Modification of adenovirus gene transfer vectors with synthetic polymers: a scientific review and technical guide

Targeted Cancer Therapy with Tumor Necrosis Factor-Alpha

Tumor necrosis factor-alpha (TNF-α), a member of the TNF superfamily, was the first cytokine to be evaluated for cancer biotherapy. However, the clinical use of TNF-α is severely limited by its toxicity. Currently, TNF-α is administered only through locoregional drug delivery systems such as isolated limb perfusion and isolated hepatic perfusion. To reduce the systemic toxicity of TNF-α, various strategies have been explored over the last several decades. This review summarizes current state-of-the-art targeted cancer therapy using TNF-α. Passive targeting, cell-based therapy, gene therapy with inducible or tissue-specific promoters, targeted polymer-DNA complexes, tumor pre-targeting, antibody-TNF-α conjugate, scFv/TNF-α fusion proteins, and peptide/TNF-α fusion proteins have all been investigated to combat cancer. Many of these agents are already in advanced clinical trials. Molecular imaging, which can significantly speed up the drug development process, and nanomedicine, which can integrate both imaging and therapeutic components, has the potential to revolutionize future cancer patient management. Cooperative efforts from scientists within multiple disciplines, as well as close partnerships among many organizations/entities, are needed to quickly translate novel TNF-α-based therapeutics into clinical investigation.

The immunogenicity of adenovirus vectors limits the multispecificity of CD8 T-cell responses to vector-encoded transgenic antigens

We investigated whether the immunogenicity of antigens delivered by recombinant E1-deleted adenovirus (Ad) is impaired by the concomitant priming of specific immunity to protein antigens of the vector. A comparative evaluation of the immunogenicity of hepatitis B surface antigen (HBsAg or S) or ovalbumin (OVA) was carried out in mice injected with either the antigen-encoding Ad vector or a corresponding plasmid DNA vaccine. Recombinant Ad, but not the plasmid DNA vaccine, induced long lasting, specific CD8 T-cell immunity to immunodominant epitopes of the two antigens. In contrast, the HBsAg-encoding pCI/S DNA, but not the Ad/S vaccine, was shown to prime CD8 T-cell responses to subdominant HBsAg epitopes. Ad/S-primed CD8 T-cell responses to immunodominant epitopes of vector-encoded or capsid-delivered Ad proteins apparently suppressed CD8 T-cell priming to subdominant HBsAg epitopes. In B-cell-deficient mice, the established, Ad-specific T-cell immunity induced by vaccination with an irrelevant Ad vector impaired the priming of HBsAg-specific CD8 T-cell responses by Ad/S. It is clear, therefore, that a T-cell immunity specific for Ad proteins (either delivered with the Ad capsid or transcribed from the Ad genome) is efficiently primed by vaccination with Ad vectors, and can limit the immunogenicity (particularly of subdominant epitopes) of Ad vector-encoded transgenic antigens.

Amine-reactive pyridylhydrazone-based PEG reagents for pH-reversible PEI polyplex shielding

PEGylation which is reversed after the therapeutic agent reaches the target cell presents an attractive feature for drug, protein or nucleic acid delivery. Amine-reactive, endosomal pH cleavable polyethylene glycol aldehyde-carboxypyridylhydrazone, N-hydroxysuccinimide esters (PEG-HZN-NHS) were synthesized and applied for bioreversible surface shielding of DNA polyplexes. Monofunctional mPEG-HZN-NHS was synthesized by reacting succinimidyl hydraziniumnicotinate with mPEG-butyraldehyde (20 kDa). Bifunctional OPSS-PEG-HZN-NHS was synthesized analogously via a omega-2-pyridyldithio-PEG (10 kDa) propionaldehyde intermediate. Polyethylenimine (PEI) polyplexes were reacted with the pH-sensitive (mPEG-HZN-NHS) or the corresponding stable (mPEG-NHS) reagent. Both types of polyplexes remained shielded at pH 7.4 as demonstrated by particle size and zeta potential measurements after 4h of incubation at 37 degrees C. Polyplex deshielding at endosomal pH 5 was observed only with the mPEG-HZN-NHS shielded particles. This was confirmed by fluorescence correlation spectroscopy using the analogous Alexa-488 fluorescently labeled bifunctional PEGylation reagents. Luciferase gene transfections with epidermal growth factor (EGF) containing polyplexes using EGF-receptor overexpressing hepatoma HUH7 cells showed an up to 16-fold enhancement in gene expression with the reversibly shielded polyplexes as compared to stably shielded polyplexes. Consistently, the reversibly shielded polyplexes mediated also an enhanced tumor specific in vivo transgene expression after intravenous administration in a subcutaneous HUH7 tumor model in SCID mice.

Harnessing the RNA interference pathway to advance treatment and prevention of hepatocellular carcinoma

Primary liver cancer is the fifth most common malignancy in the world and is a leading cause of cancer-related mortality. Available treatment for hepatocellular carcinoma (HCC), the commonest primary liver cancer, is rarely curative and there is a need to develop therapy that is more effective. Specific and powerful gene silencing that can be achieved by activating RNA interference (RNAi) has generated enthusiasm for exploiting this pathway for HCC therapy. Many studies have been carried out with the aim of silencing HCC-related cellular oncogenes or the hepatocarcinogenic hepatitis B virus (HBV) and hepatitis C virus (HCV). Proof of principle studies have demonstrated promising results, and an early clinical trial assessing RNAi-based HBV therapy is currently in progress. Although the data augur well, there are several significant hurdles that need to be overcome before the goal of RNAi-based therapy for HCC is realized. Particularly important are the efficient and safe delivery of RNAi effecters to target malignant tissue and the limitation of unintended harmful non-specific effects.