Adenovirus Vector Covalently Conjugated to Polyethylene Glycol with a Cancer-Specific Promoter Suppresses the Tumor Growth through Systemic Administration

Abstract

Gene therapy is expected to play a key role in next-generation cancer therapy together with the conventional modalities for the treatment of cancer, such as surgery, chemotherapy, and radiotherapy. 1) Use of adenovirus vectors (Adv) in gene therapy has been developed in diverse animal models and clinical trials because Adv can be propagated to high yields and has the capacity to efficiently transduce a wide variety of cell types and tissues regardless of the mitotic status of the cell. 2,3) In several clinical trials, intratumoral injection of Adv has demonstrated therapeutic efficacy against primary tumors. 4,5) However, successful cancer gene therapy also requires treatment of unresectable primary cancers and distant metastases, which are the major cause of cancer mortality. To treat unresectable primary and metastatic cancers, Adv must be administered systemically, but its effects must be restricted to tumor cells. The major disadvantage in treating cancer with systemically administered conventional Adv is related to its accumulation in the liver immediately after systemic injection, which can cause severe liver toxicity. 6)Therefore, to enable the application of Adv to the treatment of both primary and metastatic cancers, it is necessary to develop Adv with the capacity for tumor-selective distribution and gene expression after systemic administration.In a previous study, we generated a dual cancer-specific targeting vector system by using Adv covalently conjugated to polyethylene glycol (PEG), for transductional targeting, and a cancer-specific promoter, for transcriptional targeting. 7)Covalent conjugation to PEG (PEGylation) can prolong the plasma half-life of Adv, prevent hepatic uptake, and alter the tissue distribution of Adv because of the steric hindrance of the PEG. 3,7,8) We showed that systemic administration of PEGylated Adv (PEG-Ad) with 20-kDa PEG at a 45% modification ratio resulted in higher tumor-selective transgene expression than unmodified Adv.7) In addition, we showed that the telomere reverse transcriptase (TERT) promoter-driven PEG-Ad (PEG-Ad-TERT), which contained the herpes simplex virus thymidine kinase (HSVtk) gene as the therapeutic gene, induced strong antitumor effects against metastasis without any side effects. By comparison, a conventional cytomegalovirus (CMV) promoter-driven PEG-Ad produced strong antitumor effects but induced unwanted side effects. 7)Therefore, PEG-Ad-TERT can be regarded as a prototype Adv with suitable efficacy and safety for systemic cancer gene therapy against metastasis, although PEG-Ad-CMV might not be suitable. However, it is not clear whether PEGAd-TERT can be used for the treatment of unresectable primary cancers.In this study, we examined the therapeutic effects of systemically administered PEG-Ad-TERT for the treatment of primary tumors. MATERIALS AND METHODS Mice and Cell LinesFemale 5-week-old C57BL6 mice were purchased from SLC Inc. (Hamamatsu, Japan). All procedures involving animal experimentation were performed in ; 7-6-8 Saito-Asagi, Ib...

Coating with spermine-pullulan polymer enhances adenoviral transduction of mesenchymal stem cells

“…Cell viability of SP-Adv32, SP-Adv64, and SP-Adv128 infected cells was notably lower than control. Based on the results in Figure 1, a wide range (from 2 to 16 μg/mL) of SP could be used for Adv coating, and in the following experiments we chose 2 μg/mL SP as the optimal coating concentration for 2×10 9 vps/mL Adv, with a final molar ratio of SP to Adv of 2.4×10 4 . These conditions facilitated the highest transgene expression and lowest cytotoxicity and will hereafter be referred to as SP-Adv.…”

“…[9][10][11][12][13][14][15] Thus, we aimed at modifying an Adv with another suitable polymer to overcome the obstacle of MSC low transduction efficiency. Spermine-pullulan (SP), one kind of cationic polymers prepared by the conjugation of pullulan and spermine, was demonstrated to be able to efficiently transfect plasmids for in vitro gene expression in various cell types, including MSCs.…”

Current Targeting Strategies for Adenovirus Vectors in Cancer Gene Therapy

“…4A) and primary tumor (Fig. 4B) with negligible side effects [131,132]. This approach therefore may dramatically improve the therapeutic index of cancer gene therapy through both an increase in antitumor effect and a reduction in toxicity.…”

“…Covalent attachment of PEG to the Adv surface is achieved primarily by use of activated PEG-tresyl-monomethoxypolyethylene glycol (TMPEG), succinimidyl succinatemonomethoxypolyethylene glycol (SSPEG), or cyanuric chloride-monomethoxypolyethylene glycol (CCPEG)-which reacts preferentially with the e-amino terminal of lysine residues on the capsid, including those in the hexon, fiber, and penton base proteins [127][128][129]. Different types of PEG, such as those that differ in molecular weight or branch type or PEG that contains different active groups in each side chain, can be used in this approach [130][131][132][133][134][135]. Recently, Mizuguchi et al inserted biotin-binding peptide (BAP) was into the hypervariable region (HVR) 5 of the hexon, which is not involved in the binding to CAR, and then specifically conjugated PEG to the hexon HVR5 via avidin-biotin interaction [136].…”

Circumventing Antivector Immunity: Potential Use of Nonhuman Adenoviral Vectors

“…Furthermore, several groups successfully retargeted coated AdV vectors (Parker et al, 2005;Stevenson et al, 2007;Morrison et al, 2008Morrison et al, , 2009Wang et al, 2010). Although in some studies they presented similar levels of antitumoral efficacy (Morrison et al, 2009) or transgene expression (Parker et al, 2005;Stevenson et al, 2007;Morrison et al, 2008;Wang et al, 2010) to unmodified wild-type HAdV-5, others achieved a greater therapeutic effect with negligible side effects (Eto et al, 2010;Yao et al, 2010). Despite the limited retargeting efficiency in comparison with unmodified HAdV-5, the use of PEGylated AdV vectors achieved lower hepatic tropism and reduction in liver and spleen toxicity in vivo.…”