Elevated FOXG1 in glioblastoma stem cells cooperates with Wnt/ß-catenin to induce exit from quiescence.

Glioblastoma (GBM) stem cells (GSCs) display phenotypic and molecular features reminiscent of normal neural stem cells and exhibit a spectrum of cell cycle states (dormant, quiescent, proliferative). However, mechanisms controlling the transition from quiescence to proliferation in both neural stem cells (NSCs) and GSCs are poorly understood. Elevated expression of the forebrain transcription factor FOXG1 is often observed in GBMs. Here, using small-molecule modulators and genetic perturbations, we identify a synergistic interaction between FOXG1 and Wnt/ß-catenin signaling. Increased FOXG1 enhances Wnt-driven transcriptional targets, enabling highly efficient cell cycle re-entry from quiescence; however, neither FOXG1 nor Wnt is essential in rapidly proliferating cells. We demonstrate that FOXG1 overexpression supports gliomagenesis in vivo and that additional ß-catenin induction drives accelerated tumor growth. These data indicate that elevated FOXG1 cooperates with Wnt signaling to support the transition from quiescence to proliferation in GSCs.

Regional identity of human neural stem cells determines oncogenic responses to histone H3.3 mutants.

Point mutations within the histone H3.3 are frequent in aggressive childhood brain tumors known as pediatric high-grade gliomas (pHGGs). Intriguingly, distinct mutations arise in discrete anatomical regions: H3.3-G34R within the forebrain and H3.3-K27M preferentially within the hindbrain. The reasons for this contrasting etiology are unknown. By engineering human fetal neural stem cell cultures from distinct brain regions, we demonstrate here that cell-intrinsic regional identity provides differential responsiveness to each mutant that mirrors the origins of pHGGs. Focusing on H3.3-G34R, we find that the oncohistone supports proliferation of forebrain cells while inducing a cytostatic response in the hindbrain. Mechanistically, H3.3-G34R does not impose widespread transcriptional or epigenetic changes but instead impairs recruitment of ZMYND11, a transcriptional repressor of highly expressed genes. We therefore propose that H3.3-G34R promotes tumorigenesis by focally stabilizing the expression of key progenitor genes, thereby locking initiating forebrain cells into their pre-existing immature state.

Experimental models and tools to tackle glioblastoma.

Glioblastoma multiforme (GBM) is one of the deadliest human cancers. Despite increasing knowledge of the genetic and epigenetic changes that underlie tumour initiation and growth, the prognosis for GBM patients remains dismal. Genome analysis has failed to lead to success in the clinic. Fresh approaches are needed that can stimulate new discoveries across all levels: cell-intrinsic mechanisms (transcriptional/epigenetic and metabolic), cell-cell signalling, niche and microenvironment, systemic signals, immune regulation, and tissue-level physical forces. GBMs are inherently extremely challenging: tumour detection occurs too late, and cells infiltrate widely, hiding in quiescent states behind the blood-brain barrier. The complexity of the brain tissue also provides varied and complex microenvironments that direct cancer cell fates. Phenotypic heterogeneity is therefore superimposed onto pervasive genetic heterogeneity. Despite this bleak outlook, there are reasons for optimism. A myriad of complementary, and increasingly sophisticated, experimental approaches can now be used across the research pipeline, from simple reductionist models devised to delineate molecular and cellular mechanisms, to complex animal models required for preclinical testing of new therapeutic approaches. No single model can cover the breadth of unresolved questions. This Review therefore aims to guide investigators in choosing the right model for their question. We also discuss the recent convergence of two key technologies: human stem cell and cancer stem cell culture, as well as CRISPR/Cas tools for precise genome manipulations. New functional genetic approaches in tailored models will likely fuel new discoveries, new target identification and new therapeutic strategies to tackle GBM.

Does the number of wires used to close a sternotomy have an impact on deep sternal wound infection?

OBJECTIVES: We studied the influence of the number of sternotomy mechanical fixation points on deep sternal wound infection (DSWI). METHODS: Between September 2007 and February 2011, 2672 patients underwent a standard peri-sternal wire closure following a median sternotomy for a first-time cardiac surgery. Data were collected during the study period. RESULTS: The mean age of the patients was 66 ± 11 and 1978 (74.0%) were male. The mean body mass index (BMI) was 28.9 ± 9.3 and the median of the logistic EuroSCORE was 3.14, with a range of 0.88-54.1. Postoperatively, 40 (1.5%) patients developed DSWI after 14 ± 6 days, of whom 39 (92.5%) had positive deep sternal wound specimen cultures, predominantly Staphylococci (62.5%). The risk of DSWI was significantly increased in patients in whom eight or fewer paired points of sternal wire fixation were used when compared with patients in whom nine or more paired points of fixation were used (P = 0.002). Preoperative myocardial infarction (P = 0.001), elevated BMI (P = 0.046), bilateral internal mammary artery harvest (P < 0.0001), postoperative hypoxia (P < 0.0001), sepsis (P = 0.019) and postoperative inotrope use (P = 0.007) significantly increased the risk of DSWI. CONCLUSIONS: DSWI is associated with hypoxia, ischaemia, sepsis and mechanical sternal instability. DSWI may be prevented by using nine or more paired fixation points when closing with standard peri-sternal wires.

HLA class I polymorphisms are associated with development of infectious mononucleosis upon primary EBV infection.

Infectious mononucleosis (IM) is an immunopathological disease caused by EBV that occurs in young adults and is a risk factor for Hodgkin lymphoma (HL). An association between EBV-positive HL and genetic markers in the HLA class I locus has been identified, indicating that genetic differences in the HLA class I locus may alter disease phenotypes associated with EBV infection. To further determine whether HLA class I alleles may affect development of EBV-associated diseases, we analyzed 2 microsatellite markers and 2 SNPs located near the HLA class I locus in patients with acute IM and in asymptomatic EBV-seropositive and -seronegative individuals. Alleles of both microsatellite markers were significantly associated with development of IM. Specific alleles of the 2 SNPs were also significantly more frequent in patients with IM than in EBV-seronegative individuals. IM patients possessing the associated microsatellite allele had fewer lymphocytes and increased neutrophils relative to IM patients lacking the allele. These patients also displayed higher EBV titers and milder IM symptoms. The results of this study indicate that HLA class I polymorphisms may predispose patients to development of IM upon primary EBV infection, suggesting that genetic variation in T cell responses can influence the nature of primary EBV infection and the level of viral persistence.

Peritubular capillary rarefaction and lymphangiogenesis in chronic allograft failure.

BACKGROUND: Chronic renal allograft failure is a common and multifactorial but incompletely understood process with no effective treatment strategy. METHODS: We used immunohistochemistry to evaluate changes in density and turnover (proliferation) of the microvasculature and lymphatic vessels in endstage human transplant nephrectomies and control tissue derived from macroscopically normal areas of native nephrectomy specimens removed for renal carcinoma. We also examined the expression of angiogenic and lymphangiogenic growth factors in the associated inflammatory infiltrate. RESULTS: Endstage allografts showed reduced microvascular density in cortex and medulla compared with controls (P<0.0001), despite the presence of endothelial cell proliferation. However, the grafts also showed new lymphatic vessels in the tubulointerstitium, not evident in controls, and which appeared to be functional with luminal macrophages. Double labeling studies showed a subpopulation of the graft-infiltrating macrophages to be immunopositive for inducible nitric oxide synthase or vascular endothelial growth factor-C (a lymphatic-specific growth factor). B cells also strongly expressed the inflammatory and angiogenic cytokine vascular endothelial growth factor A. CONCLUSIONS: The present results identify contrasting changes in the microanatomy of vascular and lymphatic beds in endstage renal allografts associated with subpopulations of infiltrating macrophages and B cells that potentially regulate some of these changes. These cells and processes could become a new therapeutic target in chronic allograft failure.