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Judge AD, Robbins M, Tavakoli I, Levi J, Hu L, Fronda A et al.. Confirming the RNAi-mediated mechanism of action of siRNA-based cancer therapeutics in mice. J Clin Invest 119: 661-673

Tekmira Pharmaceuticals Corporation, 100-8900 Glenlyon Parkway, Burnaby, British Columbia, Canada.
The Journal of clinical investigation (Impact Factor: 13.77). 03/2009; 119(3):661-73. DOI: 10.1172/JCI37515
Source: PubMed

ABSTRACT siRNAs that specifically silence the expression of cancer-related genes offer a therapeutic approach in oncology. However, it remains critical to determine the true mechanism of their therapeutic effects. Here, we describe the preclinical development of chemically modified siRNA targeting the essential cell-cycle proteins polo-like kinase 1 (PLK1) and kinesin spindle protein (KSP) in mice. siRNA formulated in stable nucleic acid lipid particles (SNALP) displayed potent antitumor efficacy in both hepatic and subcutaneous tumor models. This was correlated with target gene silencing following a single intravenous administration that was sufficient to cause extensive mitotic disruption and tumor cell apoptosis. Our siRNA formulations induced no measurable immune response, minimizing the potential for nonspecific effects. Additionally, RNAi-specific mRNA cleavage products were found in tumor cells, and their presence correlated with the duration of target mRNA silencing. Histological biomarkers confirmed that RNAi-mediated gene silencing effectively inhibited the target's biological activity. This report supports an RNAi-mediated mechanism of action for siRNA antitumor effects, suggesting a new methodology for targeting other key genes in cancer development with siRNA-based therapeutics.

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Available from: Marjorie Robbins, Dec 02, 2014
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    • "This phenomenon , called enhanced permeability and retention effect (EPR), has been taken advantage of for delivering pharmaceuticals to solid tumors following intravenous administration (Seymour, 1992). One of the first approaches designed to deliver siRNAs to tumors was by means of liposomes and LNPs (Judge et al., 2009; Lee et al., 2010). Using this approach Bisanz and coworkers (2005) showed that intratumorally administered liposome encapsulated siRNAs targeting ECM-integrin were able to significantly reduce the size of bone tumors in a mouse xenograft model. "
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    ABSTRACT: RNA interference is a cellular mechanism by which small molecules of double stranded RNA modulate gene ex-pression acting on the concentration and/or availability of a given messenger RNA. Almost 10 years after Fire and Mello received the Nobel Prize for the discovery of this mechanism in flat worms, RNA interference is on the edge of becoming a new class of therapeutics. With various phase III studies underway, the following years will determine whether RNAi-therapeutics can rise up to the challenge and become mainstream medicines. The present review gives a thorough overview of the current status of this technology focusing on the path to the clinic of this new class of compounds.
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    • "During the recent past, there has been a remarkable progress in tumor-targeted delivery of RNAi agents (namely, small interfering RNA, or siRNA, molecules). Many lipid-and polymer-based delivery systems have shown great promise (Aleku et al., 2008; Bartlett et al., 2007; Jarvis, 2009; Judge et al., 2009; Li et al., 2008; Rozema et al., 2007; Yagi et al., 2009); among them, as of September 2013, ten cases have reached clinical trial stages in the US (ClinicalTrials.gov ID NCT00689065, 2008; ClinicalTrials.gov "
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    ABSTRACT: Tumor cells exhibit drug resistant phenotypes that decrease the efficacy of chemotherapeutic treatments. The drug resistance has a genetic basis that is caused by an abnormal gene expression. There are several types of drug resistance: efflux pumps reducing the cellular concentration of the drug, alterations in membrane lipids that reduce cellular uptake, increased or altered drug targets, metabolic alteration of the drug, inhibition of apoptosis, repair of the damaged DNA, and alteration of the cell cycle checkpoints (Gottesman et al. , 2002, Holohan et al. , 2013). siRNA is used to silence the drug resistant phenotype and prevent this drug resistance response. Of the listed types of drug resistance, pump-type resistance (e.g., high expression of ATP-binding cassette transporter proteins such as P-glycoproteins (Pgp; also known as multi-drug resistance protein 1 or MDR1)) and apoptosis inhibition (e.g., expression of anti-apoptotic proteins such as Bcl-2) are the most frequently targeted for gene silencing. The co-delivery of siRNA and chemotherapeutic drugs has a synergistic effect, but many of the current projects do not control the drug release from the nanocarrier. This means the drug payload is released before the drug resistance proteins have degraded and the drug resistance phenotype has been silenced. Current research focuses on cross-linking the carrier's polymers to prevent premature drug release, but these carriers still rely on environmental cues to release the drug payload, and the drug may be released too early. In this review, we studied the release kinetics of siRNA and chemotherapeutic drugs from a broad range of carriers. We also give examples of carriers used to co-deliver siRNA and drugs to drug-resistant tumor cells, and we examine how modifications to the carrier affect the delivery. Lastly, we give our recommendations for the future directions of the co-delivery of siRNA and chemotherapeutic drug treatments.
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    • "Highpressure tail vein injection of siRNAs (hydrodynamic delivery method) promotes accumulation of siRNA in the liver and their therapeutic potential [2] [3]. Further confirmation and progress toward clinical applications have been achieved (for review, see [4] [5] [6]) and are mostly based on the formulation of siRNA with either cationic polymers/ oligomers or within lipidic vesicles for delivery to the liver [7] [8], to tumors [9] [10] [11] [12] [13] [14] [15] [16] [17] [18] [19] [20] [21] [22] or to the mononuclear phagocyte system for immunomodulation therapy [23] [24] [25]. "
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