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Nucleic acid binding polymers (NABPs) have been extensively used as vehicles for DNA and RNA delivery. More recently, we discovered that a subset of these NABPs can also serve as anti-inflammatory agents by capturing pro-inflammatory extracellular nucleic acids and associated protein complexes that promote activation of toll-like receptors (TLRs) in diseases such as lupus erythematosus. Nucleic-acid-mediated TLR signaling also facilitates tumor progression and metastasis in several cancers, including pancreatic cancer (PC). In addition, extracellular DNA and RNA circulate on or within lipid microvesicles, such as microparticles or exosomes, which also promote metastasis by inducing pro-tumorigenic signaling in cancer cells and pre-conditioning secondary sites for metastatic establishment. Here, we explore the use of an NABP, the 3rd generation polyamidoamine dendrimer (PAMAM-G3), as an anti-metastatic agent. We show that PAMAM-G3 not only inhibits nucleic-acid-mediated activation of TLRs and invasion of PC tumor cells in vitro, but can also directly bind extracellular microvesicles to neutralize their pro-invasive effects as well. Moreover, we demonstrate that PAMAM-G3 dramatically reduces liver metastases in a syngeneic murine model of PC. Our findings identify a promising therapeutic application of NABPs for combating metastatic disease in PC and potentially other malignancies.

Osteopontin (OPN) is a secreted phosphoprotein which mediates tumorigenesis, local growth, and metastasis in a variety of cancers. It is a potential therapeutic target for the regulation of cancer metastasis. RNA aptamer technology targeting OPN may represent a clinically viable therapy. In this study, we characterize the critical sequence of an RNA aptamer, termed OPN-R3, directed against human OPN. It has a Kd of 18 nmol/l and binds specifically to human OPN as determined by RNA electrophoretic mobility assays. In MDA-MB231 human breast cancer cells examined under fluorescence microscopy, OPN-R3 ablates cell surface binding of OPN to its cell surface CD44 and αvβ3 integrin receptors. Critical enzymatic components of the OPN signal transduction pathways, PI3K, JNK1/2, Src and Akt, and mediators of extracellular matrix degradation, matrix metalloproteinase 2 (MMP2) and uroplasminogen activator (uPA), are significantly decreased following exposure to OPN-R3. OPN-R3 inhibits MDA-MB231 in vitro adhesion, migration, and invasion characteristics by 60, 50, and 65%, respectively. In an in vivo xenograft model of breast cancer, OPN-R3 significantly decreases local progression and distant metastases. On the basis of this “proof-of-concept” study, we conclude that RNA aptamer targeting of OPN has biologically relevance for modifying tumor growth and metastasis.Molecular Therapy (2008) 17 1, 153–161 doi:10.1038/mt.2008.235 [ABSTRACT FROM AUTHOR]

We have developed and validated a new tumor-targeting gene therapy strategy based upon the targeting and replacement of human telomerase reverse transcriptase (hTERT) RNA, using a trans-splicing ribozyme. By constructing novel adenoviral vectors harboring the hTERT-targeting trans-splicing ribozymes with the downstream reporter gene (Ad-Ribo-LacZ) or suicide gene (Ad-Ribo-HSVtk) driven by the cytomegalovirus (CMV) promoter, we demonstrated that this viral system selectively marks tumor cells expressing hTERT or sensitizes tumor cells to prodrug treatments. We confirmed that Ad-Ribo-LacZ successfully and selectively delivered a ribozyme that performed a highly specific trans-splicing reaction into hTERT-expressing cancer cells, both in vitro and in a peritoneal carcinomatosis nude mouse model. We also determined that the hTERT-specific expression of the suicide gene in the Ad-Ribo-HSVtk, and treatment with the corresponding prodrug, reduced tumor progression with almost the same efficacy as the strong constitutive CMV promoter-driven adenovirus, both in cancer cell lines and in nude mouse HT-29 xenografts. These observations provide the basis for a novel approach to cancer gene therapy, and demonstrate that trans-splicing ribozymes can be employed as targeting anti-cancer agents which recognize cancer-specific transcripts and reprogram them, thereby combating cancerous cells.Molecular Therapy (2007) 16 1, 74–80. doi:10.1038/sj.mt.6300282 [ABSTRACT FROM AUTHOR]

Due to the prevalence of tumor chemoresistance, the clinical response of advanced non-small cell lung cancer (NSCLC) to chemotherapy is poor. We suppressed tumor resistance to doxorubicin (Dox) in A549 cells, a human NSCLC cell line, both in vitro and in vivo in a lung tumor xenograft model, using a novel adenoviral expression system to deliver an RNA aptamer (A-p50) that specifically inhibits nuclear factor-κB (NF-κB) activation. By achieving selective, targeted, and early inhibition of NF-κB activity, we demonstrate that NF-κB plays a critical role in Dox-induced chemoresistance by regulating genes involved in proliferation (Ki-67), response to DNA damage (GADD153), antiapoptosis (Bcl-XL), and pH regulation (CA9). This Dox-induced NF-κB activation and subsequent chemoresistance is dependent on expression of p53. We also demonstrate that NF-κB promotes angiogenesis in the presence of Dox via the hypoxia-inducible factor-1α/vascular endothelial growth factor (HIF-1α/VEGF) pathway, revealing a previously unknown mechanism of NSCLC resistance to Dox. These studies provide important insights into the mechanisms of Dox-induced chemoresistance, and they demonstrate a novel, effective, and clinically practical strategy for interfering with these processes.Molecular Therapy (2007) 16 1, 66–73. doi:10.1038/sj.mt.6300320 [ABSTRACT FROM AUTHOR]

An abstract of the article "Developing siRNAs to the E2Fs to Control Vascular Growth and Remodeling," by Paloma H. Giangrande, JianXin Zhang, Juliana Layzer, Otto Hagen, Joseph R. Nevins, and Bruce A. Sullenger is presented.

Technologies that mediate targeted delivery of small interfering RNAs (siRNAs) are needed to improve the therapeutic efficacy and safety of siRNAs. Therefore, we have developed aptamer-siRNA chimeric RNAs capable of cell-type specific binding and delivery of functional siRNAs into cells. The aptamer portion of the chimeras mediates binding to PSMA, a cell-surface receptor overexpressed in prostate cancer cells and tumor vascular endothelium, while the siRNA portion targets the expression of survival genes. When applied to LNCaP cells, a prostate cancer cell line expressing PSMA, the chimeras are internalized and subsequently recognized and processed by Dicer, resulting in depletion of the siRNA target protein and cell death. In contrast, the chimeras do not bind or function in PC3 cells, a prostate cancer cell line that does not express PSMA. Thus, these studies demonstrate an approach for targeted delivery of siRNAs with a wide variety of potential applications including cancer therapeutics.Molecular Therapy (2006) 13, S35–S35; doi: 10.1016/j.ymthe.2006.08.101 [ABSTRACT FROM AUTHOR]

An abstract of the article "Retargeting Mobile Group II Introns to Repair Mutant Genes," by Monique N. Kierlin, John P. Jones III, Rob G. Coon, Jiri Perutka, Alan M. Lambowitz, and Bruce A. Sullenger is presented.