The landscape of the mesenchymal signature in brain tumours.

The complexity of glioblastoma multiforme, the most common and lethal variant of gliomas, is reflected by cellular and molecular heterogeneity at both the inter- and intra-tumoural levels. Molecular subtyping has arisen in the past two decades as a promising strategy to give better predictions of glioblastoma multiforme evolution, common disease pathways, and rational treatment options. The Cancer Genome Atlas network initially identified four molecular subtypes of glioblastoma multiforme: proneural, neural, mesenchymal and classical. However, further studies, also investigated glioma stem cells, have only identified two to three subtypes: proneural, mesenchymal and classical. The proneural-mesenchymal transition upon tumour recurrence has been suggested as a mechanism of tumour resistance to radiation and chemotherapy treatment. Glioblastoma multiforme patients with the mesenchymal subtype tend to survive shorter than other subtypes when analysis is restricted to samples with low transcriptional heterogeneity. Although the mesenchymal signature in malignant glioma may seem at odds with the common idea of the ectodermal origin of neural-glial lineages, the presence of the mesenchymal signature in glioma is supported by several studies suggesting that it can result from: (i) intrinsic expression of tumour cells affected with accumulated genetic mutations and cell of origin; (ii) tumour micro-environments with recruited macrophages or microglia, mesenchymal stem cells or pericytes, and other progenitors; (iii) resistance to tumour treatment, including radiotherapy, antiangiogenic therapy and possibly chemotherapy. Genetic abnormalities, mainly NF1 mutations, together with NF-κB transcriptional programs, are the main driver of acquiring mesenchymal-signature. This signature is far from being simply tissue artefacts, as it has been identified in single cell glioma, circulating tumour cells, and glioma stem cells that are released from the tumour micro-environment. All these together suggest that the mesenchymal signature in glioblastoma multiforme is induced and sustained via cell intrinsic mechanisms and tumour micro-environment factors. Although patients with the mesenchymal subtype tend to have poorer prognosis, they may have favourable response to immunotherapy and intensive radio- and chemotherapy.

An Engineered Optogenetic Switch for Spatiotemporal Control of Gene Expression, Cell Differentiation, and Tissue Morphogenesis.

The precise spatial and temporal control of gene expression, cell differentiation, and tissue morphogenesis has widespread application in regenerative medicine and the study of tissue development. In this work, we applied optogenetics to control cell differentiation and new tissue formation. Specifically, we engineered an optogenetic "on" switch that provides permanent transgene expression following a transient dose of blue light illumination. To demonstrate its utility in controlling cell differentiation and reprogramming, we incorporated an engineered form of the master myogenic factor MyoD into this system in multipotent cells. Illumination of cells with blue light activated myogenic differentiation, including upregulation of myogenic markers and fusion into multinucleated myotubes. Cell differentiation was spatially patterned by illumination of cell cultures through a photomask. To demonstrate the application of the system to controlling in vivo tissue development, the light inducible switch was used to control the expression of VEGF and angiopoietin-1, which induced angiogenic sprouting in a mouse dorsal window chamber model. Live intravital microscopy showed illumination-dependent increases in blood-perfused microvasculature. This optogenetic switch is broadly useful for applications in which sustained and patterned gene expression is desired following transient induction, including tissue engineering, gene therapy, synthetic biology, and fundamental studies of morphogenesis.

Luminescent difluoroboron ß-diketonate PEG-PLA oxygen nanosensors for tumor imaging.

Surface modification of nanoparticles and biosensors is a dynamic, expanding area of research for targeted delivery in vivo. For more efficient delivery, surfaces are PEGylated to impart stealth properties, long circulation, and enable enhanced permeability and retention (EPR) in tumor tissues. Previously, BF2 dbm(I)PLA was proven to be a good oxygen nanosensor material for tumor hypoxia imaging in vivo, though particles were applied directly to the tumor and surrounding region. Further surface modification is needed for this dual-emissive oxygen sensitive material for effective intravenous (IV) administration and passive and active delivery to tumors. In this paper, an efficient synthesis of a new dual-emissive material BF2 dbm(I)PLA-mPEG is presented and in vitro stability studies are conducted. It is found that fabricated nanoparticles are stable for 24 weeks as a suspension, while after 25 weeks the nanoparticles swell and both dye and polymer degradation escalates. Preliminary studies show BF2 dbm(I)PLA-mPEG nanoparticle accumulation in a window chamber mammary tumor 24 h after IV injection into mice (C57Bl/6 strain) enabling tumor oxygen imaging.

Automated measurement of microcirculatory blood flow velocity in pulmonary metastases of rats.

Because the lung is a major target organ of metastatic disease, animal models to study the physiology of pulmonary metastases are of great importance. However, very few methods exist to date to investigate lung metastases in a dynamic fashion at the microcirculatory level, due to the difficulty to access the lung with a microscope. Here, an intravital microscopy method is presented to functionally image and quantify the microcirculation of superficial pulmonary metastases in rats, using a closed-chest pulmonary window and automated analysis of blood flow velocity and direction. The utility of this method is demonstrated to measure increases in blood flow velocity in response to pharmacological intervention, and to image the well-known tortuous vasculature of solid tumors. This is the first demonstration of intravital microscopy on pulmonary metastases in a closed-chest model. Because of its minimized invasiveness, as well as due to its relative ease and practicality, this technology has the potential to experience widespread use in laboratories that specialize on pulmonary tumor research.

Restoration of intracellular ATP production in banked red blood cells improves inducible ATP export and suppresses RBC-endothelial adhesion.

Transfusion of banked red blood cells (RBCs) has been associated with poor cardiovascular outcomes. Storage-induced alterations in RBC glycolytic flux, attenuated ATP export, and microvascular adhesion of transfused RBCs in vivo could contribute, but the underlying mechanisms have not been tested. We tested the novel hypothesis that improving deoxygenation-induced metabolic flux and the associated intracellular ATP generation in stored RBCs (sRBCs) results in an increased extracellular ATP export and suppresses microvascular adhesion of RBCs to endothelium in vivo following transfusion. We show deficient intracellular ATP production and ATP export by human sRBCs during deoxygenation (impairments ~42% and 49%, respectively). sRBC pretreatment with a solution containing glycolytic intermediate/purine/phosphate precursors (i.e., "PIPA") restored deoxygenation-induced intracellular ATP production and promoted extracellular ATP export (improvement ~120% and 50%, respectively). In a nude mouse model of transfusion, adhesion of human RBCs to the microvasculature in vivo was examined. Only 2% of fresh RBCs (fRBCs) transfused adhered to the vascular wall, compared with 16% of sRBCs transfused. PIPA pretreatment of sRBCs significantly reduced adhesion to just 5%. In hypoxia, adhesion of sRBCs transfused was significantly augmented (up to 21%), but not following transfusion of fRBCs or PIPA-treated sRBCs (3.5% or 6%). Enhancing the capacity for deoxygenation-induced glycolytic flux within sRBCs increases their ability to generate intracellular ATP, improves the inducible export of extracellular anti-adhesive ATP, and consequently suppresses adhesion of stored, transfused RBCs to the vascular wall in vivo.

Cellular migration and invasion uncoupled: increased migration is not an inexorable consequence of epithelial-to-mesenchymal transition.

Metastatic dissemination requires carcinoma cells to detach from the primary tumor and invade through the basement membrane. To acquire these characteristics, epithelial tumor cells undergo epithelial-to-mesenchymal transitions (EMT), whereby cells lose polarity and E-cadherin-mediated cell-cell adhesion. Post-EMT cells have also been shown, or assumed, to be more migratory; however, there have been contradictory reports on an immortalized human mammary epithelial cell line (HMLE) that underwent EMT. In the context of carcinoma-associated EMT, it is not yet clear whether the change in migration and invasion must be positively correlated during EMT or whether enhanced migration is a necessary consequence of having undergone EMT. Here, we report that pre-EMT rat prostate cancer (PC) and HMLE cells are more migratory than their post-EMT counterparts. To determine a mechanism for increased epithelial cell migration, gene expression analysis was performed and revealed an increase in epidermal growth factor receptor (EGFR) expression in pre-EMT cells. Indeed, inhibition of EGFR in PC epithelial cells slowed migration. Importantly, while post-EMT PC and HMLE cell lines are less migratory, both remain invasive in vitro and, for PC cells, in vivo. Our study demonstrates that enhanced migration is not a phenotypic requirement of EMT, and migration and invasion can be uncoupled during carcinoma-associated EMT.

Plasmonics-enhanced and optically modulated delivery of gold nanostars into brain tumor.

Plasmonics-active gold nanostars exhibiting strong imaging contrast and efficient photothermal transduction were synthesized for a novel pulsed laser-modulated plasmonics-enhanced brain tumor microvascular permeabilization. We demonstrate a selective, optically modulated delivery of nanoprobes into the tumor parenchyma with minimal off-target distribution.

Tumor cells upregulate normoxic HIF-1α in response to doxorubicin.

Hypoxia-inducible factor 1 (HIF-1) is a master transcription factor that controls cellular homeostasis. Although its activation benefits normal tissue, HIF-1 activation in tumors is a major risk factor for angiogenesis, therapeutic resistance, and poor prognosis. HIF-1 activity is usually suppressed under normoxic conditions because of rapid oxygen-dependent degradation of HIF-1α. Here, we show that, under normoxic conditions, HIF-1α is upregulated in tumor cells in response to doxorubicin, a chemotherapeutic agent used to treat many cancers. In addition, doxorubicin enhanced VEGF secretion by normoxic tumor cells and stimulated tumor angiogenesis. Doxorubicin-induced accumulation of HIF-1α in normoxic cells was caused by increased expression and activation of STAT1, the activation of which stimulated expression of iNOS and its synthesis of nitric oxide (NO) in tumor cells. Mechanistic investigations established that blocking NO synthesis or STAT1 activation was sufficient to attenuate the HIF-1α accumulation induced by doxorubicin in normoxic cancer cells. To our knowledge, this is the first report that a chemotherapeutic drug can induce HIF-1α accumulation in normoxic cells, an efficacy-limiting activity. Our results argue that HIF-1α-targeting strategies may enhance doxorubicin efficacy. More generally, they suggest a broader perspective on the design of combination chemotherapy approaches with immediate clinical impact.

Quantitative mapping of hemodynamics in the lung, brain, and dorsal window chamber-grown tumors using a novel, automated algorithm.

OBJECTIVE: Hemodynamic properties of vascular beds are of great interest in a variety of clinical and laboratory settings. However, there presently exists no automated, accurate, technically simple method for generating blood velocity maps of complex microvessel networks. METHODS: Here, we present a novel algorithm that addresses the problem of acquiring quantitative maps by applying pixel-by-pixel cross-correlation to video data. Temporal signals at every spatial coordinate are compared with signals at neighboring points, generating a series of correlation maps from which speed and direction are calculated. User-assisted definition of vessel geometries is not required, and sequential data are analyzed automatically, without user bias. RESULTS: Velocity measurements were validated against the dual-slit method and against in vitro capillary flow with known velocities. The algorithm was tested in three different biological models in order to demonstrate its versatility. CONCLUSIONS: The hemodynamic maps presented here demonstrate an accurate, quantitative method of analyzing dynamic vascular systems.

Overcoming limitations in nanoparticle drug delivery: triggered, intravascular release to improve drug penetration into tumors.

Traditionally, the goal of nanoparticle-based chemotherapy has been to decrease normal tissue toxicity by improving drug specificity to tumors. The enhanced permeability and retention effect can permit passive accumulation into tumor interstitium. However, suboptimal delivery is achieved with most nanoparticles because of heterogeneities of vascular permeability, which limits nanoparticle penetration. Furthermore, slow drug release limits bioavailability. We developed a fast drug-releasing liposome triggered by local heat that has already shown substantial antitumor efficacy and is in human trials. Here, we show that thermally sensitive liposomes (Dox-TSL) release doxorubicin inside the tumor vasculature. Real-time confocal imaging of doxorubicin delivery to murine tumors in window chambers and histologic analysis of flank tumors illustrates that intravascular drug release increases free drug in the interstitial space. This increases both the time that tumor cells are exposed to maximum drug levels and the drug penetration distance, compared with free drug or traditional pegylated liposomes. These improvements in drug bioavailability establish a new paradigm in drug delivery: rapidly triggered drug release in the tumor bloodstream.

The combination of theophylline and endothelin receptor antagonism improves exercise performance of rats under simulated high altitude.

Decreased physical performance is a well-known consequence of rapid ascent to high altitude. Hypoxic pulmonary vasoconstriction (HPV) potentially limits cardiac output and systemic blood flow, thus preventing successful adaptation to rapid ascent. We hypothesized that pharmacological enhancement of the heart rate with theophylline, combined with reversal of HPV via endothelin blockade, could increase exercise performance at high altitude. Female Sprague-Dawley rats were treated with combinations of 1) theophylline, 2) the endothelin receptor antagonists sitaxsentan/ambrisentan, and/or 3) phosphodiesterase-5 inhibitor sildenafil and exposed to either a simulated high altitude (4,267 m) or 12% oxygen. Exercise capacity, peripheral blood flow, hemodynamics, and pulmonary leak were examined. Combination treatment with theophylline and endothelin blockade, but not with the respective single compounds, significantly prolonged run-to-fatigue time under simulated high altitude. No such efficacy was found when theophylline was combined with sildenafil. Neither theophylline nor sitaxsentan or their combination influenced breathing rates and hemoglobin oxygen saturation. Whereas under hypoxia, theophylline significantly increased muscular blood flow, and sitaxsentan increased tissue oxygenation, the combination improved both parameters but in a reduced manner. Under hypoxia, the combination treatment but not the single compounds significantly enhanced pulmonary arterial pressure compared with controls (13.1 ± 6.3 vs. 11.9 ± 5.2 mmHg), whereas mean arterial pressure remained unaffected. Pulmonary wet-to-dry weight ratios were unaffected by combination treatment. We conclude that concomitant dosing with a cardiac stimulant and endothelin antagonist can partially reverse loss of physical performance capacity under hypobaric hypoxia, independent from improving blood oxygen saturation.

Bevacizumab-induced alterations in vascular permeability and drug delivery: a novel approach to augment regional chemotherapy for in-transit melanoma.

PURPOSE: To investigate whether the systemically administered anti-VEGF monoclonal antibody bevacizumab could improve regional chemotherapy treatment of advanced extremity melanoma by enhancing delivery and tumor uptake of regionally infused melphalan (LPAM). EXPERIMENTAL DESIGN: After treatment with systemic bevacizumab or saline, changes in vascular permeability were determined by spectrophotometric analysis of tumors infused with Evan's blue dye. Changes in vascular structure and tumor hemoglobin-oxygen saturation HbO(2) were determined by intravital microscopy and diffuse reflectance spectroscopy, respectively. Rats bearing the low-VEGF secreting DM738 and the high-VEGF secreting DM443 melanoma xenografts underwent isolated limb infusion (ILI) with melphalan (LPAM) or saline via the femoral vessels. The effect of bevacizumab on terminal drug delivery was determined by immunohistochemical analysis of LPAM-DNA adducts in tumor tissues. RESULTS: Single-dose bevacizumab given three days before ILI with LPAM significantly decreased vascular permeability (50.3% in DM443, P < 0.01 and 35% in DM738, P < 0.01) and interstitial fluid pressure (57% in DM443, P < 0.01 and 50% in DM738, P = 0.01). HbO(2) decreased from baseline in mice following treatment with bevacizumab. Systemic bevacizumab significantly enhanced tumor response to ILI with LPAM in two melanoma xenografts, DM443 and DM738, increasing quadrupling time 37% and 113%, respectively (P = 0.03). Immunohistochemical analyses of tumor specimens showed that pretreatment with systemic bevacizumab markedly increased LPAM-DNA adduct formation. CONCLUSIONS: Systemic treatment with bevacizumab before regional chemotherapy increases delivery of LPAM to tumor cells and represents a novel way to augment response to regional therapy for advanced extremity melanoma.

In vivo optical molecular imaging and analysis in mice using dorsal window chamber models applied to hypoxia, vasculature and fluorescent reporters.

Optical techniques for functional imaging in mice have a number of key advantages over other common imaging modalities such as magnetic resonance imaging, positron emission tomography or computed tomography, including high resolution, low cost and an extensive library of available contrast agents and reporter genes. A major challenge to such work is the limited penetration depth imposed by tissue turbidity. We describe a window chamber technique by which these limitations can be avoided. This facilitates the study of a wide range of processes, with potential endpoints including longitudinal gene expression, vascular remodeling and angiogenesis, and tumor growth and invasion. We further describe several quantitative imaging and analysis techniques for characterizing in vivo fluorescence properties and functional endpoints, including vascular morphology and oxygenation. The procedure takes ∼2 h to complete, plus up to several weeks for tumor growth and treatment procedures.

In vivo tumor targeting by a NGR-decorated micelle of a recombinant diblock copolypeptide.

Antivascular targeting is a promising strategy for tumor therapy. This strategy has the potential to overcome many of the transport barriers associated with targeting tumor cells in solid tumors, because the tumor vasculature is directly accessible to targeting vehicles in systemic circulation. We report a novel nanoscale delivery system consisting of multivalent polymer micelles to target receptors that are preferentially upregulated in the tumor vasculature and perivascular cells, specifically CD13. To this end we utilized amphiphilic block copolymers, composed of a genetically engineered elastin-like polypeptide (ELP) that self-assemble into monodisperse spherical micelles. These polymer micelles were functionalized by incorporating the NGR tripeptide ligand, which targets the CD13 receptor, on their corona. We examined the self-assembly and in vivo tumor targeting by these NGR-functionalized nanoparticles and show that multivalent presentation of NGR by micelle self-assembly selectively targets the tumor vasculature by targeting CD13. Furthermore, we show greater vascular retention and extravascular accumulation of nanoparticles in tumor tissue compared to normal tissue, although the enhancement is modest. These results suggest that enhanced delivery to solid tumors can be achieved by targeting upregulated receptors in the tumor vasculature with multivalent ligand-presenting nanoparticles, but additional work is required to optimize such systems for multivalent targeting.

Effect of pazopanib on tumor microenvironment and liposome delivery.

Pathologic angiogenesis creates an abnormal microenvironment in solid tumors, characterized by elevated interstitial fluid pressure (IFP) and hypoxia. Emerging theories suggest that judicious downregulation of proangiogenic signaling pathways may transiently "normalize" the vascular bed, making it more suitable for drug delivery and radiotherapy. In this work, we investigate the role of pazopanib, a small-molecule inhibitor of vascular endothelial growth factor (VEGF) and platelet-derived growth factor (PDGF) receptors, on tumor IFP, angiogenesis, hypoxia, and liposomal drug delivery. Nude mice bearing A549 human non-small cell lung cancer xenografts were treated with 100 mg/kg pazopanib (n = 20) or vehicle (n = 20) through oral gavage for 8 days, followed by a one-time intravenous dose of 10 mg/kg Doxil (liposomal doxorubicin). Pazopanib treatment resulted in significant reduction of tumor IFP and decreased vessel density, assessed by CD31 staining. Despite these trends toward normalization, high-performance liquid chromatography revealed no differences in doxorubicin concentration between pazopanib-treated and control tumors, with Doxil penetration from microvessels being significantly reduced in the pazopanib group. Additionally, tumor hypoxia, evaluated by CA-IX immunostaining and confirmed in a second study by EF5 expression (n = 4, 100 mg/kg pazopanib; n = 4, vehicle), was increased in pazopanib-treated tumors. Our results suggest that the classic definition of tumor "normalization" may undermine the crucial role of vessel permeability and oncotic pressure gradients in liposomal drug delivery, and that functional measures of normalization, such as reduced IFP and hypoxia, may not occur in parallel temporal windows.

Optical imaging of tumor hypoxia dynamics.

The influence of the tumor microenvironment and hypoxia plays a significant role in determining cancer progression, treatment response, and treatment resistance. That the tumor microenvironment is highly heterogeneous with significant intratumor and intertumor variability presents a significant challenge in developing effective cancer therapies. Critical to understanding the role of the tumor microenvironment is the ability to dynamically quantify oxygen levels in the vasculature and tissue in order to elucidate the roles of oxygen supply and consumption, spatially and temporally. To this end, we describe the use of hyperspectral imaging to characterize hemoglobin absorption to quantify hemoglobin content and oxygen saturation, as well as dual emissive fluorescent∕phosphorescent boron nanoparticles, which serve as ratiometric indicators of tissue oxygen tension. Applying these techniques to a window-chamber tumor model illustrates the role of fluctuations in hemoglobin saturation in driving changes in tissue oxygenation, the two being significantly correlated (r = 0.77). Finally, a green-fluorescence-protein reporter for hypoxia inducible factor-1 (HIF-1) provides an endpoint for hypoxic stress in the tumor, which is used to demonstrate a significant association between tumor hypoxia dynamics and HIF-1 activity in an in vivo demonstration of the technique.

Immunoproteasome down-modulation enhances the ability of dendritic cells to stimulate antitumor immunity.

The process of dendritic cell (DC) maturation, critical for effective DC-based immunotherapy, also alters the proteasome such that peptides presented in the context of HLA class I are generated not by the constitutive proteasome, but by the immunoproteasome. Cytotoxic T lymphocytes (CTLs) induced by such DCs might not optimally recognize tumor cells normally expressing the constitutive proteasome. Using small interfering RNA (siRNA) transfection of DCs to inhibit expression of the 3 inducible immunoproteasome subunits in mature DCs, we found that such DCs expressed increased intracellular levels of constitutive proteasomes and presented an altered repertoire of tumor-antigenic peptides. When DCs generated from the monocytes of 3 patients with melanoma were transfected with immunoproteasome siRNA, induced to mature, and then trans-fected with RNA encoding defined melanoma antigens, these DCs were superior inducers of antigen-specific CTLs against autologous melanoma cells. This alteration of DC proteasome composition, which enhances the ability of mature antigen-loaded DCs to stimulate anti-tumor immune responses, may lead to more effective DC-based tumor immunotherapy.