The phosphoinositide 3-kinase signaling pathway as a therapeutic target in grade IV brain tumors

Brain tumors comprise a wide variety of neoplasia classified according to their cellular origin and their morphological and histological characteristics. The transformed phenotype of brain tumor cells has been extensively studied in the past years, achieving a significant progress in our understanding of the molecular pathways leading to tumorigenesis. It has been reported that the phosphoinositide 3-kinase (PI3K)/AKT signaling pathway is frequently altered in grade IV brain tumors resulting in uncontrolled cell growth, survival, proliferation, angiogenesis, and migration. This aberrant activation can be explained by oncogenic mutations in key components of the pathway or through abnormalities in its regulation. These alterations include overexpression and mutations of receptor tyrosine kinases (RTKs), mutations and deletions of the phosphatase and tensin homologue deleted on chromosome 10 (PTEN) tumor suppressor gene, encoding a lipid kinase that directly antagonized PI3K activity, and alterations in Ras signaling. Due to promising results of preclinical studies investigating the PI3K/AKT pathway in grade IV brain tumors like glioblastoma and medulloblastoma, the components of this pathway have emerged as promising therapeutic targets to treat these malignant brain tumors. Although an arsenal of small molecule inhibitors that target specific components of this signaling pathway is being developed, its successful application in the clinics remains a challenge. In this article we will review the molecular basis of the PI3K/AKT signaling pathway in malignant brain tumors, mainly focusing on glioblastoma and medulloblastoma, and we will further discuss the current status and potential of molecular targeted therapies.

[Laboratory diagnostic with regard to new anticoagulants - monitoring and influence on coagulation tests]

New oral anticoagulants promise to overcome essential drawbacks of traditional substances. They have a predictable therapeutic effect, a wide therapeutic window, only limited interaction with food and drugs and can be administered p.o. with a fixed dose. On the other hand, knowledge on the laboratory management of new anticoagulants is limited. In the present article we discuss possible indications and available assays for monitoring of Rivaroxaban, Apixaban and Dabigatran. Furthermore, we discuss interpretation of routine coagulation tests during therapy with these new drugs.

Therapeutic approaches to patients with hypereosinophilic syndromes

Hypereosinophilic syndromes (HES) are a heterogeneous group of disorders that range from asymptomatic eosinophilia > 1,500/mL to aggressive disease complicated by life-threatening end organ involvement, including endomyocardial fibrosis and thromboembolism. To complicate matters further, similar clinical manifestations can occur in the setting of marked eosinophilia due to helminth infection, drug hypersensitivity, and other causes. In the past, therapy was guided only by the exclusion of these secondary causes of eosinophilia and the severity of the clinical manifestations. More recently, the availability of novel targeted therapies and a better understanding of the etiologies of some subtypes of HES have necessitated a more structured approach.

The well-being model: a new drug interaction model for positive and negative effects

BACKGROUND: Drugs are routinely combined in anesthesia and pain management to obtain an enhancement of the desired effects. However, a parallel enhancement of the undesired effects might take place as well, resulting in a limited therapeutic usefulness. Therefore, when addressing the question of optimal drug combinations, side effects must be taken into account. METHODS: By extension of a previously published interaction model, the authors propose a method to study drug interactions considering also their side effects. A general outcome parameter identified as patient's well-being is defined by superposition of positive and negative effects. Well-being response surfaces are computed and analyzed for varying drugs pharmacodynamics and interaction types. In particular, the existence of multiple maxima and of optimal drug combinations is investigated for the combination of two drugs. RESULTS: Both drug pharmacodynamics and interaction type affect the well-being surface and the deriving optimal combinations. The effect of the interaction parameters can be explained in terms of synergy and antagonism and remains unchanged for varying pharmacodynamics. For all simulations performed for the combination of two drugs, the presence of more than one maximum was never observed. CONCLUSIONS: The model is consistent with clinical knowledge and supports previously published experimental results on optimal drug combinations. This new framework improves understanding of the characteristics of drug combinations used in clinical practice and can be used in clinical research to identify optimal drug dosing.

Antitumor activity of an epithelial cell adhesion molecule targeted nanovesicular drug delivery system

Site-specific delivery of anticancer agents to tumors represents a promising therapeutic strategy because it increases efficacy and reduces toxicity to normal tissues compared with untargeted drugs. Sterically stabilized immunoliposomes (SIL), guided by antibodies that specifically bind to well internalizing antigens on the tumor cell surface, are effective nanoscale delivery systems capable of accumulating large quantities of anticancer agents at the tumor site. The epithelial cell adhesion molecule (EpCAM) holds major promise as a target for antibody-based cancer therapy due to its abundant expression in many solid tumors and its limited distribution in normal tissues. We generated EpCAM-directed immunoliposomes by covalently coupling the humanized single-chain Fv antibody fragment 4D5MOCB to the surface of sterically stabilized liposomes loaded with the anticancer agent doxorubicin. In vitro, the doxorubicin-loaded immunoliposomes (SIL-Dox) showed efficient cell binding and internalization and were significantly more cytotoxic against EpCAM-positive tumor cells than nontargeted liposomes (SL-Dox). In athymic mice bearing established human tumor xenografts, pharmacokinetic and biodistribution analysis of SIL-Dox revealed long circulation times in the blood with a half-life of 11 h and effective time-dependent tumor localization, resulting in up to 15% injected dose per gram tissue. These favorable pharmacokinetic properties translated into potent antitumor activity, which resulted in significant growth inhibition (compared with control mice), and was more pronounced than that of doxorubicin alone and nontargeted SL-Dox at low, nontoxic doses. Our data show the promise of EpCAM-directed nanovesicular drug delivery for targeted therapy of solid tumors.

Therapeutic targeting of leukocyte trafficking across the blood-brain barrier

The central nervous system (CNS) has long been regarded as an immune privileged organ implying that the immune system avoids the CNS not to disturb its homeostasis, which is critical for proper function of neurons. Meanwhile, it is accepted that immune cells do in fact gain access to the CNS and that immune responses are mounted within this tissue. However, the unique CNS microenvironment strictly controls these immune reactions starting with tightly regulating immune cell entry into the tissue. The endothelial blood-brain barrier (BBB) and the epithelial blood-cerebrospinal fluid (CSF) barrier control immune cell entry into the CNS, which is rare under physiological conditions. During a variety of pathological conditions of the CNS such as viral or bacterial infections, or during inflammatory diseases such as multiple sclerosis (MS), immunocompetent cells readily traverse the BBB and subsequently enter the CNS parenchyma. Most of our current knowledge on the molecular mechanisms involved in immune cell entry into the CNS has been derived from studies performed in experimental autoimmune encephalomyelitis (EAE), an animal model for MS. Thus, a large part of our current knowledge on immune cell entry across the BBBs is based on the results obtained in this animal model. Similarly, knowledge on the benefits and potential risks associated with therapeutic targeting of immune cell recruitment across the BBB in human diseases are mostly derived from such treatment regimen in MS. Other mechanisms of immune cell entry into the CNS might therefore apply under different pathological conditions such as bacterial meningitis or stroke and need to be considered.

Multimodal imaging in macular diagnostics: combined OCT-SLO improves therapeutical monitoring

BACKGROUND: Digital imaging methods are a centrepiece for diagnosis and management of macular disease. A recently developed imaging device is composed of simultaneous confocal scanning laser ophthalmoscopy (SLO) and optical coherence tomography (OCT). By means of clinical samples the benefit of this technique concerning diagnostic and therapeutic follow-up will be assessed. METHODS: The combined OCT-SLO-System (Ophthalmic Technologies Inc., Toronto, Canada) allows for confocal en-face fundus imaging and high resolution OCT scanning at the same time. OCT images are obtained from transversal line scans. One light source and the identical scanning rate yield a pixel-to-pixel correspondence of images. Three-dimensional thickness maps are derived from C-scan stacking. RESULTS: We followed-up patients with cystoid macular edema, pigment epithelium detachment, macular hole, venous branch occlusion, and vitreoretinal tractions during their course of therapy. The new imaging method illustrates the reduction of cystoid volume, e.g. after intravitreal injections of either angiostatic drugs or steroids. C-scans are used for appreciation of lesion diameters, visualisation of pathologies involving the vitreoretinal interface, and quantification of retinal thickness change. CONCLUSION: The combined OCT-SLO system creates both topographic and tomographic images of the retina. New therapeutic options can be followed-up closely by observing changes in lesion thickness and cyst volumes. For clinical use further studies are needed.

[Drug therapy of type-II diabetes: tablets, insulin or a combination of these]

Optimal therapy of diabetes has to be based on the known pathophysiology of metabolic disturbances and should eventually alleviate reduced secretion of insulin as well as reduce the usually present resistance to insulin in order to normalize the average blood glucose levels. In less than 30% of patients with type-II diabetes, dietetic measures combined with increased physical activity alone, are sufficient for metabolic control, thus increasing the importance of pharmacologic treatment immensely. Biguanides are the therapeutic choice in patients with massive overweight, because they usually do not induce weight gain; however, specific contraindications (renal failure in particular) have to be taken into consideration. The effect of blood glucose lowering by biguanides is not due to increased secretion of insulin, thus neither hypoglycemias nor hyperinsulinism are induced or increased, respectively. Patients with normal or slightly increased body weight should profit best from sulfonylureas that stimulate insulin production. Combinations of sulfonylurea and biguanides or of insulin and oral antidiabetics or insulin alone have to be taken into account when monotherapy with oral antidiabetics is too inefficient; however, clear and generally accepted guidelines for correct indications of these therapeutic modalities are lacking. Particularly in long-lasting diabetes and for patients with distinct overweight an adequate therapeutic success is often not obtained with the currently available therapeutic means. Possibly, future developments will provide new therapeutic ways with drugs that increase insulin sensitivity or reduce gluconeogenesis.

Chemotherapeutic strategies against Trypanosoma brucei: drug targets vs. drug targeting

Trypanosoma brucei rhodesiense and T. b. gambiense are the causative agents of sleeping sickness, a fatal disease that affects 36 countries in sub-Saharan Africa. Nevertheless, only a handful of clinically useful drugs are available. These drugs suffer from severe side-effects. The situation is further aggravated by the alarming incidence of treatment failures in several sleeping sickness foci, apparently indicating the occurrence of drug-resistant trypanosomes. Because of these reasons, and since vaccination does not appear to be feasible due to the trypanosomes' ever changing coat of variable surface glycoproteins (VSGs), new drugs are needed urgently. The entry of Trypanosoma brucei into the post-genomic age raises hopes for the identification of novel kinds of drug targets and in turn new treatments for sleeping sickness. The pragmatic definition of a drug target is, a protein that is essential for the parasite and does not have homologues in the host. Such proteins are identified by comparing the predicted proteomes of T. brucei and Homo sapiens, then validated by large-scale gene disruption or gene silencing experiments in trypanosomes. Once all proteins that are essential and unique to the parasite are identified, inhibitors may be found by high-throughput screening. However powerful, this functional genomics approach is going to miss a number of attractive targets. Several current, successful parasiticides attack proteins that have close homologues in the human proteome. Drugs like DFMO or pyrimethamine inhibit parasite and host enzymes alike--a therapeutic window is opened only by subtle differences in the regulation of the targets, which cannot be recognized in silico. Working against the post-genomic approach is also the fact that essential proteins tend to be more highly conserved between species than non-essential ones. Here we advocate drug targeting, i.e. uptake or activation of a drug via parasite-specific pathways, as a chemotherapeutic strategy to selectively inhibit enzymes that have equally sensitive counterparts in the host. The T. brucei purine salvage machinery offers opportunities for both metabolic and transport-based targeting: unusual nucleoside and nucleobase permeases may be exploited for selective import, salvage enzymes for selective activation of purine antimetabolites.

Pathophysiology and diagnosis of cancer drug induced cardiomyopathy

The clinical manifestations of anti-cancer drug associated cardiac side effects are diverse and can range from acutely induced cardiac arrhythmias to Q-T interval prolongation, changes in coronary vasomotion with consecutive myocardial ischemia, myocarditis, pericarditis, severe contractile dysfunction, and potentially fatal heart failure. The pathophysiology of these adverse effects is similarly heterogeneous and the identification of potential mechanisms is frequently difficult since the majority of cancer patients is not only treated with a multitude of cancer drugs but might also be exposed to potentially cardiotoxic radiation therapy. Some of the targets inhibited by new anti-cancer drugs also appear to be important for the maintenance of cellular homeostasis of normal tissue, in particular during exposure to cytotoxic chemotherapy. If acute chemotherapy-induced myocardial damage is only moderate, the process of myocardial remodeling can lead to progressive myocardial dysfunction over years and eventually induce myocardial dysfunction and heart failure. The tools for diagnosing anti-cancer drug associated cardiotoxicity and monitoring patients during chemotherapy include invasive and noninvasive techniques as well as laboratory investigations and are mostly only validated for anthracycline-induced cardiotoxicity and more recently for trastuzumab-associated cardiac dysfunction.

[Monitoring of treatment in thyroid diseases]

The effectiveness of antithyroid drug treatment of Graves' hyperthyroidism is documented by measuring initially free T4 and free T3 and later free T4, free T3 and TSH. An elevated titer of the Graves'-specific thyroid stimulating antibodies is not usually rechecked before the end of the antithyroid drug therapy. Thyroxine treatment of primary hypothyroidism is controlled by TSH measurements. In patients in whom TSH levels might be affected by drugs or nonthyroid diseases, free T4 is measured in addition to TSH. The assessment of the treatment of Hashimoto's chronic thyroiditis consists of the control of the therapy of its associated hypothyroidism. In subacute thyroiditis de Quervain control of the effectiveness of the analgesic therapy is most important. To check the effect of thyroid hormone treatment given with the intent to reduce goiter size, serial sonographies are of great value. In the follow-up of patients with thyroid carcinomas, measurements of thyroglobulin (for papillary and follicular thyroid cancers) and of calcitonin (for medullary thyroid cancers) in the serum as well as thyroid scans and other imaging procedures play an important role.

New players on the center stage: sphingosine 1-phosphate and its receptors as drug targets

The recent identification of a cellular balance between ceramide and sphingosine 1-phosphate (S1P) as a critical regulator of cell growth and death has stimulated increasing research effort to clarify the role of ceramide and S1P in various diseases associated with dysregulated cell proliferation and apoptosis. S1P acts mainly, but not exclusively, by binding to and activating specific cell surface receptors, the so-called S1P receptors. These receptors belong to the class of G protein-coupled receptors that constitute five subtypes, denoted as S1P(1)-S1P(5), and represent attractive pharmacological targets to interfere with S1P action. Whereas classical receptor antagonists will directly block S1P action, S1P receptor agonists have also proven useful, as recently shown for the sphingolipid-like immunomodulatory substance FTY720. When phosphorylated by sphingosine kinase to yield FTY720 phosphate, it acutely acts as an agonist at S1P receptors, but upon prolonged presence, it displays antagonistic activity by specifically desensitizing the S1P(1) receptor subtype. This commentary will cover the most recent developments in the field of S1P receptor pharmacology and highlights the potential therapeutic benefit that can be expected from these novel drug targets in the future.

Cladophialophora bantiana: a rare cause of fungal brain abscess. Clinical aspects and new therapeutic options

Black molds or dematiaceous fungi are rare etiologic agents of intracerebral abscesses and such infections carry a high mortality of up to 70% despite combined surgical and antifungal therapy. While the growing use of immunosuppressive therapies and organ transplantation have caused an increase in the incidence of rare fungal cerebral infections, occurrence in immunocompetent hosts is also possible. We describe a 60-year-old female patient with a cerebral abscess caused by Cladophialophora bantiana. The case illustrates the clinical and radiological similarities between glioblastomas and brain abscesses and emphasizes the need to perform histological and microbiological studies prior to the initiation of any form of therapy. Long-term survival from cerebral black mold abscesses has been reported only when complete surgical resection was possible. The recommended antifungal treatment involves the use of amphotericin B combined with a triazole and, if possible, flucytosine. Highly-active new generation triazole antifungal compounds (voriconazole or posaconazole) are likely to offer improved survival rates for patients with rare mold infections. In particular, posaconazole could be a new therapeutic option given its better tolerance, lower toxicity and fewer drug-drug interactions. We discuss clinical, microbiological and practical pharmacological aspects and review current and evolving treatment options.

Individualization of 5-fluorocytosine therapy

Using a convenient and fast HPLC procedure we determined serum concentrations of the fungistatic agent 5-fluorocytosine (5-FC) in 375 samples from 60 patients treated with this drug. The mean trough concentration (n = 127) was 64.3 mg/l (range: 11.8-208.0 mg/l), the mean peak concentration (n = 122) was 99.9 mg/l (range: 25.6-263.8 mg/l), the mean nonpeak/nontrough concentration (n = 126) was 80.1 mg/l (range: 10.5-268.0 mg/l). Totally 134 (35.7%) samples were outside the therapeutic range (25-100 mg/l), 108 (28.8%) being too high, 26 (6.9%) being too low. Forty-four (73%) patients showed 5-FC serum concentrations outside the therapeutic range at least once during the treatment course. In a prospective study we performed 65 dosage predictions on 30 patients by use of a 3-point method previously developed for aminoglycoside dosage adaptation. The mean absolute prediction error of the dosage adaptation was +0.7 mg/l (range: -26.0 to +28.0 mg/l). The root mean square prediction error was 10.7 mg/l. The mean predicted concentration (65.3 mg/l) agreed very well with the mean measured concentration (64.6 mg/l). The frequency distribution of 5-FC serum concentrations indicates that 5-FC monitoring is important. The applied pharmacokinetic method allows individual adaptations of 5-FC dosage with a clinically acceptable prediction error.

Comparison of long versus short ("spot") drug-eluting stenting for long coronary stenoses

We compared spot drug-eluting stenting (DES) to full stent coverage for treatment of long coronary stenoses. Consecutive, consenting patients with a long (>20 mm) coronary lesion of nonuniform severity and indication for percutaneous coronary intervention were randomized to full stent coverage of the atherosclerotic lesion with multiple, overlapping stenting (full DES group, n = 90) or spot stenting of hemodynamically significant parts of the lesion only (defined as diameter stenosis >50%; spot DES group, n = 89). At 1-year follow-up, 14 patients with full DES (15.6%) and 5 patients (5.6%) with spot DES had a major adverse cardiac event (MACE; p = 0.031). At 3 years, MACEs occurred in 18 patients with full DES (20%) and 7 patients (7.8%) with spot DES (p = 0.019). Cox proportional hazard model showed that the risk for MACEs was almost 60% lower in patients with spot DES compared to those with full DES (hazard ratio 0.41, 95% confidence interval 0.17 to 0.98, p = 0.044). This association remained even after controlling for age, gender, lesion length, and type of stent used (hazard ratio 0.42, 95% confidence interval 0.17 to 1.00, p = 0.05). In conclusion, total lesion coverage with DES is not necessary in the presence of diffuse disease of nonuniform severity. Selective stenting of only the significantly stenosed parts of the lesion is an appropriate therapeutic alternative in this setting, offering a favorable clinical outcome.