Delivery of nucleic acids for cancer gene therapy: overcoming extra- and intra-cellular barriers

The therapeutic potential of cancer gene therapy has been limited by the difficulty of delivering genetic material to target sites. Various biological and molecular barriers exist which need to be overcome before effective nonviral delivery systems can be applied successfully in oncology. Herein, various barriers are described and strategies to circumvent such obstacles are discussed, considering both the extracellular and intracellular setting. Development of multifunctional delivery systems holds much promise for the progression of gene delivery, and a growing body of evidence supports this approach involving rational design of vectors, with a unique molecular architecture. In addition, the potential application of composite gene delivery platforms is highlighted which may provide an alternative delivery strategy to traditional systemic administration.

Potentiating the Anticancer Properties of Bisphosphonates by Nanocomplexation with the Cationic Amphipathic Peptide, RALA

Bisphosphonates (BPs) are a class of bone resorptive drug with a high affinity for the hydroxyapatite structure of bone matrices that are used for the treatment of osteoporosis. However, clinical application is limited by a common toxicity, BP-related osteonecrosis of the jaw. There is emerging evidence that BPs possess anticancer potential, but exploitation of these antiproliferative properties is limited by their toxicities. We previously reported the utility of a cationic amphipathic fusogenic peptide, RALA, to traffic anionic nucleic acids into various cell types in the form of cationic nanoparticles. We hypothesized that complexation with RALA could similarly be used to conceal a BP's hydroxyapatite affinity, and to enhance bioavailability, thereby improving anticancer efficacy. Incubation of RALA with alendronate, etidronate, risedronate, or zoledronate provoked spontaneous electrostatic formation of cationic nanoparticles that did not exceed 100 nm in diameter and that were stable over a range of temperatures and for up to 6 h. The nanoparticles demonstrated a pH responsiveness, possibly indicative of a conformational change, that could facilitate release of the BP cargo in the endosomal environment. RALA/BP nanoparticles were more potent anticancer agents than their free BP counterparts in assays investigating the viability of PC3 prostate cancer and MDA-MB-231 breast cancer cells. Moreover, RALA complexation potentiated the tumor growth delay activity of alendronate in a PC3 xenograft model of prostate cancer. Taken together, these findings further validate the use of BPs as repurposed anticancer agents.

Application of GPCR Structures for Modelling of Free Fatty Acid Receptors

Five G protein-coupled receptors (GPCRs) have been identified to be activated by free fatty acids (FFA). Among them, FFA1 (GPR40) and FFA4 (GPR120) bind long-chain fatty acids, FFA2 (GPR43) and FFA3 (GPR41) bind short-chain fatty acids and GPR84 binds medium-chain fatty acids. Free fatty acid receptors have now emerged as potential targets for the treatment of diabetes, obesity and immune diseases. The recent progress in crystallography of GPCRs has now enabled the elucidation of the structure of FFA1 and provided reliable templates for homology modelling of other FFA receptors. Analysis of the crystal structure and improved homology models, along with mutagenesis data and structure activity, highlighted an unusual arginine charge pairing interaction in FFA1-3 for receptor modulation, distinct structural features for ligand binding to FFA1 and FFA4 and an arginine of the second extracellular loop as a possible anchoring point for FFA at GPR84. Structural data will be helpful for searching novel small molecule modulators at the FFA receptors.