Fanqi Qu

An Amphiphilic Dendrimer for Effective Delivery of Small Interfering RNA and Gene Silencing In Vitro and In Vivo

An amphiphilic dendrimer bearing a hydrophobic alkyl chain and hydrophilic poly(amidoamine) dendrons is able to combine the advantageous features of lipid and dendrimer vectors to deliver a heat shock protein 27 siRNA and produce potent gene silencing and anticancer activity in vitro and in vivo in a prostate cancer model. This dendrimer can be used alternatively for treating various diseases.

PAMAM Dendrimers Mediate siRNA Delivery to Target Hsp27 and Produce Potent Antiproliferative Effects on Prostate Cancer Cells

RNA interference (RNAi) holds great promise for the treatment of inherited and acquired diseases, provided that safe and efficient delivery systems are available. Herein we report that structurally flexible triethanolamine (TEA) core PAMAM dendrimers are able to deliver an Hsp27 siRNA effectively into prostate cancer (PC‐3) cells by forming stable nanoparticles with siRNA, protecting the siRNA nanoparticles from enzymatic degradation, and enhancing cellular uptake of siRNA. The Hsp27 siRNA resulted in potent and specific gene silencing of heat‐shock protein 27, an attractive therapeutic target in castrate‐resistant prostate cancer. Silencing of the hsp27 gene led to induction of caspase‐3/7‐dependent apoptosis and inhibition of PC‐3 cell growth in vitro. In addition, the siRNA–dendrimer complexes are non‐cytotoxic under the conditions used for siRNA delivery. Altogether, TEA core PAMAM dendrimer‐mediated siRNA delivery, in combination with RNAi that specifically targets Hsp27, may constitute a promising approach for combating castrate‐resistant prostate cancer, for which there is no efficacious treatment.

Novel triazole ribonucleoside down-regulates heat shock protein 27 and induces potent anticancer activity on drug-resistant pancreatic cancer.

A series of novel 3-arylethynyltriazolyl ribonucleosides were synthesized and assessed for their anticancer activity on the drug-resistant pancreatic cancer cell line MiaPaCa-2. Among them, one compound exhibited potent apoptosis-inducing properties and anticancer activity against the pancreatic cancer model MiaPaCa-2 both in vitro and in vivo with no adverse effects. This compound did not inhibit DNA synthesis and therefore does not resemble the clinical drug gemcitabine. It did, however, significantly down-regulate the expression of heat shock protein 27 (Hsp27), a small molecular chaperone playing an important role in drug resistance and highly expressed in drug-resistant cancer forms, and thus represents the first small molecular anticancer lead with such a mode of action.

Importance of size-to-charge ratio in construction of stable and uniform nanoscale RNA/dendrimer complexes.

Formation of RNA/dendrimer complexes between various RNA molecules and PAMAM dendrimers was studied using atomic force microscopy. Our results demonstrate that effective construction of stable nanoscale and uniform RNA/dendrimer complexes depends critically on the size of the RNA molecule, the dendrimer generation and the charge ratio between the dendrimer and the RNA. Larger RNA molecules, higher generations of dendrimers and larger dendrimer-to-RNA charge ratios lead to the formation of stable, uniform nanoscale RNA/dendrimer complexes. These findings provide new insights in developing dendrimer systems for RNA delivery.

Arginine-Terminated Generation 4 PAMAM Dendrimer as an Effective Nanovector for Functional siRNA Delivery in Vitro and in Vivo

Successful therapeutic implementation of RNA interference critically depends on systems able to safely and efficiently deliver small interfering RNA (siRNA). Dendrimers are emerging as appealing nanovectors for siRNA delivery by virtue of their unique well-defined dendritic nanostructure within which is confined an intriguing cooperativity and multivalency. We have previously demonstrated that structurally flexible triethanolamine (TEA) core poly(amidoamine) (PAMAM) dendrimers of high generations are effective nanovectors for siRNA delivery in vitro and in vivo. In the present study, we have developed arginine-terminated dendrimers with the aim of combining and harnessing the unique siRNA delivery properties of the TEA-core PAMAM dendrimer and the cell-penetrating advantages of the arginine-rich motif. A generation 4 dendrimer of this family (G4Arg) formed stable dendriplexes with siRNA, leading to improved cell uptake of siRNA by comparison with its nonarginine bearing dendrimer counterpart. Moreover, G4Arg was demonstrated to be an excellent nanocarrier for siRNA delivery, yielding potent gene silencing and anticancer effects in prostate cancer models both in vitro and in vivo with no discernible toxicity. Consequently, importing an arginine residue on the surface of a dendrimer is an appealing option to improve delivery efficiency, and at the same time, the dendrimer G4Arg constitutes a highly promising nanovector for efficacious siRNA delivery and holds great potential for further therapeutic applications.

Polycationic dendrimers interact with RNA molecules: polyamine dendrimers inhibit the catalytic activity of Candida ribozymes

Various polyamine dendrimers with a triethanolamine core inhibit the activity of the Candida ribozyme by forming RNA-dendrimer complexes via electrostatic interactions.

Discovery of Novel Arylethynyltriazole Ribonucleosides with Selective and Effective Antiviral and Antiproliferative Activity

Novel ethynyltriazole ribonucleosides were synthesized using a simple and efficient two-step procedure involving Sonogashira coupling and subsequent ammonolysis. Compounds 2f and 3o inhibited hepatitis C virus (HCV) replication efficiently, whereas compound 3f demonstrated potent apoptosis-induced antiproliferative activity against pancreatic cancer MiaPaCa-2 cells both in vitro and in vivo. Most interestingly, the notable selective antiviral and antiproliferative activities were achieved respectively for 2f and 3f by modulating the ribose sugar moiety into deprotected and protected forms while retaining a similar trifluoromethylphenylethynyltriazole as the nucleobase. Preliminary structure-activity relationship study revealed that not only the ribose moiety but also the CF(3) group at the p-position of the phenyl ring and the rigid triple bond functionality contributed critically to the observed antiviral activity of 2f against HCV and antiproliferative activity of 3f against pancreatic cancer. These two compounds constitute therefore promising leads in the search for new antiviral and anticancer candidates.

Targeting heat shock factor 1 with a triazole nucleoside analog to elicit potent anticancer activity on drug-resistant pancreatic cancer

Issued from a lead optimization process, we have identified a novel triazole nucleoside analog which elicits potent anticancer activity on drug-resistant pancreatic cancer. Most importantly, this compound targets heat shock response pathways by down-regulation of heat shock transcription factor 1 and consequential down-regulation of multiple heat shock proteins HSP27, HSP70 and HSP90. Down-regulation of these proteins caused the shut-down of several oncogenic pathways and caspase-dependent apoptosis resulting in a potent anticancer effect in vitro and in vivo. These results demonstrate the potential rewards gained in searching for anticancer candidates with multimodal actions on heat shock response pathways via HSF1 down-regulation.

Arylethynyltriazole acyclonucleosides inhibit hepatitis C virus replication.

Novel acyclic triazole nucleosides with various ethynyl moieties appended on the triazole nucleobase were synthesized efficiently using a convenient one-step Sonogashira reaction in aqueous solution and under microwave irradiation. One of the compounds, 1f, inhibited HCV subgenomic replication with a 50% effective concentration (EC(50)) of 22 microg/ml and did not inhibit proliferation of the host cell at a concentration of 50 microg/ml. A preliminary SAR study suggests that the appended phenyl ring as well as the rigid triple bond linker contributes importantly to the anti-HCV activity.

Targeted delivery of Dicer-substrate siRNAs using a dual targeting peptide decorated dendrimer delivery system

UNLABELLED Small interfering RNAs (siRNA) are emerging as novel therapeutic agents, providing competent delivery systems that are available. Dendrimers, a special family of synthetic macromolecules, represent an exciting delivery platform by virtue of their well-defined dendritic structure and unique multivalency and cooperativity confined within a nanoscale volume. Here, we report a Dicer-substrate siRNA (dsiRNA) which, when delivered using a structurally flexible triethanolamine-core poly(amidoamine) dendrimer of generation 5 as the nanocarrier, gives rise to a much greater RNAi response than that produced with conventional siRNA. Further decoration of the dsiRNA/dendrimer complexes with a dual targeting peptide simultaneously promoted cancer cell targeting through interacting with integrins and cell penetration via the interaction with neuropilin-1 receptors, which led to improved gene silencing and anticancer activity. Altogether, our results disclosed here open a new avenue for therapeutic implementation of RNAi using dendrimer nanovector based targeted delivery. FROM THE CLINICAL EDITOR This study demonstrates superior therapeutic properties of siRNA when combined with a dendrimer-based targeted nano-delivery system. Similar approaches may eventually gain clinical utility following additional studies determining safety and efficacy.