Depression of the ULF geomagnetic pulsation related to ionospheric irregularities

We consider a depression in intensity of ULF magnetic pulsations, which is observed on the ground surface due to appearance of the irregularities in the ionosphere. It is supposed that oblique Alfven waves in the ULF frequency range are downgoing from the magnetosphere and the horizontal irregularities of ionospheric conductivity are created by upgoing atmospheric gravity waves from seismic source. Unlike the companion paper by Molchanov et al. (2003), we used a simple model of the ionospheric layer but took into consideration the lateral inhomogeneity of the perturbation region in the ionosphere. It is shown that ULF intensity could be essentially decreased for frequencies f = 0.001-0.1 Hz at nighttime but the change is negligible at daytime in coincidence with observational results

Folate-targeted amphiphilic cyclodextrin nanoparticles incorporating a fusogenic peptide deliver therapeutic siRNA and inhibit the invasive capacity of 3D prostate cancer tumours

The main barrier to the development of an effective RNA interference (RNAi) therapy is the lack of a suitable delivery vector. Modified cyclodextrins have emerged in recent years for the delivery of siRNA. In the present study, a folate-targeted amphiphilic cyclodextrin was formulated using DSPE-PEG5000-folate to target prostate cancer cells. The fusogenic peptide GALA was included in the formulation to aid in the endosomal release of siRNA. Targeted nanoparticles were less than 200 nm in size with a neutral surface charge. The complexes were able to bind siRNA and protect it from serum nucleases. Incubation with excess free folate resulted in a significant decrease in the uptake of targeted nanoparticles in LNCaP and PC3 cells, both of which have been reported to have differing pathways of folate uptake. There was a significant reduction in the therapeutic targets, ZEB1 and NRP1 at mRNA and protein level following treatment with targeted complexes. In preliminary functional assays using 3D spheroids, treatment of PC3 tumours with targeted complexes with ZEB1 and NRP1 siRNA resulted in more compact colonies relative to the untargeted controls and inhibited infiltration into the Matrigel™ layer

IGF:VN complexes and their role in breast cell migration

Members of the insulin-like growth factor (IGF) family are mitogenic growth factors which have been shown to play critical roles in both normal growth and development, and tumour biology. The IGF system is complex and the biological effects of the IGFs are determined by diverse interactions between many molecules, including interactions with the extracellular matrix (ECM). Recent observations have demonstrated that IGFs can associate with the ECM protein vitronectin (VN) and this interaction can modulate IGF-stimulated biological functions. It has been demonstrated previously that IGF-II can bind directly to VN, while IGF-I associates with VN indirectly via the involvement of IGF-binding proteins (IGFBPs) -2, -3, -4 and -5. As the IGF system plays important roles in both normal breast development and in the transformation and progression of breast cancer, this study aimed to describe the effects of substrate-bound IGF-I:IGFBP:VN complexes on breast cell functions and to dissect the mechanisms underlying these responses. The studies reported in this thesis demonstrate that substrate-bound IGF-I:IGFBP:VN complexes, containing IGFBP-3 and IGFBP-5, are potent stimulators of proliferation and migration in the "normal", non-tumourigenic MCF-10A breast epithelial and MCF-7 breast carcinoma cell lines. Interestingly, substrate-bound IGF-I:IGFBP:VN complexes were less effective in increasing the migration of the metastatic MDA-MB-231 breast cancer cell line. This, however, is due to these cells expressing the αvβ3 integrin which can support a highly migratory phenotype independent of IGF-I-stimulation. Taken together this suggests a particularly important role for these complexes in stimulating a highly migratory phenotype in pre-invasive or poorly metastatic breast cells. Studies using IGF-I analogues were also undertaken to establish if there was a requirement for ternary complex formation and the type-1-IGF receptor (IGF-1R) in the enhanced migration responses observed. These studies determined IGF-I:IGFBP:VN-stimulated migration to be dependent upon both heterotrimeric IGF-I:IGFBP:VN complex formation and activation of the IGF-1R. Furthermore, the enhanced cellular migration was abolished upon incubation of MCF-7 and MCF-10A cells with function blocking antibodies directed at VN-binding integrins and the IGF-IR. In addition, analysis of the signal transduction pathways underlying the enhanced cell migration revealed that the complexes stimulate a transient activation of the ERK/MAPK signaling pathway, while simultaneously producing a sustained activation of the PI3-K/AKT pathway. Optimal intracellular signaling required activation of both the IGF-1R and VN-binding integrins, as antibody mediated inhibition of either receptor led to substantial decreases in both ERK/MAPK and PI3-K/AKT pathway activation. Furthermore, experiments using pharmacological inhibitors of these pathways determined a pivotal role for PI3-K/AKT activation in substrate-bound IGF-I:IGFBP:VN-stimulated cell migration. In order to confirm an important role for the PI3-K/AKT pathway in these responses, wild-type and activated-AKT was transiently overexpressed in MCF-10A cells. Overexpression of both wild-type and activated-AKT further enhanced cellular migration in response to substrate-bound IGF-I:IGFBP:VN complexes. However, these responses still required co-activation of the IGF-1R and VN-binding integrins. In an attempt to obtain a global view of the possible molecular mechanisms underpinning IGF-I:IGFBP:VN-stimulated cell migration, oligonucleotide microarrays were used to screen for candidate genes important for the observed migratory responses. The microarray studies identified 165 genes which were differentially expressed in cells migrating in response to substrate-bound IGF-I:IGFBP:VN complexes. Gene ontology and functional analysis revealed many of these genes to be significantly associated with biological functions relevant to cancer transformation and progression, including cell growth and proliferation, cell death and cellular movement. In regard to cell migration, a number of the genes identified have previously reported roles in cellular movement, migration and metastasis, which may provide future targets to augment IGF-I:IGFBP:VN-stimulated cell migration. Taken together, the studies reported throughout this thesis have provided the first mechanistic insights into the action of IGF-I:IGFBP:VN complexes and add further evidence to support the involvement of VN-binding integrins and their co-operativity with the IGF-IR in the promotion of tumour cell migration. Importantly, identifying the molecular mechanisms by which IGF:VN complexes enhance breast cell function will lead to not only a better understanding of this critical interaction, but also aid in developing diagnostic tests and therapeutics directed at treating breast cancer

Investigating the role of neuroendocrine transdifferentiation in the progression to castration resistant prostate cancer

Androgen targeted therapies (ATT) are the most commonly used treatments in prostate cancer (PCa).While these therapies are initially effective, PCa cells are able to activate adaptive response pathways to survive these therapies and progress to castration resistant PCa (CRPC), a highly aggressive and ultimately lethal stage of the disease. Neuroendocrine transdifferentiation (NEtD), a process whereby PCa cells gain neuroendocrinelike characteristics, has been implicated in the development of CRPC. The objective of this study is to develop and characterise models of therapy-induced NEtD to investigate the role of this adaptive plasticity in the progression to CRPC

A multiple nucleotide length polymorphism (MNLP) mediates androgen regulation of IRX4 in prostate cancer

Androgens and the androgen receptor (AR) play a crucial role in the initiation and progression of prostate cancer (PCa), regulating the expression of many PCa risk-associated genes. Iroquois Homeobox 4 (IRX4) has been recently identified with PCa risk and overexpressed in PCa. We observed a down-regulation of IRX4 expression in the cells undergoing epithelial to mesenchymal transition, suggesting its potential role in PCa progression and aim to delineate the androgenmediated regulation of IRX4 in PCa

The mesenchymal-to-epithelial reverting transition is enriched in metastatic castration resistant prostate cancer and correlates with poor survival

Despite recent recognition that the epithelial-mesenchymal transition (EMT) program acts in a dynamic manner (termed Epithelial to Mesenchymal Plasticity or EMP) during carcinoma metastasis, it has largely been ignored in the discovery and development of EMT-targeted therapies. In part, this has stemmed from a lack of preclinical models that can mimic the full dynamic nature of EMP and the perception that the EMT-reverting transition [or mesenchymal-epithelial reverting transition; (MErT)] is a mere antithesis of EMT. The objective of this study was to develop the first PCa model capable of recapitulating the dynamic nature of EMP

Insulin-like growth factor-i : vitronectin complex-induced changes in gene expression effect breast cell survival and migration

Free to read on publisher website\ud \ud Recent studies have demonstrated that IGF-I associates with VN through IGF-binding proteins (IGFBP) which in turn modulate IGF-stimulated biological functions such as cell proliferation, attachment and migration. Since IGFs play important roles in transformation and progression of breast tumours, we aimed to describe the effects of IGF-I:IGFBP:VN complexes on breast cell function and to dissect mechanisms underlying these responses. In this study we demonstrate that substrate-bound\ud IGF-I:IGFBP:VN complexes are potent stimulators of MCF-7 breast cell survival, which is mediated by a transient activation of ERK/MAPK and sustained activation of PI3-K/AKT pathways.\ud \ud Furthermore, use of pharmacological inhibitors of the MAPK and PI3-K pathways confirms that both pathways are involved in IGF-I:IGFBP:VN complex-mediated increased cell survival. Microarray analysis of cells stimulated to migrate in response to IGF-I:IGFBP:VN complexes identified differential expression of genes with previously reported roles in migration, invasion and survival (Ephrin-B2, Sharp-2, Tissue-factor, Stratifin, PAI-1, IRS-1). These changes were not detected when the IGF-I analogue (\[L24]\[A31]-IGF-I), which fails to bind to the IGF-I receptor, was substituted; confirming the IGF-I-dependent differential expression of genes associated with enhanced cell migration. Taken together, these studies have established that IGF-I:IGFBP:VN complexes enhance breast cell migration and survival, processes central to facilitating metastasis. This study highlights the interdependence of ECM and growth factor interactions in biological functions critical for metastasis and identifies potential novel therapeutic targets directed at preventing breast cancer progression

Substrate-bound insulin-like growth factor (IGF)-I-IGF binding protein-vitronectin-stimulated breast cell migration is enhanced by coactivation of the phosphatidylinositide 3-Kinase/AKT pathway by alphav-integrins and the IGF-I receptor

IGF-I can bind to the extracellular matrix protein vitronectin (VN) through the involvement of IGF-binding proteins-2, -3, -4, and -5. Because IGF-I and VN have established roles in tumor cell dissemination, we were keen to investigate the functional consequences of the interaction of IGF-I, IGF binding proteins (IGFBPs), and VN in tumor cell biology. Hence, functional responses of MCF-7 breast carcinoma cells and normal nontumorgenic MCF-10A mammary epithelial cells were investigated to allow side-by-side comparisons of these complexes in both cancerous and normal breast cells. We demonstrate that substrate-bound IGF-I-IGFBP-VN complexes stimulate synergistic increases in cellular migration in both cell types. Studies using IGF-I analogs determined this stimulation to be dependent on both heterotrimeric IGF-I-IGFBP-VN complex formation and the involvement of the IGF-I receptor (IGF-IR). Furthermore, the enhanced cellular migration was abolished on incubation of MCF-7 and MCF-10A cells with function blocking antibodies directed at VN-binding integrins and the IGF-IR. Analysis of the signal transduction pathways underlying the enhanced cell migration revealed that the complexes stimulate a transient activation of the ERK/MAPK signaling pathway while simultaneously producing a sustained activation of the phosphatidylinositide 3-kinase/AKT pathway. Experiments using pharmacological inhibitors of these pathways determined a requirement for phosphatidylinositide 3-kinase/AKT activation in the observed response. Overexpression of wild type and activated AKT further increases substrate-bound IGF-I-IGFBP-VN-stimulated migration. This study provides the first mechanistic insights into the action of IGF-I-IGFBP-VN complexes and adds further evidence to support the involvement of VN-binding integrins and their cooperativity with the IGF-IR in the promotion of tumor cell migration