproteinases are membrane-bound proteins that play a role in the cellular responses to antiglioma therapy. Previously, it has been shown that treatment of glioma cells with temozolomide (TMZ) and radiation (XRT) induces the expression of metalloproteinase 14 (MMP14). To investigate the role of MMP14 in gliomagenesis, we used several chemical inhibitors which affect MMP14 expression. Of all the inhibitors tested, we found that Marimastat not only inhibits the expression of MMP14 in U87 and U251 glioma cells, but also induces cell cycle arrest. To determine the relationship between MMP14 inhibition and alteration of the cell cycle, we used an RNAi technique. Genetic knockdown of MMP14 in U87 and U251 glioma cells induced G₂/M arrest and decreased proliferation. Mechanistically, we show that TMZ and XRT regulated expression of MMP14 in clinical samples and in vitro models through downregulation of microRNA374. In vivo genetic knockdown of MMP14 significantly decreased tumor growth of glioma xenografts and improved survival of glioma-bearing mice. Moreover, the combination of MMP14 silencing with TMZ and XRT significantly improved the survival of glioma-bearing mice compared to a single modality treatment group. Therefore, we show that the inhibition of MMP14 sensitizes tumor cells to TMZ and XRT and could be used as a future strategy for antiglioma therapy.

Glioblastoma remains an incurable form of brain cancer. In this manuscript, we show that inhibition of MMP14 can potentiate the efficacy of current standard of care which includes chemo- and radiotherapy.

MMP-2 suppression abrogates irradiation-induced microtubule formation in endothelial cells by inhibiting αvβ3-mediated SDF-1/CXCR4 signaling

The majority of glioblastoma multiforme (GBM) tumors recur after radiation (IR) treatment due to increased angiogenesis and IR-induced signaling events in endothelial cells (ECs) that are involved in tumor neovascularization; however, these signaling events have yet to be well characterized. In the present study, we observed that IR (8 Gy) significantly elevated MMP-2 expression and gelatinolytic activity in 4910 and 5310 human GBM xenograft cells. In addition, ECs treated with tumor-conditioned media (CM) obtained from IR-treated 4910 and 5310 cells showed increased microtubule formation. In view of this finding, we investigated the possible anti-angiogenic effects of MMP-2 downregulation using siRNA (pM.si) in IR-treated cells. We also determined the effect of CM obtained from mock, pSV (scrambled vector) and pMMP-2.si on endothelial cell growth and vessel formation. pM.si-CM-treated ECs showed inhibited IR-CM-induced SDF-1, CXCR4, phospho-PI3K and phospho-AKT and αvβ3 expression levels. In vitro angiogenesis assays also showed that the pM.si+IR decreased IR-induced vessel formation in ECs. Immunofluorescence and immunoprecipitation experiments indicated the abrogation of αvβ3-SDF-1 interaction in pM.si-CM-treated ECs when compared to mock or pSV treatments. External supplementation of either rhMMP-2 or rhSDF-1 counteracted and noticeably reversed pM.si-inhibited SDF-1, CXCR4, phospho-PI3K and phospho-AKT expression levels and angiogenesis, thereby confirming the role of MMP-2 in the regulation of αvβ3-mediated SDF-1/CXCR4 signaling. In addition to the in vitro results, the in vivo mouse dorsal air sac model also showed reduced angiogenesis after injection of pM.si alone or in combination with IR-treated xenograft cells. In contrast, injection of mock or pSV-treated cells resulted in robust formation of characteristic neovascularization. Collectively, our data demonstrate the role of MMP-2 in the regulation of SDF-1/CXCR4 signaling-mediated angiogenesis in ECs and show the anti-angiogenic efficacy of combining MMP-2 downregulation and IR when treating patients with GBM in the future.

Notch signaling regulates tumor-induced angiogenesis in SPARC-overexpressed neuroblastoma

Despite existing aggressive treatment modalities, the prognosis for advanced stage neuroblastoma remains poor with significant long-term illness in disease survivors. Advance stage disease features are associated with tumor vascularity, and as such, angiogenesis inhibitors may prove useful along with current therapies. The matricellular protein, secreted protein acidic and rich in cysteine (SPARC), is known to inhibit proliferation and migration of endothelial cells stimulated by growth factors. Here, we sought to determine the effect of SPARC on neuroblastoma tumor cell-induced angiogenesis and to decipher the molecular mechanisms involved in angiogenesis inhibition. Conditioned medium from SPARC-overexpressed neuroblastoma cells (pSPARC-CM) inhibited endothelial tube formation, cell proliferation, induced programmed cell death and suppressed expression of pro-angiogenic molecules such as VEGF, FGF, PDGF, and MMP-9 in endothelial cells. Further analyses revealed that pSPARC-CM-suppressed expression of growth factors was mediated by inhibition of the Notch signaling pathway, and cells cultured on conditioned medium from tumor cells that overexpress both Notch intracellular domain (NICD-CM) and SPARC resumed the pSPARC-CM-suppressed capillary tube formation and growth factor expression in vitro. Further, SPARC overexpression in neuroblastoma cells inhibited neo-vascularization in vivo in a mouse dorsal air sac model. Furthermore, SPARC overexpression-induced endothelial cell death was observed by co-localization studies with TUNEL assay and an endothelial marker, CD31, in xenograft tumor sections from SPARC-overexpressed mice. Our data collectively suggest that SPARC overexpression induces endothelial cell apoptosis and inhibits angiogenesis both in vitro and in vivo.

Concanavalin-A-induced autophagy biomarkers requires membrane type-1 matrix metalloproteinase intracellular signaling in glioblastoma cells

Pre-clinical trials for cancer therapeutics support the anti-neoplastic properties of the lectin from Canavalia ensiformis (Concanavalin-A, ConA) in targeting apoptosis and autophagy in a variety of cancer cells. Given that membrane type-1 matrix metalloproteinase (MT1-MMP), a plasma membrane-anchored matrix metalloproteinase, is a glycoprotein strongly expressed in radioresistant and chemoresistant glioblastoma that mediates pro-apoptotic signalling in brain cancer cells, we investigated whether MT1-MMP could also signal autophagy. Among the four lectins tested, we found that the mannopyranoside/glucopyranoside-binding ConA, which is also well documented to trigger MT1-MMP expression, increases autophagic acidic vacuoles formation as demonstrated by Acridine Orange cell staining. Although siRNA-mediated MT1-MMP gene silencing effectively reversed ConA-induced autophagy, inhibition of the MT1-MMP extracellular catalytic function with Actinonin or Ilomastat did not. Conversely, direct overexpression of the recombinant Wt-MT1-MMP protein triggered proMMP-2 activation and green fluorescent protein-microtubule-associated protein light chain 3 puncta indicative of autophagosomes formation, while deletion of MT1-MMP's cytoplasmic domain disabled such autophagy induction. ConA-treated U87 cells also showed an upregulation of BNIP3 and of autophagy-related gene members autophagy-related protein 3, autophagy-related protein 12 and autophagy-related protein 16-like 1, where respective inductions were reversed when MT1-MMP gene expression was silenced. Altogether, we provide molecular evidence supporting the pro-autophagic mechanism of action of ConA in glioblastoma cells. We also highlight new signal transduction functions of MT1-MMP within apoptotic and autophagic pathways that often characterize cancer cell responses to chemotherapeutic drugs.

A complete compilation of matrix metalloproteinase expression in human malignant gliomas

Glioblastomas are characterized by an aggressive local growth pattern, a marked degree of invasiveness and poor prognosis. Tumor invasiveness is facilitated by the increased activity of proteolytic enzymes which are involved in destruction of the extracellular matrix of the surrounding healthy brain tissue. Elevated levels of matrix metalloproteinases (MMPs) were found in glioblastoma (GBM) cell-lines, as well as in GBM biopsies as compared with low-grade astrocytoma (LGA) and normal brain samples, indicating a role in malignant progression. A careful review of the available literature revealed that both the expression and role of several of the 23 human MMP proteins is controversely discussed and for some there are no data available at all. We therefore screened a panel of 15 LGA and 15 GBM biopsy samples for those MMPs for which there is either no, very limited or even contradictory data available. Hence, this is the first complete compilation of the expression pattern of all 23 human MMPs in astrocytic tumors. This study will support a better understanding of the specific expression patterns and interaction of proteolytic enzymes in malignant human glioma and may provide additional starting points for targeted patient therapy.

Comparative expression pattern of Matrix-Metalloproteinases in human glioblastoma cell-lines and primary cultures

Background

Glioblastomas (GBM), the most frequent malignant brain tumors in adults, are characterized by an aggressive local growth pattern and highly invasive tumor cells. This invasion is facilitated by expression of matrix metalloproteinases (MMPs), a family of zinc-dependent endopeptidases. They mediate the degradation of protein components of the extracellular matrix. Twenty-three family members are known. Elevated levels of several of them have been reported in GBM. GBM cell-lines are used for in vitro studies of cell migration and invasion. Therefore, it is essential to know their MMP expression patterns. Only limited data for some of the cell-lines are published, yet. To fill the gaps in our knowledge would help to choose suitable model systems for analysis of regulation and function of MMPs during GBM tumorigenesis, cell migration and invasion.

Findings

We analysed MMP-1, -8, -9, -10, -11, -13, -17, -19, -20, -21, -23, -24, -26, -27, and MMP-28 expression in seven GBM cell-lines (SNB-19, GaMG, U251, U87, U373, U343, U138) and in four primary cell cultures by semiquantitative RT-PCR, followed changes in the MMP expression pattern with increasing passages of cell culture and examined the influence of TNF-α and TGF-β1 stimulation on the expression of selected MMPs in U251 and U373 cells.

MMP-13, -17, -19 and -24 were expressed by all analyzed cell-lines, whereas MMP-20 and MMP-21 were not expressed by any of them. The other MMPs showed variable expression, which was dependent on passage number. Primary cells displayed a similar MMP-expression pattern as the cell-lines. In U251 and U373 cells expression of MMP-9 and MMP-19 was stimulated by TNF-α. MMP-1 mRNA expression was significantly increased in U373 cells, but not in U251 cells by this cytokine. Whereas TGF-β1 had no impact on MMP expression in U251 cells, it significantly induced MMP-11 and MMP-24 expression in U373 cells.

Conclusions

Literature-data and our own results suggest that the expression pattern of MMPs is highly variable, dependent on the cell-line and the cell-culture conditions used and that also regulation of MMP expression by cytokines is cell-line dependent. This is of high impact for the transfer of cell-culture experiments to clinical implementation.

Effects of irradiation on tumor cell survival, invasion and angiogenesis

Ionizing irradiation is a widely applied therapeutic method for the majority of solid malignant neoplasms, including brain tumors where, depending on localization, this might often be the only feasible primary intervention.Without doubt, it has been proved to be a fundamental tool available in the battlefield against cancer, offering a clear survival benefit in most cases. However, numerous studies have associated tumor irradiation with enhanced aggressive phenotype of the remaining cancer cells. A cell population manages to survive after the exposure, either because it receives sublethal doses and/or because it successfully utilizes the repair mechanisms. The biology of irradiated cells is altered leading to up-regulation of genes that favor cell survival, invasion and angiogenesis. In addition, hypoxia within the tumor mass limits the cytotoxicity of irradiation, whereas irradiation itself may worsen hypoxic conditions, which also contribute to the generation of resistant cells. Activation of cell surface receptors, such as the epidermal growth factor receptor, utilization of signaling pathways, and over-expression of cytokines, proteases and growth factors, for example the matrix metalloproteinases and vascular endothelial growth factor, protect tumor and non-tumor cells from apoptosis, increase their ability to invade to adjacent or distant areas, and trigger angiogenesis. This review will try to unfold the various molecular events and interactions that control tumor cell survival, invasion and angiogenesis and which are elicited or influenced by irradiation of the tumor mass, and to emphasize the importance of combining irradiation therapy with molecular targeting.

Engineering of clinical glioma treatment: prediction of pro-invasive molecular events in treated gliomas

The diffusely infiltrative nature of malignant gliomas is the main obstacle to successful treatment approaches. Advanced simulation models of the in vivo response to therapy conditions are expected to improve malignant glioma treatment substantially. In parallel experiments, human malignant glioma cells underwent either radiation or chemotherapy treatment (chemotreatment) with temozolomide alone, or combined chemoradiation. Cells were treated according to diverse, clinically relevant, therapeutic algorithms. Quantitative 'real-time' polymerase chain reaction (PCR) measurements were performed for target genes, namely vascular endothelial growth factor, p53, and cyclooxygenase-2, which allow a comparative evaluation of pro-invasive molecular events in treated gliomas. The proof-of-principle study simulated variable intratumoural regional conditions. Pro-invasive molecular patterns were strongly dependent on the treatment algorithm, cellular density, and drug delivery. The highest pro-invasive potential was demonstrated for simulated peripheral regions under continued chemoradiation. This result strongly supports the clinical observations of increased aggressiveness and relatively poor response to second-line therapies in post-operatively chemoradiation-treated malignant gliomas at the time of relapse. Individualized and potentially the most effective treatment algorithms can be designed using established gene expression patterns applied on primary cell cultures obtained from individual patients. Individual drug toxicity and response to anti-cancer therapy can be predicted.

Up-regulation of vimentin expression in low-density malignant glioma cells as immediate and late effects under irradiation and temozolomide treatment

Nervous system tumors are one of the leading causes of cancer related death. Specific mechanisms facilitating the invasive behavior of gliomas remain obscure. Advanced simulation models of the in vivo response to therapy conditions should potentially improve malignant glioma treatment. Expressional profiling of vimentin--one of reliable pro-invasive tumor makers--in those simulation models was the goal of this study, in order to estimate a pro-invasive response of surviving malignant glioma cells under clinically relevant therapeutic conditions. Human U87-MG malignant glioma cells were used. These cells are characterized by the wild p53-phenotype, which is relevant for the majority of primary malignant glioblastomas. Experimental design foresaw the cells to undergo either irradiation or chemo-treatment with temozolomide alone, or combined treatment. Expression profiling of vimentin was performed by quantitative "Real-Time"-PCR under all treatment conditions simulating diverse tumor regions. Here we demonstrated that vimentin expression patterns in human malignant glioma cells strongly depend on cellular density, algorithms of drug delivery and chemo/radio treatment. Substantial differences were recognized between immediate and late therapy effects. Significant increase in vimentin expression levels was detected particularly in low-density cell cultures under durable treatment with constant concentration levels of temezolomide. Simulation of variable intratumoral regional conditions (central intratumoral regions vs. disseminated malignant cells in peripheral regions) demonstrated differential response of vimentin expression in malignant glioma cell cultures treated under clinically relevant conditions. Slight ebbing of expression levels as late effects of the treatment in confluent cultures may correspond to necrotic processes clinically observed in central intratumoral regions. Contrary, in disseminated malignant cells of peripheral regions therapy resulted in vimentin-inducing effects. This is in agreement with the clinical observations of an increased aggressiveness and malignancy grade of post-operatively chemo/radio-treated malignant gliomas.

Cell cycle checkpoints: the role and evaluation for early diagnosis of senescence, cardiovascular, cancer, and neurodegenerative diseases

Maintenance of genomic integrity is critical for prevention of a wide variety of adverse cellular effects including apoptosis, cellular senescence, and malignant cell transformation. Under stress conditions and even during an unperturbed cell cycle, checkpoint proteins play the key role in genome maintenance by and mediating cellular response to DNA damage, and represent an essential part of the "cellular stress response proteome". Intact checkpoint signal transduction cascades check the presence of genome damage, trigger cell cycle arrest, and forward the information to the protein core of cell cycle machinery, replication apparatus, repair, and/or apoptotic protein cores. Genetic checkpoint defects lead to syndromes that demonstrate chromosomal instability, increased sensitivity to genotoxic stress, tissue degeneration, developmental retardation, premature aging, and cancer predisposition that is most extensively studied for the ATM-checkpoint mutated in Ataxia telangiectasia. Tissue specific epigenetic control over the function of cell cycle checkpoints can be, further, misregulated by aberrant DNA methylation status. The consequent checkpoint dysregulation may result in tissue specific degenerative processes such as degeneration and calcification of heart aortic valves, diabetic cardiomyopathy, hyperhomocysteinemic cerebrovascular, peripheral vascular and coronary heart diseases, neurodegenerative disorders (Alzheimer and Parkinson diseases, amyotrophic lateral sclerosis, glaucoma), and accelerated aging frequently accompanied with cancer. This review focuses on the checkpoints shown to be crucial for unperturbed cell cycle regulation, dysregulation of which might be considered as a potential molecular marker for early diagnosis of and therapy efficiency in neurodegenerative, cardiovascular and cancer diseases. An application of the most potent detection technologies such as "Disease Proteomics and Transcriptomics" also considered here, allows a most specific selection of diagnostic markers.

Non-sufficient cell cycle control as possible clue for the resistance of human malignant glioma cells to clinically relevant treatment conditions

OBJECTIVES

Human gliomas have a catastrophic prognosis with a median survival in the range of one year even after therapeutic treatment. Relatively high resistance towards apoptotic stimuli is the characteristic feature of malignant gliomas. Since cell cycle control has been shown to be the key mechanism controlling both apoptosis and proliferation, this study focuses on DNA damage analysis and protein expression patterns of essential cell cycle regulators P53 and P21waf1/cip1 in glioma under clinically relevant therapeutic conditions.

MATERIAL AND METHODS

U87MG cell line, characterised by wild p53-phenotype relevant for the majority of primary malignant glioblastomas, was used. Glioma cells underwent either irradiation or temozolomide treatment alone, or combined radio/chemo treatment. DNA damage was analysed by the "Comet Assay". Expression rates of target proteins were analysed using "Western-Blot" technique.

RESULTS AND CONCLUSIONS

"Comet Assay" demonstrated extensive DNA damage caused by temozolomide treatment alone and in combination with irradiation, correlating well with the low survival rate observed under these treatment conditions. In contrast, irradiation alone resulted in a relatively low DNA damage, correlating well with a high survival rate and indicating a poor therapeutic efficiency of irradiation alone. Unusually low up-regulation of P53 and P21waf1/cip1 expression patterns was produced by the hereby tested stressful conditions. A deficit in cell cycle control might be the clue to the high resistance of malignant glioma cells to established therapeutic approaches.