Staphylococcal Nuclease and Tudor Domain Containing 1 (SND1 Protein) Promotes Hepatocarcinogenesis by Inhibiting Monoglyceride Lipase (MGLL)

Staphylococcal nuclease and tudor domain containing 1 (SND1) is overexpressed in multiple cancers, including hepatocellular carcinoma (HCC), and functions as an oncogene. This study was carried out to identify novel SND1-interacting proteins to better understand its molecular mechanism of action. SND1-interacting proteins were identified by a modified yeast two-hybrid assay. Protein-protein interaction was confirmed by co-immunoprecipitation analysis. Monoglyceride lipase (MGLL) expression was analyzed by quantitative RT-PCR, Western blot, and immunohistochemistry. MGLL-overexpressing clones were analyzed for cell proliferation and cell cycle analysis and in vivo tumorigenesis in nude mice. MGLL was identified as an SND1-interacting protein. Interaction of SND1 with MGLL resulted in ubiquitination and proteosomal degradation of MGLL. MGLL expression was detected in normal human hepatocytes and mouse liver, although it was undetected in human HCC cell lines. An inverse correlation between SND1 and MGLL levels was identified in a human HCC tissue microarray as well as in the TCGA database. Forced overexpression of MGLL in human HCC cells resulted in marked inhibition in cell proliferation with a significant delay in cell cycle progression and a marked decrease in tumor growth in nude mouse xenograft assays. MGLL overexpression inhibited Akt activation that is independent of enzymatic activity of MGLL and overexpression of a constitutively active Akt rescued cells from inhibition of proliferation and restored normal cell cycle progression. This study unravels a novel mechanism of SND1 function and identifies MGLL as a unique tumor suppressor for HCC. MGLL might function as a homeostatic regulator of Akt restraining its activation.

Critical Length of PEG Grafts on lPEI/DNA Nanoparticles for Efficient in Vivo Delivery

Nanoparticle-mediated gene delivery is a promising alternative to viral methods; however, its use in vivo, particularly following systemic injection, has suffered from poor delivery efficiency. Although PEGylation of nanoparticles has been successfully demonstrated as a strategy to enhance colloidal stability, its success in improving delivery efficiency has been limited, largely due to reduced cell binding and uptake, leading to poor transfection efficiency. Here we identified an optimized PEGylation scheme for DNA micellar nanoparticles that delivers balanced colloidal stability and transfection activity. Using linear polyethylenimine (lPEI)-g-PEG as a carrier, we characterized the effect of graft length and density of polyethylene glycol (PEG) on nanoparticle assembly, micelle stability, and gene delivery efficiency. Through variation of PEG grafting degree, lPEI with short PEG grafts (molecular weight, MW 500–700 Da) generated micellar nanoparticles with various shapes including spherical, rodlike, and wormlike nanoparticles. DNA micellar nanoparticles prepared with short PEG grafts showed comparable colloidal stability in salt and serum-containing media to those prepared with longer PEG grafts (MW 2 kDa). Corresponding to this trend, nanoparticles prepared with short PEG grafts displayed significantly higher in vitro transfection efficiency compared to those with longer PEG grafts. More importantly, short PEG grafts permitted marked increase in transfection efficiency following ligand conjugation to the PEG terminal in metastatic prostate cancer-bearing mice. This study identifies that lPEI-g-PEG with short PEG grafts (MW 500–700 Da) is the most effective to ensure shape control and deliver high colloidal stability, transfection activity, and ligand effect for DNA nanoparticles in vitro and in vivo following intravenous administration.

Activation of the MDA-5-IPS-1 Viral Sensing Pathway Induces Cancer Cell Death and Type I IFN-Dependent Antitumor Immunity

Melanoma differentiation-associated gene 5 (MDA-5, IFIH1), a cytosolic innate pattern recognition receptor, functions as a first line of defense against viral infection by sensing double-stranded RNA. Ectopic expression of MDA-5 has been shown to induce cancer cell death, but the mechanism of action by which MDA-5 exerts these cytotoxic effects is unclear. Here, we demonstrate that ectopic expression of MDA-5 via replication-incompetent adenovirus (Ad.Mda-5) initiates multiple signaling cascades, culminating in cytotoxicity and type I IFN production in mouse and human prostate cancer cells. This intrinsic dual activity of MDA-5 required the adaptor protein IFNβ promoter stimulator 1 (IPS-1, MAVS) and could be functionally uncoupled. MDA-5 lacking N-terminal caspase recruitment domains (CARD) engaged an intracellular death program in cancer cells but was unable to efficiently stimulate the expression of IFNβ. In contrast to cancer cells susceptible to MDA-5-mediated cytotoxicity, normal cells were highly resistant and instead developed a robust type I IFN response. Strikingly, intratumoral delivery of Ad.Mda-5 led to regression of preestablished prostate cancers and development of long-lasting antitumor immune memory, which was primarily attributed to the activation of tumor-reactive cytotoxic T lymphocytes and/or natural killer cells. Using the CARD-truncated MDA-5 mutant, silencing of IPS-1, and antibody blockade of the IFNα/β receptor, we further demonstrate that type I IFN signaling was crucial for in situ MDA-5-induced protective antitumor immunity. Therefore, deliberately targeting the evolutionarily conserved MDA-5-IPS-1 antiviral pathway in tumors can provoke parallel tumoricidal and immunostimulatory effects that bridge innate and adaptive immune responses for the therapeutic treatment of cancer. Cancer Res; 76(8); 2166-76. ©2016 AACR.

Overcoming Akt Induced Therapeutic Resistance in Breast Cancer through siRNA and Thymoquinone Encapsulated Multilamellar Gold Niosomes

Akt overexpression in cancer causes resistance to traditional chemotherapeutics. Silencing Akt through siRNA provides new therapeutic options; however, poor in vivo siRNA pharmacokinetics impede translation. We demonstrate that acidic milieu-sensitive multilamellar gold niosomes (Nio-Au) permit targeted delivery of both Akt-siRNA and thymoquinone (TQ) in tamoxifen-resistant and Akt-overexpressing MCF7 breast cancer cells. Octadecylamine groups of functionalized gold nanoparticles impart cationic attribute to niosomes, stabilized through polyethylene glycol. TQ's aqueous insolubility renders its encapsulation within hydrophobic core, and negatively charged siRNA binds in hydrophilic region of cationic niosomes. These niosomes were exploited to effectively knockdown Akt, thereby sensitizing cells to TQ. Immunoblot studies revealed enhanced apoptosis by inducing p53 and inhibiting MDM2 expression, which was consistent with in vivo xenograft studies. This innovative strategy, using Nio-Au to simultaneously deliver siRNA (devoid of any chemical modification) and therapeutic drug, provides an efficacious approach for treating therapy-resistant cancers with significant translational potential.

Gene Therapies for Cancer: Strategies, Challenges and Successes

Gene therapy, which involves replacement of a defective gene with a functional, healthy copy of that gene, is a potentially beneficial cancer treatment approach particularly over chemotherapy, which often lacks selectivity and can cause non-specific toxicity. Despite significant progress pre-clinically with respect to both enhanced targeting and expression in a tumor-selective manner several hurdles still prevent success in the clinic, including non-specific expression, low-efficiency delivery and biosafety. Various innovative genetic approaches are under development to reconstruct vectors/transgenes to make them safer and more effective. Utilizing cutting-edge delivery technologies, gene expression can now be targeted in a tissue- and organ-specific manner. With these advances, gene therapy is poised to become amenable for routine cancer therapy with potential to elevate this methodology as a first line therapy for neoplastic diseases. This review discusses recent advances in gene therapy and their impact on a pre-clinical and clinical level.

Novel therapy of prostate cancer employing a combination of viral-based immunotherapy and a small molecule BH3 mimetic

Cancer-selective viral replication and delivery of a therapeutic immunomodulating, cancer-selective killing cytokine (mda-7/IL-24) by means of a new Cancer Terminator Virus (CTV) combined with a small molecule BH3 mimetic holds promise for treating both primary and metastatic hormone refractory prostate cancer (CaP).

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.

Abstract 5400: A novel combinatorial therapy for hepatocellular carcinoma (HCC)

The incidence of hepatocellular carcinoma (HCC) is rising in the US with parallel increase in mortality rate. Lack of effective therapy for advanced HCC mandates development of novel targeted therapies to counteract this fatal malady. Astrocyte elevated gene-1 (AEG-1), also known as metadherin (MTDH) and LYRIC, plays a pivotal role in hepatocarcinogenesis and serves as an ideal target for anti-HCC therapy. AEG-1 interacts with retinoid X receptor (RXR) and inhibits retinoic acid-induced gene expression and cell death. Retinoic acid has been evaluated for HCC treatment without promising result. Overexpression of AEG-1 might underlie the poor performance of retinoic acid in HCC clinical trials. We documented that combination of a lentivirus expressing AEG-1 shRNA (lenti.shAEG-1) and all-trans retinoic acid (ATRA) profoundly and synergistically inhibited subcutaneous human HCC xenografts in nude mice. We now have developed liver-targeted nanoplexes by conjugating poly(amidoamine) (PAMAM) dendrimers with polyethylene glycol (PEG) and lactobionic acid (PAMAM-PEG-Gal) which were complexed with AEG-1 siRNA (PAMAM-AEG-1si). PAMAM has a net positive charge that complexes with the net negative charge of the siRNA backbone, PEG increases stability of the nanoplexes and increases circulation time and the galactose binds to asialoglycoprotein receptors that are upregulated on liver cells. The polymer conjugate was characterized by 1H-NMR and optimal nanoplex formulations were characterized for surface charge and size using a zetasizer Nano ZS. We established orthotopic xenografts of human HCC cell QGY-7703 expressing luciferase (QGY-luc) in the livers of athymic nude mice and monitored tumor development by bioluminescence imaging (BLI). One week after tumor establishment mice were treated with PAMAM-siCon, PAMAM-siCon+ATRA, PAMAM-AEG-1si and PAMAM-AEG-1si+ATRA by 8 i.v. injections over 4 weeks, and sacrificed 2 weeks after the last injection. In the control group the tumor developed aggressively. ATRA showed little effect due to high AEG-1 levels in QGY-luc cells. PAMAM-AEG-1si showed significant reduction in tumor growth and the combination of PAMAM-AEG-1si+ATRA showed profound and synergistic inhibition so that the tumors were almost undetectable by BLI. Measurement of liver weight at the end of the experiment corroborated these findings. Analysis of AEG-1 mRNA in tumor samples showed a marked decrease in AEG-1 level by PAMAM-AEG-1si indicating efficacy of in vivo knockdown. The group treated with PAMAM-AEG-1si+ATRA nanoplexes showed increased necrosis, inhibition of proliferation and increased apoptosis when compared to other groups. Liver is an ideal organ for RNAi therapy and ATRA is an approved anti-cancer agent. Our exciting observations suggest that the combinatorial approach might be an effective way to combat HCC and need to be evaluated stringently in endogenous mouse models of HCC for a potential Phase I/II clinical trial.

Citation Format: Jyoti Srivastava, Devaraja Rajasekaran, Ayesha Siddiq, Rachel Gredler, Chadia L. Robertson, Maaged A. Akiel, Xue-Ning Shen, Kareem A.N. Ebeid, Aliasger K. Salem, Paul B. Fisher, Devanand Sarkar. A novel combinatorial therapy for hepatocellular carcinoma (HCC). [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 5400. doi:10.1158/1538-7445.AM2015-5400

Design and Characterization of Novel EphA2 Agonists for Targeted Delivery of Chemotherapy to Cancer Cells

The development of novel, targeted delivery agents for anti-cancer therapies requires the design and optimization of potent and selective tumor-targeting agents that are stable and amenable to conjugation with chemotherapeutic drugs. While short peptides represent potentially an excellent platform for these purposes, they often get degraded and are eliminated too rapidly in vivo. In this study, we used a combination of nuclear magnetic resonance-guided structure-activity relationships along with biochemical and cellular studies to derive a novel tumor-homing agent, named 123B9, targeting the EphA2 tyrosine kinase receptor ligand-binding domain. Conjugating 123B9 to the chemotherapeutic drug paclitaxel (PTX) via a stable linker results in an agent that is significantly more effective than the unconjugated drug in both a pancreatic cancer xenograft model and a melanoma lung colonization and metastases model. Hence, 123B9 could represent a promising strategy for the development of novel targeted therapies for cancer.

Novel ZnO hollow-nanocarriers containing paclitaxel targeting folate-receptors in a malignant pH-microenvironment for effective monitoring and promoting breast tumor regression

Low pH in the tumor micromilieu is a recognized pathological feature of cancer. This attribute of cancerous cells has been targeted herein for the controlled release of chemotherapeutics at the tumour site, while sparing healthy tissues. To this end, pH-sensitive, hollow ZnO-nanocarriers loaded with paclitaxel were synthesized and their efficacy studied in breast cancer in vitro and in vivo. The nanocarriers were surface functionalized with folate using click-chemistry to improve targeted uptake by the malignant cells that over-express folate-receptors. The nanocarriers released ~75% of the paclitaxel payload within six hours in acidic pH, which was accompanied by switching of fluorescence from blue to green and a 10-fold increase in the fluorescence intensity. The fluorescence-switching phenomenon is due to structural collapse of the nanocarriers in the endolysosome. Energy dispersion X-ray mapping and whole animal fluorescent imaging studies were carried out to show that combined pH and folate-receptor targeting reduces off-target accumulation of the nanocarriers. Further, a dual cell-specific and pH-sensitive nanocarrier greatly improved the efficacy of paclitaxel to regress subcutaneous tumors in vivo. These nanocarriers could improve chemotherapy tolerance and increase anti-tumor efficacy, while also providing a novel diagnostic read-out through fluorescent switching that is proportional to drug release in malignant tissues.

The role of AEG-1 in the development of liver cancer

AEG-1 is an oncogene that is overexpressed in all cancers, including hepatocellular carcinoma. AEG-1 plays a seminal role in promoting cancer development and progression by augmenting proliferation, invasion, metastasis, angiogenesis and chemoresistance, all hallmarks of aggressive cancer. AEG-1 mediates its oncogenic function predominantly by interacting with various protein complexes. AEG-1 acts as a scaffold protein, activating multiple protumorigenic signal transduction pathways, such as MEK/ERK, PI3K/Akt, NF-κB and Wnt/β-catenin while regulating gene expression at transcriptional, post-transcriptional and translational levels. Our recent studies document that AEG-1 is fundamentally required for activation of inflammation. A comprehensive and convincing body of data currently points to AEG-1 as an essential component critical to the onset and progression of cancer. The present review describes the current knowledge gleaned from patient and experimental studies as well as transgenic and knockout mouse models, on the impact of AEG-1 on hepatocarcinogenesis.

Mcl-1 is an important therapeutic target for oral squamous cell carcinomas

Oral and oropharyngeal cancers are the sixth most common cancers worldwide. Despite intensive investigation, oral squamous cell carcinomas (OSCC) represent a clinical challenge resulting in significant morbidity and mortality. Resistance to cell death is common in OSCC and is often mediated by the Bcl-2 family proteins. Among all anti-apoptotic Bcl-2 family members, Mcl-1 functions as a major survival factor, particularly in solid cancers. Despite the confirmed importance of Mcl-1 in several neoplasms, the role of Mcl-1 in OSCC survival has yet to be explored. In this study, we found that knocking down Mcl-1 sensitized OSCC cells to ABT-737, which binds to Bcl-2/Bcl-xL but not Mcl-1. We report for the first time that a BH3 mimetic, Sabutoclax, which functions as an inhibitor of all anti-apoptotic Bcl-2 proteins, induced cancer-specific cell death in an Mcl-1-dependent manner through both apoptosis and toxic mitophagy. In vivo studies demonstrated that Sabutoclax alone decreased tumor growth in a carcinogen-induced tongue OSCC mouse model. In a combination regimen, Sabutoclax and COX-2 inhibitor, Celecoxib, synergistically inhibited the growth of OSCC in vitro and also significantly reduced OSCC tumor growth in vivo. Overall, these results identify Mcl-1 as a therapeutic prospective target in OSCC.

Combination of Nanoparticle-Delivered siRNA for Astrocyte Elevated Gene-1 (AEG-1) and All-trans Retinoic Acid (ATRA): An Effective Therapeutic Strategy for Hepatocellular Carcinoma (HCC)

Hepatocellular carcinoma (HCC) is a fatal cancer with no effective therapy. Astrocyte elevated gene-1 (AEG-1) plays a pivotal role in hepatocarcinogenesis and inhibits retinoic acid-induced gene expression and cell death. The combination of a lentivirus expressing AEG-1 shRNA and all-trans retinoic acid (ATRA) profoundly and synergistically inhibited subcutaneous human HCC xenografts in nude mice. We have now developed liver-targeted nanoplexes by conjugating poly(amidoamine) (PAMAM) dendrimers with polyethylene glycol (PEG) and lactobionic acid (Gal) (PAMAM-PEG-Gal) which were complexed with AEG-1 siRNA (PAMAM-AEG-1si). The polymer conjugate was characterized by (1)H-NMR, MALDI, and mass spectrometry; and optimal nanoplex formulations were characterized for surface charge, size, and morphology. Orthotopic xenografts of human HCC cell QGY-7703 expressing luciferase (QGY-luc) were established in the livers of athymic nude mice and tumor development was monitored by bioluminescence imaging (BLI). Tumor-bearing mice were treated with PAMAM-siCon, PAMAM-siCon+ATRA, PAMAM-AEG-1si, and PAMAM-AEG-1si+ATRA. In the control group the tumor developed aggressively. ATRA showed little effect due to high AEG-1 levels in QGY-luc cells. PAMAM-AEG-1si showed significant reduction in tumor growth, and the combination of PAMAM-AEG-1si+ATRA showed profound and synergistic inhibition so that the tumors were almost undetectable by BLI. A marked decrease in AEG-1 level was observed in tumor samples treated with PAMAM-AEG-1si. The group treated with PAMAM-AEG-1si+ATRA nanoplexes showed increased necrosis, inhibition of proliferation, and increased apoptosis when compared to other groups. Liver is an ideal organ for RNAi therapy and ATRA is an approved anticancer agent. Our exciting observations suggest that the combinatorial approach might be an effective way to combat HCC.

Scavenger Receptors: Emerging Roles in Cancer Biology and Immunology

Scavenger receptors constitute a large family of evolutionally conserved protein molecules that are structurally and functionally diverse. Although scavenger receptors were originally identified based on their capacity to scavenge modified lipoproteins, these molecules have been shown to recognize and bind to a broad spectrum of ligands, including modified and unmodified host-derived molecules or microbial components. As a major subset of innate pattern recognition receptors, scavenger receptors are mainly expressed on myeloid cells and function in a wide range of biological processes, such as endocytosis, adhesion, lipid transport, antigen presentation, and pathogen clearance. In addition to playing a crucial role in maintenance of host homeostasis, scavenger receptors have been implicated in the pathogenesis of a number of diseases, e.g., atherosclerosis, neurodegeneration, or metabolic disorders. Emerging evidence has begun to reveal these receptor molecules as important regulators of tumor behavior and host immune responses to cancer. This review summarizes our current understanding on the newly identified, distinct functions of scavenger receptors in cancer biology and immunology. The potential of scavenger receptors as diagnostic biomarkers and novel targets for therapeutic interventions to treat malignancies is also highlighted.

Astrocyte Elevated Gene-1 (AEG-1) Regulates Lipid Homeostasis

Astrocyte elevated gene-1 (AEG-1), also known as MTDH (metadherin) or LYRIC, is an established oncogene. However, the physiological function of AEG-1 is not known. To address this question, we generated an AEG-1 knock-out mouse (AEG-1KO) and characterized it. Although AEG-1KO mice were viable and fertile, they were significantly leaner with prominently less body fat and lived significantly longer compared with wild type (WT). When fed a high fat and cholesterol diet (HFD), WT mice rapidly gained weight, whereas AEG-1KO mice did not gain weight at all. This phenotype of AEG-1KO mice is due to decreased fat absorption from the intestines, not because of decreased fat synthesis or increased fat consumption. AEG-1 interacts with retinoid X receptor (RXR) and inhibits RXR function. In enterocytes of AEG-1KO mice, we observed increased activity of RXR heterodimer partners, liver X receptor and peroxisome proliferator-activated receptor-α, key inhibitors of intestinal fat absorption. Inhibition of fat absorption in AEG-1KO mice was further augmented when fed an HFD providing ligands to liver X receptor and peroxisome proliferator-activated receptor-α. Our studies reveal a novel role of AEG-1 in regulating nuclear receptors controlling lipid metabolism. AEG-1 may significantly modulate the effects of HFD and thereby function as a unique determinant of obesity.

Molecular-genetic imaging of cancer

Molecular-genetic imaging of cancer using nonviral delivery systems has great potential for clinical application as a safe, efficient, noninvasive tool for visualization of various cellular processes including detection of cancer, and its attendant metastases. In recent years, significant effort has been expended in overcoming technical hurdles to enable clinical adoption of molecular-genetic imaging. This chapter will provide an introduction to the components of molecular-genetic imaging and recent advances on each component leading to safe, efficient clinical applications for detecting cancer. Combination with therapy, namely, generating molecular-genetic theranostic constructs, will provide further impetus for clinical translation of this promising technology.

Examination of Epigenetic and other Molecular Factors Associated with mda-9/Syntenin Dysregulation in Cancer Through Integrated Analyses of Public Genomic Datasets

mda-9/Syntenin (melanoma differentiation-associated gene 9) is a PDZ domain containing, cancer invasion-related protein. In this study, we employed multiple integrated bioinformatic approaches to identify the probable epigenetic factors, molecular pathways, and functionalities associated with mda-9 dysregulation during cancer progression. Analyses of publicly available genomic data (e.g., expression, copy number, methylation) from TCGA, GEO, ENCODE, and Human Protein Atlas projects led to the following observations: (a) mda-9 expression correlates with both copy number and methylation level of an intronic CpG site (cg1719774) located downstream of the CpG island, (b) cg1719774 methylation is a likely prognostic marker in glioma, (c) among 22 cancer types, melanoma exhibits the highest mda-9 level, and lowest level of methylation at cg1719774, (d) cg1719774 hypomethylation is also associated with histone modifications (at the mda-9 locus) indicative of more active transcription, (e) using Gene Set Enrichment Analysis (GSEA), and the Virtual Gene Overexpression or Repression (VIGOR) analytical scheme, we were able to predict mda-9's association with extracellular matrix organization (e.g., MMPs, collagen, integrins), IGFBP2 and NF-κB signaling pathways, phospholipid metabolism, cytokines (e.g., interleukins), CTLA-4, and components of complement cascade pathways. Indeed, previous publications have shown that many of the aforementioned genes and pathways are associated with mda-9's functionality.

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.

Astrocyte Elevated Gene-1 (AEG-1) Contributes to Non-thyroidal Illness Syndrome (NTIS) Associated with Hepatocellular Carcinoma (HCC)

Non-thyroidal illness syndrome (NTIS), characterized by low serum 3,5,3'-triiodothyronine (T3) with normal l-thyroxine (T4) levels, is associated with malignancy. Decreased activity of type I 5'-deiodinase (DIO1), which converts T4 to T3, contributes to NTIS. T3 binds to thyroid hormone receptor, which heterodimerizes with retinoid X receptor (RXR) and regulates transcription of target genes, such as DIO1. NF-κB activation by inflammatory cytokines inhibits DIO1 expression. The oncogene astrocyte elevated gene-1 (AEG-1) inhibits RXR-dependent transcription and activates NF-κB. Here, we interrogated the role of AEG-1 in NTIS in the context of hepatocellular carcinoma (HCC). T3-mediated gene regulation was analyzed in human HCC cells, with overexpression or knockdown of AEG-1, and primary hepatocytes from AEG-1 transgenic (Alb/AEG-1) and AEG-1 knock-out (AEG-1KO) mice. Serum T3 and T4 levels were checked in Alb/AEG-1 mice and human HCC patients. AEG-1 and DIO1 levels in human HCC samples were analyzed by immunohistochemistry. AEG-1 inhibited T3-mediated gene regulation in human HCC cells and mouse hepatocytes. AEG-1 overexpression repressed and AEG-1 knockdown induced DIO1 expression. An inverse correlation was observed between AEG-1 and DIO1 levels in human HCC patients. Low T3 with normal T4 was observed in the sera of HCC patients and Alb/AEG-1 mice. Inhibition of co-activator recruitment to RXR and activation of NF-κB were identified to play a role in AEG-1-mediated down-regulation of DIO1. AEG-1 thus might play a role in NTIS associated with HCC and other cancers.

Tumor-specific expression and detection of a CEST reporter gene

PURPOSE

To develop an imaging tool that enables the detection of malignant tissue with enhanced specificity using the exquisite spatial resolution of MRI.

METHODS

Two mammalian gene expression vectors were created for the expression of the lysine-rich protein (LRP) under the control of the cytomegalovirus (CMV) promoter and the progression elevated gene-3 promoter (PEG-3 promoter) for constitutive and tumor-specific expression of LRP, respectively. Using those vectors, stable cell lines of rat 9L glioma, 9L(CMV-LRP) and 9L(PEG-LRP) , were established and tested for CEST contrast in vitro and in vivo.

RESULTS

9L(PEG-LRP) cells showed increased CEST contrast compared with 9L cells in vitro. Both 9L(CMV-LRP) and 9L(PEG-LRP) cells were capable of generating tumors in the brains of mice, with a similar growth rate to tumors derived from wild-type 9L cells. An increase in CEST contrast was clearly visible in tumors derived from both 9L(CMV-LRP) and 9L(PEG-LRP) cells at 3.4 ppm.

CONCLUSION

The PEG-3 promoter:LRP system can be used as a cancer-specific, molecular-genetic imaging reporter system in vivo. Because of the ubiquity of MR imaging in clinical practice, sensors of this class can be used to translate molecular-genetic imaging rapidly.

In vivo modeling of malignant glioma: the road to effective therapy

Despite an increased emphasis on developing new therapies for malignant gliomas, they remain among the most intractable tumors faced today as they demonstrate a remarkable ability to evade current treatment strategies. Numerous candidate treatments fail at late stages, often after showing promising preclinical results. This disconnect highlights the continued need for improved animal models of glioma, which can be used to both screen potential targets and authentically recapitulate the human condition. This review examines recent developments in the animal modeling of glioma, from more established rat models to intriguing new systems using Drosophila and zebrafish that set the stage for higher throughput studies of potentially useful targets. It also addresses the versatility of mouse modeling using newly developed techniques recreating human protocols and sophisticated genetically engineered approaches that aim to characterize the biology of gliomagenesis. The use of these and future models will elucidate both new targets and effective combination therapies that will impact on disease management.

Astrocyte elevated gene-1 and c-Myc cooperate to promote hepatocarcinogenesis in mice

Astrocyte elevated gene-1 (AEG-1) and c-Myc are overexpressed in human hepatocellular carcinoma (HCC) functioning as oncogenes. AEG-1 is transcriptionally regulated by c-Myc, and AEG-1 itself induces c-Myc by activating the Wnt/β-catenin-signaling pathway. We now document the cooperation of AEG-1 and c-Myc in promoting hepatocarcinogenesis by analyzing hepatocyte-specific transgenic mice expressing either AEG-1 (albumin [Alb]/AEG-1), c-Myc (Alb/c-Myc), or both (Alb/AEG-1/c-Myc). Wild-type and Alb/AEG-1 mice did not develop spontaneous HCC. Alb/c-Myc mice developed spontaneous HCC without distant metastasis, whereas Alb/AEG-1/c-Myc mice developed highly aggressive HCC with frank metastasis to the lungs. Induction of carcinogenesis by N-nitrosodiethylamine significantly accelerated the kinetics of tumor formation in all groups. However, in Alb/AEG-1/c-Myc, the effect was markedly pronounced with lung metastasis. In vitro analysis showed that Alb/AEG-1/c-Myc hepatocytes acquired increased proliferation and transformative potential with sustained activation of prosurvival and epithelial-mesenchymal transition-signaling pathways. RNA-sequencing analysis identified a unique gene signature in livers of Alb/AEG-1/c-Myc mice that was not observed when either AEG-1 or c-Myc was overexpressed. Specifically, Alb/AEG-1/c-Myc mice overexpressed maternally imprinted noncoding RNAs (ncRNAs), such as Rian, Meg-3, and Mirg, which are implicated in hepatocarcinogenesis. Knocking down these ncRNAs significantly inhibited proliferation and invasion by Alb/AEG-1/c-Myc hepatocytes.

CONCLUSION

Our studies reveal a novel cooperative oncogenic effect of AEG-1 and c-Myc that might explain the mechanism of aggressive HCC. Alb/AEG-1/c-Myc mice provide a useful model to understand the molecular mechanism of cooperation between these two oncogenes and other molecules involved in hepatocarcinogenesis. This model might also be of use for evaluating novel therapeutic strategies targeting HCC.

AEG-1-AKT2: A novel complex controlling the aggressiveness of glioblastoma

Expression of AEG-1 (also known as MTDH or LYRIC) is elevated in many cancers including glioblastoma multiforme (GBM), in which it functions as an oncogene. AEG-1 activates AKT signaling and physically interacts with AKT2 in GBM. Disruption of this interaction reduces glioma cell survival and invasion, uncovering a novel potential target for development of an effective therapy against GBM.

Sequential release of drugs from hollow manganese ferrite nanocarriers for breast cancer therapy

Single drug therapies for cancer are often ineffective and may not provide long term clinical benefits.

Designing Novel Nanoformulations Targeting Glutamate Transporter Excitatory Amino Acid Transporter 2: Implications in Treating Drug Addiction

Chronic drug abuse is associated with elevated extracellular glutamate concentration in the brain reward regions. Deficit of glutamate clearance has been identified as a contributing factor that leads to enhanced glutamate concentration following extended drug abuse. Importantly, normalization of glutamate level through induction of glutamate transporter 1 (GLT1)/ excitatory amino acid transporter 2 (EAAT2) expression has been described in several in vivo studies. GLT1 upregulators including ceftriaxone, a beta-lactam antibiotic, have been effective in attenuating drug-seeking and drug-consumption behavior in rodent models. However, potential obstacles toward clinical translation of GLT1 (EAAT2) upregulators as treatment for drug addiction might include poor gastrointestinal absorption, serious peripheral adverse effects, and/or suboptimal CNS concentrations. Given the growing success of nanotechnology in targeting CNS ailments, nanoformulating known GLT1 (EAAT2) upregulators for selective uptake across the blood brain barrier presents an ideal therapeutic approach for treating drug addiction. In this review, we summarize the results obtained with promising GLT1 (EAAT2) inducing compounds in animal models recapitulating drug addiction. Additionally, the various nanoformulations that can be employed for selectively increasing the CNS bioavailability of GLT1 (EAAT2) upregulators are discussed. Finally, the applicability of GLT1 (EAAT2) induction via central delivery of drug-loaded nanoformulations is described.

AEG-1 regulates retinoid X receptor and inhibits retinoid signaling

Retinoid X receptor (RXR) regulates key cellular responses such as cell growth and development, and this regulation is frequently perturbed in various malignancies, including hepatocellular carcinoma (HCC). However, the molecule(s) that physically govern this deregulation are mostly unknown. Here, we identified RXR as an interacting partner of astrocyte-elevated gene-1 (AEG-1)/metadherin (MTDH), an oncogene upregulated in all cancers. Upon interaction, AEG-1 profoundly inhibited RXR/retinoic acid receptor (RAR)-mediated transcriptional activation. Consequently, AEG-1 markedly protected HCC and acute myelogenous leukemia (AML) cells from retinoid- and rexinoid-induced cell death. In nontumorigenic cells and primary hepatocytes, AEG-1/RXR colocalizes in the nucleus in which AEG-1 interferes with recruitment of transcriptional coactivators to RXR, preventing transcription of target genes. In tumor cells and AEG-1 transgenic hepatocytes, overexpressed AEG-1 entraps RXR in cytoplasm, precluding its nuclear translocation. In addition, ERK, activated by AEG-1, phosphorylates RXR that leads to its functional inactivation and attenuation of ligand-dependent transactivation. In nude mice models, combination of all-trans retinoic acid (ATRA) and AEG-1 knockdown synergistically inhibited growth of human HCC xenografts. The present study establishes AEG-1 as a novel homeostatic regulator of RXR and RXR/RAR that might contribute to hepatocarcinogenesis. Targeting AEG-1 could sensitize patients with HCC and AML to retinoid- and rexinoid-based therapeutics.

Noninvasive approaches for detecting and monitoring bladder cancer

Bladder cancer is the second most common cancer of the urinary tract. Despite existing multiapproach treatment strategies, including radical cystectomy, bladder-sparing therapy with transurethral resection, chemotherapy and radiotherapy, patients with deeply invasive bladder cancers display poor prognosis, with a survival rate of only 30-50%. This can be avoided through proper surveillance and monitoring. Several genetic factors contribute to the progression of bladder cancer, and these molecules serve as cancer biomarkers. Blood, plasma, serum and urine are commonly analyzed for the presence of biomarkers, which can be both nuclear as well as mitochondrial in nature. This review discusses the efficacy of such biomarkers as well as highlights some potential prognostic markers in the field of noninvasive bladder cancer detection.

Reversing translational suppression and induction of toxicity in pancreatic cancer cells using a chemoprevention gene therapy approach

Pancreatic cancer is an aggressive disease with limited therapeutic options. Melanoma differentiation-associated gene-7/interleukin-24 (mda-7/IL-24), a potent antitumor cytokine, shows cancer-specific toxicity in a vast array of human cancers, inducing endoplasmic reticulum stress and apoptosis, toxic autophagy, an antitumor immune response, an antiangiogenic effect, and a significant "bystander" anticancer effect that leads to enhanced production of this cytokine through autocrine and paracrine loops. Unfortunately, mda-7/IL-24 application in pancreatic cancer has been restricted because of a "translational block" occurring after Ad.5-mda-7 gene delivery. Our previous research focused on developing approaches to overcome this block and increase the translation of the MDA-7/IL-24 protein, thereby promoting its subsequent toxic effects in pancreatic cancer cells. We demonstrated that inducing reactive oxygen species (ROS) after adenoviral infection of mda-7/IL-24 leads to greater translation into MDA-7/IL-24 protein and results in toxicity in pancreatic cancer cells. In this study we demonstrate that a novel chimeric serotype adenovirus, Ad.5/3-mda-7, displays greater efficacy in delivering mda-7/IL-24 compared with Ad.5-mda-7, although overall translation of the protein still remains low. We additionally show that d-limonene, a dietary monoterpene known to induce ROS, is capable of overcoming the translational block when used in combination with adenoviral gene delivery. This novel combination results in increased polysome association of mda-7/IL-24 mRNA, activation of the preinitiation complex of the translational machinery in pancreatic cancer cells, and culminates in mda-7/IL-24-mediated toxicity.

Analysis of global changes in gene expression induced by human polynucleotide phosphorylase (hPNPase(old-35))

As a strategy to identify gene expression changes affected by human polynucleotide phosphorylase (hPNPase(old-35)), we performed gene expression analysis of HeLa cells in which hPNPase(old-35) was overexpressed. The observed changes were then compared to those of HO-1 melanoma cells in which hPNPase(old-35) was stably knocked down. Through this analysis, 90 transcripts, which positively or negatively correlated with hPNPase(old-35) expression, were identified. The majority of these genes were associated with cell communication, cell cycle, and chromosomal organization gene ontology categories. For a number of these genes, the positive or negative correlations with hPNPase(old-35) expression were consistent with transcriptional data extracted from the TCGA (The Cancer Genome Atlas) expression datasets for colon adenocarcinoma (COAD), skin cutaneous melanoma (SKCM), ovarian serous cyst adenocarcinoma (OV), and prostate adenocarcinoma (PRAD). Further analysis comparing the gene expression changes between Ad.hPNPase(old-35) infected HO-1 melanoma cells and HeLa cells overexpressing hPNPase(old-35) under the control of a doxycycline-inducible promoter, revealed global changes in genes involved in cell cycle and mitosis. Overall, this study provides further evidence that hPNPase(old-35) is associated with global changes in cell cycle-associated genes and identifies potential gene targets for future investigation.

Role of the staphylococcal nuclease and tudor domain containing 1 in oncogenesis (review)

The staphylococcal nuclease and tudor domain containing 1 (SND1) is a multifunctional protein overexpressed in breast, prostate, colorectal and hepatocellular carcinomas and malignant glioma. Molecular studies have revealed the multifaceted activities of SND1 involved in regulating gene expression at transcriptional as well as post-transcriptional levels. Early studies identified SND1 as a transcriptional co-activator. SND1 is also a component of RNA-induced silencing complex (RISC) thus mediating RNAi function, a regulator of mRNA splicing, editing and stability, and plays a role in maintenance of cell viability. Such diverse actions allow the SND1 to modulate a complex array of molecular networks, thereby promoting carcinogenesis. Here, we describe the crucial role of SND1 in cancer development and progression, and highlight SND1 as a potential target for therapeutic intervention.

Regulation of Myc function by ARF: Checkpoint for Myc-induced oncogenesis

The alterative reading frame (ARF) protein is unique in its capacity to interact with Mdm2 thus facilitating p53-dependent cell cycle arrest and apoptosis. ARF also acts in a p53-independent manner in which it binds to Myc and interferes with transcriptional activation by Myc thereby inhibiting Myc-induced cell proliferation and transformation. Interestingly, ARF does not interfere with apoptosis induction by Myc. ARF-Myc interaction studies have been performed with mouse p19(ARF). Human p14(ARF) provides functions similar to p19(ARF). However, p14(ARF) has limited sequence homology with p19(ARF) and these proteins show subtle functional differences, especially in the contexts of immortalization and senescence. The studies by Amente et al. confirm that interaction of p14(ARF) with Myc also interferes with the transcriptional activity of Myc thus establishing the general role of ARF as a checkpoint for Myc-induced oncogenesis.

Astrocyte elevated gene-1 interacts with Akt isoform 2 to control glioma growth, survival, and pathogenesis

The oncogene astrocyte elevated gene-1 (AEG-1; MTDH) is highly expressed in glioblastoma multiforme (GBM) and many other types of cancer, where it activates multiple signaling pathways that drive proliferation, invasion, angiogenesis, chemoresistance, radioresistance, and metastasis. AEG-1 activates the Akt signaling pathway and Akt and c-Myc are positive regulators of AEG-1 transcription, generating a positive feedback loop between AEG-1 and Akt in regulating tumorigenesis. Here, we describe in GBM cells a direct interaction between an internal domain of AEG-1 and the PH domain of Akt2, a major driver in GBM. Expression and interaction of AEG-1 and Akt2 are elevated in GBM and contribute to tumor cell survival, proliferation, and invasion. Clinically, in silico gene expression and immunohistochemical analyses of patient specimens showed that AEG-1 and Akt2 expression correlated with GBM progression and reduced patient survival. AEG-1-Akt2 interaction prolonged stabilization of Akt2 phosphorylation at S474, regulating downstream signaling cascades that enable cell proliferation and survival. Disrupting AEG-1-Akt2 interaction by competitive binding of the Akt2-PH domain led to reduced cell viability and invasion. When combined with AEG-1 silencing, conditional expression of Akt2-PH markedly increased survival in an orthotopic mouse model of human GBM. Our study uncovers a novel molecular mechanism by which AEG-1 augments glioma progression and offers a rationale to block AEG-1-Akt2 signaling function as a novel GBM treatment.

Abstract 72: Analyzing the role of Astrocyte Elevated Gene-1 (AEG-1) in hepatocarcinogenesis using a knockout mouse model

The oncogene Astrocyte Elevated Gene-1 (AEG-1) is overexpressed in a wide variety of human cancers. In vitro and in vivo nude mouse xenograft studies have established the tumor-promoting role of AEG-1. Activation of multiple signaling pathways, such as NF-κB, PI3K/Akt, Wnt/β-catenin and MEK/ERK, has been attributed to mediate oncogenesis by AEG-1. To better understand the role AEG-1 plays in the onset and progression of cancer and to identify key mechanism(s) of AEG-1 action, we generated a novel AEG-1 knockout mouse (AEG-1-/-). We studied hepatocarcinogenesis in this model because AEG-1 is overexpressed in more than 90% of human hepatocellular carcinoma (HCC) patients and is believed to play a key regulatory role in progression of the disease. AEG-1-/- mice were viable with normal development. We first compared the aging associated phenotype of WT and AEG-1-/- mice. At 16 months of age spontaneous tumor development in lungs and liver was observed in some cohorts of untreated WT mice (n=20). Such tumorigenesis was not detected in any of the AEG-1-/- mice. Additionally, age-associated inflammatory infiltrates were observed in the internal organs of WT but not AEG-1-/- mice. To initiate HCC, WT and AEG-1-/- mice were treated with diethylnitrosamine (DEN) at 2 weeks of age. At 32 weeks WT mice showed a marked hepatocarcinogenic response while AEG-1-/- mice exhibited profound resistance to tumor formation. The hepatocarcinogenic response was further evaluated by DEN initiation followed by daily phenobarbital treatment. WT mice exhibited an intensified hepatocarcinogenic response evidenced by large necrotic liver tumors at 28 weeks of age with a 52% rate of lung metastasis. AEG-1-/- mice remained remarkably resistant even to this combinatorial treatment with no distant metastasis. No difference in the activation of Akt, ERK and β-catenin signaling was observed between WT and AEG-1-/- mice indicating that these pathways may not be regulated by AEG-1 under physiological conditions. However, marked inhibition of NF-κB activation was observed in AEG-1-/- mice. Lipopolysaccharide (LPS)-induced NF-κB luciferase reporter activity, nuclear translocation of p65 subunit of NF-κB and induction of IL-1β and IL-6 were markedly attenuated in primary hepatocytes and macrophages isolated from AEG-1-/- versus WT mice. Chronic inflammation and NF-κB activation play a causal role in hepatocarcinogenesis. Inhibition of NF-κB activation in hepatocytes and macrophages profoundly abrogates HCC development in mouse models. Our findings in AEG-1-/- mice confirm a fundamental role of AEG-1 in NF-κB activation. Here we demonstrate that lack of AEG-1 protects from generalized inflammation thereby suppressing spontaneous as well as experimental tumorigenesis. AEG-1-/-mice might be a useful model to study inflammation and cancer in diverse organ systems.

Citation Format: Chadia L. Robertson, Jyoti Srivastava, Ayesha Siddiq, Rachel Gredler, Devaraja Rajasekaran, Maaged Akiel, Xue-Ning Shen, Knarik Arkun, Shobha Ghosh, Mark A. Subler, Jolene Windle, Paul B. Fisher, Devanand Sarkar. Analyzing the role of Astrocyte Elevated Gene-1 (AEG-1) in hepatocarcinogenesis using a knockout mouse model. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 72. doi:10.1158/1538-7445.AM2014-72

MDA-9/Syntenin regulates differentiation and angiogenesis programs in head and neck squamous cell carcinoma

Little is known about the molecular pathways regulating poor differentiation and invasion of head and neck squamous cell carcinoma (HNSCC). In the present study, we aimed to determine the role of MDA-9/Syntenin, a metastasis associated molecule in HNSCC tumorigenesis. Elevated MDA-9/Syntenin expression was evident in 67% (54/81) primary HNSCC tumors (p=0.001-0.002) and 69% (9/13) pre-neoplastic tissues (p=0.02-0.03). MDA-9/Syntenin overexpression was associated with the stage (p=0.001), grade (p=0.001) and lymph node metastasis (p=0.0001). Silencing of MDA-9/Syntenin in 3 poorly differentiated HNSCC cell lines induced squamous epithelial cell differentiation, disrupted angiogenesis and reduced tumor growth in vitro and in vivo. We confirmed SPRR1B and VEGFR1 as the key molecular targets of MDA-9/Syntenin on influencing HNSCC differentiation and angiogenesis respectively. MDA-9/Syntenin disrupted SPRR1B expression interacting through its PDZ1 domain and altered VEGFR1 expression in vitro and in vivo. VEGFR1 co-localized with MDA-9/Syntenin in HNSCC cell lines and primary tumor. Downregulation of growth regulatory molecules CyclinD1, CDK4, STAT3, PI3K and CTNNB1 was also evident in the MDA-9/Syntenin depleted cells, which was reversed following over-expression of MDA-9/Syntenin in immortalized oral epithelial cells. Our results suggest that early induction of MDA-9/Syntenin expression influences HNSCC progression and should be further evaluated for potential biomarker development.

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.

Suppression of miR-184 in malignant gliomas upregulates SND1 and promotes tumor aggressiveness

BACKGROUND

Malignant glioma is an aggressive cancer requiring new therapeutic targets. MicroRNAs (miRNAs) regulate gene expression post transcriptionally and are implicated in cancer development and progression. Deregulated expressions of several miRNAs, specifically hsa-miR-184, correlate with glioma development.

METHODS

Bioinformatic approaches were used to identify potential miR-184-regulated target genes involved in malignant glioma progression. This strategy identified a multifunctional nuclease, SND1, known to be overexpressed in multiple cancers, including breast, colon, and hepatocellular carcinoma, as a putative direct miR-184 target gene. SND1 levels were evaluated in patient tumor samples and human-derived cell lines. We analyzed invasion and signaling in vitro through SND1 gain-of-function and loss-of-function. An orthotopic xenograft model with primary glioma cells demonstrated a role of miR-184/SND1 in glioma pathogenesis in vivo.

RESULTS

SND1 is highly expressed in human glioma tissue and inversely correlated with miR-184 expression. Transfection of glioma cells with a miR-184 mimic inhibited invasion, suppressed colony formation, and reduced anchorage-independent growth in soft agar. Similar phenotypes were evident when SND1 was knocked down with siRNA. Additionally, knockdown (KD) of SND1 induced senescence and improved the chemoresistant properties of malignant glioma cells. In an orthotopic xenograft model, KD of SND1 or transfection with a miR-184 mimic induced a less invasive tumor phenotype and significantly improved survival of tumor bearing mice.

CONCLUSIONS

Our study is the first to show a novel regulatory role of SND1, a direct target of miR-184, in glioma progression, suggesting that the miR-184/SND1 axis may be a useful diagnostic and therapeutic tool for malignant glioma.

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.

Genetic deletion of AEG-1 prevents hepatocarcinogenesis

Activation of the oncogene AEG-1 (MTDH, LYRIC) has been implicated recently in the development of hepatocellular carcinoma (HCC). In mice, HCC can be initiated by exposure to the carcinogen DEN, which has been shown to rely upon activation of NF-κB in liver macrophages. Because AEG-1 is an essential component of NF-κB activation, we interrogated the susceptibility of mice lacking the AEG-1 gene to DEN-induced hepatocarcinogenesis. AEG-1-deficient mice displayed resistance to DEN-induced HCC and lung metastasis. No difference was observed in the response to growth factor signaling or activation of AKT, ERK, and β-catenin, compared with wild-type control animals. However, AEG-1-deficient hepatocytes and macrophages exhibited a relative defect in NF-κB activation. Mechanistic investigations showed that IL6 production and STAT3 activation, two key mediators of HCC development, were also deficient along with other biologic and epigenetics findings in the tumor microenvironment, confirming that AEG-1 supports an NF-κB-mediated inflammatory state that drives HCC development. Overall, our findings offer in vivo proofs that AEG-1 is essential for NF-κB activation and hepatocarcinogenesis, and they reveal new roles for AEG-1 in shaping the tumor microenvironment for HCC development.

Chemoprevention gene therapy (CGT) of pancreatic cancer using perillyl alcohol and a novel chimeric serotype cancer terminator virus

Conditionally replication competent adenoviruses (Ads) that selectively replicate in cancer cells and simultaneously express a therapeutic cytokine, such as melanoma differentiation associated gene- 7/Interleukin-24 (mda-7/IL-24), a Cancer Terminator Virus (CTV-M7), hold potential for treating human cancers. To enhance the efficacy of the CTV-M7, we generated a chimeric Ad.5 and Ad.3 modified fiber bipartite CTV (Ad.5/3-CTV-M7) that can infect tumor cells in a Coxsackie Adenovirus receptor (CAR) independent manner, while retaining high infectivity in cancer cells containing high CAR. Although mda-7/IL-24 displays broad-spectrum anticancer properties, pancreatic ductal adenocarcinoma (PDAC) cells display an intrinsic resistance to mda-7/IL-24-mediated killing due to an mda-7/IL-24 mRNA translational block. However, using a chemoprevention gene therapy (CGT) approach with perillyl alcohol (POH) and a replication incompetent Ad to deliver mda-7/IL-24 (Ad.mda-7) there is enhanced conversion of mda-7/IL-24 mRNA into protein resulting in pancreatic cancer cell death in vitro and in vivo in nude mice containing human PDAC xenografts. This combination synergistically induces mda-7/IL-24-mediated cancer-specific apoptosis by inhibiting anti-apoptotic Bcl-xL and Bcl-2 protein expression and inducing an endoplasmic reticulum (ER) stress response through induction of BiP/GRP-78, which is most evident in chimeric-modified non-replicating Ad.5/3- mda-7- and CTV-M7-infected PDAC cells. Moreover, Ad.5/3-CTV-M7 in combination with POH sensitizes therapy-resistant MIA PaCa-2 cell lines over-expressing either Bcl-2 or Bcl-xL to mda-7/IL-24-mediated apoptosis. Ad.5/3-CTV-M7 plus POH also exerts a significant antitumor 'bystander' effect in vivo suppressing both primary and distant site tumor growth, confirming therapeutic utility of Ad.5/3-CTV-M7 plus POH in PDAC treatment, where all other current treatment strategies in clinical settings show minimal efficacy.

AEG-1 promoter-mediated imaging of prostate cancer

We describe a new imaging method for detecting prostate cancer, whether localized or disseminated and metastatic to soft tissues and bone. The method relies on the use of imaging reporter genes under the control of the promoter of AEG-1 (MTDH), which is selectively active only in malignant cells. Through a systemic, nanoparticle-based delivery of the imaging construct, lesions can be identified through bioluminescence imaging and single-photon emission computed tomography in the PC3-ML murine model of prostate cancer at high sensitivity. This approach is applicable for the detection of prostate cancer metastases, including bone lesions for which there is no current reliable agent for noninvasive clinical imaging. Furthermore, the approach compares favorably with accepted and emerging clinical standards, including PET with [(18)F]fluorodeoxyglucose and [(18)F]sodium fluoride. Our results offer a preclinical proof of concept that rationalizes clinical evaluation in patients with advanced prostate cancer.

Characterization of the canine mda-7 gene, transcripts and expression patterns

Human melanoma differentiation associated gene-7/interleukin-24 (mda-7/IL-24) displays potent growth suppressing and cell killing activity against a wide variety of human and rodent cancer cells. In this study, we identified a canine ortholog of the human mda-7/IL-24 gene located within a cluster of IL-10 family members on chromosome 7. The full-length mRNA sequence of canine mda-7 was determined, which encodes a 186-amino acid protein that has 66% similarity to human MDA-7/IL-24. Canine MDA-7 is constitutively expressed in cultured normal canine epidermal keratinocytes (NCEKs), and its expression levels are increased after lipopolysaccharide stimulation. In cultured NCEKs, the canine mda-7 pre-mRNA is differentially spliced, via exon skipping and alternate 5'-splice donor sites, to yield five splice variants (canine mda-7sv1, canine mda-7sv2, canine mda-7sv3, canine mda-7sv4 and canine mda-7sv5) that encode four protein isoforms of the canine MDA-7 protein. These protein isoforms have a conserved N-terminus (signal peptide sequence) and are dissimilar in amino acid sequences at their C-terminus. Canine MDA-7 is not expressed in primary canine tumor samples, and most tumor derived cancer cell lines tested, like its human counterpart. Unlike human MDA-7/IL-24, canine mda-7 mRNA is not expressed in unstimulated or lipopolysaccharide (LPS), concanavalin A (ConA) or phytohemagglutinin (PHA) stimulated canine peripheral blood mononuclear cells (PBMCs). Furthermore, in-silico analysis revealed that canonical canine MDA-7 has a potential 28 amino acid signal peptide sequence that can target it for active secretion. This data suggests that canine mda-7 is indeed an ortholog of human mda-7/IL-24, its protein product has high amino acid similarity to human MDA-7/IL-24 protein and it may possess similar biological properties to human MDA-7/IL-24, but its expression pattern is more restricted than its human ortholog.

Design, synthesis and bioevaluation of an EphA2 receptor-based targeted delivery system

Because of its overexpression in a range of solid tumors, the EphA2 receptor is a validated target for cancer therapeutics. We recently described a new targeted delivery system based on specific EphA2-targeting peptides conjugated with the chemotherapeutic agent paclitaxel. Here, we investigate the chemical determinants responsible for the stability and degradation of these agents in plasma. Introducing modifications in both the peptide and the linker between the peptide and paclitaxel resulted in drug conjugates that are both long-lived in rat plasma and that markedly decrease tumor size in a prostate cancer xenograft model compared with paclitaxel alone treatment. These studies identify critical rate-limiting degradation sites on the peptide-drug conjugates, enabling the design of agents with increased stability and efficacy. These results provide support for our central hypothesis that peptide-drug conjugates targeting EphA2 represent an innovative and potentially effective strategy to selectively deliver cytotoxic drugs to cancer cells.