SPARC is a matricellular glycoprotein and a putative radioresistance-reversal-gene. We therefore explored the possibility of SPARC expression on medulloblastoma radiosensitivity in vitro and in vivo. The combined treatment of the SPARC and irradiation resulted in increased cell death when compared to cells treated with irradiation alone in vitro and in vivo. SPARC expression prior to irradiation suppressed checkpoints-1,-2 and p53 phosphorylation and DNA repair gene XRCC1. We also demonstrate that SPARC expression suppressed irradiation induced SOX-4 mediated DNA repair. These results provide evidence of the anti-tumor effect of combining SPARC with irradiation as a new therapeutic strategy for the treatment of medulloblastoma.
SPARC; SOX4; Medulloblastoma; Radiosensitization
Glioblastoma (GBM) is the most common and malignant primary adult brain cancer. Allelic deletion on chromosome 14q plays an important role in the pathogenesis of GBM, and this site was thought to harbor multiple tumor suppressor genes associated with GBM, a region that also encodes microRNA-203 (miR-203). In this study, we sought to identify the role of miR-203 as a tumor suppressor in the pathogenesis of GBM. We analyzed the miR-203 expression data of GBM patients in 10 normal and 495 tumor tissue samples derived from The Cancer Genome Atlas data set. Quantitative real-time PCR and in situ hybridization in 10 high-grade GBM and 10 low-grade anaplastic astrocytoma tumor samples showed decreased levels of miR-203 expression in anaplastic astrocytoma and GBM tissues and cell lines. Exogenous expression of miR-203 using a plasmid expressing miR-203 precursor (pmiR-203) suppressed glioma cell proliferation, migration, and invasion. We determined that one relevant target of miR-203 was Robo1, given that miR-203 expression decreased mRNA and protein levels as determined by RT-PCR and Western blot analysis. Moreover, cotransfection experiments using a luciferase-based transcription reporter assay have shown direct regulation of Robo1 by miR-203. We also show that Robo1 mediates miR-203 mediated antimigratory functions as up-regulation of Robo1 abrogates miR-203 mediated antimigratory effects. We also show that miR-203 expression suppressed ERK phosphorylation and MMP-9 expression in glioma cells. Furthermore, we demonstrate that miR-203 inhibits migration of the glioma cells by disrupting the Robo1/ERK/MMP-9 signaling axis. Taken together, these studies demonstrate that up-regulation of Robo1 in response to the decrease in miR-203 in glioma cells is responsible for glioma tumor cell migration and invasion.
glioma; miR-203; Robo1; cell migration; invasion
Dynamic cell interaction with ECM components has profound influence in cancer progression. SPARC is a component of the ECM, impairs the proliferation of different cell types and modulates tumor cell aggressive features. We previously reported that SPARC expression significantly impairs medulloblastoma tumor growth in vivo. In this study, we demonstrate that expression of SPARC inhibits medulloblastoma cell proliferation. MTT assay indicated a dose-dependent reduction in tumor cell proliferation in adenoviral mediated expression of SPARC full length cDNA (Ad-DsRed-SP) in D425 and UW228 cells. Flow cytometric analysis showed that Ad-DsRed-SP-infected cells accumulate in the G2/M phase of cell cycle. Further, immunoblot and immunoprecipation analyses revealed that SPARC induced G2/M cell cycle arrest was mediated through inhibition of the Cyclin-B-regulated signaling pathway involving p21 and Cdc2 expression. Additionally, expression of SPARC decreased STAT3 phosphorylation at Tyr-705; constitutively active STAT3 expression reversed SPARC induced G2/M arrest. Ad-DsRed-SP significantly inhibited the pre-established orthotopic tumor growth and tumor volume in nude-mice. Immunohistochemical analysis of tumor sections from mice treated with Ad-DsRed-SP showed decreased immunoreactivity for pSTAT3 and increased immunoreactivity for p21 compared to tumor section from mice treated with mock and Ad-DsRed. Taken together our studies further reveal that STAT3 plays a key role in SPARC induced G2/M arrest in medulloblastoma cells. These new findings provide a molecular basis for the mechanistic understanding of the effects of SPARC on medulloblastoma tumor cell proliferation.
SPARC; STAT3; Cell cycle; medulloblastoma
The matricellular glycoprotein Secreted Protein Acidic and Rich in Cysteine (SPARC) plays an important role in the regulation of cell adhesion and proliferation as well as in tumorigenesis and metastasis. Earlier, we reported that, in addition to its potent anti-angiogenic functions, SPARC also induces apoptosis in medulloblastoma cells, mediated by autophagy. We therefore sought to investigate the underlying molecular mechanism through which SPARC inhibits migration and invasion of Daoy medulloblastoma cells, both in vitro and in vivo. For this study, we used SPARC-overexpressing stable Daoy medulloblastoma cells. SPARC overexpression in Daoy medulloblastoma cells inhibited migration and invasion in vitro. Additionally, SPARC overexpression significantly suppressed the activity of Rho, Rac and Cdc42, which all regulate the actin cytoskeleton. This suppression was accompanied by an increase in the phosphorylation of Src at TYR-416, which led to a loss of actin stress fibers and focal contacts and a decrease in the phosphorylation level of cofilin. The reduced phosphorylation level of cofilin, which is indicative of receding Rho function, in turn led to inhibition of active Rho A. To confirm the role of SPARC in inhibition of migration and invasion of Daoy medulloblastoma cells, we transfected parental and SPARC-overexpressing Daoy cells with a plasmid vector carrying siRNA against SPARC. Transfection with SPARC siRNA reversed Src-mediated disruption of the cytoskeleton organization as well as dephosphorylation of cofilin and activation of Rho A. Taken together, these results establish SPARC as an effector of Src-induced cytoskeleton disruption in Daoy medulloblastoma cells, which subsequently led to decreased migration and invasion.
SPARC; Src; Migration; Invasion; Rho; Rac; Cdc42
Secreted Protein Acidic and Rich in Cysteine (SPARC) participate in the regulation of morphogenesis and cellular differentiation through its modulation of cell-matrix interactions. We previously reported that SPARC expression significantly impairs medulloblastoma tumor growth in vivo. In this study, we show that Adenoviral-mediated overexpression of SPARC cDNA (Ad-DsRed-SP) elevated the expression of the neuronal markers NeuN, Nestin, Neurofilament (NF) and MAP-2 in medulloblastoma cells and induced neuron like differentiation. SPARC overexpression decreased Signal Transducer and Activator of Transcription 3 (STAT3) phosphorylation; constitutive expression of STAT3 reversed SPARC-mediated expression of neuronal markers. We also show that Notch signaling is suppressed in the presence of SPARC, as well as the Notch effector basic helix-loop-helix (bHLH) transcription factor hairy and enhancer of split 1 (HES1). Notch signaling was found to be responsible for the decreased STAT3 phosphorylation in response to SPARC expression. Furthermore, expression of SPARC decreased the production of IL-6 and supplemented IL-6-abrogated, SPARC-mediated suppression of Notch signaling and expression of neuronal markers. Immunohistochemical analysis of tumor sections from mice treated with Ad-DsRed-SP showed increased immunoreactivity for the neuronal markers and a decrease in Notch1 expression and phosphorylation of STAT3. Taken together, our results suggest that SPARC induces expression of neuronal markers in medulloblastoma cells through its inhibitory effect on IL-6 regulated suppression of Notch pathway-mediated STAT3 signaling, thus giving further support to the potential use of SPARC as a therapeutic candidate for medulloblastoma treatment. Findings show that SPARC-induced neuronal differentiation can sensitize medulloblastoma cells for therapy.
SPARC; Notch1; STAT3; neuronal differentiation; NeuN
Matrix metalloproteinases (MMPs) are a family of proteinases known to play a role in cell migration. In the present study, we evaluated the role of MMP-2 on tropism of human cord blood derived stem cells (hUCBSCs) in a human medulloblastoma tumor model. Consequences of MMP-2 inhibition on stem cell tropism towards medulloblastoma were studied in terms of stem cell migration by using cell culture inserts, transwell chamber assay, western blotting for MMP-2 and migratory molecules, and immunohistochemistry. Conditioned medium from Daoy/D283 cells infected with adenoviral vector encoding MMP-2 siRNA (Ad-MMP-2 si) reduced stem cell migration as compared to conditioned medium from mock and scrambled vector (Ad-SV) infected cells. In addition, MMP-2 inhibition in the tumor cells decreased the expression of SDF1 in the tumor conditioned medium, which results in impaired SDF1/CXCR4 signaling leading to decreased stem cell tropism towards the tumor cells. We further show that MMP-2 inhibition in the tumor cells repressed stem cell tropism towards medulloblastoma tumors in vivo. In summary, we conclude that hUCBSCs can integrate into human medulloblastoma after local delivery and that MMP-2 expression by the tumor cells mediates this response through the SDF1/CXCR4 axis.
MMP-2; Medulloblastoma; Human umbilical cord blood stem cells; migration; tropism; SDF1; CXCR4
Prostate cancer is one of the most commonly diagnosed cancers and the second leading cause of cancer deaths in Americans. The high mortality rate is mainly attributed to the invasiveness and metastasis of advanced prostate cancer. Targeting the molecules involved in metastasis could be an effective mode of treatment for prostate cancer. In this study, the therapeutic potential of siRNA-mediated targeting of matrix metalloproteinase-9 (MMP-9), urokinase plasminogen activator receptor (uPAR), and cathepsin B (CB) in prostate cancer was carried out using single and bi-cistronic siRNA expressing constructs. Down regulation of MMP-9, uPAR and CB inhibited matrigel invasion, in vitro angiogenesis and wound healing migration ability of PC3 and DU145 prostate cancer cell lines. In addition, the siRNA treatments induced apoptosis in the tumor cells as determined by TUNEL and DNA laddering assays. An attempt to elucidate the apoptotic pathway showed the involvement of FAS-mediated activation of caspases-8 and -7. Further, mice with orthotropic prostate tumors treated with siRNA expressing vectors showed significant inhibition in tumor growth and migration. In conclusion, we report that the siRNA mediated knockdown of MMP-9, uPAR and CB inhibits invasiveness and migration of prostate cancer cells and leads to apoptosis both in vitro and in vivo.
RNAi; MMP-9; uPAR; Cathepsin; Prostate cancer; Apoptosis
Vascular endothelial growth factor (VEGF) is one of the most important angiogenic growth factors for tumor angiogenesis. Here, we sought to explore whether RNA interference (RNAi) targeting Matrix metalloproteinase-2 (MMP-2) could disrupt VEGF mediated angiogenesis in lung cancer. MMP-2 siRNA inhibited lung cancer cell-induced tube formation of endothelial cells in vitro; addition of recombinant human-MMP-2 restored angiogenesis. MMP-2 transcriptional suppression decreased VEGF, PI3K protein levels, and AKT phosphorylation in lung cancer cells. In addition, MMP-2 suppression decreased Hypoxia inducible factor-1α (HIF-1α), a transcription factor for VEGF, as determined by Electrophoretic mobility shift assay (EMSA). We also show that MMP-2 suppression disrupted phosphatidylinositol 3-kinase (PI3K) dependent VEGF expression; ectopic expression of myr-AKT restored VEGF inhibition. Further, MMP-2 suppression decreased the interaction of integrin-αVβ3 and MMP-2 as confirmed by immunoprecipitation analyses. Studies with either function blocking integrin-αVβ3 antibody or MMP-2 specific inhibitor (ARP-100) indicate that suppression of MMP-2 decreased integrin-αVβ3-mediated induction of PI3K/AKT leading to decreased VEGF expression. Moreover, A549 xenograft tissue sections from mice that treated with MMP-2 siRNA showed reduced expression of VEGF, and the angiogenic marker, Factor-VIII. The inhibition of tumor angiogenesis in MMP-2 suppressed tumor sections was associated with decreased co-localization of integrin-αVβ3 and MMP-2. In summary, these data provide new insights into the mechanisms underlying MMP-2-mediated VEGF expression in lung tumor angiogenesis.
MMP-2; siRNA; VEGF; angiogenesis; lung cancer
siRNA mediated transcriptional knockdown of urokinase plasminogen activator receptor (uPAR) and matrix metalloproteinase-9 (MMP-9), alone or in combination, inhibits uPAR and/or MMP-9 expression and induces apoptosis in the human glioblastoma xenograft cell lines 4910 and 5310. siRNA against uPAR (pU-Si), MMP-9 (pM-Si), or both (pUM-Si) induced apoptosis and was associated with the cleavage of caspases-8, -3 and PARP. Furthermore, protein levels of the Fas receptor (APO-1/CD-95) were increased following transcriptional inactivation of uPAR and/or MMP-9. In addition, Fas siRNA against the Fas death receptor blocked apoptosis induced by pU-Si, pM-Si or pUM-Si, thereby indicating the role for Fas signaling in pU-Si, pM-Si or pUM-Si-mediated apoptotic cell death of human glioma xenograft cells. Thus, transcriptional inactivation of uPAR and/or MMP-9 enhanced localization of Fas death receptor, Fas-associated death domain-containing protein (FADD), and procaspase-8 into lipid rafts. Additionally, disruption of lipid rafts with methyl beta cyclodextrin (MβCD) prevented Fas clustering and pU-Si, pM-Si or pUM-Si-induced apoptosis, which is indicative of co-clustering of Fas death receptor into lipid rafts in glioblastoma xenograft cells lines 4910 and 5310. These data indicate the crucial role of the clusters of apoptotic signaling molecule-enriched rafts in programmed cell death, acting as concentrators of death receptors and downstream signaling molecules, and as the linchpin from which a potent death signal is launched in uPAR and/or MMP-9 down regulated cells.
uPAR; MMP-9; siRNA; Lipid raft; apoptosis; Fas
Abrogation of apoptosis for prolonged cell survival is essential in cancer progression. In our previous studies, we showed the MMP-2 downregulation induced apoptosis in cancer cell lines. Here, we attempt to investigate the exact molecular mechanism of how MMP-2 depletion leads to apoptosis in glioma xenograft cell lines.
MMP-2 transcriptional suppression by MMP-2siRNA (pM) induces apoptosis associated with PARP, caspase-8 and -3 cleavage in human glioma xenograft cells 4910 and 5310. Western blotting and cytokine array showed significant decrease in the cellular and secreted levels of TNF-α with concomitant reduction in TNFR1, TRADD, TRAF2, RIP, IKKβ and pIκBα expression levels resulting in inhibition of p65 phosphorylation and nuclear translocation in pM-treated cells when compared to mock and pSV controls. In addition MMP-2 suppression led to elevated Fas-L, Fas and FADD expression levels along with increased p38 and JNK phosphorylation. The JNK-activity assay showed prolonged JNK activation in pM-transfected cells. Specific inhibition of p38 with SB203580 did not show any effect whereas inhibition of JNK phosphorylation with SP600125 notably reversed pM-induced cleavage of PARP, caspase-8 and -3, demonstrating a significant role of JNK in pM-induced cell death. Supplementation of rhMMP-2 counteracted the effect of pM by remarkably elevating TNF-α, TRADD, IKKβ and pIκBα expression and decreasing FADD, Fas-L, and phospho-JNK levels. The EMSA analysis indicated significant reversal of pM-inhibited NF-κB activity by rhMMP-2 treatment which rescued cells from pM-induced cell death. In vivo studies indicated that pM treatment diminished intracranial tumor growth and the immuno histochemical analysis showed decreased phospho-p65 and enhanced phospho-JNK levels that correlated with increased TUNEL-positive apoptotic cells in pM-treated tumor sections.
In summary, our study implies a role of MMP-2 in the regulation of TNF-α mediated constitutive NF-κB activation and Fas-mediated JNK mediated apoptosis in glioma xenograft cells in vitro and in vivo.
Medulloblastoma and neuroblastoma belong to a group of neoplasms designated as primitive neuroectodermal tumors (PNETs). Secreted Protein, Acidic and Rich in Cysteine (SPARC) is a matrix-associated glycoprotein that influences a variety of cellular activities in vitro and in vivo. Here, we provide evidence that expression of SPARC cDNA induces autophagy in PNET cells followed by apoptotic cell death. SPARC-induced autophagy was morphologically characterized by (i) the formation of membrane-bound autophagic vacuoles (AVO), (ii) increase in the levels of microtubule-associated protein light chain 3 (LC3) and (iii) induction of the lysososmal enzyme cathepsin B. Cathepsin B, in turn induced mitochondrial release of cytochrome c and activated caspase-3, events that signify the onset of apoptotic cell death. In agreement with these observations, inhibition of autophagy by 3-MA reduced AVO formation and LC3 and inhibited apoptosis, suggesting that autophagy plays a role in SPARC-mediated apoptosis. Blocking cathepsin B expression with a specific inhibitor of cathepsin B suppressed apoptosis but did not affect autophagy, which suggests that cathepsin B is a molecular link between autophagy and apoptosis. In summary, these findings demonstrate that SPARC expression induces autophagy, which results in the elevation of cathepsin B and subsequent mitochondria-mediated apoptosis.
SPARC; Apoptosis; Autophagy; Cathepsin B; PNET; Bid
In our earlier reports, we showed that downregulation of uPA and uPAR inhibited glioma tumor angiogenesis in SNB19 cells, and intraperitoneal injection of a hairpin shRNA expressing plasmid targeting uPA and uPAR inhibited angiogenesis in nude mice. The exact mechanism by which inhibition of angiogenesis takes place is not clearly understood.
In the present study, we have attempted to investigate the mechanism by which uPA/uPAR downregulation by shRNA inhibits angiogenesis in endothelial and glioblastoma cell lines. uPA/uPAR downregulation by shRNA in U87 MG and U87 SPARC co-cultures with endothelial cells inhibited angiogenesis as assessed by in vitro angiogenesis assay and in vivo dorsal skin-fold chamber model in nude mice. Protein antibody array analysis of co-cultures of U87 and U87 SPARC cells with endothelial cells treated with pU2 (shRNA against uPA and uPAR) showed decreased angiogenin secretion and angiopoietin-1 as well as several other pro-angiogenic molecules. Therefore, we investigated the role of angiogenin and found that nuclear translocation, ribonucleolytic and 45S rRNA synthesis, which are all critical for angiogenic function of angiogenin, were significantly inhibited in endothelial cells transfected with uPA, uPAR and uPA/uPAR when compared with controls. Moreover, uPA and uPAR downregulation significantly inhibited the phosphorylation of Tie-2 receptor and also down regulated FKHR activation in the nucleus of endothelial cells via the GRB2/AKT/BAD pathway. Treatment of endothelial cells with ruPA increased angiogenin secretion and angiogenin expression as determined by ELISA and western blotting in a dose-dependent manner. The amino terminal fragment of uPA down regulated ruPA-induced angiogenin in endothelial cells, thereby suggesting that uPA plays a critical role in positively regulating angiogenin in glioblastoma cells.
Taken together, our results suggest that uPA/uPAR downregulation suppresses angiogenesis in endothelial cells induced by glioblastoma cell lines partially by downregulation of angiogenin and by inhibition of the angiopoietin-1/AKT/FKHR pathway.
Involvement of MMP-9, uPAR and cathepsin B in adhesion, migration, invasion, proliferation, metastasis and tumor growth has been well established. In the present study, MMP-9, uPAR and cathepsin B genes were downregulated in glioma xenograft cells using shRNA plasmid constructs and we evaluated the involvement of integrins and changes in their adhesion, migration and invasive potential.
MMP-9, uPAR and cathepsin B single shRNA plasmid constructs were used to downregulate these molecules in xenograft cells. We also used MMP-9/uPAR and MMP-9/cathepsin B bicistronic constructs to evaluate the cumulative effects. MMP-9, uPAR and cathepsin B downregulation significantly inhibits xenograft cell adhesion to several extracellular matrix proteins. Treatment with MMP-9, uPAR and cathepsin B shRNA of xenografts led to the downregulation of several alpha and beta integrins. In all the assays, we noticed more prominent effects with the bicistronic plasmid constructs when compared to the single plasmid shRNA constructs. FACS analysis demonstrated the expression of αVβ3, α6β1 and α9β1 integrins in xenograft cells. Treatment with bicistronic constructs reduced αVβ3, α6β1 and α9β1 integrin expressions in xenograft injected nude mice. Migration and invasion were also inhibited by MMP-9, uPAR and cathepsin B shRNA treatments as assessed by spheroid migration, wound healing, and Matrigel invasion assays. As expected, bicistronic constructs further inhibited the adhesion, migration and invasive potential of the xenograft cells as compared to individual treatments.
Downregulation of MMP-9, uPAR and cathespin B alone and in combination inhibits adhesion, migration and invasive potential of glioma xenografts by downregulating integrins and associated signaling molecules. Considering the existence of integrin inhibitor-resistant cancer cells, our study provides a novel and effective approach to inhibiting integrins by downregulating MMP-9, uPAR and cathepsin B in the treatment of glioma.
Matrix metalloproteinase-2 (MMP-2) is known to degrade the collagen IV, play a role in radiation-induced lung injury. We therefore investigated the anti-tumor effects of combining MMP-2 inhibition using an adenovirus expressing siRNA against MMP-2 (Ad-MMP-2-Si) with radiation therapy (IR) on A549 lung cancer cells in vitro and in vivo. IR increased MMP-2 mRNA, protein and activity in lung cancer cells. MMP-2 inhibition along with IR enhanced radiosensitivity as determined by clonogenic assay, flow cytometry, and TUNEL assay. We show that MMP-2 inhibition prior to irradiation reduced p53 phosphorylation, with a corresponding reduction in the expression of the p53 downstream target gene p21Cip1/Waf1. Irradiated tumor cells induced the FoxM1-mediated DNA repair gene, XRCC1 and Checkpoint-2/1, which were abrogated with combined treatment of Ad-MMP-2-Si and IR. Further, the combination of Ad-MMP-2-Si with radiotherapy significantly increased anti-tumor efficacy in vivo compared to either agent alone. Indeed, histological analysis of tumor sections collected from the combination group revealed more apoptotic cells. These studies suggest that MMP-2 inhibition in combination with radiotherapy abrogates G2 cell cycle arrest leading to apoptosis and provide evidence of the anti-tumor efficacy of combining MMP-2 inhibition with irradiation as a new therapeutic strategy for the effective treatment of NSCLC patients.
MMP-2; FoxM1; G2/M arrest; radiosensitization; A549
Stat3, a member of the signal transducer and activator of transcription family, has the potential to mediate cell survival, growth and differentiation. Stat3 is constitutively activated in numerous cancers, including more than 50% of breast cancers. Previous studies demonstrated that constitutively activated Stat3 plays an important role in breast cancer development and progression by promoting cell proliferation and inhibiting apoptosis. The present study was designed to investigate the potential use of RNA interference (RNAi) to block Stat3 expression and activation, as well as the subsequent effect on human breast cancer cell growth. Our studies show that knockdown of STAT3 expression by siRNA reduced expression of Bcl-xL and survivin in MDA-MB-231 cells, and also led to Fas mediated intrinsic apoptotic pathway by activating Caspases -8, -9, -3 and PARP 1 cleavage. In nude mice, pRNAi-Stat3 significantly suppressed tumor growth compared with controls. It also suppressed Stat3 expression, and downregulated BcL-xL and upregulated Fas, Fas-L and cleaved Caspase 3 expression within the tumor, which significantly induced apoptosis and led to tumor suppression. Thus, targeting Stat3 signaling using siRNA may serve as a novel therapeutic strategy for the treatment of breast cancers expressing constitutively activated Stat3.
Stat3; apoptosis; Fas/Fas-L
Invasive tumors, including gliomas, utilize proteinases to degrade extracellular matrix components and diffuse into the adjacent tissues or migrate towards distant ones. In addition, proteinase activity is required for the formation of new blood vessels within the tumor. Levels of the proteinase matrix metalloproteinase-2 (MMP-2) are highly increased in gliomas. In this study, we examined the effect of the downregulation of MMP-2 via adenovirus-mediated siRNA in gliomas. Here, we show that siRNA delivery significantly decreased levels of MMP-2 in the glioblastoma cell lines U-87 and U-251. U-87 and U-251 cells showed impaired invasion through matrigel as well as decreased migration from tumor spheroids transfected with Ad-MMP-2. Additionally, tumor-induced angiogenesis was decreased in in vitro experiments in cultured human endothelial cells (HMEC) in serum-free conditioned medium of glioblastoma cells transfected with these constructs and co-cultures of glioma cells with HMEC. We also observed decreased angiogenesis in the in vivo dorsal skin-fold chamber model. Moreover, MMP-2 inhibition induced apoptotic cell death in vitro, and suppressed tumor growth of pre-established U-251 intracranial xenografts in nude mice. Thus, specific targeting of MMP-2 may provide a novel, efficient approach for the treatment of gliomas and improve the poor outcomes of patients with these brain tumors.
MMP-2; gliomas; U-87; invasion; angiogenesis; intracranial; adenovirus; siRNAs
Angiogenesis, the recruitment of new blood vessels, is an essential component of tumor progression. Malignant brain tumors are highly vascularized and their growth is angiogenesis-dependent. As such, inhibition of the sprouting of new capillaries from pre-existing blood vessels is one of the most promising antiglioma therapeutic approaches. Numerous classes of molecules have been implicated in regulating angiogenesis and, thus, novel agents that target and counteract angiogenesis are now being developed. The therapeutic trials of a number of angiogenesis inhibitors as antiglioma drugs are currently under intense investigation. Preliminary studies of angiogenic blockade in glioblastoma have been promising and several clinical trials are now underway to develop optimum treatment strategies for antiangiogenic agents. This review will cover state-of-the-art antiangiogenic targets for brain tumor treatment and discuss future challenges. An increased understanding of the angiogenic process, the diversity of its inducers and mediators, appropriate drug schedules and the use of these agents with other modalities may lead to radically new treatment regimens to achieve maximal efficacy.
angiogenesis; brain tumor; clinical trial; vascular endothelial factor; vascular niche
Matrix metalloproteinase-2 (MMP-2) expression is often upregulated in advanced cancers and known to play important role in tumor angiogenesis. We previously showed that adenoviral-mediated delivery of siRNA for MMP-2 (Ad-MMP-2-Si) inhibited lung cancer growth, angiogenesis and metastasis. In this study, we investigated the signaling mechanisms involved in Ad-MMP-2-Si-mediated inhibition of angiogenesis. Ad-MMP-2-Si treatment inhibited neo-vascularization in vivo as determined by mouse dorsal air sac model, and conditioned medium from Ad-MMP-2-Si-infected A549 lung cancer cells (Ad-MMP-2-Si-CM) inhibited endothelial tube formation in vitro. Ad-MMP-2-Si-CM decreased proliferation as determined by Ki-67 immunofluorescence and induced apoptosis in endothelial cells as determined by TUNEL assay. Furthermore, Ad-MMP-2-Si-CM inhibited AKT phosphorylation and induced phosphorylation of ERK-MAPKs in endothelial cells. Overexpression of constitutively active-AKT reversed the Ad-MMP-2-Si-CM-mediated inhibition of tube formation and induction of ERK phosphorylation. Conversely, Ad-MMP-2-Si-CM induced TIMP-3 expression, and the interaction of VEGFR2 and TIMP-3 was determined by co-immunoprecipitation experiments. TIMP-3 induction was mediated by ERK activation. In addition, electrophoretic mobility shift and chromatin immunoprecipitation assays demonstrate that Sp1 transcription factor mediated Ad-MMP-2-Si-CM-stimulated increase of TIMP-3. Vasculature destruction was confirmed with co-localization studies with TUNEL and an endothelial marker, CD31, in tumor sections of Ad-MMP-2-Si-treated mice. Our data collectively suggest MMP-2 inhibition induces endothelial apoptosis in vivo and inhibits endothelial tube formation. These experiments provide the first evidence that inhibition of p-AKT and induction of p-ERK1/2 are crucial events in the induction of TIMP-3-mediated endothelial apoptosis in MMP-2 inhibited lung tumors.
ERK; TIMP-3; MMP-2; siRNA; angiogenesis; apoptosis; lung cancer
Novel strategies are needed to prevent the high mortality rates of several types of cancer. These high rates stem from tumor resistance to radiation therapy, which is thought to result from the induction of matrix metalloproteinases and plasminogen activators. In the present study, we show that the modulation of MMP-9 expression, using adenoviral-mediated transfer of the antisense MMP-9 gene (Ad-MMP-9), affects breast cancer sensitivity to radiation.
In the present study, we used antisense MMP-9 adenoviral construct (Ad-MMP-9) to downregulate the expression of MMP-9 in MDA MB 231 breast cancer cell lines in vitro prior to irradiation and subsequently incubated cells in hypoxic condition. In vivo studies were performed with orthotopic breast tumors and the radiosensitivity evaluated both in vitro and in vivo.
Ad-MMP-9 infection resulted in downregulation of radiation-induced levels of hypoxia-inducible factor 1 alpha (HIF1α) and MMP-9 under hypoxic conditions in MDA MB 231 breast cancer cells. In addition, Ad-MMP-9 in combination with radiation decreased levels of the transcription factors NF-κB and AP 1, both of which contribute to the radioresistance of breast tumors. Finally, the triggering of the Fas-Fas-L apoptotic cascade, which resulted in the cleavage of PARP-1 and caspases 10, 3 and 7, signifies the efficiency of combined treatment of Ad-MMP-9 and radiation. Treatment with Ad-MMP-9 plus radiation completely regressed tumor growth in orthotopic breast cancer model.
In summary, integrating gene therapy (adenovirus-mediated inhibition of MMP-9) with radiotherapy could have a synergistic effect, thereby improving the survival of patients with breast cancer.
Ad-MMP-9; Radiation; Orthotopic breast tumor; Hypoxia; Tumor growth
Matrix metalloproteinases (MMPs) comprise a class of secreted zinc-dependent endopeptidases implicated in the metastatic potential of tumor cells due to their ability to degrade the extracellular matrix (ECM) and basement membrane. Matrix metalloproteinase-2 (MMP-2) has been detected in high levels and correlates with invasiveness in human melanoma. We have studied the effect of adenovirus-mediated transfer of small interfering RNA (siRNA) against MMP-2 in the human melanoma cell line A2058. The delivery of these double-stranded RNA molecules represents an efficient technology in silencing disease-causing genes with known sequences at the post-transcriptional level. siRNA against MMP-2 mRNA (Ad-MMP-2) was found to decrease MMP-2 protein expression and activity in melanoma cells as demonstrated by western blotting and gelatin zymography. Furthermore, infection of cells with Ad-MMP-2 inhibited cellular migration and invasion as indicated by spheroid and matrigel assays. We also observed dose-dependent suppression of vascular network formation in an angiogenesis assay. Finally, we developed a nude mouse spinal metastatic model to investigate the local effects of tumor metastasis. Intravenous tail vein injection with Ad-MMP-2 on days 5, 9, and 11 resulted in complete retention of neurological function as compared to control and scrambled vector (Ad-SV)-treated groups that showed complete paraplegia by day 14 ± 2 days. Hematoxylin and eosin staining revealed decreased tumor size in the Ad-MMP-2-treated animals. This novel experimental model revealed that adenoviral-mediated transfer of RNA interference against MMP-2 results in the retention of neurological function and significantly inhibited tumor growth.
MMP-2; melanoma; invasion; spheroid migration; angiogenesis; metastatic model
We previously showed that MMP-9 inhibition using an adenoviral-mediated delivery of MMP-9 siRNA (Ad-MMP-9), caused senescence in medulloblastoma cells. Regardless of whether or not, Ad-MMP-9 would induce apoptosis, the possible signaling mechanism is still obscure. In this report, we demonstrate that Ad-MMP-9 induced apoptosis in DAOY cells as determined by propidium iodide and TUNEL staining. Ad-MMP-9 infection induced the release of cytochrome-c, activation of caspases-9-3, and cleavage of PARP. Ad-MMP-9 infection stimulated ERK, and EMSA indicated an increase in NF-κB activation. ERK inhibition, using kinase dead mutant for ERK, ameliorated NF-κB activation and caspase-mediated apoptosis in Ad-MMP-9 infected cells. β1-integrin expression in Ad-MMP-9 infected cells also increased, and this increase was reversed by the reintroduction of MMP-9. We found that, addition of β1 blocking antibodies inhibited Ad-MMP-9-induced ERK activation. Taken together, our results indicate that MMP-9 inhibition induces apoptosis due to altered β1 integrin expression in medulloblastoma. In addition, ERK activation plays an active role in this process and functions upstream of NF-κB activation to initiate the apoptotic signal.
apoptosis; cytochrome C; ERK; Integrin β1; MMP-9; NFκB
We have previously reported that the downregulation of MMP-2 by adenovirus-mediated delivery of MMP-2 siRNA (Ad-MMP-2) reduced spheroid invasion and angiogenesis in vitro, and, metastasis and tumor growth in vivo. In this study, we investigated the mechanism of Ad-MMP-2-mediated growth inhibition in vitro and in vivo. Ad-MMP-2 infection led to the induction of apoptosis as determined by TUNEL assay, Annexin-V staining and PARP-1 cleavage in a dose-dependent manner in A549 cells. Ad-MMP-2 decreased the content of the anti-apoptotic members of the Bcl-2 family proteins (Bcl-2 and Bcl-xL) and increased the content of the pro-apoptotic members of the Bcl-2 family (Bax and Bcl-xS) as determined by immunoblotting analysis. Furthermore, Ad-MMP-2-mediated apoptosis was accompanied by increase in truncated Bid, release of cytochrome-c, and the activation of caspases-8, -9 and -3. Immunoblot analysis showed that Ad-MMP-2 infection caused upregulation of Fas/Fas-L and FADD. And Anti-Fas-L antibody reversed Ad-MMP-2-induced apoptosis. TIMP-3, an endogenous inhibitor of MMP-2, which cleaves Fas-L and activates the Fas/Fas-L inducing apoptotic pathway, was increased in Ad-MMP-2-treated cells. Adenovirus-mediated expression of MMP-2 siRNA in human lung xenografts in vivo resulted in increased immunostaining of Fas, Fas-L, cleaved Bid and TIMP-3. This is the first report, to our knowledge, showing that MMP-2 inhibition upregulates TIMP-3 levels, which in turn, promotes apoptosis in lung cancer.
CD95 (APO/Fas); Fas-L; caspase-8; Cytochrome-c; Apoptosis; MMP-2; TIMP-3
The serine protease urokinase-type plasminogen activator (uPA) plays a significant role in tumor cell invasion and metastasis when bound to its specific receptor, uPAR (also known as CD87). In addition to the uPA-uPAR system, matrix metalloproteinases (MMPs) are involved in tumor cell invasion and metastasis. In this study, we achieved specific inhibition of uPAR and MMP-9 using RNAi technology. We introduced small interfering RNA (siRNA) to downregulate the expression of uPAR and MMP-9 (pUM) in breast cancer cell lines (MDA MB 231 and ZR 75 1). In vitro angiogenesis studies indicated a decrease in the angiogenic potential of the treated cells; in particular, a remarkable decrease was observed in the cells treated with bicistronic construct (pUM) in comparision to the controls. Additionally, bicistronic construct inhibited the formation of capillary-like structures in in vivo models of angiogenesis. Similarly, the invasive potential and migration decreased dramatically when treated with the bicistronic construct as shown by matrigel invasion and migration assays. These results suggest a synergistic effect from the simultaneous downregulation of uPAR and MMP-9. We also assessed the levels of phosphorylated forms of MAPK, ERK, and AKT signaling pathway molecules and found reduction in the levels of these molecules in cells treated with the bicistronic construct as compared to the control cells. Furthermore, targeting both uPAR and MMP-9 totally regressed orthotopic breast tumors in nude mice. In conclusion, our results provide evidence that the simultaneous downregulation of uPAR and MMP-9 using RNAi technology may provide an effective tool for breast cancer therapy.
RNAi; uPAR; MMP-9; Invasion; Angiogenesis; Tumor growth
The purpose of this study was to evaluate the therapeutic potential of using plasmid expressed RNAi targeting uPAR and uPA to treat human glioma.
In the present study, we have used plasmid based RNAi to simultaneously downregulate the expression of uPAR and uPA in SNB19 glioma cell lines and EGFR overexpressing 4910 human glioma xenografts in vitro and in vivo, and evaluate the intraperitoneal route for RNAi expressing plasmid administered to target intracranial glioma.
Plasmid mediated RNAi targeting uPAR and uPA did not induce OAS1 expression as seen from RT-PCR analysis. In 4910 EGFR-over expressing cells, downregulation of uPAR and uPA induced the downregulation of EGFR and VEGF and inhibited angiogenesis in both in vitro and in vivo angiogenic assays. In addition, invasion and migration were inhibited as indicated by in vitro spheroid cell migration, matrigel invasion and spheroid invasion assays. We did not observe OAS1 expression in mice with pre-established intracranial tumors, which were given intraperitoneal injections of plasmid expressing siRNA targeting uPAR and uPA. Furthermore, the siRNA plasmid targeting uPAR and uPA caused regression of pre-established intracranial tumors when compared to the control mice.
In conclusion the plasmid expressed RNAi targeting uPAR and uPA via the intraperitoneal route has potential clinical applications for the treatment of glioma.
uPAR; uPA; glioma EGFR; VEGF
The involvement of matrix metalloproteinases (MMPs) has been suggested in cellular mechanisms leading to medulloblastoma (MB), the most common malignant brain tumor in children. A significant association of the expression levels of MMP-9 with survival and M stage suggests that patients with medulloblastoma metastatic disease at diagnosis may benefit from the anti-MMP therapy. Here, we have evaluated the tumorigenicity of medulloblastoma cells after infection with an adenovirus containing a 21 bp siRNA sequence of human MMP-9 gene (Ad-MMP-9). Infection of Daoy medulloblastoma cells with Ad-MMP-9 reduced MMP-9 activity and protein levels compared with parental and Ad-SV controls. Ad-MMP-9 decreased the number of viable Daoy cells in a concentration-dependent manner. FACS analysis indicated Ad-MMP-9 infection caused a dose-dependent cell cycle arrest in the G0/G1 phase. Ad-MMP-9-induced cell cycle arrest appears to be mediated by the ERK MAPK pathway and the cell cycle inhibitors p16INK4 and is phenotypically indistinguishable from senescence. Ad-MMP-9 treatment inhibited medulloblastoma tumor growth in an intracranial model and was mediated by upregulation of p16 expression. These studies validate the usefulness of targeting MMP-9 and provide a novel perspective in the treatment of medulloblastoma.
MMP-9; siRNA; medulloblastoma; tumor