CellNeighborEX: deciphering neighbor-dependent gene expression from spatial transcriptomics data

Cells have evolved their communication methods to sense their microenvironments and send biological signals. In addition to communication using ligands and receptors, cells use diverse channels including gap junctions to communicate with their immediate neighbors. Current approaches, however, cannot effectively capture the influence of various microenvironments. Here, we propose a novel approach to investigate cell neighbor-dependent gene expression (CellNeighborEX) in spatial transcriptomics (ST) data. To categorize cells based on their microenvironment, CellNeighborEX uses direct cell location or the mixture of transcriptome from multiple cells depending on ST technologies. For each cell type, CellNeighborEX identifies diverse gene sets associated with partnering cell types, providing further insight. We found that cells express different genes depending on their neighboring cell types in various tissues including mouse embryos, brain, and liver cancer. Those genes are associated with critical biological processes such as development or metastases. We further validated that gene expression is induced by neighboring partners via spatial visualization. The neighbor-dependent gene expression suggests new potential genes involved in cell-cell interactions beyond what ligand-receptor co-expression can discover.

MDA-9/Syntenin in the tumor and microenvironment defines prostate cancer bone metastasis

Bone metastasis is a frequent and incurable consequence of advanced prostate cancer (PC). An interplay between disseminated tumor cells and heterogeneous bone resident cells in the metastatic niche initiates this process. Melanoma differentiation associated gene-9 (mda-9/Syntenin/syndecan binding protein) is a prometastatic gene expressed in multiple organs, including bone marrow-derived mesenchymal stromal cells (BM-MSCs), under both physiological and pathological conditions. We demonstrate that PDGF-AA secreted by tumor cells induces CXCL5 expression in BM-MSCs by suppressing MDA-9-dependent YAP/MST signaling. CXCL5-derived tumor cell proliferation and immune suppression are consequences of the MDA-9/CXCL5 signaling axis, promoting PC disease progression. mda-9 knockout tumor cells express less PDGF-AA and do not develop bone metastases. Our data document a previously undefined role of MDA-9/Syntenin in the tumor and microenvironment in regulating PC bone metastasis. This study provides a framework for translational strategies to ameliorate health complications and morbidity associated with advanced PC.

Cytoplasmic-delivery of polyinosine-polycytidylic acid inhibits pancreatic cancer progression increasing survival by activating Stat1-CCL2-mediated immunity

BACKGROUND

Pancreatic ductal adenocarcinoma (PDAC) is an aggressive cancer without effective therapies and with poor prognosis, causing 7% of all cancer-related fatalities in the USA. Considering the lack of effective therapies for this aggressive cancer, there is an urgent need to define newer and more effective therapeutic strategies. Polyinosine-polycytidylic acid (pIC) is a synthetic double-stranded RNA (dsRNA) which directly activates dendritic cells and natural killer cells inhibiting tumor growth. When pIC is delivered into the cytoplasm using polyethyleneimine (PEI), pIC-PEI, programmed-cell death is induced in PDAC. Transfection of [pIC]PEI into PDAC cells inhibits growth, promotes toxic autophagy and also induces apoptosis in vitro and in vivo in animal models.

METHODS

The KPC transgenic mouse model that recapitulates PDAC development in patients was used to interrogate the role of an intact immune system in vivo in PDAC in response to [pIC]PEI. Antitumor efficacy and survival were monitored endpoints. Comprehensive analysis of the tumor microenvironment (TME) and immune cells, cytokines and chemokines in the spleen, and macrophage polarization were analyzed.

RESULTS

Cytosolic delivery of [pIC]PEI induces apoptosis and provokes strong antitumor immunity in vivo in immune competent mice with PDAC. The mechanism underlying the immune stimulatory properties of [pIC]PEI involves Stat1 activation resulting in CCL2 and MMP13 stimulation thereby provoking macrophage polarization. [pIC]PEI induces apoptosis via the AKT-XIAP pathway, as well as macrophage differentiation and T-cell activation via the IFNγ-Stat1-CCL2 signaling pathways in PDAC. In transgenic tumor mouse models, [pIC]PEI promotes robust and profound antitumor activity implying that stimulating the immune system contributes to biological activity. The [pIC]PEI anti-PDAC effects are enhanced when used in combination with a standard of care (SOC) treatment, that is, gemcitabine.

CONCLUSIONS

In summary, [pIC]PEI treatment is non-toxic toward normal pancreatic cells while displaying strong cytotoxic and potent immune activating activities in PDAC, making it an attractive therapeutic when used alone or in conjunction with SOC therapeutic agents, potentially providing a safe and effective treatment protocol with translational potential for the effective therapy of PDAC.

Dual Targeting of the PDZ1 and PDZ2 Domains of MDA-9/Syntenin Inhibits Melanoma Metastasis

Genome-wide gene expression analysis and animal modeling indicate that melanoma differentiation associated gene-9 (mda-9, Syntenin, Syndecan binding protein, referred to as MDA-9/Syntenin) positively regulates melanoma metastasis. The MDA-9/Syntenin protein contains two tandem PDZ domains serving as a nexus for interactions with multiple proteins that initiate transcription of metastasis-associated genes. Although targeting either PDZ domain abrogates signaling and prometastatic phenotypes, the integrity of both domains is critical for full biological function. Fragment-based drug discovery and NMR identified PDZ1i, an inhibitor of the PDZ1 domain that effectively blocks cancer invasion in vitro and in vivo in multiple experimental animal models. To maximize disruption of MDA-9/Syntenin signaling, an inhibitor has now been developed that simultaneously binds and blocks activity of both PDZ domains. PDZ1i was joined to the second PDZ binding peptide (TNYYFV) with a PEG linker, resulting in PDZ1i/2i (IVMT-Rx-3) that engages both PDZ domains of MDA-9/Syntenin. IVMT-Rx-3 blocks MDA-9/Syntenin interaction with Src, reduces NF-κB activation, and inhibits MMP-2/MMP-9 expression, culminating in repression of melanoma metastasis. The in vivo antimetastatic properties of IVMT-Rx-3 are enhanced when combined with an immune-checkpoint inhibitor. Collectively, our results support the feasibility of engineering MDA-9 dual-PDZ inhibitors with enhanced antimetastatic activities and applications of IVMT-Rx-3 for developing novel therapeutic strategies effectively targeting melanoma and in principle, a broad spectrum of human cancers that also overexpress MDA-9/Syntenin.

Chemoresistance in pancreatic ductal adenocarcinoma: Overcoming resistance to therapy

Pancreatic ductal adenocarcinoma (PDAC), a prominent cause of cancer deaths worldwide, is a highly aggressive cancer most frequently detected at an advanced stage that limits treatment options to systemic chemotherapy, which has provided only marginal positive clinical outcomes. More than 90% of patients with PDAC die within a year of being diagnosed. PDAC is increasing at a rate of 0.5-1.0% per year, and it is expected to be the second leading cause of cancer-related mortality by 2030. The resistance of tumor cells to chemotherapeutic drugs, which can be innate or acquired, is the primary factor contributing to the ineffectiveness of cancer treatments. Although many PDAC patients initially responds to standard of care (SOC) drugs they soon develop resistance caused partly by the substantial cellular heterogeneity seen in PDAC tissue and the tumor microenvironment (TME), which are considered key factors contributing to resistance to therapy. A deeper understanding of molecular mechanisms involved in PDAC progression and metastasis development, and the interplay of the TME in all these processes is essential to better comprehend the etiology and pathobiology of chemoresistance observed in PDAC. Recent research has recognized new therapeutic targets ushering in the development of innovative combinatorial therapies as well as enhancing our comprehension of several different cell death pathways. These approaches facilitate the lowering of the therapeutic threshold; however, the possibility of subsequent resistance development still remains a key issue and concern. Discoveries, that can target PDAC resistance, either alone or in combination, have the potential to serve as the foundation for future treatments that are effective without posing undue health risks. In this chapter, we discuss potential causes of PDAC chemoresistance and approaches for combating chemoresistance by targeting different pathways and different cellular functions associated with and mediating resistance.

Enhanced Cancer Therapy Using an Engineered Designer Cytokine Alone and in Combination With an Immune Checkpoint Inhibitor

melanoma differentiation associated gene-7 or Interleukin-24 (mda-7, IL-24) displays expansive anti-tumor activity without harming corresponding normal cells/tissues. This anticancer activity has been documented in vitro and in vivo in multiple preclinical animal models, as well as in patients with advanced cancers in a phase I clinical trial. To enhance the therapeutic efficacy of MDA-7 (IL-24), we engineered a designer cytokine (a "Superkine"; IL-24S; referred to as M7S) with enhanced secretion and increased stability to engender improved "bystander" antitumor effects. M7S was engineered in a two-step process by first replacing the endogenous secretory motif with an alternate secretory motif to boost secretion. Among four different signaling peptides, the insulin secretory motif significantly enhanced the secretion of MDA-7 (IL-24) protein and was chosen for M7S. The second modification engineered in M7S was designed to enhance the stability of MDA-7 (IL-24), which was accomplished by replacing lysine at position K122 with arginine. This engineered "M7S Superkine" with increased secretion and stability retained cancer specificity. Compared to parental MDA-7 (IL-24), M7S (IL-24S) was superior in promoting anti-tumor and bystander effects leading to improved outcomes in multiple cancer xenograft models. Additionally, combinatorial therapy using MDA-7 (IL-24) or M7S (IL-24S) with an immune checkpoint inhibitor, anti-PD-L1, dramatically reduced tumor progression in murine B16 melanoma cells. These results portend that M7S (IL-24S) promotes the re-emergence of an immunosuppressive tumor microenvironment, providing a solid rationale for prospective translational applications of this therapeutic designer cytokine.

The quest to develop an effective therapy for neuroblastoma

Neuroblastoma (NB) is a common solid extracranial tumor developing in pediatric populations. NB can spontaneously regress or grow and metastasize displaying resistance to therapy. This tumor is derived from primitive cells, mainly those of the neural crest, in the sympathetic nervous system and usually develops in the adrenal medulla and paraspinal ganglia. Our understanding of the molecular characteristics of human NBs continues to advance documenting abnormalities at the genome, epigenome, and transcriptome levels. The high-risk tumors have MYCN oncogene amplification, and the MYCN transcriptional regulator encoded by the MYCN oncogene is highly expressed in the neural crest. Studies on the biology of NB has enabled a more precise risk stratification strategy and a concomitant reduction in the required treatment in an expanding number of cases worldwide. However, newer treatment strategies are mandated to improve outcomes in pediatric patients who are at high-risk and display relapse. To improve outcomes and survival rates in such high-risk patients, it is necessary to use a multicomponent therapeutic approach. Accuracy in clinical staging of the disease and assessment of the associated risks based on biological, clinical, surgical, and pathological criteria are of paramount importance for prognosis and to effectively plan therapeutic approaches. This review discusses the staging of NB and the biological and genetic features of the disease and several current therapies including targeted delivery of chemotherapy, novel radiation therapy, and immunotherapy for NB.

Theranostic Tripartite Cancer Terminator Virus for Cancer Therapy and Imaging

Simple Summary

An optimum cancer therapeutic virus should embody unique properties, including an ability to: Selectively procreate and kill tumor but not normal cells; produce a secreted therapeutic molecule (with broad-acting anti-cancer effects on primary and distant metastatic cells because of potent “bystander” activity); and monitor therapy non-invasively by imaging primary and distant metastatic cancers. We previously created a broad-spectrum, cancer-selective and replication competent therapeutic adenovirus that embodies two of these properties, i.e., specifically reproduces in cancer cells and produces a therapeutic cytokine, MDA-7/IL-24, a “cancer terminator virus” (CTV). We now expand on this concept and demonstrate the feasibility of producing a tripartite CTV (TCTV) selectively expressing three genes from three distinct promoters that replicate in the cancer cells while producing MDA-7/IL-24 and an imaging gene (i.e., luciferase). This novel first-in-class tripartite “theranostic” TCTV expands the utility of therapeutic viruses to non-invasively image and selectively destroy primary tumors and metastases.

Abstract

Combining cancer-selective viral replication and simultaneous production of a therapeutic cytokine, with potent “bystander” anti-tumor activity, are hallmarks of the cancer terminator virus (CTV). To expand on these attributes, we designed a next generation CTV that additionally enables simultaneous non-invasive imaging of tumors targeted for eradication. A unique tripartite CTV “theranostic” adenovirus (TCTV) has now been created that employs three distinct promoters to target virus replication, cytokine production and imaging capabilities uniquely in cancer cells. Conditional replication of the TCTV is regulated by a cancer-selective (truncated PEG-3) promoter, the therapeutic component, MDA-7/IL-24, is under a ubiquitous (CMV) promoter, and finally the imaging capabilities are synchronized through another cancer selective (truncated tCCN1) promoter. Using in vitro studies and clinically relevant in vivo models of breast and prostate cancer, we demonstrate that incorporating a reporter gene for imaging does not compromise the exceptional therapeutic efficacy of our previously reported bipartite CTV. This TCTV permits targeted treatment of tumors while monitoring tumor regression, with potential to simultaneously detect metastasis due to the cancer-selective activity of reporter gene expression. This “theranostic” virus provides a new genetic tool for distinguishing and treating localized and metastatic cancers.

MDA-9/Syntenin (SDCBP): Novel gene and therapeutic target for cancer metastasis

The primary cause of cancer-related death from solid tumors is metastasis. While unraveling the mechanisms of this complicated process continues, our ability to effectively target and treat it to decrease patient morbidity and mortality remains disappointing. Early detection of metastatic lesions and approaches to treat metastases (both pharmacological and genetic) are of prime importance to obstruct this process clinically. Metastasis is complex involving both genetic and epigenetic changes in the constantly evolving tumor cell. Moreover, many discrete steps have been identified in metastatic spread, including invasion, intravasation, angiogenesis, attachment at a distant site (secondary seeding), extravasation and micrometastasis and tumor dormancy development. Here, we provide an overview of the metastatic process and highlight a unique pro-metastatic gene, melanoma differentiation associated gene-9/Syntenin (MDA-9/Syntenin) also called syndecan binding protein (SDCBP), which is a major contributor to the majority of independent metastatic events. MDA-9 expression is elevated in a wide range of carcinomas and other cancers, including melanoma, glioblastoma multiforme and neuroblastoma, suggesting that it may provide an appropriate target to intervene in metastasis. Pre-clinical studies confirm that inhibiting MDA-9 either genetically or pharmacologically profoundly suppresses metastasis. An additional benefit to blocking MDA-9 in metastatic cells is sensitization of these cells to a second therapeutic agent, which converts anti-invasion effects to tumor cytocidal effects. Continued mechanistic and therapeutic insights hold promise to advance development of truly effective therapies for metastasis in the future.

Mechanism of internalization of MDA-7/IL-24 protein and its cognate receptors following ligand-receptor docking

Melanoma differentiation associated gene-7 (mda-7/IL-24) is a member of the IL-10 family of cytokines, with ubiquitous direct and "bystander" tumor-selective killing properties. MDA-7/IL-24 protein binds distinct type II cytokine heterodimeric receptor complexes, IL-20R1/IL-20R2, IL-22R1/IL-20R1 and IL-22R1/IL-20R2. Recombinant MDA-7/IL-24 protein induces endogenous mda-7/IL-24 expression in a receptor-dependent manner; since A549 cells that lack a complete set of cognate receptors are not responsive to exogenous protein. The mechanism of MDA-7/IL-24 ligand-receptor biology is not well understood. We explored the interaction of MDA-7/IL-24 with its' receptors and the consequences of ligand-receptor docking. Using both pharmacological and genetic approaches we demonstrate that MDA-7/IL-24 internalization employs the clathrin-mediated endocytic pathway leading to degradation of receptors via the lysosomal/ubiquitin proteosomal pathway. This clathrin-mediated endocytosis is dynamin-dependent. This study resolves a novel mechanism of MDA-7/IL-24 protein "bystander" function, which involves receptor/protein-mediated internalization and receptor degradation.

Regulation of neuroblastoma migration, invasion, and in vivo metastasis by genetic and pharmacological manipulation of MDA-9/Syntenin

Despite multi-modality treatments, prognosis for advanced stage neuroblastoma (NB) remains challenging with residual long-term disabilities in survivors. Advanced stage NB is metastatic, which is a principal cause of cancer-related deaths. We presently document a primary role of MDA-9 in NB progression and define the molecular mechanisms by which MDA-9 promotes transformed phenotypes. NB cell lines and clinical samples display elevated MDA-9 expression and bioinformatic analysis supports an association between elevated MDA-9 and bone metastasis and poor prognosis. Genetic (shmda-9, mda-9 siRNA) or pharmacological (small molecule inhibitor of protein-protein interactions; PDZ1i) blockade of MDA-9 decreases NB migration, invasion, and metastasis. Blocking mda-9 expression or disrupting MDA-9 partner protein interactions downregulates integrin α6 and β4, diminishing Src activity and suppressing Rho-Rac-Cdc42 activity. These signaling changes inhibit cofilin and matrix metalloproteinases reducing in vitro and in vivo NB cell migration. Overexpression of integrin α6 and β4 rescues the invasion phenotype and increases Src activity, supporting integrins as essential regulators of MDA-9-mediated NB migration and invasion. We identify MDA-9 as a key contributor to NB pathogenesis and show that genetic or pharmacological inhibition suppresses NB pathogenesis by an integrin-mediated Src-disruption pathway.

Recent insights into apoptosis and toxic autophagy: The roles of MDA-7/IL-24, a multidimensional anti-cancer therapeutic

Apoptosis and autophagy play seminal roles in maintaining organ homeostasis. Apoptosis represents canonical type I programmed cell death. Autophagy is viewed as pro-survival, however, excessive autophagy can promote type II cell death. Defective regulation of these two obligatory cellular pathways is linked to various diseases, including cancer. Biologic or chemotherapeutic agents, which can reprogram cancer cells to undergo apoptosis- or toxic autophagy-mediated cell death, are considered effective tools for treating cancer. Melanoma differentiation associated gene-7 (mda-7) selectively promotes these effects in cancer cells. mda-7 was identified more than two decades ago by subtraction hybridization showing elevated expression during induction of terminal differentiation of metastatic melanoma cells following treatment with recombinant fibroblast interferon and mezerein (a PKC activating agent). MDA-7 was classified as a member of the IL-10 gene family based on its chromosomal location, and the presence of an IL-10 signature motif and a secretory sequence, and re-named interleukin-24 (MDA-7/IL-24). Multiple studies have established MDA-7/IL-24 as a potent anti-cancer agent, which when administered at supra-physiological levels induces growth arrest and cell death through apoptosis and toxic autophagy in a wide variety of tumor cell types, but not in corresponding normal/non-transformed cells. Furthermore, in a phase I/II clinical trial, MDA-7/IL-24 administered by means of a non-replicating adenovirus was well tolerated and displayed significant clinical activity in patients with multiple advanced cancers. This review examines our current comprehension of the role of MDA-7/IL-24 in mediating cancer-specific cell death via apoptosis and toxic autophagy.

Suppression of Prostate Cancer Pathogenesis Using an MDA-9/Syntenin (SDCBP) PDZ1 Small-Molecule Inhibitor

Metastasis is the primary determinant of death in patients with diverse solid tumors and MDA-9/Syntenin (SDCBP), a pro-metastatic and pro-angiogenic gene, contributes to this process. Recently, we documented that by physically interacting with IGF-1R, MDA-9/Syntenin activates STAT3 and regulates prostate cancer pathogenesis. These observations firmly established MDA-9/Syntenin as a potential molecular target in prostate cancer. MDA-9/Syntenin contains two highly homologous PDZ domains predicted to interact with a plethora of proteins, many of which are central to the cancerous process. An MDA-9/Syntenin PDZ1 domain-targeted small molecule (PDZ1i) was previously developed using fragment-based drug discovery (FBDD) guided by NMR spectroscopy and was found to be well-tolerated in vivo, had significant half-life (t _1/2 = 9 hours) and displayed substantial anti-prostate cancer preclinical in vivo activity. PDZ1i blocked tumor cell invasion and migration in vitro, and metastasis in vivo Hence, we demonstrate that PDZ1i an MDA-9/Syntenin PDZ1 target-specific small-molecule inhibitor displays therapeutic potential for prostate and potentially other cancers expressing elevated levels of MDA-9/Syntenin.

Dormancy and cancer stem cells: An enigma for cancer therapeutic targeting

Dormancy occurs when cells remain viable but stop proliferating. When most of a cancer population undergoes this phenomenon, the result is called tumor dormancy, and when a single cancer cell undergoes this process, it is termed quiescence. Cancer stem cells (CSCs) share several overlapping characteristics and signaling pathways with dormant cancer cells, including therapy resistance, and an ability to metastasize and evade the immune system. Cancer cells can be broadly grouped into dormancy-competent CSCs (DCCs), cancer-repopulating cells (CRCs), dormancy-incompetent CSCs and disseminated tumor cells (DTCs). The settings in which cancer cells exploit the dormancy phase to survive and adapt are: (i) primary cancer dormancy; (ii) metastatic dormancy; (iii) therapy-induced dormancy; and (iv) immunologic dormancy. Dormancy, therapy resistance and plasticity of CSCs are fundamentally interconnected processes mediated through mechanisms involving reversible genetic alterations. Niches including metastatic, bone marrow, and perivascular are known to harbor dormant cancer cells. Mechanisms of dormancy induction are complex and multi-factorial and can involve angiogenic switching, addictive oncogene inhibition, immunoediting, anoikis, therapy, autophagy, senescence, epigenetic, and biophysical regulation. Therapy can have opposing effects on cancer cells with respect to dormancy; some therapies can induce dormancy, while others can reactivate dormant cells. There is a lack of consensus relative to the value of therapy-induced dormancy, i.e., some researchers view dormancy induction as a beneficial strategy as it can lead to metastasis inhibition, while others argue that reactivating dormant cancer cells and then eliminating them through therapy are a better approach. More focused investigations of intrinsic cell kinetics and environmental dynamics that promote and maintain cancer cells in a dormant state, and the long-term consequences of dormancy are critical for improving current therapeutic treatment outcomes.

Regulation of protective autophagy in anoikis-resistant glioma stem cells by SDCBP/MDA-9/Syntenin

Glioblastoma multiforme (GBM) is a frequent and aggressive glial tumor, containing a small population of therapy-resistant cells, glioma stem cells (GSCs). Current dogma suggests that tumors regrow from GSCs, and these cells contribute to therapy resistance, poor prognosis, and recurrence; highlighting the importance of GSCs in glioma pathophysiology and therapeutic targeting. Macroautophagy/autophagy-based cellular homeostasis can be changed from pro-survival to pro-cell death by modulating SDCBP/MDA-9/Syntenin (syndecan binding protein)-mediated signaling. In nonadherent conditions, GSCs display protective autophagy and anoikis-resistance, which correlates with expression of SDCBP/MDA-9/Syntenin. Conversely, SDCBP/MDA-9/Syntenin silencing induces autophagic death in GSCs, indicating that SDCBP/MDA-9/Syntenin regulates protective autophagy in GSCs under anoikis conditions. This process is mediated through phosphorylation of the anti-apoptotic protein BCL2 accompanied with suppression of high levels of autophagic proteins (ATG5, LAMP1, LC3B) through EGFR signaling. SDCBP/MDA-9/Syntenin-mediated regulation of BCL2 and EGFR phosphorylation is achieved through PTK2/FAK and PRKC/PKC signaling. When SDCBP/MDA-9/Syntenin is absent, this protective mechanism is deregulated, leading to highly elevated and sustained levels of autophagy and consequently decreased cell survival. Our recent paper reveals a novel functional link between SDCBP/MDA-9/Syntenin expression and protective autophagy in GSCs. These new insights into SDCBP/MDA-9/Syntenin-mediated regulation and maintenance of GSCs present leads for developing innovative combinatorial cancer therapies.

Recombinant MDA-7/IL24 Suppresses Prostate Cancer Bone Metastasis through Downregulation of the Akt/Mcl-1 Pathway

Prostate cancer is a principal cause of cancer-associated morbidity in men. Although 5-year survival of patients with localized prostate cancer approaches 100%, survival decreases precipitously after metastasis. Bone is the preferred site for disseminated prostate cancer cell colonization, altering the equilibrium of bone homeostasis resulting in weak and fragile bones. Currently, no curative options are available for prostate cancer bone metastasis. Melanoma differentiation associated gene-7 (MDA-7)/IL24 is a well-studied cytokine established as a therapeutic in a wide array of cancers upon delivery as a gene therapy. In this study, we explored the potential anticancer properties of MDA-7/IL24 delivered as a recombinant protein. Using bone metastasis experimental models, animals treated with recombinant MDA-7/IL24 had significantly less metastatic lesions in their femurs as compared with controls. The inhibitory effects of MDA-7/IL24 on bone metastasis resulted from prostate cancer-selective killing and inhibition of osteoclast differentiation, which is necessary for bone resorption. Gain- and loss-of-function genetic approaches document that prosurvival Akt and Mcl-1 pathways are critically important in the antibone metastatic activity of MDA-7/IL24. Our previous findings showed that MDA-7/IL24 gene therapy plus Mcl-1 inhibitors cooperate synergistically. Similarly, an Mcl-1 small-molecule inhibitor synergized with MDA-7/IL24 and induced robust antibone metastatic activity. These results expand the potential applications of MDA-7/IL24 as an anticancer molecule and demonstrate that purified recombinant protein is nontoxic in preclinical animal models and has profound inhibitory effects on bone metastasis, which can be enhanced further when combined with an Mcl-1 inhibitory small molecule. Mol Cancer Ther; 17(9); 1951-60. ©2018 AACR.

The MDA-9/Syntenin/IGF1R/STAT3 Axis Directs Prostate Cancer Invasion

Although prostate cancer is clinically manageable during several stages of progression, survival is severely compromised once cells invade and metastasize to distant organs. Comprehending the pathobiology of invasion is required for developing efficacious targeted therapies against metastasis. Based on bioinformatics data, we predicted an association of melanoma differentiation-associated gene-9 [syntenin, or syndecan binding protein (SDCBP)] in prostate cancer progression. Using tissue samples from various Gleason stage prostate cancer patients with adjacent normal tissue, a series of normal prostate and prostate cancer cell lines (with differing tumorigenic/metastatic properties), mda-9/syntenin-manipulated variants (including loss-of-function and gain-of-function cell lines), and CRISPR/Cas9 stable MDA-9/Syntenin knockout cells, we now confirm the relevance of and dependence on MDA-9/syntenin in prostate cancer invasion. MDA-9/Syntenin physically interacted with insulin-like growth factor-1 receptor following treatment with insulin-like growth factor binding protein-2 (IGFBP2), regulating downstream signaling processes that enabled STAT3 phosphorylation. This activation enhanced expression of MMP2 and MMP9, two established enzymes that positively regulate invasion. In addition, MDA-9/syntenin-mediated upregulation of proangiogenic factors including IGFBP2, IL6, IL8, and VEGFA also facilitated migration of prostate cancer cells. Collectively, our results draw attention to MDA-9/Syntenin as a positive regulator of prostate cancer metastasis, and the potential application of targeting this molecule to inhibit invasion and metastasis in prostate cancer and potentially other cancers.Significance: This study provides new mechanistic insight into the proinvasive role of MDA-9/Syntenin in prostate cancer and has potential for therapeutic application to prevent prostate cancer metastasis. Cancer Res; 78(11); 2852-63. ©2018 AACR.

mda-7/IL-24 Mediates Cancer Cell-Specific Death via Regulation of miR-221 and the Beclin-1 Axis

Melanoma differentiation-associated gene-7/IL-24 (mda-7/IL-24) displays broad-spectrum anticancer activity in vitro, in vivo in preclinical animal models, and in a phase I/II clinical trial in patients with advanced cancers without harming normal cells or tissues. Here we demonstrate that mda-7/IL-24 regulates a specific subset of miRNAs, including cancer-associated miR-221. Either ectopic expression of mda-7/IL-24 or treatment with recombinant His-MDA-7 protein resulted in downregulation of miR-221 and upregulation of p27 and PUMA in a panel of cancer cells, culminating in cell death. Mda-7/IL-24-induced cancer cell death was dependent on reactive oxygen species induction and was rescued by overexpression of miR-221. Beclin-1 was identified as a new transcriptional target of miR-221, and mda-7/IL-24 regulated autophagy through a miR-221/beclin-1 feedback loop. In a human breast cancer xenograft model, miR-221-overexpressing MDA-MB-231 clones were more aggressive and resistant to mda-7/IL-24-mediated cell death than parental clones. This is the first demonstration that mda-7/IL-24 directly regulates miRNA expression in cancer cells and highlights the novelty of the mda-7/IL-24-miR-221-beclin-1 loop in mediating cancer cell-specific death. Cancer Res; 77(4); 949-59. ©2016 AACR.

Knockout of MDA-9/Syntenin (SDCBP) expression in the microenvironment dampens tumor-supporting inflammation and inhibits melanoma metastasis

Cancer development and progression to metastasis is a complex process, which largely depends on bidirectional communication between tumor cells and their microenvironment. Melanoma differentiation associated gene-9 (mda-9, also known as Syntenin-1, SDCBP), a gene first cloned by our group, is robustly expressed in multiple cancers including melanoma and contributes to invasion and metastasis in a tumor cell-intrinsic manner. However, the role of MDA-9/Syntenin in the tumor cell-extrinsic microenvironment remains unclear even though MDA-9/Syntenin is ubiquitously expressed in most organs that are active metastatic sites for melanoma, e.g., lung, lymph node, brain, and liver. In this study, we explored the effect of environmental mda-9/syntenin expression on melanoma growth and metastasis using multiple immunocompetent animal models, syngeneic B16 xenograft and intravenous B16 mouse model and a genetically engineered mouse (GEM) model of melanoma. Host-deficient expression of mda-9/syntenin in mice negatively impacted on subcutaneously implanted B16 tumor growth and lung metastasis. Absence of MDA-9/Syntenin in the lung microenvironment suppressed tumor growth by modulating in situ Interleukin 17A (IL17A) expression and impaired the recruitment of myeloid derived suppressor cells (MDSCs) and Th17 cells as compared to genetically wild type animals. Additionally, loss of mda-9/syntenin expression in a spontaneous melanoma model (melanocyte-specific pten loss and BrafV600E mutation) significantly delayed tumor initiation and suppressed metastasis to the lymph nodes and lungs. The present study highlights a novel role of mda-9/syntenin in tumor-promoting inflammation and immune suppression. These observations along with other documented roles of MDA-9/Syntenin in cancer and metastasis support the potential relevance of MDA-9/Syntenin in the carcinogenic process and as a target for developing improved therapies by using either genetic or pharmacologic approaches to treat and prevent melanoma and other cancers.

mda-7/IL-24 Induces Cell Death in Neuroblastoma through a Novel Mechanism Involving AIF and ATM

Advanced stages of neuroblastoma, the most common extracranial malignant solid tumor of the central nervous system in infants and children, are refractive to therapy. Ectopic expression of melanoma differentiation-associated gene-7/interleukin-24 (mda-7/IL-24) promotes broad-spectrum antitumor activity in vitro, in vivo in preclinical animal models, and in a phase I clinical trial in patients with advanced cancers without harming normal cells. mda-7/IL-24 exerts cancer-specific toxicity (apoptosis or toxic autophagy) by promoting endoplasmic reticulum stress and modulating multiple signal transduction pathways regulating cancer cell growth, invasion, metastasis, survival, and angiogenesis. To enhance cancer-selective expression and targeted anticancer activity of mda-7/IL-24, we created a tropism-modified cancer terminator virus (Ad.5/3-CTV), which selectively replicates in cancer cells producing robust expression of mda-7/IL-24 We now show that Ad.5/3-CTV induces profound neuroblastoma antiproliferative activity and apoptosis in a caspase-3/9-independent manner, both in vitro and in vivo in a tumor xenograft model. Ad.5/3-CTV promotes these effects through a unique pathway involving apoptosis-inducing factor (AIF) translocation into the nucleus. Inhibiting AIF rescued neuroblastoma cells from Ad.5/3-CTV-induced cell death, whereas pan-caspase inhibition failed to promote survival. Ad.5/3-CTV infection of neuroblastoma cells increased ATM phosphorylation instigating nuclear translocation and increased γ-H2AX, triggering nuclear translocation and intensified expression of AIF. These results were validated further using two ATM small-molecule inhibitors that attenuated PARP cleavage by inhibiting γ-H2AX, which in turn inhibited AIF changes in Ad.5/3-CTV-infected neuroblastoma cells. Taken together, we elucidate a novel pathway for mda-7/IL-24-induced caspase-independent apoptosis in neuroblastoma cells mediated through modulation of AIF, ATM, and γ-H2AX. Cancer Res; 76(12); 3572-82. ©2016 AACR.

Pancreatic Cancer Combination Therapy Using a BH3 Mimetic and a Synthetic Tetracycline

Improved treatments for pancreatic cancer remain a clinical imperative. Sabutoclax, a small-molecule BH3 mimetic, inhibits the function of antiapoptotic Bcl-2 proteins. Minocycline, a synthetic tetracycline, displays antitumor activity. Here, we offer evidence of the combinatorial antitumor potency of these agents in several preclinical models of pancreatic cancer. Sabutoclax induced growth arrest and apoptosis in pancreatic cancer cells and synergized with minocycline to yield a robust mitochondria-mediated caspase-dependent cytotoxicity. This combinatorial property relied upon loss of phosphorylated Stat3 insofar as reintroduction of activated Stat3-rescued cells from toxicity. Tumor growth was inhibited potently in both immune-deficient and immune-competent models with evidence of extended survival. Overall, our results showed that the combination of sabutoclax and minocycline was highly cytotoxic to pancreatic cancer cells and safely efficacious in vivo.

The Quest for an Effective Treatment for an Intractable Cancer: Established and Novel Therapies for Pancreatic Adenocarcinoma

With therapies that date back to the 1950s, and few newly approved treatments in the last 20 years, pancreatic cancer remains a significant challenge for the development of novel therapeutics. Current regimens have successfully extended patient survival, although they still lead to prognoses measured in months rather than years. The genetic diversity inherent in pancreatic tumors forms the roadblocks that must be overcome in future therapeutics. Recent insight into the genetic patterns found in tumor cells may provide clues leading to better understanding of the challenges hindering the development of treatments. Here, we review currently used drugs and established combination therapies that comprise the standard of care for a highly recalcitrant disease. Novel approaches can improve upon current therapies in a variety of ways. Enhancing specificity, such that growth inhibition and cytotoxic effects act preferentially on tumor cells, is one approach to advance treatments. This can be accomplished through the targeting of extracellular markers specific to cancer cells. Additionally, enlisting natural defenses and overcoming tumor-driven immune suppression could prove to be a useful tactic. Recent studies utilizing these approaches have yielded promising results and could contribute to an ongoing effort battling a particularly difficult cancer.

Targeting tumor invasion: the roles of MDA-9/Syntenin

INTRODUCTION

Melanoma differentiation-associated gene - 9 (MDA-9)/Syntenin has become an increasingly popular focus for investigation in numerous cancertypes. Originally implicated in melanoma metastasis, it has diverse cellular roles and is consistently identified as a regulator of tumor invasion and angiogenesis. As a potential target for inhibiting some of the most lethal aspects of cancer progression, further insight into the function of MDA-9/Syntenin is mandatory.

AREAS COVERED

Recent literature and seminal articles were reviewed to summarize the latest collective understanding of MDA-9/Syntenin's role in normal and cancerous settings. Insights into its participation in developmental processes are included, as is the functional significance of the N- and C-terminals and PDZ domains of MDA-9/Syntenin. Current reports highlight the clinical significance of MDA-9/Syntenin expression level in a variety of cancers, often correlating directly with reduced patient survival. Also presented are assessments of roles of MDA-9/Syntenin in cancer progression as well as its functions as an intracellular adapter molecule.

EXPERT OPINION

Multiple studies demonstrate the importance of MDA-9/Syntenin in tumor invasion and progression. Through the use of novel drug design approaches, this protein may provide a worthwhile therapeutic target. As many conventional therapies do not address, or even enhance, tumor invasion, an anti-invasive approach would be a worthwhile addition in cancer therapy.

Pancreatic cancer-specific cell death induced in vivo by cytoplasmic-delivered polyinosine-polycytidylic acid

Polyinosine-polycytidylic acid [pIC] is a synthetic dsRNA that acts as an immune agonist of TLR3 and RLR to activate dendritic and natural killer cells that can kill tumor cells. pIC can also trigger apoptosis in pancreatic ductal adenocarcinoma cells (PDAC) but its mechanism of action is obscure. In this study, we investigated the potential therapeutic activity of a formulation of pIC with polyethylenimine ([pIC](PEI)) in PDAC and investigated its mechanism of action. [pIC](PEI) stimulated apoptosis in PDAC cells without affecting normal pancreatic epithelial cells. Mechanistically, [pIC](PEI) repressed XIAP and survivin expression and activated an immune response by inducing MDA-5, RIG-I, and NOXA. Phosphorylation of AKT was inhibited by [pIC](PEI) in PDAC, and this event was critical for stimulating apoptosis through XIAP and survivin degradation. In vivo administration of [pIC](PEI) inhibited tumor growth via AKT-mediated XIAP degradation in both subcutaneous and quasi-orthotopic models of PDAC. Taken together, these results offer a preclinical proof-of-concept for the evaluation of [pIC](PEI) as an immunochemotherapy to treat pancreatic cancer.

Novel mechanism of MDA-7/IL-24 cancer-specific apoptosis through SARI induction

Subtraction hybridization combined with induction of cancer cell terminal differentiation in human melanoma cells identified melanoma differentiation-associated gene-7/interleukin-24 (mda-7/IL-24) and SARI (suppressor of AP-1, induced by IFN) that display potent antitumor activity. These genes are not constitutively expressed in cancer cells and forced expression of mda-7/IL-24 (Ad.mda-7) or SARI (Ad.SARI) promotes cancer-specific cell death. Ectopic expression of mda-7/IL-24 induces SARI mRNA and protein in a panel of different cancer cells, leading to cell death, without harming corresponding normal cells. Simultaneous inhibition of K-ras downstream extracellular signal-regulated kinase 1/2 signaling in pancreatic cancer cells reverses the translational block of MDA-7/IL-24 and induces SARI expression and cell death. Using SARI-antisense-based approaches, we demonstrate that SARI expression is necessary for mda-7/IL-24 antitumor effects. Secreted MDA-7/IL-24 protein induces antitumor "bystander" effects by promoting its own expression. Recombinant MDA-7/IL-24 (His-MDA-7) induces SARI expression, supporting the involvement of SARI in the MDA-7/IL-24-driven autocrine loop, culminating in antitumor effects. Moreover, His-MDA-7, after binding to its cognate receptors (IL-20R1/IL-20R2 or IL-22R/IL-20R2), induces intracellular signaling by phosphorylation of p38 MAPK, leading to transcription of a family of growth arrest and DNA damage inducible (GADD) genes, culminating in apoptosis. Inhibition of p38 MAPK fails to induce SARI following Ad.mda-7 infection. These findings reveal the significance of the mda-7/IL-24-SARI axis in cancer-specific killing and provide a potential strategy for treating both local and metastatic disease.

Selected approaches for rational drug design and high throughput screening to identify anti-cancer molecules

Structure-based modeling combined with rational drug design, and high throughput screening approaches offer significant potential for identifying and developing lead compounds with therapeutic potential. The present review focuses on these two approaches using explicit examples based on specific derivatives of Gossypol generated through rational design and applications of a cancer-specificpromoter derived from Progression Elevated Gene-3. The Gossypol derivative Sabutoclax (BI-97C1) displays potent anti-tumor activity against a diverse spectrum of human tumors. The model of the docked structure of Gossypol bound to Bcl-XL provided a virtual structure-activity-relationship where appropriate modifications were predicted on a rational basis. These structure-based studies led to the isolation of Sabutoclax, an optically pure isomer of Apogossypol displaying superior efficacy and reduced toxicity. These studies illustrate the power of combining structure-based modeling with rational design to predict appropriate derivatives of lead compounds to be empirically tested and evaluated for bioactivity. Another approach to cancer drug discovery utilizes a cancer-specific promoter as readouts of the transformed state. The promoter region of Progression Elevated Gene-3 is such a promoter with cancer-specific activity. The specificity of this promoter has been exploited as a means of constructing cancer terminator viruses that selectively kill cancer cells and as a systemic imaging modality that specifically visualizes in vivo cancer growth with no background from normal tissues. Screening of small molecule inhibitors that suppress the Progression Elevated Gene-3-promoter may provide relevant lead compounds for cancer therapy that can be combined with further structure-based approaches leading to the development of novel compounds for cancer therapy.

The secreted protein acidic and rich in cysteine (SPARC) induces endoplasmic reticulum stress leading to autophagy-mediated apoptosis in neuroblastoma

Our previous studies showed that overexpression of secreted protein acidic and rich in cysteine (SPARC) induced autophagy-mediated apoptosis in PNET cells. In the present study, we attempted to elucidate the molecular mechanisms and signaling cascades associated with SPARC overexpression in combination with radiation therapy that eventually leads to autophagy-mediated apoptosis in neuroblastoma. SPARC expression in SK-N-AS and NB-1691 cells demonstrated the activation of caspase 3, cleavage of PARP and induction of apoptosis. The experiments to unravel the mechanisms associated with autophagy-apoptosis illustrated that SPARC overexpression triggered endoplasmic reticulum (ER) stress and thereby unfolded protein response (UPR). This was apparent with the activation of stress receptors, inositol-requiring enzyme (IRE 1α), RNA-dependent protein kinase (PKR)-like ER kinase (PERK) and BiP. This study further demonstrated the induction of transcription factor CHOP as a result of IRE-JNK activation in response to increased SPARC levels. Inhibition of ER stress and JNK activation led to inhibition of autophagy-mediated apoptosis. Further, the apparent expression of ER stress molecules among the orthotopic tumors treated by SPARC overexpression plasmids substantiated our in vitro observations. Taken together, these results illustrate the critical role of ER stress in regulating autophagy-mediated apoptosis in SPARC-overexpressed neuroblastoma cells and radiation treatment.

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.

SPARC overexpression inhibits cell proliferation in neuroblastoma and is partly mediated by tumor suppressor protein PTEN and AKT

Secreted protein acidic and rich in cysteine (SPARC) is also known as BM-40 or Osteonectin, a multi-functional protein modulating cell–cell and cell–matrix interactions. In cancer, SPARC is not only linked with a highly aggressive phenotype, but it also acts as a tumor suppressor. In the present study, we sought to characterize the function of SPARC and its role in sensitizing neuroblastoma cells to radio-therapy. SPARC overexpression in neuroblastoma cells inhibited cell proliferation in vitro. Additionally, SPARC overexpression significantly suppressed the activity of AKT and this suppression was accompanied by an increase in the tumor suppressor protein PTEN both in vitro and in vivo. Restoration of neuroblastoma cell radio-sensitivity was achieved by overexpression of SPARC in neuroblastoma cells in vitro and in vivo. To confirm the role of the AKT in proliferation inhibited by SPARC overexpression, we transfected neuroblastoma cells with a plasmid vector carrying myr-AKT. Myr-AKT overexpression reversed SPARC-mediated PTEN and increased proliferation of neuroblastoma cells in vitro. PTEN overexpression in parallel with SPARC siRNA resulted in decreased AKT phosphorylation and proliferation in vitro. Taken together, these results establish SPARC as an effector of AKT-PTEN-mediated inhibition of proliferation in neuroblastoma in vitro and in vivo.

Abstract 4758: Self-assembled superparamagnetic iron oxide nanoparticles for targeted cancer therapy

Surface engineered iron oxide nanoparticles offer greater potential for targeted gene therapy as compared to many of the current treatment modalities for cancer. The intrinsic superparamagnetism of iron oxide nanoparticles along with a bio-inspired coating to circumvent the physiological and cellular barriers suggests their usefulness as an efficient non-invasive therapeutic option to invoke the desired response at the tumor site. In the present study, a novel functionalized iron oxide nanoparticle based polyplex system that explores the greater potentials of self-assembly together with magnetic targeting is employed for “smart targeting” and to improve therapeutic index. Poly (L-glutamic acid) functionalized iron oxide nanoparticles (Feg) were synthesized and complexed with plasmid DNA containing the gene of interest in the presence of carboxymethyl chitosan (CMCS). The preliminary characterization of the nanoparticles was performed by X-ray diffraction and FT-IR analysis. The formation and the internalization of Feg-CMCS-DNA polyplex occurred irrespective of the type of DNA as illustrated by gel retardation assay and Prussian blue staining, respectively. The Feg-CMCS nanoparticles, when conjugated with secreted protein acidic and rich in cysteine (SPARC)-overexpressing plasmid, showed excellent cytocompatibility (evident from MTT assay, morphology and organization of cytoskeleton) with comparable in vitro biofunctionality (illustrated by western blot analysis) as that of a commonly used transfection agent. The supramolecular assembly of the (Feg-CMCS-SPARC) polyplex system was manifested by scanning and transmission electron micrographs. The mechanism of internalization of the polyplex system and the role of magnetic field in enhancing the internalization were observed by transmission electron microscopy. Further, Feg-CMCS-SPARC polyplex transfection resulted in significant inhibition of in vitro tumor angiogenesis. This study highlights the superior efficacy of Feg-CMCS-SPARC self-assembled polyplex system for use as a localized therapeutic drug in vivo at the tumor site.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 4758. doi:1538-7445.AM2012-4758

Abstract 3453: SPARC overexpression inhibits cell proliferation in neuroblastoma and is partly mediated by tumor suppressor protein PTEN and AKT

Secreted protein acidic and rich in cysteine (SPARC) is also known as BM-40 or Osteonectin a multi-functional protein modulating cell-cell and cell-matrix interactions. In cancer, SPARC is not only linked with a highly aggressive phenotype, but it also acts as a tumor suppressor. In the present study, we sought to characterize the function of SPARC and its role in sensitizing neuroblastoma cells to radio-therapy. SPARC overexpression in neuroblastoma cells inhibited cell proliferation in vitro. Additionally, SPARC overexpression significantly suppressed the activity of AKT and this suppression was accompanied by an increase in the tumor suppressor protein PTEN both in vitro and in vivo. Restoration of neuroblastoma cell radio-sensitivity was achieved by overexpression of SPARC in neuroblastoma cells in vitro and in vivo. To confirm the role of the AKT in proliferation inhibited by SPARC overexpression, we transfected neuroblastoma cells with a plasmid vector carrying myr-AKT. AKT overexpression reversed SPARC-mediated PTEN and increased proliferation of neuroblastoma cells in vitro. PTEN overexpression in parallel with SPARC siRNA resulted in decreased AKT phosphorylation and proliferation in vitro. Taken together, these results establish SPARC as an effector of AKT-PTEN-mediated inhibition of proliferation in neuroblastoma in vitro and in vivo.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 3453. doi:1538-7445.AM2012-3453

Abstract 4992: SPARC overexpression induces ER stress leading to autophagy-mediated apoptosis in neuroblastoma cells

Neuroblastoma is the most common extracranial solid tumor affecting children. Long-term survival for children (older than 18 months of age) with advanced disease is poor despite aggressive multimodal therapy. Normal cellular apoptosis is affected in multiple ways in a variety of diseases, including cancer. Our earlier studies showed that SPARC overexpression induced autophagy-mediated apoptosis in PNET cells. In the present study, we attempt to determine the signaling cascade associated with initiation of autophagy and apoptosis as a result of SPARC overexpression in combination with radiation. As demonstrated by TUNEL assay, neuroblastoma cells showed increased apoptosis with the combination treatment as compared to treatment with either SPARC or radiation alone. In corroboration, we also observed activation of caspase 3, and cleavage of PARP and Bid as determined by Western blotting. The combination treatment triggered endoplasimic reticulum (ER) stress and thereby an unfolded protein (UPR) response. This was apparent with the activation of stress receptors, pancreatic ER kinase (PERK) and inositol-requiring enzyme (IRE 1), as shown by western blotting. ER stress led to mitochondrial dysfunction through activation of eukaryotic initiation factor 2α (eIF2 α; another ER resident protein). In addition, we demonstrate that overexpression of SPARC induced IRE-JNK activation, leading to induction of the transcription factor CHOP. Inhibition of ER stress (or JNK activation) led to inhibition of autophagy-mediated apoptosis as demonstrated by decreased levels of LC3-II, and cleavage of caspase 3, PARP and Bid. Taken together, these results demonstrate the involvement of ER stress in regulating autophagy-mediated apoptosis in neuroblastoma cells treated with radiation and SPARC overexpression.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 4992. doi:1538-7445.AM2012-4992

Abstract 4358: Notch signaling regulates tumor-induced angiogenesis in SPARC-overexpressed neuroblastoma

Despite existing aggressive treatment modalities, survival 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. SPARC (also known as BM-40 or osteonectin), a matricellular protein, is known to inhibit the proliferation and migration of endothelial cells stimulated by growth factors and induces endothelial cell apoptosis. 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. SPARC overexpression in neuroblastoma cells inhibited neo-vascularization in vivo as determined by the mouse dorsal air sac model. In addition, conditioned medium from SPARC-overexpressed neuroblastoma cancer cells (pSPARC-CM) inhibited endothelial tube formation in vitro. SPARC-overexpressed tumor cell conditioned medium decreased proliferation (as determined by MTT assay and Ki-67 immunofluorescence) and induced apoptosis in endothelial cells (as determined by TUNEL assay). Furthermore, SPARC-overexpressed tumor cell conditioned medium inhibited expression of the pro-angiogenic molecules VEGF, FGF, PDFG, and MMP-9 as determined by human angiogenesis-PCR array. In addition to the inhibition of growth factors, SPARC-overexpressed tumor cell conditioned medium inhibited Notch signaling molecules in HMEC cells as determined by Western blotting. Conditioned medium from neuroblastoma cells overexpressed with Notch intracellular domain after SPARC overexpression, induced growth factors and led to increased tube formation in vitro. In vivo endothelial cell death was confirmed by co-localization studies with TUNEL assay, and an endothelial marker, CD31, in tumor sections from SPARC-overexpressed mice. Our data collectively suggest that SPARC overexpression induces endothelial cell apoptosis in vivo and inhibits angiogenesis both in vitro and in vivo.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 4358. doi:1538-7445.AM2012-4358

SPARC stimulates neuronal differentiation of medulloblastoma cells via the Notch1/STAT3 pathway

Secreted protein acidic and rich in cysteine (SPARC) participates 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, and MAP-2 in medulloblastoma cells and induced neuron-like differentiation. SPARC overexpression decreased 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 interleukin 6 (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.

Suppression of MMP-2 attenuates TNF-α induced NF-κB activation and leads to JNK mediated cell death in glioma

Background

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.

Methodology/Principal Findings

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.

Conclusion/Significance

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.

Abstract 3468: MMP-9 inhibition abolishes hypoxia-induced angiogenesis in medulloblastoma

Hypoxia-inducible factor-1 (HIF-1) transcription factor is a critical mediator of the hypoxic response and upregulates expression of various proteins that promote angiogenesis and many other survival pathways in cancer. Overexpression of HIF-1α and matrix metalloproteinase-9 (MMP-9) is common in human cancers, including medulloblastoma, and is correlated with a malignant phenotype. Therefore, we investigated the effects of hypoxia-induced MMP-9 on angiogenesis in medulloblastoma cells. Western blotting and immunohistochemical analysis showed that hypoxia enhanced stabilization of HIF-1α and expression of VEGF and MMP-9 in medulloblastoma cells in vivo and in vitro. Further, endothelial tube formation assay in vitro and dorsal air sac assay in vivo showed that hypoxia enhanced angiogenesis in medulloblastoma cells. Transcriptional inactivation of MMP-9 using siRNA (pMMP-9-Si) inhibited hypoxia-induced stabilization of HIF-1α, and induced expression of VEGF and prolyl hydroxylase. Moreover, supplementation of human recombinant MMP-9 in MMP-9-Si-transfected cells restored VEGF expression and angiogenesis. In summary, the results of the present study indicate that MMP-9 upregulation could be an important mediator of tumor hypoxia-induced angiogenesis. Therefore, inhibition of MMP-9 could be an effective therapeutic strategy for the treatment of hypoxic medulloblastoma cells.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 3468. doi:10.1158/1538-7445.AM2011-3468

Abstract 4787: MMP-2 RNA interference leads to decreased NF-κB activation and induced JNK-mediated apoptosis by modulating TRADD-TRAF2-FADD interactions in glioma

MMP-2 belongs to a family of extracellular matrix metalloproteinases (MMPs) that play a pivotal role in the degradation of the ECM, thereby enhancing the invasive and metastatic potential of cancer cells. Our study unveiled a new mechanism of how MMP-2 RNA interference inhibits NF-κB activation. Essentially, siRNA against MMP-2 (pM) modulated the interactions between the adaptor protein TRADD-TRAF2 and TRADD-FADD, which consequently hindered the nuclear localization and DNA binding activity of NF-κB. This, in turn, led to apoptosis. Furthermore, pM treatment led to RIP cleavage and remarkable increases in the expression levels of FADD and activated MAP kinases, p38 MAPK and JNK. The prolonged activation of JNK resulted in phosphorylation of c-Jun. Treatments with specific JNK1 inhibitor (SP600125) reduced and significantly reversed the pro-apoptotic effect of pM, thereby suggesting a role of JNK in pM-induced cell death. Supplementation of recombinant human MMP-2 to pM-transfected cells restored the inhibited DNA binding activity of NF-κB and rescued cells from the pro-apoptotic effect of pM. Here, we demonstrate that the simultaneous inhibition of NF-κB activation and sustained activation of JNK play significant roles in pM-mediated apoptosis in human xenograft glioma cells. In addition, our results show that the specific downregulation of MMP-2 diminished intracranial tumor growth in vivo. The inhibition of tumor growth after pM treatment was associated with decreased MMP-2 expression, inhibited NF-κB activation, and enhanced phospho-JNK levels. In conclusion, the present study elucidates an underlying mechanism of pM-induced cell death in vitro as well as decreased tumor development in vivo.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 4787. doi:10.1158/1538-7445.AM2011-4787

Abstract 1493: Tumor-associated soluble uPAR enhances endothelial cell migration by staffing into lipid rafts

The expression of urokinase plasminogen activator receptor (uPAR), a heavily glycosylated glycosyl-phosphatidylinositol (GPI)-anchored cell surface receptor, induces cell migration, and its expression correlates with the malignant phenotype of various cancers. The soluble form of uPAR (s-uPAR), which is found in the circulation of cancer patients, is associated with tumor malignancy and serves as a prognostic marker for various cancers. As such, in the current study, we analyzed the effect of s-uPAR from glioblastoma tumor cell conditioned medium (TCM) on endothelial cell migration. Here, we present evidence that s-uPAR from tumor cells augments migration and invasion on vitronectin and fibronectin matrices of human umbilical vein endothelial cells (HUVEC). The membrane fraction of HUVEC, which were cultured on TCM, had increased amounts of s-uPAR recruited into the membranes of endothelial cells. Co-localization studies for GM1 ganglioside receptor (a lipid raft marker) and uPAR further demonstrated s-uPAR recruitment into lipid rafts of HUVEC. Further, western blot analysis for uPAR in lipid raft fractions from HUVEC cells grown on TCM confirmed s-uPAR recruiting onto HUVEC cell membranes. Moreover, the addition of functional blocking uPAR antibodies to TCM mitigated s-uPAR-enhanced HUVEC migration and invasion. Our data suggest that s-uPAR from tumor cells might be involved in the recruitment of endothelial cells in the tumor microenvironment.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 1493. doi:10.1158/1538-7445.AM2011-1493

MMP-2 mediates mesenchymal stem cell tropism towards medulloblastoma tumors

Matrix metalloproteinases (MMPs) are a family of proteinases known to have a role in cell migration. In the present study, we evaluated the role of MMP-2 on tropism of human umbilical 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 small interfering RNA (siRNA) (Ad-MMP-2 si)-reduced stem cell migration as compared with conditioned medium from mock and scrambled vector (Ad-SV) infected cells. In addition, MMP-2 inhibition in the tumor cells decreased the expression of stromal cell-derived factor 1 (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.

uPAR/cathepsin B overexpression reverse angiogenesis by rescuing FAK phosphorylation in uPAR/cathepsin B down regulated meningioma

BACKGROUND

Meningiomas are the most commonly occurring intracranial tumors and account for approximately 15-20% of central nervous system tumors. Surgery and radiation therapy is a common treatment for brain tumors, however, patients whose tumors recur after such treatments have limited therapeutic options. Earlier studies have reported important roles of uPA, uPAR and cathepsin B in tumor progression.

METHODOLOGY/PRINCIPAL FINDINGS

In the present study, we examined the therapeutic significance of RNAi-mediated simultaneous down regulation of these proteolytic networks using two bicistronic siRNA constructs, pUC (uPAR/cathepsin B) and pU2 (uPA/uPAR) either alone or in combination with radiation in two different meningioma cell lines. Transfection of meningioma cells with pUC and pU2 significantly reduced angiogenesis as compared to control treatment both in vitro and in vivo nude mice model. This effect is mediated by inhibiting angiogenic molecules (Ang-1, Ang-2 and VEGF). Expression of focal adhesion kinase (FAK) is elevated in malignant meningioma, yet the role of intrinsic FAK activity in promoting tumor progression remains undefined. We found that pUC treatment reduced FAK phosphorylation at Y925 more efficiently compared to pU2 treatment. In immunoprecipitation assay, we found pronounced reduction of FAK (Y925) interaction with Grb2 in meningioma cells transfected with pUC with and without irradiation. Transient over-expression of uPAR and cathepsin B by full length uPAR/cathepsin B (FLpU/C) in pUC transfected meningioma cells promoted vascular phenotype, rescued expression of Ang-1, Ang-2, VEGF, FAK (Y925) and Grb2 both in vitro and in vivo mice model.

CONCLUSION/SIGNIFICANCE

These studies provide the first direct proof that bicistronic siRNA construct for uPAR and cathepsin B (pUC) reduces Y925-FAK activity and this inhibition is rescued by overexpression of both uPAR and cathepsin B which clearly demonstrates that pUC could thus be a potential therapeutic approach as an anti-angiogenic agent in meningioma.

Downregulation of uPA/uPAR inhibits intermittent hypoxia-induced epithelial-mesenchymal transition (EMT) in DAOY and D283 medulloblastoma cells

Hypoxia is known to induce overexpression of the urokinase plasminogen activator (uPA) and its receptor (uPAR) and thus overexpression promotes uPAR-mediated survival signaling in various cancers. Moreover, hypoxia/ overexpression of uPAR in cancer cells promote the epithelial-mesenchymal transition (EMT) and thereby invasiveness and metastasis. In this study, we show that intermittent hypoxia has a more pronounced effect than chronic hypoxia and contributes to EMT, invasion and migration in medulloblastoma cells. Intermittent hypoxia induced expression of mesenchymal markers (i.e., SNAIL, Vimentin and N-cadherin) and reduced expression of epithelial markers (i.e., Zo-1, E-cadherin) in medulloblastoma cells. Further, intermittent hypoxia also leads to enhancement in cell invasion, migration and angiogenesis in medulloblastoma cells. Intermittent hypoxia also inhibited expression of pro-anti-apoptotic proteins (Bax and Bad), and induced expression of anti-pro-apoptotic proteins (Bcl2 and Bcl-xL), and activation of ERK in medulloblastoma cells. Transcriptional inactivation of either uPA or uPAR inhibits the intermittent hypoxia-induced invasion and migration, and expression of Vimentin. uPA/ uPAR downregulation also induces E-cadherin expression and inhibits activation of ERK. Thus, transcriptional inactivation of either uPA or uPAR enhances the apoptotic response in medulloblastoma cells exposed to intermittent hypoxia. This study provides evidence of the anti-tumor efficacy of down-regulation of uPA or uPAR in medulloblastoma tumors to target hypoxia-induced cell EMT, invasion and migration, to achieve better therapeutic outcomes in the treatment of malignant medulloblastoma.

Suppression of uPAR retards radiation-induced invasion and migration mediated by integrin β1/FAK signaling in medulloblastoma

BACKGROUND

Despite effective radiotherapy for the initial stages of cancer, several studies have reported the recurrence of various cancers, including medulloblastoma. Here, we attempt to capitalize on the radiation-induced aggressive behavior of medulloblastoma cells by comparing the extracellular protease activity and the expression pattern of molecules, known to be involved in cell adhesion, migration and invasion, between non-irradiated and irradiated cells.

METHODOLOGY/PRINCIPAL FINDINGS

We identified an increase in invasion and migration of irradiated compared to non-irradiated medulloblastoma cells. RT-PCR analysis confirmed increased expression of uPA, uPAR, focal adhesion kinase (FAK), N-Cadherin and integrin subunits (e.g., α3, α5 and β1) in irradiated cells. Furthermore, we noticed a ∼2-fold increase in tyrosine phosphorylation of FAK in irradiated cells. Immunoprecipitation studies confirmed increased interaction of integrin β1 and FAK in irradiated cells. In addition, our results show that overexpression of uPAR in cancer cells can mimic radiation-induced activation of FAK signaling. Moreover, by inhibiting FAK phosphorylation, we were able to reduce the radiation-induced invasiveness of the cancer cells. In this vein, we studied the effect of siRNA-mediated knockdown of uPAR on cell migration and adhesion in irradiated and non-irradiated medulloblastoma cells. Downregulation of uPAR reduced the radiation-induced adhesion, migration and invasion of the irradiated cells, primarily by inhibiting phosphorylation of FAK, Paxillin and Rac-1/Cdc42. As observed from the immunoprecipitation studies, uPAR knockdown reduced interaction among the focal adhesion molecules, such as FAK, Paxillin and p130Cas, which are known to play key roles in cancer metastasis. Pretreatment with uPAR shRNA expressing construct reduced uPAR and phospho FAK expression levels in pre-established medulloblastoma in nude mice.

CONCLUSION/SIGNIFICANCE

Taken together, our results show that radiation enhances uPAR-mediated FAK signaling and by targeting uPAR we can inhibit radiation-activated cell adhesion and migration both in vitro and in vivo.

Urokinase plasminogen activator receptor and/or matrix metalloproteinase-9 inhibition induces apoptosis signaling through lipid rafts in glioblastoma xenograft cells

Small interfering RNA (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 caspase-8, caspase-3, and poly(ADP-ribose) polymerase. 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, and procaspase-8 into lipid rafts. Additionally, disruption of lipid rafts with methyl β cyclodextrin prevented Fas clustering and pU-Si-, pM-Si-, or pUM-Si-induced apoptosis, which is indicative of coclustering of Fas death receptor into lipid rafts in the glioblastoma xenograft cell 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-downregulated cells.

MMP-2 alters VEGF expression via alphaVbeta3 integrin-mediated PI3K/AKT signaling in A549 lung cancer cells

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, phosphatidylinositol 3-kinase (PI3K) protein levels and AKT phosphorylation in lung cancer cells. In addition, MMP-2 suppression decreased hypoxia inducible factor-1alpha (HIF-1alpha), a transcription factor for VEGF, as determined by electrophoretic mobility shift assay (EMSA). We also show that MMP-2 suppression disrupted PI3K dependent VEGF expression; ectopic expression of myr-AKT restored VEGF inhibition. Further, MMP-2 suppression decreased the interaction of integrin-alphaVbeta3 and MMP-2 as confirmed by immunoprecipitation analyses. Studies with either function blocking integrin-alphaVbeta3 antibody or MMP-2 specific inhibitor (ARP-100) indicate that suppression of MMP-2 decreased integrin-alphaVbeta3-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-alphaVbeta3 and MMP-2. In summary, these data provide new insights into the mechanisms underlying MMP-2-mediated VEGF expression in lung tumor angiogenesis.

Abstract 1313: SPARC enhances radiosensitivity by inhibiting radiation-induced SOX-4 transcription factor in medulloblastoma

Radiotherapy is frequently applied to control local tumors and works by directly killing tumor cells and inducing apoptosis of tumor vascular endothelial cells. Recently, it has been demonstrated that expression of secreted protein, acidic and rich in cysteine (SPARC), a member of the matricellular family of proteins that modulate cell-cell and cell-matrix interactions, correlates with radio-resistance in several tumor types. We therefore investigated the anti-tumor effects of combining exogenously expressing SPARC full length cDNA with irradiation (IR) on medulloblastoma in vitro and in vivo. We studied a combination response of SPARC overexpression and IR; specifically, we determined cell survival using clonogenic assay, conducted cell cycle analysis using flow cytometry, and assessed apoptosis using TUNEL staining in vitro in D283 and DAOY medulloblastoma cells. We demonstrated that SPARC overexpression prevented IR-induced p53 upregulation and p53 phosphorylation on serine 15. Irradiated tumor cells induced SOX-4-mediated DNA repair gene XRCC1, checkpoints-2, 1 and p53, which were abrogated with combined treatment of SPARC overexpression and IR as determined by western blotting. Further, DAOY orthotopic tumors treated with combined exogenously expressed SPARC and IR showed significantly greater growth inhibition than tumors treated with IR alone. These results suggest that SPARC overexpression in combination with radiotherapy can inhibit SOX-4-mediated DNA repair mechanisms induced by radiation and provide evidence of the anti-tumor efficacy of combining SPARC overexpression with ionizing radiation as a new therapeutic strategy for the effective treatment of medulloblastoma patients.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 1313.

Abstract 2330: MMP-2 regulates Rac1- and Cdc42-mediated cell migration via integrin αVβ3/FAK in U87 and U251 glioblastoma cell lines

Gliomas, the most common form of brain tumors, are characterized by a capacity to invade through normal brain tissue. This infiltrative character is the hallmark of poor prognosis. A greater understanding of the molecular determinants that drive cell motility may lead to improved therapy. The molecules of the extracellular matrix are involved in organization of the cytoskeleton and activation of intracellular signaling that is required for the regulation of cell adhesion and migration. Here, we show that the downregulation of matrix metalloproteinase-2 (MMP-2; gelatinase A) using an adenoviral vector expressing siRNA (Ad-MMP-2-Si) inhibited cell migration in U87 and U251 glioblastoma cell lines as determined by spheroid migration and wound-healing assays. Transcriptional inactivation of MMP-2 altered interaction of MMP-2 and the integrin-αVβ3 as determined by immunoprecipitation and co-localization studies. In addition, downregulation of MMP-2 inhibited the complex formation of FAK, integrin-αVβ3 and 14-3-3ζ, which in turn decreased the activation of GTP-bound forms of Rac1 and Cdc42. Transfection of the cells with constitutively active Rac1 and Cdc42 reversed Ad-MMP-2-Si-blocked cell migration and gelatin degrading. Further, administration of recombinant human MMP-2 reversed MMP-2 siRNA-inhibited GTP-bound forms of Rac1 and Cdc42. Additionally, functionally blocking integrin-αVβ3 antibody inhibited GTP-bound forms of Rac1 and Cdc42, thereby revealing that the interaction of MMP-2 and integrin-αVβ3 plays a critical role in cell migration. In summary, our data demonstrate that the inhibition of MMP-2 inhibits integrin-αVβ3/FAK-mediated migration by reducing the GTP-bound forms of Rac1 and Cdc42 in U87 and U251 glioblastoma cell lines.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 2330.

Abstract 2291: Downregulation of uPA/uPAR inhibits epithelial to mesenchymal transition (EMT) in intermittent hypoxic DAOY and D283 medulloblastoma cells

Medulloblastoma is the most common, rapidly growing tumor of the cerebellum, which arises in childhood and has a tendency to metastasize via cerebrospinal fluid (CSF) pathways. In addition to surgical resection, post-operative radiotherapy and chemotherapy are the mainstays in treating patients with medulloblastoma. However, these tumors remain among the most challenging pediatric brain tumors. Factors related to the tumor microenvironment are being recognized as fundamental to tumor progression, increased resistance and metastasis. Hypoxia, one of these factors, leads to epigenetic and genetic adaptation of clones and increased EMT, invasiveness and metastasis. Thus, hypoxia is closely associated with tumorigenesis and provides tumors the ability to outgrow the existing vasculature. In this study, we show that intermittent hypoxia has a more pronounced effect than chronic hypoxia and is responsible for EMT, invasion, migration, and survival of hypoxic-conditioned medulloblastoma cells. We also show that Akt and SNAIL are activated under hypoxia, and this response is blocked by plasmid vector-mediated delivery of uPA/uPAR siRNA. The linkage of uPAR to Akt activation under hypoxia provides one mechanism by which uPAR may regulate SNAIL, and thus, promote EMT. The results presented here suggest that, in cells that express high levels of uPAR, induction and maintenance of EMT depends on simultaneous activation of numerous cell-signaling factors downstream of uPAR. This study provides valuable evidence of the anti-tumor efficacy of plasmid vector-mediated delivery of uPA/uPAR siRNA in hypoxic-conditioned medulloblastoma cells to target intermittent hypoxia-induced cell invasion, migration, angiogenesis and EMT and to achieve better therapeutic outcomes in the treatment of malignant medulloblastomas

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 2291.

Abstract 2286: SPARC stimulates neuronal differentiation of medulloblastoma cells via the IL-6/STAT3 pathway

Secreted Protein Acidic and Rich in Cysteine (SPARC), a 37-kDa glycoprotein, participates in the regulation of morphogenesis and cellular differentiation through its modulation of cell-matrix interactions. We have reported previously that SPARC expression significantly impairs medulloblastoma tumor growth in vivo. In this study, we show that the ectopic expression of SPARC induces neuronal differentiation in medulloblastoma cells. Adenovirus-mediated expression of SPARC cDNA (Ad-DsRed-SP) elevated the expression of neuronal markers NeuN, Nestin and MAP-2 in medulloblastoma cells. SPARC expression decreased STAT3 phosphorylation and constitutive expression of STAT3 reversed SPARC-mediated neuronal differentiation. Moreover, our results show that SPARC expression not only inhibited interleukin (IL)-6 but also attenuated IL-6-mediated STAT3 phosphorylation in medulloblastoma cells. Taken together, our results suggest that SPARC induced neuronal differentiation of medulloblastoma tumor cells through its inhibitory effect on IL-6-mediated STAT3 signaling. Immunohistochemical analysis of tumor sections from mice treated with Ad-DsRed-SP showed increased staining for the neuronal markers NeuN, Nestin and MAP-2. Overall, our results demonstrate that SPARC promotes neuronal differentiation and inhibits tumor growth, thereby further supporting the potential use of SPARC as a therapeutic target for medulloblastoma.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 2286.

The role of MMP-9 in the anti-angiogenic effect of secreted protein acidic and rich in cysteine

Background:

Secreted protein acidic and rich in cysteine (SPARC), a matricellular glycoprotein, modulates cellular interaction with the extracellular matrix and is capable of altering the growth of various cancers. We therefore sought to determine the effect of SPARC expression on medulloblastoma tumour growth and angiogenesis.

Methods:

To this extent, we selected three SPARC full-length cDNA overexpressed clones (Daoy-SP). Consequences of SPARC overexpression were studied in terms of cell growth, angiogenesis using co-culture assay in vitro, dorsal skin-fold chamber assay in vivo, PCR Array for human angiogenic genes, as well as western blotting for angiogenic molecules and tumour growth, in an orthotopic tumour model.

Results:

The SPARC protein and mRNA levels were increased by approximately three-fold in Daoy-SP cells compared with parental (Daoy-P) and vector (Daoy-EV) controls. Daoy-SP clones reduced tumour cell-induced angiogenesis in vitro and in vivo, and formed small tumours with fewer blood vessels when compared with controls. Matrix metalloprotease-9 (MMP-9) and vascular endothelial growth factor (VEGF) expression were decreased in Daoy-SP clones. Further, inhibition of MMP-9 expression caused SPARC-mediated inhibition of angiogenesis and tumour growth as MMP-9 rescued SPARC-mediated anti-angiogenic effect in vitro and tumour growth inhibition in vivo.

Conclusion:

Overexpression of SPARC decreases angiogenesis, which leads to decreased tumour growth. Further, the role of MMP-9 could be attributed to the anti-angiogenic effect of SPARC.