BackgroundMany different types of nanoparticles, magnetic nanoparticles being just a category among them, offer exciting opportunities for technologies at the interfaces between chemistry, physics and biology. Some magnetic nanoparticles have already been utilized in clinical practice as contrast enhancing agents for magnetic resonance imaging (MRI). However, their physicochemical properties are constantly being improved upon also for other biological applications, such as magnetically-guided delivery systems for different therapeutics. By exposure of magnetic nanoparticles with attached therapeutics to an external magnetic field with appropriate characteristics, they are concentrated and retained at the preferred site which enables the targeted delivery of therapeutics to the desired spot.ConclusionsThe idea of binding chemotherapeutics to magnetic nanoparticles has been around for 30 years, however, no magnetic nanoparticles as delivery systems have yet been approved for clinical practice. Recently, binding of nucleic acids to magnetic nanoparticles has been demonstrated as a successful non-viral transfection method of different cell lines in vitro. With the optimization of this method called magnetofection, it will hopefully become another form of gene delivery for the treatment of cancer.

Despite the high mortality from metastatic cancer, therapeutic targets to prevent metastasis are limited. Efforts to identify genetic aberrations that predispose tumors to metastasis have been mostly unsuccessful. To understand the nature of candidate targets for metastatic disease, we performed an in silico screen to identify drugs that can inhibit a gene expression signature associated with epithelial-mesenchymal transition (EMT). Compounds discovered through this method, including those previously identified, appeared to restrict metastatic capacity through a common mechanism, the ability to modulate the fluidity of cell membranes. Treatment of breast cancer cell lines with the putative antimetastasis agents reduced membrane fluidity, resulting in decreased cell motility, stem celllike properties, and EMT in vitro, and the drugs also inhibited spontaneous metastasis in vivo. When fluidity was unchanged, the antimetastasis compounds could no longer restrict metastasis, indicating a causal association between fluidity and metastasis. We further demonstrate that fluidity can be regulated by cellular cholesterol flux, as the cholesterol efflux channel ABCA1 potentiated metastatic behaviors in vitro and in vivo. The requirement for fluidity was further supported by the finding in breast cancer patients that ABCA1 was overexpressed in 41% of metastatic tumors, reducing time to metastasis by 9 years. Collectively, our findings reveal increased membrane fluidity as a necessary cellular feature of metastatic potential that can be controlled by many currently available drugs, offering a viable therapeutic opportunity to prevent cancer metastasis.

Superparamagnetic iron oxide nanoparticles (SPIONs) are used as delivery systems for different therapeutics including nucleic acids for magnetofection-mediated gene therapy. The aim of our study was to evaluate physicochemical properties, biocompatibility, cellular uptake and trafficking pathways of the custom-synthesized SPIONs for their potential use in magnetofection. Custom-synthesized SPIONs were tested for size, shape, crystalline composition and magnetic behavior using a transmission electron microscope, X-ray diffractometer and magnetometer. SPIONs were dispersed in different aqueous media to obtain ferrofluids, which were tested for pH and stability using a pH meter and zetameter. Cytotoxicity was determined using the MTS and clonogenic assays. Cellular uptake and trafficking pathways were qualitatively evaluated by transmission electron microscopy and quantitatively by inductively coupled plasma atomic emission spectrometry. SPIONs were composed of an iron oxide core with a diameter of 8–9 nm, coated with a 2-nm-thick layer of silica. SPIONs, dispersed in 0.9% NaCl solution, resulted in a stable ferrofluid at physiological pH for several months. SPIONs were not cytotoxic in a broad range of concentrations and were readily internalized into different cells by endocytosis. Exposure to neodymium-iron-boron magnets significantly increased the cellular uptake of SPIONs, predominantly into malignant cells. The prepared SPIONs displayed adequate physicochemical and biomedical properties for potential use in magnetofection. Their cellular uptake was dependent on the cell type, and their accumulation within the cells was dependent on the duration of exposure to an external magnetic field.

Cancer immuno-gene therapy is an introduction of nucleic acids encoding immunostimulatory proteins, such as cytokine interleukin 12 (IL-12), into somatic cells to stimulate an immune response against a tumor. Various methods can be used for the introduction of nucleic acids into cells; magnetofection involves binding of nucleic acids to magnetic nanoparticles with subsequent exposure to an external magnetic field. Here we show that surface modified superparamagnetic iron oxide nanoparticles (SPIONs) with a combination of polyacrylic acid (PAA) and polyethylenimine (PEI) (SPIONs-PAA-PEI) proved to be safe and effective for magnetofection of cells and tumors in mice. Magnetofection of cells with plasmid DNA encoding reporter gene using SPIONs-PAA-PEI was superior in transfection efficiency to commercially available SPIONs. Magnetofection of murine mammary adenocarcinoma with plasmid DNA encoding IL-12 using SPIONs-PAA-PEI resulted in significant antitumor effect and could be further refined for cancer immuno-gene therapy.

The Epithelial-Mesenchymal Transition (EMT) is a developmental program that provides cancer cells with the characteristics necessary for metastasis, including increased motility and stem cell properties. The cellular and molecular mechanisms underlying this process are not yet fully understood, hampering efforts to develop therapeutics. In recent years, it has become apparent that EMT is accompanied by wholesale changes in diverse signaling pathways that are initiated by proteins at the plasma membrane (PM). The PM contains thousands of lipid and protein species that are dynamically and spatially organized into lateral membrane domains, an example of which are lipid rafts. Since one of the major functions of rafts is modulation of signaling originating at the PM, we hypothesized that the signaling changes occurring during an EMT are associated with alterations in PM organization. To test this hypothesis, we used Giant Plasma Membrane Vesicles (GPMVs) to study the organization of intact plasma membranes isolated from live cells. We observed that induction of EMT significantly destabilized lipid raft domains. Further, this reduction in stability was crucial for the maintenance of the stem cell phenotype and EMT-induced remodeling of PM-orchestrated pathways. Exogenously increasing raft stability by feeding cells with ω-3 polyunsaturated fatty acid docosahexaenoic acid (DHA) repressed these phenotypes without altering EMT markers, and inhibited the metastatic capacity of breast cancer cells. Hence, modulating raft properties regulates cell phenotype, suggesting a novel approach for targeting the impact of EMT in cancer.