A Multistep In Silico Approach Identifies Potential Glioblastoma Drug Candidates via Inclusive Molecular Targeting of Glioblastoma Stem Cells

Glioblastoma (GBM) is the highest grade of glioma for which no effective therapy is currently available. Despite extensive research in diagnosis and therapy, there has been no significant improvement in GBM outcomes, with a median overall survival continuing at a dismal 15-18 months. In recent times, glioblastoma stem cells (GSCs) have been identified as crucial drivers of treatment resistance and tumor recurrence, and GBM therapies targeting GSCs are expected to improve patient outcomes. We used a multistep in silico screening strategy to identify repurposed candidate drugs against selected therapeutic molecular targets in GBM with potential to concomitantly target GSCs. Common differentially expressed genes (DEGs) were identified through analysis of multiple GBM and GSC datasets from the Gene Expression Omnibus (GEO) and The Cancer Genome Atlas (TCGA). For identification of target genes, we selected the genes with most significant effect on overall patient survival. The relative mRNA and protein expression of the selected genes in TCGA control versus GBM samples was also validated and their cancer dependency scores were assessed. Drugs targeting these genes and their corresponding proteins were identified from LINCS database using Connectivity Map (CMap) portal and by in silico molecular docking against each individual target using FDA-approved drug library from the DrugBank database, respectively. The molecules thus obtained were further evaluated for their ability to cross blood brain barrier (BBB) and their likelihood of resulting in drug resistance by acting as p-glycoprotein (p-Gp) substrates. The growth inhibitory effect of these final shortlisted compounds was examined on a panel of GBM cell lines and compared with temozolomide through the drug sensitivity EC50 values and AUC from the PRISM Repurposing Secondary Screen, and the IC50 values were obtained from GDSC portal. We identified RPA3, PSMA2, PSMC2, BLVRA, and HUS1 as molecular targets in GBM including GSCs with significant impact on patient survival. Our results show GSK-2126458/omipalisib, linifanib, drospirenone, eltrombopag, nilotinib, and PD198306 as candidate drugs which can be further evaluated for their anti-tumor potential against GBM. Through this work, we identified repurposed candidate therapeutics against GBM utilizing a GSC inclusive targeting approach, which demonstrated high in vitro efficacy and can prospectively evade drug resistance. These drugs have the potential to be developed as individual or combination therapy to improve GBM outcomes.

Diffuse midline glioma invasion and metastasis rely on cell-autonomous signaling

BACKGROUND

Diffuse midline gliomas (DMG) are pediatric tumors with negligible 2-year survival after diagnosis characterized by their ability to infiltrate the central nervous system. In the hope of controlling the local growth and slowing the disease, all patients receive radiotherapy. However, distant progression occurs frequently in DMG patients. Current clues as to what causes tumor infiltration circle mainly around the tumor microenvironment, but there are currently no known determinants to predict the degree of invasiveness.

METHODS

In this study, we use patient-derived glioma stem cells (GSCs) to create patient-specific 3D avatars to model interindividual invasion and elucidate the cellular supporting mechanisms.

RESULTS

We show that GSC models in 3D mirror the invasive behavior of the parental tumors, thus proving the ability of DMG to infiltrate as an autonomous characteristic of tumor cells. Furthermore, we distinguished 2 modes of migration, mesenchymal and ameboid-like, and associated the ameboid-like modality with GSCs derived from the most invasive tumors. Using transcriptomics of both organoids and primary tumors, we further characterized the invasive ameboid-like tumors as oligodendrocyte progenitor-like, with highly contractile cytoskeleton and reduced adhesion ability driven by crucial over-expression of bone morphogenetic pathway 7 (BMP7). Finally, we deciphered MEK, ERK, and Rho/ROCK kinases activated downstream of the BMP7 stimulation as actionable targets controlling tumor cell motility.

CONCLUSIONS

Our findings identify 2 new therapeutic avenues. First, patient-derived GSCs represent a predictive tool for patient stratification in order to adapt irradiation strategies. Second, autocrine and short-range BMP7-related signaling becomes a druggable target to prevent DMG spread and metastasis.

Preliminary Effects of a Guided Self-Change Intervention on Perceived Risk and Self-Efficacy in University Students Engaging in Cannabis or Alcohol Misuse

Guided Self-Change (GSC) is a Motivational Interviewing (MI)-based early intervention program, infused with Cognitive Behavioral Therapy (CBT), for individuals with substance use problems. In this study, we implemented a 4-session GSC program with the innovative addition of mindfulness-based techniques at a minority-serving institution to reduce substance use and negative consequences among self-referred university students. We investigated processes that may be associated with behavior change, including perceived risk of use and self-efficacy ratings among university students who reported their primary substance of choice was cannabis (n = 18) or alcohol (n = 18). The sample of 36 participants (Mage = 24.4, SDage = 5, range 18-37) mostly identified as female (58.3%), then male (41.7%); 52.8% identified as Hispanic/Latine, 22.2% as Black or African American, and 19.5% as a sexual minority. Among cannabis primary using students, results indicated that the perceived risk of weekly cannabis use, confidence to change, and readiness to change showed statistically significant increases from pre- to post-assessment. Among alcohol primary using students, confidence to change and readiness to change showed statistically significant increases from pre- to post-assessments. All results yielded large effect sizes, which may be inflated due to the small sample size. Findings suggest that over the course of participation in a brief, 4-session targeted GSC program, there were significant increases in perceived risk and self-efficacy among minority university students who engage in primary cannabis or primary alcohol use.

Towards deciphering glioblastoma intra-tumoral heterogeneity: The importance of integrating multidimensional models

Glioblastoma (GBM) is the most common and severe form of brain cancer among adults. Its aggressiveness is largely attributed to its complex and heterogeneous biology that despite maximal surgery and multimodal chemoradiation treatment, inevitably recurs. Traditional large-scale profiling approaches have contributed substantially to the understanding of patient-to-patient inter-tumoral differences in GBM. However, it is now clear that biological differences within an individual (intra-tumoral heterogeneity) are also a prominent factor in treatment resistance and recurrence of GBM and will likely require integration of data from multiple recently developed omics platforms to fully unravel. Here we dissect the growing geospatial model of GBM, which layers intra-tumoral heterogeneity on a GBM stem cell (GSC) precursor, single cell, and spatial level. We discuss potential unique and inter-dependant aspects of the model including potential discordances between observed genotypes and phenotypes in GBM.

Oncolytic herpes simplex viruses for the treatment of glioma and targeting glioblastoma stem-like cells

Glioblastoma (GBM) is one of the most lethal cancers, having a poor prognosis and a median survival of only about 15 months with standard treatment (surgery, radiation, and chemotherapy), which has not been significantly extended in decades. GBM demonstrates remarkable cellular heterogeneity, with glioblastoma stem-like cells (GSCs) at the apex. GSCs are a subpopulation of GBM cells that possess the ability to self-renew, differentiate, initiate tumor formation, and manipulate the tumor microenvironment (TME). GSCs are no longer considered a static population of cells with specific markers but are quite flexible phenotypically and in driving tumor heterogeneity and therapeutic resistance. In light of these features, they are a critical target for successful GBM therapy. Oncolytic viruses, in particular oncolytic herpes simplex viruses (oHSVs), have many attributes for therapy and are promising agents to target GSCs. oHSVs are genetically-engineered to selectively replicate in and kill cancer cells, including GSCs, but not normal cells. Moreover, oHSV can induce anti-tumor immune responses and synergize with other therapies, such as chemotherapy, DNA repair inhibitors, and immune checkpoint inhibitors, to potentiate treatment effects and reduce GSC populations that are partly responsible for chemo- and radio-resistance. Herein, we present an overview of GSCs, activity of different oHSVs, clinical trial results, and combination strategies to enhance efficacy, including therapeutic arming of oHSV. Throughout, the therapeutic focus will be on GSCs and studies specifically targeting these cells. Recent clinical trials and approval of oHSV G47Δ in Japan for patients with recurrent glioma demonstrate the efficacy and promise of oHSV therapy.

The STAT3-Regulated Autophagy Pathway in Glioblastoma

Glioblastoma (GBM) is the most common primary brain malignancy in adults with a dismal prognosis. Despite advances in genomic analysis and surgical technique and the development of targeted therapeutics, most treatment options are ineffective and mainly palliative. Autophagy is a form of cellular self-digestion with the goal of recycling intracellular components to maintain cell metabolism. Here, we describe some recent findings that suggest GBM tumors are more sensitive to the excessive overactivation of autophagy leading to autophagy-dependent cell death. GBM cancer stem cells (GSCs) are a subset of the GBM tumor population that play critical roles in tumor formation and progression, metastasis, and relapse, and they are inherently resistant to most therapeutic strategies. Evidence suggests that GSCs are able to adapt to a tumor microenvironment of hypoxia, acidosis, and lack of nutrients. These findings have suggested that autophagy may promote and maintain the stem-like state of GSCs as well as their resistance to cancer treatment. However, autophagy is a double-edged sword and may have anti-tumor properties under certain conditions. The role of the STAT3 transcription factor in autophagy is also described. These findings provide the basis for future research aimed at targeting the autophagy-dependent pathway to overcome the inherent therapeutic resistance of GBM in general and to specifically target the highly therapy-resistant GSC population through autophagy regulation.

Expansion Microscopy-based imaging for visualization of mitochondria in Drosophila ovarian germline stem cells

Recent studies have shown that mitochondrial morphology can modulate organelle function and greatly affect stem cell behavior, thus affecting tissue homeostasis. As such, we previously showed that the accumulation of fragmented mitochondria in aged Drosophila ovarian germline stem cells (GSCs) contributes to age-dependent GSC loss. However, standard immunofluorescence methods to examine mitochondrial morphology yield images with insufficient resolution for rigorous analysis, while 3-dimensional electron microscopy examination of mitochondrial morphology is labor intensive and allows only limited sampling of mitochondria. To overcome these issues, we utilized the expansion microscopy technique to expand GSC samples by 4-fold in combination with mitochondrial immunofluorescence labeling. Here, we present a simple, inexpensive method for nanoscale optical imaging of mitochondria in the germline. This protocol may be beneficial for studies that require visualization of mitochondria or other fine subcellular structures in the Drosophila ovary.

Performance of Afirma genomic sequencing classifier and histopathological outcome are associated with patterns of atypia in Bethesda category III thyroid nodules

BACKGROUND

Data on Afirma's genomic sequencing classifier (GSC) performance in atypia of undetermined significance (AUS) subcategories is limited. This study investigated GSC performance in AUS nodules with architectural atypia (AUS-A), cytological atypia (AUS-C), architectural and cytological atypia (AUS-AC), and predominantly Hürthle cells (AUS-HC).

METHODS

This study retrieved consecutive thyroid nodules having a recurrent cytologic diagnosis of AUS with qualifiers and a concurrent GSC diagnostic result. All nodules were followed by either surgical intervention or clinical and/or ultrasound monitoring (≥6 months). GSC benign call rate (BCR), rate of histology-proven malignancy, and diagnostic parameters of GSC were calculated for individual AUS subcategories. Statistical analysis was performed using the Fisher exact test.

RESULTS

A total of 135 AUS nodules fulfilled inclusion criteria, including 79 AUS-A, 9 AUS-C, 29 AUS-AC, and 18 AUS-HC. BCR was 72.2%, 66.7%, 44.8%, and 77.8% in AUS-A, AUS-C, AUS-AC, and AUS-HC, respectively. AUS-A showed a greater BCR than AUS-AC (p < .05). All GSC-benign nodules were considered benign on clinical or surgical follow-up. Among GSC-suspicious nodules, histology-proven malignancies represented 4.5% of AUS-A, 0% of AUS-C, 56.3% of AUS-AC, and 25.0% of AUS-HC cases. AUS-AC demonstrated a higher malignant rate compared with AUS-A (p < .05). GSC offers 100% NPV and a wide range (5%-56%) of PPV across all AUS subcategories. AUS-AC demonstrated a greater PPV compared with AUS-A (p < .05).

CONCLUSION

BCR of GSC and malignant rates associated with suspicious GSC may differ in various AUS subcategories. GSC-suspicious nodules with both architectural and cytologic atypia are more likely to be malignant. These findings may improve clinical triage and/or management of patients with AUS thyroid nodules.

RSL3 triggers glioma stem cell differentiation via the Tgm2/AKT/ID1 signaling axis

RSL3 is a synthetic molecule that inactivates glutathione peroxidase 4 to induce ferroptosis. However, its effect on glioma stem cells (GSC) remains unclear. In this study, we found that RSL3 significantly suppressed GSC proliferation and induced their differentiation into astrocytes, which was accompanied by the downregulation of stemness-related markers, including Nestin and Sox2. Combined transcriptome and proteome analyses further revealed that RSL3 promoted GSC differentiation by suppressing transglutaminase 2 (Tgm2), but not by ferroptosis-related pathways. Tgm2 overexpression in CSC2078 cells rescued the changes in stemness-related markers and differentiation caused by RSL3, which was mediated by inhibitor of DNA binding 1 (ID1) activation. Further studies identified ID1 as a downstream signaling target of Tgm2. Blocking the phosphoinositide-3 kinase (PI3K)/Akt pathway with LY294002 suppressed PI3K, p-Akt, and ID1 levels but not Tgm2. Tgm2 overexpression abrogated the changes in PI3K, p-Akt, and ID1 levels caused by LY294002. Taken together, we demonstrate that RSL3 does not induce ferroptosis; instead, it inhibits GSC proliferation and triggers their differentiation by suppressing the Tgm2/Akt/ID1 signaling axis.

Integrative analysis of cell adhesion molecules in glioblastoma identified prostaglandin F2 receptor inhibitor (PTGFRN) as an essential gene

Background

Glioblastoma (GBM) is the most common primary malignant brain tumor in adults exhibiting infiltration into surrounding tissues, recurrence, and resistance to therapy. GBM infiltration is accomplished by many deregulated factors such as cell adhesion molecules (CAMs), which are membrane proteins that participate in cell-cell and cell-ECM interactions to regulate survival, proliferation, migration, and stemness.

Methods

A comprehensive bioinformatics analysis of CAMs (n = 518) in multiple available datasets revealed genetic and epigenetic alterations among CAMs in GBM. Univariate Cox regression analysis using TCGA dataset identified 127 CAMs to be significantly correlated with survival. The poor prognostic indicator PTGFRN was chosen to study its role in glioma. Silencing of PTGFRN in glioma cell lines was achieved by the stable expression of short hairpin RNA (shRNA) against the PTGFRN gene. PTGFRN was silenced and performed cell growth, migration, invasion, cell cycle, and apoptosis assays. Neurosphere and limiting dilution assays were also performed after silencing of PTGFRN in GSCs.

Results

Among the differentially regulated CAMs (n = 181, 34.9%), major proportion of them were found to be regulated by miRNAs (n = 95, 49.7%) followed by DNA methylation (n = 32, 16.7%), and gene copy number variation (n = 12, 6.2%). We found that PTGFRN to be upregulated in GBM tumor samples and cell lines with a significant poor prognostic correlation with patient survival. Silencing PTGFRN diminished cell growth, colony formation, anchorage-independent growth, migration, and invasion and led to cell cycle arrest and induction of apoptosis. At the mechanistic level, silencing of PTGFRN reduced pro-proliferative and promigratory signaling pathways such as ERK, AKT, and mTOR. PTGFRN upregulation was found to be due to the loss of its promoter methylation and downregulation of miR-137 in GBM. PTGFRN was also found to be higher in glioma stem-like cells (GSCs) than the matched differentiated glioma cells (DGCs) and is required for GSC growth and survival. Silencing of PTGFRN in GSCs reduced transcript levels of reprogramming factors (Olig2, Pou3f2, Sall2, and Sox2).

Conclusion

In this study, we provide a comprehensive overview of the differential regulation of CAMs and the probable causes for their deregulation in GBM. We also establish an oncogenic role of PTGFRN and its regulation by miR-137 in GBM, thus signifying it as a potential therapeutic target.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12885-022-09682-2.

Diagnostic performance of the second-generation molecular tests in the assessment of indeterminate thyroid nodules: A systematic review and meta-analysis

OBJECTIVE

The objective of this systematic review and meta-analysis was to evaluate the diagnostic performance of the second-generation molecular tests in the diagnosis of thyroid nodules with indeterminate fine-needle aspiration biopsy results.

METHODS

We searched PubMed, Google Scholar, Scopus, and Cochrane Library for studies published between January 2017 and March 2021. Inclusion criteria were indeterminate thyroid results from fine-needle aspiration (FNA) that included Bethesda categories III and IV, use of Afirma GSC, Thyroseq v3, and ThyGeNext as an index test, and conclusive histopathological results. Studies with no post-surgical diagnoses were excluded. For each included study, sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) were obtained. Sensitivity and specificity were pooled jointly using a bivariate binomial random-effects model. Statistical significance was indicated at p-value less than 0.05.

RESULTS

Our search yielded 431 non-duplicate articles, of which 15 were included in the study (7 GSC, 6 Thyroseq v3, and 2 ThyGeNext). ThyGeNext studies were excluded from the meta-analysis due to the small sample size. Pooled data for GSC studies on 472 thyroid nodules showed a sensitivity of 96.6 (95% confidence interval: 89.7-98.9%), specificity of 52.9% (23.4-80.5%), PPV of 63% (51-74%), and NPV of 96% (94-98%). Pooled data for ThyroSeq studies on 530 thyroid nodules showed a sensitivity of 95.1% (91.1-97.4%), specificity of 49.6% (29.3-70.1%), PPV of 70% (55-83%), and NPV of 92% (86-97%). There was no statistically significant difference in diagnostic performances of the two tests (p-values for sensitivity = 0.89, specificity = 0.82, PPV = 0.43, NPV = 0.17).

CONCLUSION

High sensitivity and high NPV in GSC and Thyroseq v3 have potential to help rule out malignancy among thyroid nodules with indeterminate cytology results. There was no difference in diagnostic performances between the two molecular tests indicating that either test is appropriate to determine the malignancy of thyroid nodules. Further long-term outcome data are warranted to make a clear recommendation.

Comparison of Afirma GEC and GSC to Nodules Without Molecular Testing in Cytologically Indeterminate Thyroid Nodules

Background

Analysis of cytologically indeterminate thyroid nodules with Afirma Gene Expression Classifier (GEC) and Genomic Sequencing Classifier (GSC) can reduce surgical rate and increase malignancy rate of surgically resected indeterminate nodules.

Methods

Retrospective cohort analysis of all adults with cytologically indeterminate thyroid nodules from January 2013 through December 2019. We compared surgical and malignancy rates of those without molecular testing to those with GEC or GSC, analyzed test performance between GEC and GSC, and identified variables associated with molecular testing.

Results

468 indeterminate thyroid nodules were included. No molecular testing was performed in 273, 71 had GEC, and 124 had GSC testing. Surgical rate was 68% in the group without molecular testing, 59% in GEC, and 40% in GSC. Malignancy rate was 20% with no molecular testing, 22% in GEC, and 39% in GSC (P = 0.022). GEC benign call rate (BCR) was 46%; sensitivity, 100%; specificity, 61%; and positive predictive value (PPV), 28%. GSC BCR was 60%; sensitivity, 94%; specificity, 76%; and PPV, 41%. Those with no molecular testing had larger nodule size, preoperative growth of nodules, and constrictive symptoms and those who underwent surgery in the no molecular testing group had higher body mass index, constrictive symptoms, higher Thyroid Imaging Reporting and Data System and Bethesda classifications. Type of provider was also associated with the decision to undergo surgery.

Conclusion

Implementation of GEC showed no effect on surgical or malignancy rate, but GSC resulted in significantly lower surgical and higher malignancy rates. This study provides insight into the factors that affect the real-world use of these molecular markers preoperatively in indeterminate thyroid nodules.

Ionizing Radiation Induces Resistant Glioblastoma Stem-Like Cells by Promoting Autophagy via the Wnt/β-Catenin Pathway

Therapeutic resistance in recurrent glioblastoma multiforme (GBM) after concurrent chemoradiotherapy (CCRT) is a challenging issue. Although standard fractionated radiation is essential to treat GBM, it has led to local recurrence along with therapy-resistant cells in the ionizing radiation (IR) field. Lines of evidence showed cancer stem cells (CSCs) play a vital role in therapy resistance in many cancer types, including GBM. However, the molecular mechanism is poorly understood. Here, we proposed that autophagy could be involved in GSC induction for radioresistance. In a clinical setting, patients who received radiation/chemotherapy had higher LC3II expression and showed poor overall survival compared with those with low LC3 II. In a cell model, U87MG and GBM8401 expressed high level of stemness markers CD133, CD44, Nestin, and autophagy marker P62/LC3II after receiving standard fractionated IR. Furthermore, Wnt/β-catenin proved to be a potential pathway and related to P62 by using proteasome inhibitor (MG132). Moreover, pharmacological inhibition of autophagy with BAF and CQ inhibit GSC cell growth by impairing autophagy flux as demonstrated by decrease Nestin, CD133, and SOX-2 levels. In conclusion, we demonstrated that fractionated IR could induce GSCs with the stemness phenotype by P62-mediated autophagy through the Wnt/β-catenin for radioresistance. This study offers a new therapeutic strategy for targeting GBM in the future.

Mitochondria's Role in the Maintenance of Cancer Stem Cells in Glioblastoma

Glioblastoma (GBM), one of the deadliest primary brain malignancies, is characterized by a high recurrence rate due to its limited response to existing therapeutic strategies such as chemotherapy, radiation therapy, and surgery. Several mechanisms and pathways have been identified to be responsible for GBM therapeutic resistance. Glioblastoma stem cells (GSCs) are known culprits of GBM resistance to therapy. GSCs are characterized by their unique self-renewal, differentiating capacity, and proliferative potential. They form a heterogeneous population of cancer stem cells within the tumor and are further divided into different subpopulations. Their distinct molecular, genetic, dynamic, and metabolic features distinguish them from neural stem cells (NSCs) and differentiated GBM cells. Novel therapeutic strategies targeting GSCs could effectively reduce the tumor-initiating potential, hence, a thorough understanding of mechanisms involved in maintaining GSCs' stemness cannot be overemphasized. The mitochondrion, a regulator of cellular physiological processes such as autophagy, cellular respiration, reactive oxygen species (ROS) generation, apoptosis, DNA repair, and cell cycle control, has been implicated in various malignancies (for instance, breast, lung, and prostate cancer). Besides, the role of mitochondria in GBM has been extensively studied. For example, when stressors, such as irradiation and hypoxia are present, GSCs utilize specific cytoprotective mechanisms like the activation of mitochondrial stress pathways to survive the harsh environment. Proliferating GBM cells exhibit increased cytoplasmic glycolysis in comparison to terminally differentiated GBM cells and quiescent GSCs that rely more on oxidative phosphorylation (OXPHOS). Furthermore, the Warburg effect, which is characterized by increased tumor cell glycolysis and decreased mitochondrial metabolism in the presence of oxygen, has been observed in GBM. Herein, we highlight the importance of mitochondria in the maintenance of GSCs.

PRMT6 methylation of RCC1 regulates mitosis, tumorigenicity, and radiation response of glioblastoma stem cells

Aberrant cell proliferation is a hallmark of cancer, including glioblastoma (GBM). Here we report that protein arginine methyltransferase (PRMT) 6 activity is required for the proliferation, stem-like properties, and tumorigenicity of glioblastoma stem cells (GSCs), a subpopulation in GBM critical for malignancy. We identified a casein kinase 2 (CK2)-PRMT6-regulator of chromatin condensation 1 (RCC1) signaling axis whose activity is an important contributor to the stem-like properties and tumor biology of GSCs. CK2 phosphorylates and stabilizes PRMT6 through deubiquitylation, which promotes PRMT6 methylation of RCC1, which in turn is required for RCC1 association with chromatin and activation of RAN. Disruption of this pathway results in defects in mitosis. EPZ020411, a specific small-molecule inhibitor for PRMT6, suppresses RCC1 arginine methylation and improves the cytotoxic activity of radiotherapy against GSC brain tumor xenografts. This study identifies a CK2α-PRMT6-RCC1 signaling axis that can be therapeutically targeted in the treatment of GBM.

Aging shifts mitochondrial dynamics toward fission to promote germline stem cell loss

Changes in mitochondrial dynamics (fusion and fission) are known to occur during stem cell differentiation; however, the role of this phenomenon in tissue aging remains unclear. Here, we report that mitochondrial dynamics are shifted toward fission during aging of Drosophila ovarian germline stem cells (GSCs), and this shift contributes to aging-related GSC loss. We found that as GSCs age, mitochondrial fragmentation and expression of the mitochondrial fission regulator, Dynamin-related protein (Drp1), are both increased, while mitochondrial membrane potential is reduced. Moreover, preventing mitochondrial fusion in GSCs results in highly fragmented depolarized mitochondria, decreased BMP stemness signaling, impaired fatty acid metabolism, and GSC loss. Conversely, forcing mitochondrial elongation promotes GSC attachment to the niche. Importantly, maintenance of aging GSCs can be enhanced by suppressing Drp1 expression to prevent mitochondrial fission or treating with rapamycin, which is known to promote autophagy via TOR inhibition. Overall, our results show that mitochondrial dynamics are altered during physiological aging, affecting stem cell homeostasis via coordinated changes in stemness signaling, niche contact, and cellular metabolism. Such effects may also be highly relevant to other stem cell types and aging-induced tissue degeneration.

Drosophila YBX1 homolog YPS promotes ovarian germ line stem cell development by preferentially recognizing 5-methylcytosine RNAs

5-Methylcytosine (m⁵C) is a RNA modification that exists in tRNAs and rRNAs and was recently found in mRNAs. Although it has been suggested to regulate diverse biological functions, whether m⁵C RNA modification influences adult stem cell development remains undetermined. In this study, we show that Ypsilon schachtel (YPS), a homolog of human Y box binding protein 1 (YBX1), promotes germ line stem cell (GSC) maintenance, proliferation, and differentiation in the Drosophila ovary by preferentially binding to m⁵C-containing RNAs. YPS is genetically demonstrated to function intrinsically for GSC maintenance, proliferation, and progeny differentiation in the Drosophila ovary, and human YBX1 can functionally replace YPS to support normal GSC development. Highly conserved cold-shock domains (CSDs) of YPS and YBX1 preferentially bind to m⁵C RNA in vitro. Moreover, YPS also preferentially binds to m⁵C-containing RNAs, including mRNAs, in germ cells. The crystal structure of the YBX1 CSD-RNA complex reveals that both hydrophobic stacking and hydrogen bonds are critical for m⁵C binding. Overexpression of RNA-binding-defective YPS and YBX1 proteins disrupts GSC development. Taken together, our findings show that m⁵C RNA modification plays an important role in adult stem cell development.

WD40 protein Wuho controls germline homeostasis via TRIM-NHL tumor suppressor Mei-p26 in Drosophila

WD40 proteins control many cellular processes via protein interactions. Drosophila Wuho (Wh, a WD40 protein) controls fertility, although the involved mechanisms are unclear. Here, we show that Wh promotion of Mei-p26 (a human TRIM32 ortholog) function maintains ovarian germ cell homeostasis. Wh and Mei-p26 are epistatically linked, with wh and mei-p26 mutants showing nearly identical phenotypes, including germline stem cell (GSC) loss, stem-cyst formation due to incomplete cytokinesis between GSCs and daughter cells, and overproliferation of GSC progeny. Mechanistically, Wh interacts with Mei-p26 in different cellular contexts to induce cell type-specific effects. In GSCs, Wh and Mei-p26 promote BMP stemness signaling for proper GSC division and maintenance. In GSC progeny, Wh and Mei-p26 silence nanos translation, downregulate a subset of microRNAs involved in germ cell differentiation and suppress ribosomal biogenesis via dMyc to limit germ cell mitosis. We also found that the human ortholog of Wh (WDR4) interacts with TRIM32 in human cells. Our results show that Wh is a regulator of Mei-p26 in Drosophila germ cells and suggest that the WD40-TRIM interaction may also control tissue homeostasis in other stem cell systems.

Molecular and cellular intratumoral heterogeneity in primary glioblastoma: clinical and translational implications

Glioblastoma (GBM), the most common primary malignant brain tumor in adults, is associated with significant morbidity and mortality despite maximal safe resection followed by chemo- and radiotherapy. GBMs contain self-renewing, tumorigenic glioma stem cells that contribute to tumor initiation, heterogeneity, therapeutic resistance, and recurrence. Intratumoral heterogeneity (ITH) of GBMs is also a major contributing factor to poor clinical outcomes associated with these high-grade glial tumors. Herein, the authors summarize recent discoveries and advances in the molecular and phenotypic characterization of GBMs with particular focus on ITH. In so doing, they attempt to highlight recent advances in molecular signatures/properties and metabolic alterations in an effort to clarify translational implications that may ultimately improve clinical outcomes.

The exocyst functions in niche cells to promote germline stem cell differentiation by directly controlling EGFR membrane trafficking

The niche controls stem cell self-renewal and differentiation in animal tissues. Although the exocyst is known to be important for protein membrane trafficking and secretion, its role in stem cells and niches has never been reported. Here, this study shows that the exocyst functions in the niche to promote germline stem cell (GSC) progeny differentiation in the Drosophila ovary by directly regulating EGFR membrane trafficking and signaling. Inactivation of exocyst components in inner germarial sheath cells, which form the differentiation niche, causes a severe GSC differentiation defect. The exocyst is required for maintaining niche cells and preventing BMP signaling in GSC progeny by promoting EGFR membrane targeting and signaling through direct association with EGFR. Finally, it is also required for EGFR membrane targeting, recycling and signaling in human cells. Therefore, this study reveals a novel function of the exocyst in niche cells to promote stem cell progeny differentiation by directly controlling EGFR membrane trafficking and signaling in vivo, and also provides important insight into how the niche controls stem cell progeny differentiation at the molecular level.

Generation of Inducible Gene-Switched GAL4 Expressed in the Drosophila Female Germline Stem Cell Niche

The stem cell niche, a regulatory microenvironment, houses and regulates stem cells for maintenance of tissues throughout an organism's lifespan. While it is known that stem cell function declines with age, the role of niche cells in this decline is not completely understood. Drosophila exhibits a short lifespan with well-characterized ovarian germline stem cells (GSCs) and niche compartments, providing a good model with which to study stem cell biology. However, no inducible tools for temporal and spatial control of gene expression in the GSC-niche unit have been previously developed for aging studies. The current UAS-GAL4 systems are not ideal for aging studies because fly physiological aging may be affected by the temperature shifts used to manipulate GAL4 activity. Additionally, the actual needs of the aged niche may be masked by continuously driven gene expression. Since GeneSwitch GAL4 is conveniently activated by the steroid RU486 (mifepristone), we conducted an enhancer-trap screen to isolate GeneSwitch GAL4 lines with expression in the GSC-niche unit. We identified six lines with expression in germarial somatic cells, and two lines (#2305 and #2261) with expression in niche cap cells, the major constituent of the GSC niche. The use of lines #2305 or #2261 to overexpress Drosophila insulin-like peptide 2, which maintains GSC lifespan, in aged niche cap cells significantly delayed age-dependent GSC loss. These results support the notion that insulin signaling is beneficial for maintaining aged stem cells and also validate the utility of our GeneSwitch GAL4 lines for studying stem cell aging.

Independent Comparison of the Afirma Genomic Sequencing Classifier and Gene Expression Classifier for Cytologically Indeterminate Thyroid Nodules

Background: For thyroid nodules with indeterminate cytology, the Afirma Gene Expression Classifier (GEC) identified benign nodules to reduce diagnostic surgery, though many nodules classified as suspicious still proved histopathologically benign. The current Afirma Genomic Sequencing Classifier (GSC) demonstrates improved specificity, suggesting more nodules will have a benign result (benign call rate [BCR]), but independent data are needed to confirm this in clinical practice. Methods: Retrospective analysis was performed of all Bethesda III or IV cytology thyroid nodules ≥1 cm tested with GEC (between January 1, 2011, and July 19, 2017) or GSC (between July 20, 2017, and August 27, 2018) at the authors' institution. Afirma testing was not performed reflectively for all nodules with Bethesda III or IV cytology, but rather was applied based on physician-patient decision making. Demographic, sonographic, and cytologic data were collected. The BCR for GEC- versus GSC-tested nodules was compared and further stratified by Bethesda classifications. Results: The study evaluated 600 nodules in 563 patients tested with either GEC (n = 486) or GSC (n = 114). The BCR was 233/486 (47.9%) for the GEC compared to 75/114 (65.8%) for the GSC (p = 0.0006). Hürthle-cell cytology was present in 99/486 (20.4%) nodules in the GEC group compared to 31/114 (27.2%) nodules in the GSC group (p = 0.28). The GSC BCR was significantly higher than the GEC BCR for Bethesda III nodules characterized by Hürthle cells (p = 0.006), but the BCRs were similar for nodules with architectural or cytologic atypia. In Bethesda IV nodules suspicious for follicular neoplasm, BCR for the GEC and GSC were similar (p = 0.68), but for cytology suspicious for Hürthle-cell neoplasm, the GSC BCR was 68.2% (15/22) compared to the GEC BCR of 16.4% (10/61; p < 0.0001). Positive predictive value in resected nodules with a suspicious result was 16/32 (50%) for GSC nodules and 75/221 (33.9%) for GEC nodules (p = 0.1). Conclusions: The higher BCR for the GSC compared to the GEC for indeterminate thyroid nodules, predominantly among nodules with Hürthle-cell cytology, will likely lead to further reduction in surgical management.

Knockdown of long non-coding RNA PCAT1 in glioma stem cells promotes radiation sensitivity

This study aimed to investigate the function of glioma stem cells (GSCs) and the role of PCAT1. This study dissociated the differences between GSCs and glioma cells in terms of apoptosis rate and γH2AX positive cells levels after radiation. Microarray was carried out to detect that expressed PCAT1, and it was testified by RT-qPCR. After transfection, GSCs were used to investigate the influence of PCAT1 on radiation sensitivity. Sphere-formation capability was first examined. Cell apoptosis rate after radiation of 0 Gy or 6 Gy was analyzed by flow cytometry, and the level of γH2AX positive cells after 6 Gy radiation were compared. CCK8 assay was used to investigate the cell proliferation and RT-qPCR was used to examine miR-129-5p and HMGB1 expression. GSCs exhibited great capability in sphere formation and lower expression in apoptosis and γH2AX positive cells rates after 6 Gy radiation. PCAT1 had higher expression in GSCs. PCAT1 knockdown restrained the sphere-formation ability, increased the apoptosis rate and DNA damage under the treatment of radiation. Moreover, knockdown of PCAT1 inhibited the cell proliferation. In addition, silencing PCAT1 could increase the expression of miR-129-5p and decrease the expression of HMGB1. PCAT1 was overexpressed in GSCs and played a facilitating role in radiation resistance.

Smad-Independent BMP Signaling in Somatic Cells Limits the Size of the Germline Stem Cell Pool

In developing organisms, proper tuning of the number of stem cells within a niche is critical for the maintenance of adult tissues; however, the involved mechanisms remain largely unclear. Here, we demonstrate that Thickveins (Tkv), a type I bone morphogenetic protein (BMP) receptor, acts in the Drosophila developing ovarian soma through a Smad-independent pathway to shape the distribution of BMP signal within the niche, impacting germline stem cell (GSC) recruitment and maintenance. Somatic Tkv promotes Egfr signaling to silence transcription of Dally, which localizes BMP signals on the cell surface. In parallel, Tkv promotes Hh signaling, which promotes escort cell cellular protrusions and upregulates expression of the Drosophila BMP homolog, Dpp, forming a positive feedback loop that enhances Tkv signaling and strengthens the niche boundary. Our results reveal a role for non-canonical BMP signaling in the soma during GSC establishment and generally illustrate how complex, cell-specific BMP signaling mediates niche-stem cell interactions.

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Tkv, a BMP receptor, in the developing ovarian soma controls fertility

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Knockdown Tkv in the developing soma causes ectopic germline stem cell (GSC) accumulation

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Tkv in the soma controls GSC number by limiting BMPs within the GSC niche

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BMP-Tkv signaling in the soma limits GSC number via Egfr and Hh signaling

A Targeted RNAi Screen Reveals Drosophila Female-Sterile Genes That Control the Size of Germline Stem Cell Niche During Development

Adult stem cells maintain tissue homeostasis. This unique capability largely depends on the stem cell niche, a specialized microenvironment, which preserves stem cell identity through physical contacts and secreted factors. In many cancers, latent tumor cell niches are thought to house stem cells and aid tumor initiation. However, in developing tissue and cancer it is unclear how the niche is established. The well-characterized germline stem cells (GSCs) and niches in the Drosophila melanogaster ovary provide an excellent model to address this fundamental issue. As such, we conducted a small-scale RNAi screen of 560 individually expressed UAS-RNAi lines with targets implicated in female fertility. RNAi was expressed in the soma of larval gonads, and screening for reduced egg production and abnormal ovarian morphology was performed in adults. Twenty candidates that affect ovarian development were identified and subsequently knocked down in the soma only during niche formation. Feminization factors (Transformer, Sex lethal, and Virilizer), a histone methyltransferase (Enhancer of Zeste), a transcriptional machinery component (Enhancer of yellow 1), a chromatin remodeling complex member (Enhancer of yellow 3) and a chromosome passenger complex constituent (Incenp) were identified as potentially functioning in the control of niche size. The identification of these molecules highlights specific molecular events that are critical for niche formation and will provide a basis for future studies to fully understand the mechanisms of GSC recruitment and maintenance.

The natural HLA ligandome of glioblastoma stem-like cells: antigen discovery for T cell-based immunotherapy

Glioblastoma is the most frequent malignant primary brain tumor. In a hierarchical tumor model, glioblastoma stem-like cells (GSC) play a major role in tumor initiation and maintenance as well as in therapy resistance and recurrence. Thus, targeting this cellular subset may be key to effective immunotherapy. Here, we present a mass spectrometry-based analysis of HLA-presented peptidomes of GSC and glioblastoma patient specimens. Based on the analysis of patient samples (n = 9) and GSC (n = 3), we performed comparative HLA peptidome profiling against a dataset of normal human tissues. Using this immunopeptidome-centric approach we could clearly delineate a subset of naturally presented, GSC-associated HLA ligands, which might serve as highly specific targets for T cell-based immunotherapy. In total, we identified 17 antigens represented by 41 different HLA ligands showing natural and exclusive presentation both on GSC and patient samples. Importantly, in vitro immunogenicity and antigen-specific target cell killing assays suggest these peptides to be epitopes of functional CD8+ T cell responses, thus rendering them prime candidates for antigen-specific immunotherapy of glioblastoma.

DICER governs characteristics of glioma stem cells and the resulting tumors in xenograft mouse models of glioblastoma

The RNAse III endonuclease DICER is a key regulator of microRNA (miRNA) biogenesis and is frequently decreased in a variety of malignancies. We characterized the role of DICER in glioblastoma (GB), specifically demonstrating its effects on the ability of glioma stem-like cells (GSCs) to form tumors in a mouse model of GB. DICER silencing in GSCs reduced their stem cell characteristics, while tumors arising from these cells were more aggressive, larger in volume, and displayed a higher proliferation index and lineage differentiation. The resulting tumors, however, were more sensitive to radiation treatment. Our results demonstrate that DICER silencing enhances the tumorigenic potential of GSCs, providing a platform for analysis of specific relevant miRNAs and development of potentially novel therapies against GB.

A novel gene signature based on five glioblastoma stem-like cell relevant genes predicts the survival of primary glioblastoma

PURPOSE

Primary glioblastoma (pGBM) is the most common and lethal type of neoplasms in the central nervous system, while the existing biomarkers, lacking consideration on the stemness changes of GBM cells, are not specific enough to predict the complex prognosis respectively. We aimed to build a high-efficiency prediction gene signature related to GBM cell stemness and investigate its prognostic value in primary glioblastoma.

METHODS

Differentially expressed genes were screened in GSE23806 database. The selected genes were then verified by univariate Cox regression in 591 patients from four enormous independent databases, including the Chinese Glioma Genome Atlas (CGGA), TCGA, REMBRANDT and GSE16011. Finally, the intersected genes were included to build the gene signature. GO analysis and GSEA were carried out to explore the bioinformatic implication.

RESULTS

The novel five-gene signature was used to identify high- and low-risk groups in the four databases, and the high-risk group showed notably poorer prognosis (P < 0.05). Gene ontology (GO) terms including "immune response", "apoptotic process", and "angiogenesis" were picked out by GO analysis and GSEA, which revealed that the gene signature was highly possibly related to the stemness of GSCs and predicting the prognosis of GBM effectively.

CONCLUSION

We built a gene signature with five glioblastoma stem-like cell (GSC) relevant genes, and predicted the survival in four independent databases effectively, which is possibly related to the stemness of GSCs in pGBM. Several GO terms were investigated to be correlated to the signature. The signature can predict the prognosis of glioblastoma efficiently.

DIGIT Is a Conserved Long Noncoding RNA that Regulates GSC Expression to Control Definitive Endoderm Differentiation of Embryonic Stem Cells

Long noncoding RNAs (lncRNAs) exhibit diverse functions, including regulation of development. Here, we combine genome-wide mapping of SMAD3 occupancy with expression analysis to identify lncRNAs induced by activin signaling during endoderm differentiation of human embryonic stem cells (hESCs). We find that DIGIT is divergent to Goosecoid (GSC) and expressed during endoderm differentiation. Deletion of the SMAD3-occupied enhancer proximal to DIGIT inhibits DIGIT and GSC expression and definitive endoderm differentiation. Disruption of the gene encoding DIGIT and depletion of the DIGIT transcript reveal that DIGIT is required for definitive endoderm differentiation. In addition, we identify the mouse ortholog of DIGIT and show that it is expressed during development and promotes definitive endoderm differentiation of mouse ESCs. DIGIT regulates GSC in trans, and activation of endogenous GSC expression is sufficient to rescue definitive endoderm differentiation in DIGIT-deficient hESCs. Our study defines DIGIT as a conserved noncoding developmental regulator of definitive endoderm.

Malignant Glioma In Vitro Models: On the Utilization of Stem-like Cells

Recent publications on the molecular characterization of malignant glioma have had profound impact on the appreciation of tumoral heterogeneity within and between patients. Both these phenomena are implicated in the variability in clinical outcome between patients, as well as the inevitable recurrence of these tumors after conventional treatment. The advent of selective cell culture protocols for the propagation of patient-derived glioma stem-like cells (GSCs) provides researchers the ability to selectively study the cells that could be at the root of tumor proliferation and resistance to therapy. As these techniques are widely applied in contemporary studies and becoming the preferred in vitro model, molecular characterization of GSCs is considered pivotal for the identification and advancement of novel therapies for this devastating disease. This review aims to provide an overview of canonical molecular alterations defining subtypes of malignant glioma as derived from genotypic, transcriptomic and epigenetic profiling in relation to their representation in GSC models. The distribution of these hallmark alterations as found in characterization studies of GSCs is compared between publications. Finally, conclusions of these studies with respect to coverage of driving alterations and translational relevance are provided. By doing so, we provide a contemporary overview of scientific results derived from GSC models and hopefully create appreciation of the advantages and caveats of utilizing these models for studying malignant glioma.

Glioblastoma stem-like cells secrete the pro-angiogenic VEGF-A factor in extracellular vesicles

Glioblastoma multiforme (GBM) are mortifying brain tumours that contain a subpopulation of tumour cells with stem-like properties, termed glioblastoma stem-like cells (GSCs). GSCs largely contribute to tumour initiation, propagation and resistance to current anti-cancer therapies. GSCs are situated in perivascular niches, closely associated with brain microvascular endothelial cells, thereby involved in bidirectional molecular and cellular interactions. Moreover, extracellular vesicles are suspected to carry essential information that can adapt the microenvironment to the tumour’s needs, including tumour-induced angiogenesis. In GBM, extracellular vesicles produced by differentiated tumour cells and GSCs were demonstrated to disseminate locally and at distance. Here, we report that the pro-angiogenic pro-permeability factor VEGF-A is carried in extracellular vesicles secreted from ex vivo cultured patient-derived GSCs. Of note, extracellular vesicle-derived VEGF-A contributes to the in vitro elevation of permeability and angiogenic potential in human brain endothelial cells. Indeed, VEGF-A silencing in GSCs compromised in vitro extracellular vesicle-mediated increase in permeability and angiogenesis. From a clinical standpoint, extracellular vesicles isolated from circulating blood of GBM patients present higher levels of VEGF-A, as compared to healthy donors. Overall, our results suggest that extracellular vesicle-harboured VEGF-A targets brain endothelial cells and might impact their ability to form new vessels. Thus, tumour-released EV cargo might emerge as an instrumental part of the tumour-induced angiogenesis and vascular permeability modus operandi in GBM.

The transcriptional modulator HMGA2 promotes stemness and tumorigenicity in glioblastoma

Glioblastoma (GBM) contains a population of stem-like cells that promote tumor invasion and resistance to therapy. Identifying and targeting stem cell factors in GBM may lead to the development of more effective therapies. High Mobility Group AT-hook 2 (HMGA2) is a transcriptional modulator that mediates motility and self-renewal in normal and cancer stem cells. We identified increased expression of HMGA2 in the majority of primary human GBM tumors and cell lines compared to normal brain. Additionally, HMGA2 expression was increased in CD133+ GBM neurosphere cells compared to CD133- cells. Targeting HMGA2 with lentiviral short hairpin RNA (shRNA) led to decreased GBM stemness, invasion, and tumorigenicity. Ectopic expression of HMGA2 in GBM cell lines promoted stemness, invasion, and tumorigenicity. Our data suggests that targeting HMGA2 in GBM may be therapeutically beneficial.

Short-Term Differentiation of Glioblastoma Stem Cells Induces Hypoxia Tolerance

Glioblastoma is the most common and malignant brain cancer. In spite of surgical removal, radiation and chemotherapy, this cancer recurs within short time and median survival after diagnosis is less than a year. Glioblastoma stem cells (GSCs) left in the brain after surgery is thought to explain the inevitable recurrence of the tumor. Although hypoxia is a prime factor contributing to treatment resistance in many cancers, its effect on GSC has been little studied. Especially how differentiation influences the tolerance to acute hypoxia in GSCs is not well explored. We cultured GSCs from three patient biopsies and exposed these and their differentiated (1- and 4-weeks) progeny to acute hypoxia while monitoring intracellular calcium and mitochondrial membrane potential (ΔΨ_m). Undifferentiated GSCs were not hypoxia tolerant, showing both calcium overload and mitochondrial depolarization. One week differentiated cells were the most tolerant to hypoxia, preserving intracellular calcium stability and ΔΨ_m during 15 min of acute hypoxia. After 4 weeks of differentiation, mitochondrial mass was significantly reduced. In these cells calcium homeostasis was maintained during hypoxia, although the mitochondria were depolarized, suggesting a reduced mitochondrial dependency. Basal metabolic rate increased by differentiation, however, low oxygen consumption and high ΔΨ_m in undifferentiated GSCs did not provide hypoxia tolerance. The results suggest that undifferentiated GSCs are oxygen dependent, and that limited differentiation induces relative hypoxia tolerance. Hypoxia tolerance may be a factor involved in high-grade malignancy. This warrants a careful approach to differentiation as a glioblastoma treatment strategy.

Without children is required for Stat-mediated zfh1 transcription and for germline stem cell differentiation

Tissue homeostasis is maintained by balancing stem cell self-renewal and differentiation. How surrounding cells support this process has not been entirely resolved. Here we show that the chromatin and telomere-binding factor Without children (Woc) is required for maintaining the association of escort cells (ECs) with germ cells in adult ovaries. This tight association is essential for germline stem cell (GSC) differentiation into cysts. Woc is also required in larval ovaries for the association of intermingled cells (ICs) with primordial germ cells. Reduction in the levels of two other proteins, Stat92E and its target Zfh1, produce phenotypes similar to woc in both larval and adult ovaries, suggesting a molecular connection between these three proteins. Antibody staining and RT-qPCR demonstrate that Zfh1 levels are increased in somatic cells that contact germ cells, and that Woc is required for a Stat92E-mediated upregulation of zfh1 transcription. Our results further demonstrate that overexpression of Zfh1 in ECs can rescue GSC differentiation in woc-deficient ovaries. Thus, Zfh1 is a major Woc target in ECs. Stat signalling in niche cells has been previously shown to maintain GSCs non-autonomously. We now show that Stat92E also promotes GSC differentiation. Our results highlight the Woc-Stat-Zfh1 module as promoting somatic encapsulation of germ cells throughout their development. Each somatic cell type can then provide the germline with the support it requires at that particular stage. Stat is thus a permissive factor, which explains its apparently opposite roles in GSC maintenance and differentiation.

Poly(ADP-ribose) glycohydrolase and poly(ADP-ribose)-interacting protein Hrp38 regulate pattern formation during Drosophila eye development

Drosophila Hrp38, a homolog of human hnRNP A1, has been shown to regulate splicing, but its function can be modified by poly(ADP-ribosyl)ation. Notwithstanding such findings, our understanding of the roles of poly(ADP-ribosyl)ated Hrp38 on development is limited. Here, we have demonstrated that Hrp38 is essential for fly eye development based on a rough-eye phenotype with disorganized ommatidia observed in adult escapers of the hrp38 mutant. We also observed that poly(ADP-ribose) glycohydrolase (Parg) loss-of-function, which caused increased Hrp38 poly(ADP-ribosyl)ation, also resulted in the rough-eye phenotype with disrupted ommatidial lattice and reduced number of photoreceptor cells. In addition, ectopic expression of DE-cadherin, which is required for retinal morphogenesis, fully rescued the rough-eye phenotype of the hrp38 mutant. Similarly, Parg mutant eye clones had decreased expression level of DE-cadherin with orientation defects, which is reminiscent of DE-cadherin mutant eye phenotype. Therefore, our results suggest that Hrp38 poly(ADP-ribosyl)ation controls eye pattern formation via regulation of DE-cadherin expression, a finding which has implications for understanding the pathogenic mechanisms of Hrp38-related Fragile X syndrome and PARP1-related retinal degeneration diseases.

Comparison of glioma stem cells to neural stem cells from the adult human brain identifies dysregulated Wnt- signaling and a fingerprint associated with clinical outcome

Glioblastoma is the most common brain tumor. Median survival in unselected patients is <10 months. The tumor harbors stem-like cells that self-renew and propagate upon serial transplantation in mice, although the clinical relevance of these cells has not been well documented. We have performed the first genome-wide analysis that directly relates the gene expression profile of nine enriched populations of glioblastoma stem cells (GSCs) to five identically isolated and cultivated populations of stem cells from the normal adult human brain. Although the two cell types share common stem- and lineage-related markers, GSCs show a more heterogeneous gene expression. We identified a number of pathways that are dysregulated in GSCs. A subset of these pathways has previously been identified in leukemic stem cells, suggesting that cancer stem cells of different origin may have common features. Genes upregulated in GSCs were also highly expressed in embryonic and induced pluripotent stem cells. We found that canonical Wnt-signaling plays an important role in GSCs, but not in adult human neural stem cells. As well we identified a 30-gene signature highly overexpressed in GSCs. The expression of these signature genes correlates with clinical outcome and demonstrates the clinical relevance of GSCs.