Novel cationic non-viral vectors
The first generation cationic lipid DC-chol has been used in 8 different clinical trials and proven to be effective and non-toxic. However, they do not efficiently condense DNA. A self-assembled nanoparticle formulation (LPD) containing lipid, polycation and DNA has been developed. Its activity is similar to that of an adenoviral vector. It has been used in a clinical trial treating children with Canavan's disease. Intravenous LPD formulation containing protamine sulfate has also been developed for transfecting cells in the lung. We have recently discovered new methods to prepare lipoplex with very small size and with enhanced stability and activity. It is an ongoing effort of this lab to test and improve the cationic non-viral vectors.
Targeting siRNA to tumor cells
We have developed self-assembled nanoparticles covalently attached with either tamoxifen or anisamide ligand that binds to surface estrogen or sigma receptor, respectively, over-expressed in the human tumor cells. The target-specific nanoparticles can be used to deliver siRNA and other oligonucleotides to down-regulate target oncogenes, resulting in the apoptosis and/or the chemosensitization of the tumor cells. When the anisamide-targeted formulation was intravenously injected into tumor-bearing mice in a xenograft model, 70-80% of the injected siRNA per gram of tissue accumulated in the tumor resulting in nearly total silencing of the target oncogenes through out the entire tumor. Such unprecedented high efficiency of drug delivery is a very encouraging result. We have also delivered therapeutic siRNA to melanoma tumor cells metastasized in the lung and showed significant reduction in the tumor load in the treated animals.
Nanoparticle vectors evading reticuloendothelial system (RES)
We have developed a core/shell type nanoparticle, called LPD, for delivery of plasmid DNA, antisense oligonucleotides and siRNA. The shell lipid bilayerinteracts with the core by charge-charge interaction and is hence a supported bilayer with enhanced stability. It can be modified with a high level (~10 mol%) of polyethylene glycol (PEG). The highly PEGylated LPD nanoparticles showed very low liver and spleen uptake due to the presence of a brush layer of PEG protecting and shielding the particle surface. The RES evading nanoparticles showed unusually high uptake by the tumor due to the enhanced permeability and retention (EPR) effect. Current research is to improve the endosome escape of the entrapped genes into the cytoplasm of the target cells.
Immuno/gene therapy of cervical cancer
One of the cationic non-viral vectors developed in our lab, i.e., LPD nanoparticles, shows strong affinity for the antigen presenting cells (APC) such as dendritic cells and macrophages. After uptake, LPD strongly activates the dendritic cells for maturation and antigen presentation. We have tested the vaccine carrier activity of LPD in a cervical cancer model. Since most of the human cervical cancers is HPV positive and expresses E7 protein, we have used LPD to deliver a peptide epitope of E7 to mouse dendritic cells (DC) and elicit a strong antigen-specific CTL activity. Immunized mice are completely resistant to the challenge of TC-1 tumor which is a HPV-positive cervical cancer model. Mice bearing large TC-1 tumor undergoes complete regression after a single s.c. injection of LPD/E7. Thus, both prophylactic and therapeutic immunities can be elicited by LPD carrying a tumor antigen.
We have recently discovered that the adjuvant activity of LPD mainly comes from the cationic lipid DOTAP. A very simple formulation containing the E7 peptide entrapped in DOTAP liposomes induces TC-1 tumor regression after a single s.c. injection. Obviously, DOTAP does more than just the delivery of the antigen to DC. It also activates DC via several different signaling pathways leading to maturation and antigen presentation by DC. We are currently investigating the mechanism by which cationic lipid activates DC, with the goal of developing more potent and less toxic cancer vaccines.
Gallery of Research Photos
Click above to examine a series of photos and slides developed throughout
the course of Dr. Huang's research at University of Tennessee and University of
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