New targets for RNA interference (RNAi)-based cancer therapy are constantly emerging from the increasing knowledge on key molecular pathways that are paramount for carcinogenesis. Nevertheless, in vivo delivery of small interfering RNA (siRNA) remains a crucial challenge for therapeutic success. siRNAs on their own are not taken up by most mammalian cells in a way that preserves their activity. Moreover, when applied in vivo, siRNA-based approaches are all limited by poor penetration into the target tissue and low silencing efficiency. To circumvent these limitations, we have developed novel polymerized polyglycerol-based dendrimer core shell structures to deliver siRNA to tumors in vivo. These cationic dendrimers can strongly improve the stability of the siRNA, its intracellular trafficking, its silencing efficacy, and its accumulation in the tumor environment owing to the enhanced permeability and retention effect. Here, we show that our dendritic nanocarriers exhibited low cytotoxicity and high efficacy in delivering active siRNA into cells. With use of human glioblastoma and murine mammary adenocarcinoma cell lines as model systems, these siRNA-dendrimer polyplexes silenced the luciferase gene, ectopically overexpressed in these cells. Importantly, significant gene silencing was accomplished in vivo within 24 h of treatment with our luciferase siRNA-nanocarrier polyplexes, as measured by noninvasive intravital bioluminescence imaging. Moreover, our siRNA-nanocarriers show very low levels of toxicity as no significant weight loss was observed after intravenous administration of the polyplexes. We show a proof of concept for siRNA delivery in vivo using a luciferase-based model. We predict that in vivo silencing of important cell growth and angiogenesis regulator genes in a selective manner will justify this approach as a successful anticancer therapy.

RNA interference provides great opportunities for treating diseases from genetic disorders, infection, and cancer. The successful application of small interference RNA (siRNA) in cells with high transfection efficiency and low cytotoxicity is, however, a major challenge in gene-mediated therapy. Several pH-responsive core shell architectures have been designed that contain a nitrogen shell motif and a polyglycerol core, which has been prepared by a two-step protocol involving the activation of primary and secondary hydroxyl groups by phenyl chloroformate and amine substitution. Each polymer was analyzed by particle size and ζ potential measurements, whereas the respective polyplex formation was determined by ethidium bromide displacement assay, atomic force microscopy (AFM), and surface charge analysis. The in vitro gene silencing properties of the different polymers were evaluated by using a human epithelial carcinoma cell (HeLaS3) line with different proteins (Lamin, CDC2, MAPK2). Polyplexes yielded similar knockdown efficiencies as HiPerFect controls, with comparably low cytotoxicity. Therefore, these efficient and highly biocompatible dendritic polyamines are promising candidates for siRNA delivery in vivo.

ABSTRACT:Sartans are very effective drugs for treatment of hypertension, heart failure, and other cardiovascular disorders. They antagonize the effects of angiotensin II at the AT 1 receptor and display p.o. bioavailability rates of 13 to 80%. Because some sartans sterically resemble dipeptide derivatives, we investigated whether they are transported by peptide transporters. We first assessed the effects of sartans on . In contrast to cefadroxil, no PEPT1-specific uptake of valsartan and losartan was found. We conclude that the sartans tested in this study display high-affinity interaction with PEPTs but are not transported themselves. However, they strongly inhibit hPEPT1-mediated uptake of dipeptides and cefadroxil.Sartans such as losartan, valsartan, irbesartan, and eprosartan are blockers of the angiotensin II type 1 receptor. They have proven to be effective in the treatment of hypertension, renal diseases, heart failure, ventricular hypertrophy, dilation, arrhythmias, and dysfunction with overall reduced cardiovascular morbidity and mortality and fewer negative side effects than the classic angiotensin-converting enzyme inhibitors (for review, see

Angiotensin-converting enzyme (ACE) inhibitors are often regarded as substrates for the H ϩ /peptide transporters (PEPT)1 and PEPT2. Even though the conclusions drawn from published data are quite inconsistent, in most review articles PEPT1 is claimed to mediate the intestinal absorption of ACE inhibitors and thus to determine their oral availability. We systematically investigated the interaction of a series of ACE inhibitors with PEPT1 and PEPT2. First, we studied the effect of 14 ACE inhibitors including new drugs on the uptake of the dipeptide [14 C]glycylsarcosine into human intestinal Caco-2 cells constitutively expressing PEPT1 and rat renal SKPT cells expressing PEPT2. In a second approach, the interaction of ACE inhibitors with heterologously expressed human PEPT1 and PEPT2 was determined. In both assay systems, zofenopril and fosinopril were found to have very high affinity for binding to peptide transporters. Medium to low affinity for transporter interaction was found for benazepril, quinapril, trandolapril, spirapril, cilazapril, ramipril, moexipril, quinaprilat, and perindopril. For enalapril, lisinopril, and captopril, very weak affinity or lack of interaction was found. Transport currents of PEPT1 and PEPT2 expressed in Xenopus laevis oocytes were recorded by the two-electrode voltage-clamp technique. Statistically significant, but very low currents were only observed for lisinopril, enalapril, quinapril, and benazepril at PEPT1 and for spirapril at PEPT2. For the other ACE inhibitors, electrogenic transport activity was extremely low or not measurable at all. The present results suggest that peptide transporters do not control intestinal absorption and renal reabsorption of ACE inhibitors.Angiotensin-converting enzyme (ACE) inhibitors are effective drugs for the treatment of hypertension, congestive heart failure, postmyocardial infarction, and diabetic nephropathy (Bertrand, 2004;Wong et al., 2004). The compounds inhibit the rate-limiting enzyme in the formation of angiotensin II, thereby reducing its capability for binding to its receptor. After oral administration as the primary route, most ACE inhibitors display absorption rates of 30 to 100% of a dose (Steinhilber et al., 2005). Because many ACE inhibitors sterically resemble AlaPro dipeptide or Xaa-Ala-Pro tripeptide structures, it was hypothesized that they share the same intestinal transport route as di-and tripeptides (for review, see Bai and Amidon, 1992;Amidon and Sadée, 1999). Di-and tripeptides are taken up into intestinal cells by the low-affinity H ϩ /peptide cotransporter PEPT1. In the kidney tubule, di-and tripeptides are reabsorbed by PEPT1 and by the high-affinity H ϩ /peptide cotransporter PEPT2 (for review, see Nielsen and Brodin, 2003;Daniel and Kottra, 2004;Terada and Inui, 2004;Biegel et al., 2006). ␤-Lactam antibiotics and antivirals such as valacyclovir were unequivocally demonstrated to use PEPT1 and PEPT2 for intestinal absorption or renal reabsorption, respectively (Bretschneider et al., 1999;Nielsen and Brod...

The successful application of gene therapy through DNA transfection into the cell is still a great challenge in ongoing research. Hyperbranched polyamines are highly branched macromolecules, and have gained significant attention in the last two decades, due to their relative ease of preparation, their shape, and their multi-functionality.This review deals with the syntheses of various hyperbranched polyamines that are prepared through a one-step polymerization process. Furthermore, we present the current status of polyamines as gene carriers and describe their versatility, and their properties such as structure-property dependency, gene transfection efficiency, and cytotoxicity profiles of hyperbranched polyamines.