Andrea Weiss

North Atlantic Oscillation modulates total ozone winter trends

The North Atlantic Oscillation (NAO) is modulating the Earths ozone shield such that the calculated anthropogenic total ozone decrease is enhanced over Europe whereas over the North Atlantic region it is reduced (for the last 30 years). Including the NAO in a statistical model suggests a more uniform chemical winter trend compared to the strong longitudinal variation reported earlier. At Arosa (Switzerland) the trend is reduced to −2.4% per decade compared to −3.2% and at Reykjavik (Iceland) it is enhanced to −3.8% compared to 0%. The revised trend is slightly below the predictions by 2D chemical models. Decadal ozone variability is linked to variations in the dynamical structure of the atmosphere, as reflected in the tropopause pressure. The latter varies in concert with the NAO index with a distinct geographical pattern.

In vivo anti-tumor activity of the organometallic ruthenium(II)-arene complex [Ru(η6-p-cymene)Cl2(pta)] (RAPTA-C) in human ovarian and colorectal carcinomas

Based on the clinical success of platinum-based anti-cancer drugs such as cisplatin, carboplatin and oxaliplatin, a variety of other metal-based anti-cancer compounds are being investigated. In particular, a number of ruthenium-based compounds have been identified which exhibit unique biochemical properties and reduced toxicity profiles compared to the clinically used platinum-based drugs. We have developed a series of organometallic ruthenium(II)-arene complexes that were shown to exert anti-metastatic activity with relatively minor activity on primary tumor growth. Here, we show that the prototype compound, [Ru(η6-p-cymene)Cl2(pta)], where pta = 1,3,5-triaza-7-phosphaadamantane (RAPTA-C), reduces the growth of primary tumors in preclinical models for ovarian and colorectal carcinomas. When administered daily at relatively low doses (0.2 mg kg−1), RAPTA-C was shown to significantly reduce the growth of the A2780 ovarian carcinoma transplanted onto the chicken chorioallantoic membrane model. Similar activity was observed in LS174T colorectal carcinoma in athymic mice, albeit at a higher dose. In both models, a clear inhibition of microvessel density was observed, confirming the previously discovered anti-angiogenic mechanism of RAPTA-C. Biodistribution studies with radiolabeled (103Ru) RAPTA-C indicate that the compound is rapidly cleared from the organs and the bloodstream through excretion by the kidneys. As such, RAPTA-C is a promising compound for translation to clinical evaluation.

Chemical and dynamical contributions to ozone profile trends of the Payerne (Switzerland) balloon soundings

Long-term changes in the vertical ozone distribution over Switzerland are examined for the period 1967–2000. A statistical trend analysis is performed accounting for chemical and dynamical variability. The tropopause pressure, the North Atlantic oscillation (NAO), the Arctic oscillation (AO), and the quasi-biennial oscillation (QBO) are used as dynamical quantities. In addition, the solar effect and an ozone depletion factor (ODF), which describes the joint effect of stratospheric chlorine and aerosol loading, are included. A term is allowed for an unexplained linear trend. The various influences on ozone are estimated employing stepwise regression. Tropopause pressure and lower stratospheric ozone (10–19 km) variability are found to be strongly linked throughout the year. The NAO-AO indices show a negative correlation with lower stratospheric ozone in winter-spring. A positive correlation of NAO-AO and ozone is found in the middle stratosphere (23–30 km) during late summer to early winter. There is a solar signal in the middle stratosphere which becomes strongly significant in summer. The QBO signal is prominent at the height of the ozone maximum in winter-spring. The unexplained trends are much larger than the contributions of the ODF, suggesting that mechanisms other than midlatitude in situ chemistry are mostly responsible for the observed ozone loss. In the lowermost stratosphere (10–15 km), the observed ozone trends are found to be caused by dynamics. Above, the residual ozone trend (in percent) is independent of height and in the range of −2% to −5% per decade up to 30 km.

Angiostatic kinase inhibitors to sustain photodynamic angio-occlusion

Targeted angiostatic therapy receives major attention for the treatment of cancer and exudative age‐related macular degeneration (AMD). Photodynamic therapy (PDT) has been used as an effective clinical approach for these diseases. As PDT can cause an angiogenic response in the treated tissue, combination of PDT with anti‐angiogenic compounds should lead to improved therapy. This study was undertaken to test the clinically used small molecule kinase inhibitors Nexavar® (sorafenib), Tarceva® (erlotinib) and Sutent® (sunitinib) for this purpose, and to compare the results to the combination of Visudyne®‐PDT with Avastin® (bevacizumab) treatment. When topically applied to the chicken chorioallantoic membrane at embryo development day (EDD) 7, a clear inhibition of blood vessel development was observed, with sorafenib being most efficient. To investigate the combination with phototherapy, Visudyne®‐PDT was first applied on EDD11 to close all <100 μm vessels. Application of angiostatics after PDT resulted in a significant decrease in vessel regrowth in terms of reduced vessel density and number of branching points/mm2. As the 50% effective dose (ED50) for all compounds was approximately 10‐fold lower, Sorafenib outperformed the other compounds. In vitro, all kinase inhibitors decreased the viability of human umbilical vein endothelial cells. Sunitinib convincingly inhibited the in vitro migration of endothelial cells. These results suggest the therapeutic potential of these compounds for application in combination with PDT in anti‐cancer approaches, and possibly also in the treatment of other diseases where angiogenesis plays an important role.

Angiogenesis inhibition for the improvement of photodynamic therapy: The revival of a promising idea

Photodynamic therapy (PDT) is a minimally invasive form of treatment, which is clinically approved for the treatment of angiogenic disorders, including certain forms of cancer and neovascular eye diseases. Although the concept of PDT has existed for a long time now, it has never made a solid entrance into the clinical management of cancer. This is likely due to secondary tissue reactions, such as inflammation and neoangiogenesis. The recent development of clinically effective angiogenesis inhibitors has lead to the initiation of research on the combination of PDT with such angiostatic targeted therapies. Preclinical studies in this research field have shown promising results, causing a revival in the field of PDT. This review reports on the current research efforts on PDT and vascular targeted combination therapies. Different combination strategies with angiogenesis inhibition and vascular targeting approaches are discussed. In addition, the concept of increasing PDT selectivity by targeted delivery of photosensitizers is presented. Furthermore, the current insights on sequencing the therapy arms of such combinations will be discussed in light of vascular normalization induced by angiogenesis inhibition.

Angiostatic treatment prior to chemo- or photodynamic therapy improves anti-tumor efficacy

Tumor vasculature is known to be poorly organized leading to increased leakage of molecules to the extravascular space. This process can potentially increase interstitial fluid pressure impairing intra-tumoral blood flow and oxygen supply, and can affect drug uptake. Anti-angiogenic therapies are believed to reduce vascular permeability, potentially reducing interstitial fluid pressure and improving the extravasation of small molecule-based chemotherapeutics. Here we show that pretreatment of human ovarian carcinoma tumors with sub-optimal doses of the VEGFR targeting tyrosine kinase inhibitor axitinib, but not the EGFR targeting kinase inhibitor erlotinib, induces a transient period of increased tumor oxygenation. Doxorubicin administered within this window was found to enter the extravascular tumor space more rapidly compared to doxorubicin when applied alone or outside this time window. Treatment with the chemotherapeutics, doxorubicin and RAPTA-C, as well as applying photodynamic therapy during this period of elevated oxygenation led to enhanced tumor growth inhibition. Improvement of therapy was not observed when applied outside the window of increased oxygenation. Taken together, these findings further confirm the hypothesis of angiostasis-induced vascular normalization and also help to understand the interactions between anti-angiogenesis and other anti-cancer strategies.

Low-dose angiostatic tyrosine kinase inhibitors improve photodynamic therapy for cancer: lack of vascular normalization

Photodynamic therapy (PDT) is an effective clinical treatment for a number of different cancers. PDT can induce hypoxia and inflammation, pro‐angiogenic side effects, which may counteract its angio‐occlusive mechanism. The combination of PDT with anti‐angiogenic drugs offers a possibility for improved anti‐tumour outcome. We used two tumour models to test the effects of the clinically approved angiostatic tyrosine kinase inhibitors sunitinib, sorafenib and axitinib in combination with PDT, and compared these results with the effects of bevacizumab, the anti‐VEGF antibody, for the improvement of PDT. Best results were obtained from the combination of PDT and low‐dose axitinib or sorafenib. Molecular analysis by PCR revealed that PDT in combination with axitinib suppressed VEGFR‐2 expression in tumour vasculature. Treatment with bevacizumab, although effective as monotherapy, did not improve PDT outcome. In order to test for tumour vessel normalization effects, axitinib was also applied prior to PDT. The absence of improved PDT outcome in these experiments, as well as the lack of increased oxygenation in axitinib‐treated tumours, suggests that vascular normalization did not occur. The current data imply that there is a future for certain anti‐angiogenic agents to further improve the efficacy of photodynamic anti‐cancer therapy.

Optimization of drug combinations using Feedback System Control

We describe a protocol for the discovery of synergistic drug combinations for the treatment of disease. Synergistic drug combinations lead to the use of drugs at lower doses, which reduces side effects and can potentially lead to reduced drug resistance, while being clinically more effective than the individual drugs. To cope with the extremely large search space for these combinations, we developed an efficient combinatorial drug screening method called the Feedback System Control (FSC) technique. Starting with a broad selection of drugs, the method follows an iterative approach of experimental testing in a relevant bioassay and analysis of the results by FSC. First, the protocol uses a cell viability assay to generate broad dose-response curves to assess the efficacy of individual compounds. These curves are then used to guide the dosage input of each drug to be tested in combination. Data from applied drug combinations are input into the differential evolution (DE) algorithm, which predicts new combinations to be tested in vitro. This process identifies optimal drug-dose combinations, while saving orders of magnitude in experimental effort. The complete optimization process is estimated to take ∼4 weeks. FSC does not require insight into the disease mechanism, and it has therefore been applied to find combination therapies for many different pathologies, including cancer and infectious diseases, and it has also been used in organ transplantation.

A streamlined search technology for identification of synergistic drug combinations

A major key to improvement of cancer therapy is the combination of drugs. Mixing drugs that already exist on the market may offer an attractive alternative. Here we report on a new model-based streamlined feedback system control (s-FSC) method, based on a design of experiment approach, for rapidly finding optimal drug mixtures with minimal experimental effort. We tested combinations in an in vitro assay for the viability of a renal cell adenocarcinoma (RCC) cell line, 786-O. An iterative cycle of in vitro testing and s-FSC analysis was repeated a few times until an optimal low dose combination was reached. Starting with ten drugs that target parallel pathways known to play a role in the development and progression of RCC, we identified the best overall drug combination, being a mixture of four drugs (axitinib, erlotinib, dasatinib and AZD4547) at low doses, inhibiting 90% of cell viability. The removal of AZD4547 from the optimized drug combination resulted in 80% of cell viability inhibition, while still maintaining the synergistic interaction. These optimized drug combinations were significantly more potent than monotherapies of all individual drugs (p < 0.001, CI < 0.3).

Combination of ruthenium(II)-arene complex [Ru(η 6 - p -cymene)Cl 2 (pta)] (RAPTA-C) and the epidermal growth factor receptor inhibitor erlotinib results in efficient angiostatic and antitumor activity

Ruthenium-based compounds show strong potential as anti-cancer drugs and are being investigated as alternatives to other well-established metal-based chemotherapeutics. The organometallic compound [Ru(η6-p-cymene)Cl2(pta)], where pta = 1,3,5-triaza-7-phosphaadamantane (RAPTA-C) exhibits broad acting anti-tumor efficacy with intrinsic angiostatic activity. In the search for an optimal anti-angiogenesis drug combination, we identified synergistic potential between RAPTA-C and the epidermal growth factor receptor (EGFR) inhibitor, erlotinib. This drug combination results in strong synergistic inhibition of cell viability in human endothelial (ECRF24 and HUVEC) and human ovarian carcinoma (A2780 and A2780cisR) cells. Additionally, erlotinib significantly enhances the cellular uptake of RAPTA-C relative to treatment with RAPTA-C alone in human ovarian carcinoma cells, but not endothelial cells. Drug combinations induce the formation of chromosome bridges that persist after mitotic exit and delay abscission in A2780 and A2780cisR, therefore suggesting initiation of cellular senescence. The therapeutic potential of these compounds and their combination is further validated in vivo on A2780 tumors grown on the chicken chorioallantoic membrane (CAM) model, and in a preclinical model in nude mice. Immunohistochemical analysis confirms effective anti-angiogenic and anti-proliferative activity in vivo, based on a significant reduction of microvascular density and a decrease in proliferating cells.