Identification of Genes Potentially Regulated by Human Polynucleotide Phosphorylase (hPNPaseold-35) Using Melanoma as a Model

Human Polynucleotide Phosphorylase (hPNPaseold-35 or PNPT1) is an evolutionarily conserved 3′→5′ exoribonuclease implicated in the regulation of numerous physiological processes including maintenance of mitochondrial homeostasis, mtRNA import and aging-associated inflammation. From an RNase perspective, little is known about the RNA or miRNA species it targets for degradation or whose expression it regulates; except for c-myc and miR-221. To further elucidate the functional implications of hPNPaseold-35 in cellular physiology, we knocked-down and overexpressed hPNPaseold-35 in human melanoma cells and performed gene expression analyses to identify differentially expressed transcripts. Ingenuity Pathway Analysis indicated that knockdown of hPNPaseold-35 resulted in significant gene expression changes associated with mitochondrial dysfunction and cholesterol biosynthesis; whereas overexpression of hPNPaseold-35 caused global changes in cell-cycle related functions. Additionally, comparative gene expression analyses between our hPNPaseold-35 knockdown and overexpression datasets allowed us to identify 77 potential “direct” and 61 potential “indirect” targets of hPNPaseold-35 which formed correlated networks enriched for cell-cycle and wound healing functional association, respectively. These results provide a comprehensive database of genes responsive to hPNPaseold-35 expression levels; along with the identification new potential candidate genes offering fresh insight into cellular pathways regulated by PNPT1 and which may be used in the future for possible therapeutic intervention in mitochondrial- or inflammation-associated disease phenotypes

Therapy of pancreatic cancer via an EphA2 receptor-targeted delivery of gemcitabine.

First line treatment for pancreatic cancer consists of surgical resection, if possible, and a subsequent course of chemotherapy using the nucleoside analogue gemcitabine. In some patients, an active transport mechanism allows gemcitabine to enter efficiently into the tumor cells, resulting in a significant clinical benefit. However, in most patients, low expression of gemcitabine transporters limits the efficacy of the drug to marginal levels, and patients need frequent administration of the drug at high doses, significantly increasing systemic drug toxicity. In this article we focus on a novel targeted delivery approach for gemcitabine consisting of conjugating the drug with an EphA2 targeting agent. We show that the EphA2 receptor is highly expressed in pancreatic cancers, and accordingly, the drug-conjugate is more effective than gemcitabine alone in targeting pancreatic tumors. Our preliminary observations suggest that this approach may provide a general benefit to pancreatic cancer patients and offers a comprehensive strategy for enhancing delivery of diverse therapeutic agents to a wide range of cancers overexpressing EphA2, thereby potentially reducing toxicity while enhancing therapeutic efficacy

Autophagy switches to apoptosis in prostate cancer cells infected with melanoma differentiation associated gene-7/interleukin-24 (mda-7/IL-24)

MDA-7/IL-24 has noteworthy potential as an anticancer therapeutic because of its diversity of antitumor properties, its lack of toxicity toward normal cells and tissues, and its safety and efficacy as evidenced in a phase I clinical trial. In a recent study, we document that Ad.mda-7-induced ER stress and ceramide production leads to early autophagy that subsequently switches to apoptosis in human prostate cancer cells. During the apoptotic phase, the MDA-7/IL-24 protein physically interacts with Beclin 1 and this interaction might inhibit Beclin 1 function culminating in apoptosis. Conversely, Ad.mda-7 infection leads to calpain-mediated cleavage of the Atg5 protein that might also facilitate a biochemical switch from autophagy to apoptosis. Our recent paper reveals novel aspects of the interplay between autophagy and apoptosis that underlie the cytotoxic action of MDA-7/IL-24 in prostate cancer cells. These new insights into MDA-7/IL-24 action provide intriguing leads for developing innovative combinatorial approaches for prostate cancer therapy

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

Multifunction Protein Staphylococcal Nuclease Domain Containing 1 (SND1) Promotes Tumor Angiogenesis in Human Hepatocellular Carcinoma through Novel Pathway That Involves Nuclear Factor κB and miR-221

Staphylococcal nuclease domain-containing 1 (SND1) is a multifunctional protein that is overexpressed in multiple cancers, including hepatocellular carcinoma (HCC). Stable overexpression of SND1 in Hep3B cells expressing a low level of SND1 augments, whereas stable knockdown of SND1 in QGY-7703 cells expressing a high level of SND1 inhibits establishment of xenografts in nude mice, indicating that SND1 promotes an aggressive tumorigenic phenotype. In this study we analyzed the role of SND1 in regulating tumor angiogenesis, a hallmark of cancer. Conditioned medium from Hep3B-SND1 cells stably overexpressing SND1 augmented, whereas that from QGY-SND1si cells stably overexpressing SND1 siRNA significantly inhibited angiogenesis, as analyzed by a chicken chorioallantoic membrane assay and a human umbilical vein endothelial cell differentiation assay. We unraveled a linear pathway in which SND1-induced activation of NF-κB resulted in induction of miR-221 and subsequent induction of angiogenic factors Angiogenin and CXCL16. Inhibition of either of these components resulted in significant inhibition of SND1-induced angiogenesis, thus highlighting the importance of this molecular cascade in regulating SND1 function. Because SND1 regulates NF-κB and miR-221, two important determinants of HCC controlling the aggressive phenotype, SND1 inhibition might be an effective strategy to counteract this fatal malady

MDA-9/syntenin is a key regulator of glioma pathogenesis

The extraordinary invasiveness of human glioblastoma multiforme (GBM) contributes to treatment failure and the grim prognosis of patients diagnosed with this tumor. Consequently, it is imperative to define further the cellular mechanisms that control GBM invasion and identify promising novel therapeutic targets. Melanoma differentiation associated gene–9 (MDA-9/syntenin) is a highly conserved PDZ domain–containing scaffolding protein that promotes invasion and metastasis in vitro and in vivo in human melanoma models. To determine whether MDA-9/syntenin is a relevant target in GBM, we investigated its expression in tumor samples and involvement in GBM invasion and angiogenesis

Theranostic Tripartite Cancer Terminator Virus for Cancer Therapy and Imaging

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