Management of germ cell tumors in children: Approaches to cure

The introduction of cisplatinum chemotherapy and current advances in the surgical treatment have resulted in a dramatic improvement of the prognosis of children with malignant germ cell tumors (GCT). Cisplatinum chemotherapy generally results in sufficient systemic tumor control, but local relapses may still occur in patients who did not receive adequate local treatment. Therefore, the therapeutic consideration must take into account age, primary site of the tumor, and its histology. In gonadal tumors, there is a high chance of primary complete resection since these tumors tend to be encapsulated, and particularly testicular GCT are often detected at a low tumor stage. In contrast, a primary complete resection may be impossible in large nongonadal tumors such as sacrococcygeal or mediastinal GCT. In these tumors, a neoadjuvant or pre-operative chemotherapy after clinical diagnosis by imaging and evaluation of tumor markers significantly facilitates complete resection on delayed surgery. In addition, the impact of chemotherapy on local tumor control may be enhanced by locoregional hyperthermia. In most intracranial GCT complete resection is impossible and may be associated with significant morbidity. Nevertheless, biopsy is essential for diagnosis in nonsecreting tumors. In intracranial GCT, radiotherapy significantly contributes to local tumor control, and doses are stratified according to histology. These general considerations have been integrated into national and international cooperative treatment protocols. In most current protocols, treatment is stratified according to an initial risk assessment that includes the parameters age, site, histology, stage, completeness of resection and the tumor markers alpha(1)-fetoprotein (AFP) and human choriogonadotropin (beta-HCG). With such modern protocols overall cure rates above 80% can be achieved. Moreover, the previously high-risk groups may now expect a favorable prognosis with this risk-adapted treatment, whereas an increasing number of low-risk patients are treated expectantly or with significantly reduced chemotherapy. As current biologic studies reveal distinct genetic patterns in childhood GCT, it can be expected that further combined clinical and genetic studies will be valuable for risk assessment of childhood GCT

Methods to study the roles of Rho GTPases in platelet function

Platelets are a critical cell for prevention of bleeding. Part of the response to the formation of the thrombus is the activation of the actin cytoskeleton, with an inability to effectively activate the cytoskeleton linked to thrombus formation defects and instability. The control of this process is linked to activation of the Rho GTPases, Cdc42, Rac1, and RhoA, although additional small GTPases such as Rif and Rap have been shown to play roles in platelet function.Here we describe the methodology to accurately understand how Rho GTPases are activated in platelets. Due to the technical limitations of working with platelets, such as their lack of ability to be transfected, the majority of work has been carried out either using inhibitors of Rho GTPases or within knockout mouse models. Studies can be conducted both in suspension samples and in spread platelets. In suspension the platelets will undergo a shape change response, but will not be able to spread. In spread platelets it is possible to examine the effects of the matrix environment, such as concentration, type, and stiffness on Rho GTPase function within platelet activation and platelet spreading

Glycoprotein receptor mediated regulation of platelet morphology

Spreading platelets sequentially form filopodia, lamellipodia, and stress fibres. This thesis demonstrates the formation of each actin structure in spread platelets, and in addition the formation of a novel actin structure, which I have termed an actin nodule. Actin nodules require Src kinase activation, and actin polymerisation, but are negatively correlated to ROCK and myosin-II activation. This thesis has investigated the role of WAVE-l, Rho kinase (ROCK) and myosin-II in spreading and aggregate stability in vitro and in vivo. ROCK or myosin-II inhibition, prevents stress fibre formation leading to appearance of splits and holes (termed fenestrations) in spread platelets on collagen. In addition, ROCK or myosin-II inhibition compromises aggregate stability on collagen at arterial rates of flow. Lamellipodia formation is inhibited in WAVE-rl - platelets spread on CRP, whilst shape change and aggregation downstream of GPVI is severely disrupted. However, GPCR agonists induce full lamellipodia formation on fibrinogen in WAVE-I-I. Aggregate formation on collagen under arterial rates of flow is unaffected further indicating . WAVE-2 can compensate for WAVE-I. Thus, WAVE-l maybe differentially regulated downstream of GPCR and glycoprotein signalling. The actin regulatory proteins, Spin-90, Β-Pix and Nck are tyrosine phosphorylated by multiple platelet agonists, but do not form a complex upon platelet adhesion. However, B-Pix is heavily phosphorylated downstream of the collagen receptor integrin, a2BI. I speculate B-Pix may play an important role in connecting PLCyl to Rac activation

Quantum Dot Imaging Agents: Haematopoietic Cell Interactions and Biocompatibility

Quantum dots (QDs) are semi-conducting nanoparticles that have been developed for a range of biological and non-biological functions. They can be tuned to multiple different emission wavelengths and can have significant benefits over other fluorescent systems. Many studies have utilised QDs with a cadmium-based core; however, these QDs have since been shown to have poor biological compatibility. Therefore, other QDs, such as indium phosphide QDs, have been developed. These QDs retain excellent fluorescent intensity and tunability but are thought to have elevated biological compatibility. Herein we discuss the applicability of a range of QDs to the cardiovascular system. Key disease states such as myocardial infarction and stroke are associated with cardiovascular disease (CVD), and there is an opportunity to improve clinical imaging to aide clinical outcomes for these disease states. QDs offer potential clinical benefits given their ability to perform multiple functions, such as carry an imaging agent, a therapy, and a targeting motif. Two key cell types associated with CVD are platelets and immune cells. Both cell types play key roles in establishing an inflammatory environment within CVD, and as such aid the formation of pathological thrombi. However, it is unclear at present how and with which cell types QDs interact, and if they potentially drive unwanted changes or activation of these cell types. Therefore, although QDs show great promise for boosting imaging capability, further work needs to be completed to fully understand their biological compatibility

Should aspirin be replaced with ADP blockers or anti-GPVI to manage thrombosis?

Platelets have a pivotal role in maintaining cardiovascular homeostasis. They are kept docile by endothelial derived mediators. Aberration in haemostatic balance predisposes an individual to an elevated risk of a pro-thrombotic environment. Anti-platelet therapy has been a key component to reduce this risk. However, understanding how these medications affect the balance between activation and inhibition of platelets is critical. There is now evidence that a key antiplatelet therapy – aspirin, may not be the most efficacious medicine of choice, as it can compromise both platelet inhibition and activation pathways. In this review the rationale of aspirin as an anti-thrombotic drug has been critically discussed. This review looks at how recent published trials are asking key questions on the efficacy and safety of aspirin in countering cardiovascular diseases. There is an increasing portfolio of evidence that identifies that although aspirin is a very cheap and accessible drug, it may be used in a manner that is not always beneficial to a patient, and a more nuanced and targeted use of aspirin may increase its clinical benefit and maximize patient response. The questions around the use of aspirin raises the potential for changes in its clinical use for dual anti-platelet therapy. This highlights the need to ensure that treatment is targeted in the most effective manner, and that other anti-platelet therapies may well be more efficacious and beneficial for CVD patients in their standard and personalized approaches

Actin on trafficking: could actin guide directed receptor transport?

Here, we present emerging ideas surrounding the interplay between the actin cytoskeleton and receptor transport and activation. The bulk of actin dynamics in cells is thought to contribute to architecture and mobility. Actin also contributes to trafficking, acting as a molecular scaffold, providing force to deform membranes, facilitating vesicle abscission or propelling a vesicle through the cytoplasm1,2 and recent studies highlight important connections between the directed trafficking of receptors and the impact on cell migration and actin dynamics. Additionally, a number of newly described actin nucleation promoting factors, such as the vesicle associated protein WASH, reveal unexpected roles of actin in membrane traffic and suggest that the cell dedicates a significant proportion of its regulation of actin dynamics to controlling trafficking