Blood-Brain Barrier Breakdown Determines Differential Therapeutic Outcome in Genetically Diverse Forms of Medulloblastoma.

Medulloblastoma driven by Wnt/β-catenin and Sonic hedgehog pathway mutations show favorable and poor patient survival upon treatment, respectively. In this Cancer Cell issue, Phoenix and colleagues (2016) report disruption of the blood-brain barrier by Wif1 specifically in Wnt-driven medulloblastoma, resulting in increased treatment response and survival in mouse models.

In vitro models of the blood-brain barrier.

The blood-brain barrier (BBB) proper is composed of endothelial cells (ECs) of the cerebral microvasculature, which are interconnected by tight junctions (TJs) that in turn form a physical barrier restricting paracellular flux. Tight control of vascular permeability is essential for the homeostasis and functionality of the central nervous system (CNS). In vitro BBB models have been in use for decades and have been of great benefit in the process of investigating and understanding the cellular and molecular mechanisms underlying BBB establishment.

Analysis of angiogenesis in the developing mouse central nervous system.

In order to study basic mechanisms of sprouting angiogenesis, researchers worldwide rely on the use of model tissues such as rodent retina, which becomes vascularized postnatally, to study the growth of blood vessels. By definition, models have to be simple, recapitulating angiogenic processes in a stereotyped and relatively easy accessible manner, allowing the application of standardized analyses. These criteria also apply in an ideal manner to the embryonic mouse hindbrain, which becomes vascularized by sprouting angiogenesis from a preformed perineural vascular plexus, leading to the stereotypical formation of a capillary subventricular plexus.

The Wnt/planar cell polarity signaling pathway contributes to the integrity of tight junctions in brain endothelial cells.

Wnt morphogens released by neural precursor cells were recently reported to control blood-brain barrier (BBB) formation during development. Indeed, in mouse brain endothelial cells, activation of the Wnt/β-catenin signaling pathway, also known as the canonical Wnt pathway, was shown to stabilize endothelial tight junctions (TJs) through transcriptional regulation of the expression of TJ proteins. Because Wnt proteins activate several distinct β-catenin-dependent and independent signaling pathways, this study was designed to assess whether the noncanonical Wnt/Par/aPKC planar cell polarity (PCP) pathway might also control TJ integrity in brain endothelial cells.

Wnt signaling in the vasculature.

The development of the vascular system requires orchestrated activities of various molecular pathways to assure the formation of a hierarchically branched tubular network. Furthermore, endothelial cell (EC) populations are heterogeneous to meet organ-specific requirements in the mature vasculature. This developmental scheme is probably best represented by the acquisition and maintenance of unique barrier properties known as the blood-brain barrier (BBB) in microvessels of the central nervous system (CNS).

Endothelial Wnt/β-catenin signaling inhibits glioma angiogenesis and normalizes tumor blood vessels by inducing PDGF-B expression.

Endothelial Wnt/β-catenin signaling is necessary for angiogenesis of the central nervous system and blood-brain barrier (BBB) differentiation, but its relevance for glioma vascularization is unknown. In this study, we show that doxycycline-dependent Wnt1 expression in subcutaneous and intracranial mouse glioma models induced endothelial Wnt/β-catenin signaling and led to diminished tumor growth, reduced vascular density, and normalized vessels with increased mural cell attachment. These findings were corroborated in GL261 glioma cells intracranially transplanted in mice expressing dominant-active β-catenin specifically in the endothelium.

Combined modality treatment of oral and oropharyngeal cancer including neoadjuvant intraarterial cisplatin and radical surgery followed by concurrent radiation and chemotherapy with weekly docetaxel - three year results of a pilot study.

Background: A new four-modality treatment of primary oral and oropharyngeal squamous cell carcinomas was evaluated with regard to feasibility, tolerance, and survival.

Patients And Methods: Seventy three operable patients (100%) with histologically proven untreated stage I to stage IV disease received at least one cycle of neoadjuvant intraarterial chemotherapy with 150 mg/m(2) cisplatin neutralized with sodium thiosulphate, followed by radical operation for the tumour with a simultaneous selective neck dissection (clinically negative neck), or modified radical neck dissection (nodal involvement), followed by adjuvant chemoradiation over 5 weeks (51.9 Gy, systemic docetaxel 25 mg/m(2), once every week).

In vitro cytotoxic dose-relation of cisplatin and sodium thiosulphate in human tongue and oesophageal squamous carcinoma cell lines.

Background: Intraarterial chemotherapy of oral and oropharyngeal cancer with cisplatin (cis-diamminedichloroplatinum [II]) has experienced a revival in the last decade. Side-effects of the therapy were very low with concomitant systemic infusion of the neutralizing agent sodium thiosulphate. The requisite dose of the chemotherapeutic agent which safely leads to apoptosis of oral cancer cells has not yet been assessed in vitro, nor has the combination of cisplatin and sodium thiosulphate been examined for the potential reduction of cytotoxicity in oral cancer cells.