Targeted Liposomal Drug Delivery: Overview of the Current Applications and Challenges.

In drug development, it is not uncommon that an active substance exhibits efficacy in vitro but lacks the ability to specifically reach its target in vivo. As a result, targeted drug delivery has become a primary focus in the pharmaceutical sciences. Since the approval of Doxil in 1995, liposomes have emerged as a leading nanoparticle in targeted drug delivery.

Lyophilization of Nanoparticles, Does It Really Work? Overview of the Current Status and Challenges.

Nanoparticles are being increasingly used as drug delivery systems to enhance the delivery to and uptake by target cells and to reduce off-target toxicity of free drugs. However, although the advantages of nanoparticles as drug carriers are clear, there are still some limitations, especially in maintaining their long-term stability. Lyophilization, also known as freeze-drying, has been heavily investigated as a solution to this problem.

Liposomes in Cancer Therapy: How Did We Start and Where Are We Now.

Since their first discovery in the 1960s by Alec Bangham, liposomes have been shown to be effective drug delivery systems for treating various cancers. Several liposome-based formulations received approval by the U.S.

Insight into the function of active site residues in the catalytic mechanism of human ferrochelatase.

Ferrochelatase catalyzes the insertion of ferrous iron into a porphyrin macrocycle to produce the essential cofactor, heme. In humans this enzyme not only catalyzes the terminal step, but also serves a regulatory step in the heme synthesis pathway. Over a dozen crystal structures of human ferrochelatase have been solved and many variants have been characterized kinetically.

Safe Nanoparticles: Are We There Yet?

The field of nanotechnology has grown over the last two decades and made the transition from the benchtop to applied technologies. Nanoscale-sized particles, or nanoparticles, have emerged as promising tools with broad applications in drug delivery, diagnostics, cosmetics and several other biological and non-biological areas. These advances lead to questions about nanoparticle safety.

Liposomes Targeting P21 Activated Kinase-1 (PAK-1) and Selective for Secretory Phospholipase A (sPLA) Decrease Cell Viability and Induce Apoptosis in Metastatic Triple-Negative Breast Cancer Cells.

P21 activated kinases (or group I PAKs) are serine/threonine kinases whose expression is altered in prostate and breast cancers. PAK-1 activity is inhibited by the small molecule "Inhibitor targeting PAK-1 activation-3" (IPA-3), which has selectivity for PAK-1 but is metabolically unstable. Secretory Group IIA phospholipase A (sPLA) expression correlates to increased metastasis and decreased survival in many cancers.

Sterically stabilized liposomes targeting P21 (RAC1) activated kinase-1 and secreted phospholipase A suppress prostate cancer growth and metastasis.

Metastatic prostate cancer (PCa) has a very high mortality rate in men, in Western countries and lacks reliable treatment. The advanced-stage PCa cells overexpress P21 (RAC1) activated kinase-1 (PAK1) and secreted phospholipase A (sPLA) suggesting the potential utility of pharmacologically targeting these molecules to treat metastatic PCa. The small molecule, inhibitor targeting PAK1 activation-3 (IPA3) is a highly specific allosteric inhibitor of PAK1; however, it is metabolically unstable once in the plasma thus, limiting its utility as a chemotherapeutic agent.

Effect of P21-activated kinase 1 (PAK-1) inhibition on cancer cell growth, migration, and invasion.

P21-activated kinase-1 (PAK-1) is a serine/threonine kinase involved in multiple signaling pathways that mediate cellular functions such as cytoskeletal motility, cell proliferation, and survival. PAK-1 expression is altered in various cancers, including prostate and breast. Our recent studies showed that prostate cancer cells expressing higher levels of PAK-1 were resistant to the cytotoxic effects of the PAK-1 inhibitor, inhibitor targeting PAK-1 activation-3 (IPA-3), compared to those with lower expression.

Identification and characterization of solvent-filled channels in human ferrochelatase.

Ferrochelatase catalyzes the formation of protoheme from two potentially cytotoxic products, iron and protoporphyrin IX. While much is known from structural and kinetic studies on human ferrochelatase of the dynamic nature of the enzyme during catalysis and the binding of protoporphyrin IX and heme, little is known about how metal is delivered to the active site and how chelation occurs. Analysis of all ferrochelatase structures available to date reveals the existence of several solvent-filled channels that originate at the protein surface and continue to the active site.

Altered orientation of active site residues in variants of human ferrochelatase. Evidence for a hydrogen bond network involved in catalysis.

Ferrochelatase catalyzes the terminal step in heme biosynthesis, the insertion of ferrous iron into protoporphyrin to form protoheme IX. The crystal structures of human ferrochelatase both with and without the protoporphyrin substrate bound have been determined previously. The substrate-free enzyme has an open active site pocket, while in the substrate-bound enzyme, the active site pocket is closed around the porphyrin macrocycle and a number of active site residues have reoriented side chains.

Production and characterization of erythropoietic protoporphyric heterodimeric ferrochelatases.

Mutations resulting in diminished activity of the dimeric enzyme ferrochelatase are a prerequisite for the inherited disorder erythropoietic protoporphyria (EPP). Patients with clinical EPP have only 10% to 30% of normal levels of ferrochelatase activity, and although many patients with EPP have one mutant allele and one "low-expression" normal allele, the possibility remains that, for some, low ferrochelatase activity may result from an EPP mutation that has an impact on both subunits of the wild-type/mutant heterodimer. Here we present data for 12 ferrochelatase wild-type/EPP mutant heterodimers showing that some mutations result in heterodimers with the residual activity anticipated from individual constituents, whereas others result in heterodimers with significantly lower activity than would be predicted.