Conserved Activity of Reassociated Homotetrameric Protein Subunits Released from Mesoporous Silica Nanoparticles

Mesoporous silica nanoparticles (MSN) with enlarged pores were prepared and characterized, and reversibly dissociated subunits of concanavalin A were entrapped in the mesopores, as shown by multiple biochemical and material characterizations. When loaded in the MSN, we demonstrated protein stability from proteases and, upon release, the subunits reassociated into active proteins shown through mannose binding and o-phthalaldehyde fluorescence. We have demonstrated a versatile and facile method to load homomeric proteins into MSN with potential applications in enhancing the delivery of large therapeutic proteins.

Caveolin-1 mediates inflammatory breast cancer cell invasion via the Akt1 pathway and RhoC GTPase

With a propensity to invade the dermal lymphatic vessels of the skin overlying the breast and readily metastasize, inflammatory breast cancer (IBC) is arguably the deadliest form of breast cancer. We previously reported that caveolin-1 is overexpressed in IBC and that RhoC GTPase is a metastatic switch responsible for the invasive phenotype. RhoC-driven invasion requires phosphorylation by Akt1. Using a reliable IBC cell line we set out to determine if caveolin-1 expression affects RhoC-mediated IBC invasion. Caveolin-1 was down regulated by introduction of siRNA or a caveolin scaffolding domain. The ability of the cells to invade was tested and the status of Akt1 and RhoC GTPase examined. IBC cell invasion is significantly decreased when caveolin-1 is down regulated. Activation of Akt1 is decreased when caveolin-1 is down regulated, leading to decreased phosphorylation of RhoC GTPase. Thus, we report here that caveolin-1 overexpression mediates IBC cell invasion through activation Akt1, which phosphorylates RhoC GTPase.

Heparin enhances uptake of platelet factor 4/heparin complexes by monocytes and macrophages

BACKGROUND

Heparin-induced thrombocytopenia (HIT) is an iatrogenic complication of heparin therapy caused by antibodies to a self-antigen, platelet factor (4) and heparin. The reasons why antibodies form to PF4/heparin, but not to PF4 bound to other cellular glycosaminoglycans are poorly understood.

OBJECTIVE

To investigate differences in cellular responses to cell-bound PF4 and PF4/heparin complexes, we studied the internalization of each by peripheral blood-derived monocytes, dendritic cells and neutrophils.

METHODS AND RESULTS

Using unlabeled and fluorescently-labeled antigen and/or labeled monoclonal antibody to PF4/heparin complexes (KKO), we show that PF4/heparin complexes are taken up by monocytes in a heparin-dependent manner and are internalized by human monocytes and dendritic cells, but not by neutrophils. Complexes of PF4/low-molecular-weight heparin and complexes composed of heparin and murine PF4, protamine or lysozyme are internalized similarly, suggesting a common endocytic pathway. Uptake of complexes is mediated by macropinocytosis, as shown by inhibition using cytochalasin D and amiloride. Internalized complexes are transported intact to late endosomes, as indicated by co-staining of vesicles with KKO and lysosomal associated membrane protein-2 (LAMP-2). Lastly, we show that cellular uptake is accompanied by expression of MHCII and CD83 co-stimulatory molecules.

CONCLUSIONS

Taken together, these studies establish a distinct role for heparin in enhancing antigen uptake and activation of the initial steps in the cellular immune response to PF4-containing complexes.

Geometry of the edge of chaos in a low-dimensional turbulent shear flow model

We investigate the geometry of the edge of chaos for a nine-dimensional sinusoidal shear flow model and show how the shape of the edge of chaos changes with increasing Reynolds number. Furthermore, we numerically compute the scaling of the minimum perturbation required to drive the laminar attracting state into the turbulent region. We find this minimum perturbation to scale with the Reynolds number as Re(-2).

Scaling of chaos versus periodicity: how certain is it that an attractor is chaotic?

The character of the time-asymptotic evolution of physical systems can have complex, singular behavior with variation of a system parameter, particularly when chaos is involved. A perturbation of the parameter by a small amount ε can convert an attractor from chaotic to nonchaotic or vice versa. We call a parameter value where this can happen ε uncertain. The probability that a random choice of the parameter is ε uncertain commonly scales like a power law in ε. Surprisingly, two seemingly similar ways of defining this scaling, both of physical interest, yield different numerical values for the scaling exponent. We show why this happens and present a quantitative analysis of this phenomenon.

Mimicking red blood cell lipid membrane to enhance the hemocompatibility of large-pore mesoporous silica

Mesoporous silica nanoparticles (MSNs) have been repeatedly demonstrated as potential drug-delivery devices. The study of biocompatibility and interaction of these materials with the various cell types is of great interest with regard to the development of viable pharmaceutical products. By mimicking the cholesterol, phosphatidylcholine, and phosphatidylethanolamine composition of the outer leaflet of a human red blood cell (RBC), lipid-bilayer-coated mesoporous silica particles show considerably improved hemocompatibility over phosphatidylcholine-coated and uncoated large-pore MSN (l-MSN). These inorganic/organic composite nanomaterials are shown to be capable of interfacing with RBCs without damaging the cells even at relatively high concentrations, as observed through electron microscopy, UV-vis spectroscopy, and flow cytometry analyses. Interestingly, the absence of cholesterol in the outer bilayer composition is shown to produce toxic effects without resulting in hemolysis. By maintaining the ζ potential of lipid-bilayer-functionalized MSNs similar to that of the hemolytic l-MSNs, we demonstrate that the bilayer composition, and not the surface charge, plays a significant role in determining the hemocompatibility of MSN-based materials.

Abstract P6-12-15: Preclinical testing of a novel platelet derived growth factor receptor alpha (PDGFRa) inhibitor in inflammatory breast cancer

Inflammatory breast cancer (IBC) is the most lethal form of locally advanced breast cancer and carries a guarded prognosis. IBC presents with a “lumpless” primary tumor, which rapidly infiltrates and forms tumor emboli within the dermal lymphatic vessels of the skin overlying the breast. It is clear from the recent research advancements that IBC is a unique entity, not only in its clinical presentation, disease progression and response to therapy but also in its molecular expression profile. Therefore, it is essential to carry out molecular expression studies in IBC compared to non-IBC as well as to pursue these differences to study their effects on IBC phenotype. Our laboratory has demonstrated that the platelet derived growth factor receptor alpha (PDGFRa) is significantly over expressed in IBC patient samples (between 15-36%) compared to non-IBC patient samples. Using multiple approaches we demonstrate the PDGFRα activation signature in IBC patient samples and cell lines. Our data demonstrates that PDGFRα is constitutively active and localized in the cytoplasm of IBC cells. Although the receptor is intracellular, PDGFRα signaling remains intact. Thus, PDGFRα is an attractive target for therapy. Here we show that a novel PDGFR inhibitor, crenolanib, which specifically targets active PDGFR, is able to significantly inhibit IBC tumor growth and progression. In nude mice, 200 mm3 orthotopic IBC tumors did not increase in size when the mice were treated with crenolanib. In contrast, mice treated with vehicle control demonstrated a 4-fold increase in tumor growth over the 2-week course of the experiment. In addition, by using a novel in vitro IBC emboli growth model, we demonstrate that crenolanib prevents IBC tumor emboli formation and acts to sensitize IBC cells to chemotherapeutic agents. We were able to achieve a similar level of IBC cell killing with a 10-fold lower dose of chemotherapeutic agents compared to the agents by themselves. Together, these data demonstrate that PDGFRα is a viable target in IBC patients and that crenolanib is a potent and effective therapeutic agent against IBC cells.

Citation Information: Cancer Res 2013;73(24 Suppl): Abstract nr P6-12-15.

Polymer-based stimuli-responsive nanosystems for biomedical applications

The application of organic polymers and inorganic/organic hybrid systems in numerous fields of biotechnology has seen a considerable growth in recent years. Typically, organic polymers with diverse structures, compositional variations and differing molecular weights have been utilized to assemble polymeric nanosystems such as polymeric micelles, polymersomes, and nanohydrogels with unique features and structural properties. The architecture of these polymeric nanosystems involves the use of both hydrophobic and hydrophilic polymeric blocks, making them suitable as vehicles for diagnostic and therapeutic applications. Recently, "smart" or "intelligent" polymers have attracted significant attention in the biomedical field wherein careful introduction of specific polymeric modalities changes a banal polymeric nanosystem to an advanced stimuli-responsive nanosystem capable of performing extraordinary functions in response to an internal or external trigger such as pH, temperature, redox, enzymes, light, magnetic, or ultrasound. Further, incorporation of inorganic nanoparticles such as gold, silica, or iron oxide with surface-bound stimuli-responsive polymers offers additional advantages and multifunctionality in the field of nanomedicine. This review covers the physical properties and applications of both organic and organic/inorganic hybrid nanosystems with specific recent breakthroughs in drug delivery, imaging, tissue engineering, and separations and provides a brief discussion on the future direction.

Abstract P6-06-03: Caveolin-1: A potential mediator of RhoC GTPase driven Inflammatory breast cancer cell invasion

The proposed study focuses on Inflammatory Breast Cancer (IBC), which is one of the most aggressive forms of locally advanced breast cancer. IBC is an understudied disease in terms of identifying various molecular entities that could potentially be responsible for the aggressiveness of this disease. Recent advancements reveal that IBC has a unique molecular profile when compared with non-IBC. Caveolin-1 is found to have opposite expression pattern in IBC versus non-IBC. Our lab has shown that Caveolin-1 is found to be over-expressed in IBC whereas in non-IBC its expression is much reduced compared to normal mammary epithelial cells.

Caveolin-1 is known to be associated with specialized lipid rafts in the plasma membrane called ‘caveolae’. ‘Caveolin scaffolding domain (CSD)’ from amino acids 82–101 concentrates variety of signaling molecules such as growth factor receptors, protein kinases, heterotrimeric G proteins and Rho GTPases. Thus it is known as a potential regulator of many signaling pathways. Rho GTPases are members of the Ras superfamily of small GTP binding proteins involved in cytoskeletal rearrangements during cell motility and invasion. Our lab has previously shown that RhoC GTPase is over expressed in IBC and that exogenous expression of RhoC GTPase produces motile and invasive phenotype in human mammary epithelial cells (HMECs) similar to SUM149 IBC cells. Thus the overall objective of this study is to determine if caveolin-1 over expression mediates the RhoC GTPase driven invasive phenotype of IBC via its scaffolding action.

The first objective of this study is to elucidate the effect of caveolin-1 over expression on SUM149 IBC cell invasion. This was done by down regulating caveolin-1 to a level that is comparable to human mammary epithelial cells (HMECs) by using si caveolin-1. With the same si caveolin-1 or exogenous CSD synthetic peptide, we performed Matrigel invasion assays followed by cell viability and proliferation assay. Si caveolin-1 did not produce significant changes in cell viability over the period of four days as well as in Ki-67 staining which was used as a proliferation marker. Caveolin-1 down regulation reduced cell invasion by 90% compared to untreated cells. Similarly, exogenous CSD synthetic peptide treatment reduced SUM149 cell invasion significantly. In order to understand caveolin-1 localization in SUM149 cells, we performed immuno gold labeling of caveolin-1 by transmission electron microscopy as well as sucrose gradient centrifugation. Both these methods showed distinct pool of cytoplasmic caveolin-1 in addition to plasma membrane associated caveolin-1. Co-localization of caveolin-1 and RhoC GTPase was studied by co-transfecting cells with GFP-caveolin-1 and RFP-RhoC GTPase.

Thus, this data suggests potential role of caveolin-1 over expression in regulating IBC cell invasion. Due to its ability to concentrate variety of signaling molecules, caveolin-1 could act as a principle regulator of several downstream events that make cells motile and invasive through RhoC GTPase activation. Thus studying caveolin-1 localization and effect of its regulation on the signaling pathways could help understand the important molecular mechanisms in IBC.

Citation Information: Cancer Res 2012;72(24 Suppl):Abstract nr P6-06-03.

Bactericidal/permeability increasing protein: a multifaceted protein with functions beyond LPS neutralization

Bactericidal permeability increasing protein (BPI), a 55-60 kDa protein, first reported in 1975, has gone a long way as a protein with multifunctional roles. Its classical role in neutralizing endotoxin (LPS) raised high hopes among septic shock patients. Today, BPI is not just a LPS-neutralizing protein, but a protein with diverse functions. These functions can be as varied as inhibition of endothelial cell growth and inhibition of dendritic cell maturation, or as an anti-angiogenic, chemoattractant or opsonization agent. Though the literature available is extremely limited, it is fascinating to look into how BPI is gaining major importance as a signalling molecule. In this review, we briefly summarize the recent research focused on the multiple roles of BPI and its use as a therapeutic.

Differential effects of vitamin D treatment on inflammatory and non-inflammatory breast cancer cell lines

Vitamin D is a known regulator of breast cancer cell proliferation, apoptosis, migration, invasion and differentiation in vitro. Recent studies have suggested a preventative role for vitamin D in breast cancer development and suggested a possible therapeutic application of vitamin D for patients with various forms of breast cancer. Inflammatory breast cancer (IBC) is a highly aggressive and phenotypically unique form of breast cancer that has a very poor prognosis. IBC invades the dermal lymphatics of the breast as tumor emboli early in the course of the disease. Because of the invasive nature of IBC, novel therapeutics are needed desperately. In the current study we examined the effect of the active form of vitamin D, calcitriol, treatment on the aggressive IBC phenotype. Herein we demonstrate that although the vitamin D receptor (VDR) is present in both IBC and non-IBC cell lines, the effect of vitamin D treatment is significant only on the IBC cells. SUM149 IBC cells showed increased protein concentration in response to 24 h of calcitriol exposure; likely mediated by an increase in protein synthesis as opposed to increased cellular proliferation. In addition, treatment with 100 nM calcitriol showed a significant decrease in SUM149 migration (67.8 % decrease, P = 0.030), invasion (43.9 % decrease, P = 0.015), and tumor spheroid size (69.4 % decrease, P = 0.018) compared to nontreated control groups. Finally, calcitriol treatment of SUM149 cells led to significantly fewer IBC experimental metastases as compared to control. Our study demonstrates that calcitriol treatment of SUM149 affected several of the processes important for IBC metastasis but had little effect on MDA-MB-231 cells. Therefore, calcitriol treatment may have the potential to decrease the rate and incidence of metastasis in IBC patients.

P5-01-01: Identification, Validation and Assessment of Transcriptional Relevance of a PDGFR-Activation Signature in (Inflammatory) Breast Cancer

Introduction. Breast cancer can be divided into several subgroups characterized by unique patterns of pathway activation. Platelet-derived growth factor receptor (PDGFR) signalling has not yet been included in this classification scheme, although it has been reported to be a potential target for therapy. In this study, we have constructed a PDGFR-activation signature and investigated its relevance in breast cancer.

Materials and Methods. Sixteen PDGFR-modulated genes were identified by intersecting two published PDGFR-modulated gene lists. The resulting gene signature was applied onto a publicly available gene expression data set of GIST (GSE17743) using principle component analysis. The segregation of PDGFR- and KIT-mutated GIST samples was investigated using permutation analysis and classification sensitivity and specificity were assessed. Using the regression coefficients from the first principal component, a PDGFR-activation score was constructed and applied onto a second data set in order to validate the score (GSE1923). Finally, the score was applied onto a gene expression data set of 389 breast cancer ***samples, including 137 samples from patients with IBC.

Results. Sixteen PDGFR-modulated genes (NR4A1, EGR3, JUNB, IER3, TIEG, JUN, BCL3, MYC, NR4A3, PLAU, MCL1, DUSP1, DUSP5, DUSP6, SGK, GADD45A) were able to discriminate PDGFR-mutated GIST samples from KIT-mutated GIST samples with a sensitivity of 75% and a specificity of 85%. Application of the PDGFR-activation score onto a data set of control and PDGF-treated glioblastoma cells showed a significant increase in the PDGFR-activation score in the treated condition (P=0.0302). Application of the PDGFR-signature onto our series of IBC and nIBC samples demonstrated a significant and molecular subtype-independent increase in PDGFR-activation in IBC (P=0.0015; FDR=3%). In addition, in our series of nIBC samples only, PDGFR-activation was associated with decreased DMFS and RFS (P=0.0038 and P=0.0137 respectively). In fact, PDGFR-activation was an independent prognosticator in a multivariate model incorporating the molecular subtypes.

Discussion. We identified a gene signature composed of 16 genes able to predict PDGFR-activation in tissue samples by gene expression analysis. PDGFR-activation is significantly increased in samples from patients with IBC, an aggressive form of locally advanced breast cancer. In addition, in nIBC, PDGFR-activation is associated with DMFS and RFS, independently of the molecular subtypes suggesting that PDGFR-activation might add another level of clinically relevant heterogeneity in breast cancer.

Citation Information: Cancer Res 2011;71(24 Suppl):Abstract nr P5-01-01.

Evaluation of the physiological significance of botrocetin/ von Willebrand factor in vitro signaling

BACKGROUND

A signaling pathway is difficult, if not impossible, to elucidate in platelets using only in vivo studies. Likewise, the physiological significance of signaling information obtained exclusively from in vitro observations is unknown. Therefore, both in vitro and in vivo experiments are required to establish the physiological significance of a signaling pathway.

OBJECTIVE

To evaluate the physiological significance of signaling data obtained from botrocetin (bt)/von Willebrand factor (VWF)-stimulated washed platelets.

METHOD

Stable thrombus formation in response to FeCl(3)-induced injury of the mouse carotid artery was used to evaluate the physiological significance of signaling data obtained from bt/VWF-stimulated washed platelets.

RESULTS

Syk, PLCgamma2, Galphaq and P2Y12, but not LAT, were found either to be required for or to affect stable thrombus formation. Prior in vitro studies had demonstrated that LAT is not required for bt/VWF-induced platelet aggregation in the presence of exogenous fibrinogen. These data provide the first demonstration of the in vivo role for these signaling molecules in GPIb-dependent/initiated signal transduction and are consistent with the signaling pathway deduced from in vitro studies of bt/VWF-stimulated washed platelets using metabolic inhibitors and knockout mice.

CONCLUSION

The broad agreement between the in vitro and the in vivo results establish that bt/VWF stimulation of washed platelets can provide physiologically significant glycoprotein Ib-dependent/initiated signaling data.

Incorrectly aligned fly leads inside the ECG machine causing 'ischaemic' changes

We describe a case in which a young woman was inappropriately diagnosed as having ischaemic heart disease after presenting with exertional neck pain and an abnormal ECG. Diffuse Q-wave and T-wave inversion changes were later attributed to erroneous placement of fly leads inside the ECG machine at a recent service. Clinicians should be aware of this uncommon cause of incorrect lead connections, which can result in unnecessary investigations and treatment.

Can old people on oral anticoagulants be safely managed as out-patients?

Of 62 patients (mean age 75, range 65-92 years) referred to an out-patient anticoagulant clinic specifically for those aged 65 years or more, treatment was considered unsafe in only one patient and was discontinued. Minor bleeding which did not require a significant change in management was recorded on 25 (7%) of 381 clinic visits and one major haemorrhage occurred requiring emergency hospital admission. Anticoagulation was maintained within the therapeutic range on 284 (75%) visits. The results confirm that with appropriate out-patient care and supervision, the risks of oral anticoagulant therapy in the elderly need be no greater than in younger patients.

Significance of single serum urate estimations in acutely hospitalized elderly patients

Clinical, pharmacological and biochemical correlates of hyperuricaemia were studied in 399 consecutive patients aged over 70 years admitted to hospital with acute medical illness. Hyperuricaemia was significantly related to renal impairment and to the use of diuretics, but to no other recognized associations of gout, including typical or atypical joint symptoms. 'Routine' measurement of serum uric acid alone or as a component of biochemical profiles in acute illness in the elderly appears unjustified, particularly since raised levels may encourage inappropriate use of urate-lowering therapy.

Eosinophilic colitis as a complication of the hypereosinophilic syndrome

A patient with the hypereosinophilic syndrome complicated by a severe eosinophilic colitis is reported. The association has not previously been recorded.