PRESS survey: PREvention of surgical site infection-a global pan-specialty survey of practice protocol

Background

Surgical site infections (SSI) complicate up to 40% of surgical procedures, leading to increased patient morbidity and mortality. Previous research identified disparities in SSI prevention guidelines and clinical practices across different institutions. The study aims to identify variations in SSI prevention practices within and between specialties and financial systems and provide a representation of existing SSI preventative measures to help improve the standardization of SSI prevention practices.

Methods

This collaborative cross-sectional survey will be aimed at pan-surgical specialties internationally. The study has been designed and will be reported in line with the CROSS and CHERRIES standards. An international study steering committee will design and internally validate the survey in multiple consensus-based rounds. This will be based on SSI prevention measures outlined in the CDC (2017), WHO (2018), NICE (2019), Wounds UK (2020) and the International Surgical Wound Complications Advisory Panel (ISWCAP) guidelines. The questionnaire will include demographics, SSI surveillance, preoperative, peri-operative and postoperative SSI prevention. Data will be collected on participants' surgical specialty, operative grade, of practice and financial healthcare system of practice. The online survey will be designed and disseminated using QualtricsXM Platform™ through national and international surgical colleges and societies, in addition to social media and snowballing. Data collection will be open for 3 months with reminders, and raking will be used to ascertain the sample. Responses will be analyzed, and the chi-square test used to evaluate the impact of SSI prevention variables on responses.

Discussion

Current SSI prevention practice in UK Vascular surgery varies considerably, with little consensus on many measures. Given the inconsistency in guidelines on how to prevent SSIs, there is a need for standardization. This survey will investigate the disparity in SSI preventative measures between different surgical fields and countries.

Genome-wide profiling of patient-derived glioblastoma stem-like cells reveals recurrent genetic and transcriptomic signatures associated with brain tumors

PURPOSE

Patient-derived cancer cell lines can be very useful to investigate genetic as well as epigenetic mechanisms of transformation and to test new drugs. In this multi-centric study, we performed genomic and transcriptomic characterization of a large set of patient-derived glioblastoma (GBM) stem-like cells (GSCs).

METHODS

94 (80 I surgery/14 II surgery) and 53 (42 I surgery/11 II surgery) GSCs lines underwent whole exome and trascriptome analysis, respectively.

RESULTS

Exome sequencing revealed TP53 as the main mutated gene (41/94 samples, 44%), followed by PTEN (33/94, 35%), RB1 (16/94, 17%) and NF1 (15/94, 16%), among other genes associated to brain tumors. One GSC sample bearing a BRAF p.V600E mutation showed sensitivity in vitro to a BRAF inhibitor. Gene Ontology and Reactome analysis uncovered several biological processes mostly associated to gliogenesis and glial cell differentiation, S - adenosylmethionine metabolic process, mismatch repair and methylation. Comparison of I and II surgery samples disclosed a similar distribution of mutated genes, with an overrepresentation of mutations in mismatch repair, cell cycle, p53 and methylation pathways in I surgery samples, and of mutations in receptor tyrosine kinase and MAPK signaling pathways in II surgery samples. Unsupervised hierarchical clustering of RNA-seq data produced 3 clusters characterized by distinctive sets of up-regulated genes and signaling pathways.

CONCLUSION

The availability of a large set of fully molecularly characterized GCSs represents a valuable public resource to support the advancement of precision oncology for the treatment of GBM.

Abstract 1246: Single-cell profiles of multiplexed in vivo models facilitate the characterization of phenotypic plasticity and invasion in glioblastoma

The lethality of glioblastoma and the failure of surgical treatment are in part attributable to the invasive properties of this cancer; however, our understanding of the cell-biological process is limited due to the complex representation of invasion phenotype in glioblastoma models. Here, to overcome this limitation, we developed an in vivo approach with human glioblastoma spheroid lines multiplexed for mouse intracranial xenografts. We validated this with 20 patient-derived models and identified, by 3’end single-cell RNA-sequencing (scRNA-seq) coupled with deconvolution analysis, in vivo models capable of infiltrating along the periphery of either neurons or blood vessels. We previously found that the diverse malignant cells in glioblastoma specimens exist in a limited set of four cellular states: neural progenitor-like (NPC-like), oligodendrocyte progenitor-like (OPC-like), astrocyte-like (AC-like), and mesenchymal-like (MES-like), with potential for state plasticity under the influence of tumor microenvironment. To determine whether or not the cell state heterogeneity is implicated in glioblastoma invasion, we profiled and characterized programs, states, and clonality of invading glioblastoma cells by comparing cells from the contralateral invasive edge to their counterparts residing at the original bulk tumor. This analysis showed evidence of a bi-directional state transitioning model for cells undergoing distinct environmental spaces. Exploration of cell state distribution at the primary tumors revealed that presence of an OPC-like state was significantly associated with invasion phenotype regardless of the infiltration routes. Our results suggest that cellular plasticity may be a prerequisite for the topographically diffusive nature of glioblastoma, urging further assessment by perturbing critical regulators of the cellular state programs. In conclusion, this work describes multiplexed in vivo models as an enabling platform for the rapid interrogation of patient-derived xenografts, coupling the molecularly measurable states with functional identity driving malignant phenotypes such as cancer invasion.

Citation Format: Toshiro Hara, Rony Chanoch-Myers, Alissa Greenwald, Lillian Bussema, Jinan Behnan, Rossella Galli, Hiroaki Wakimoto, Itay Tirosh, Mario Suvà. Single-cell profiles of multiplexed in vivo models facilitate the characterization of phenotypic plasticity and invasion in glioblastoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 1246.

Aberrant L-Fucose Accumulation and Increased Core Fucosylation Are Metabolic Liabilities in Mesenchymal Glioblastoma

Glioblastoma (GBM) is a common and deadly form of brain tumor in adults. Dysregulated metabolism in GBM offers an opportunity to deploy metabolic interventions as precise therapeutic strategies. To identify the molecular drivers and the modalities by which different molecular subgroups of GBM exploit metabolic rewiring to sustain tumor progression, we interrogated the transcriptome, the metabolome, and the glycoproteome of human subgroup-specific GBM sphere-forming cells (GSC). L-fucose abundance and core fucosylation activation were elevated in mesenchymal (MES) compared with proneural GSCs; this pattern was retained in subgroup-specific xenografts and in subgroup-affiliated human patient samples. Genetic and pharmacological inhibition of core fucosylation significantly reduced tumor growth in MES GBM preclinical models. Liquid chromatography-mass spectrometry (LC-MS)-based glycoproteomic screening indicated that most MES-restricted core-fucosylated proteins are involved in therapeutically relevant GBM pathological processes, such as extracellular matrix interaction, cell adhesion, and integrin-mediated signaling. Selective L-fucose accumulation in MES GBMs was observed using preclinical minimally invasive PET, implicating this metabolite as a potential subgroup-restricted biomarker.Overall, these findings indicate that L-fucose pathway activation in MES GBM is a subgroup-specific dependency that could provide diagnostic markers and actionable therapeutic targets.

SIGNIFICANCE

Metabolic characterization of subgroup-specific glioblastoma (GBM) sphere-forming cells identifies the L-fucose pathway as a vulnerability restricted to mesenchymal GBM, disclosing a potential precision medicine strategy for targeting cancer metabolism.

Asymptomatic bacteriuria in candidates for active treatment of renal stones: results from an international multicentric study on more than 2600 patients

The occurrence of asymptomatic bacteriuria concomitant to urolithiasis is an issue for patients undergoing renal stone treatment. Disposing of a preoperative urine culture is essential to reduce the risk of septic events. The endpoint of the study is to report which characteristics of candidates for renal stone treatment are frequently associated with positive urine culture. 2605 patients were retrospectively enrolled from 14 centers; inclusion criteria were age > 18 and presence of a single renal stone 1-2 cm in size. The variables collected included age, gender, previous renal surgery, comorbidities, skin-to-stone distance, stone size, location, density, presence of hydronephrosis. After a descriptive analysis, the association between continuous and categorical variables and the presence of positive urine culture was assessed using a logistic regression model. Overall, 240/2605 patients (9%) had preoperative bacteriuria. Positive urine culture was more frequent in females, patients with previous renal interventions, chronic kidney disease, congenital anomalies, larger stones, increased density. Multivariate analysis demonstrated that previous renal interventions (OR 2.6; 95% CI 1.9-3.4; p < 0.001), renal-related comorbidities (OR 1.31; 95% CI 1.19-1.4; p < 0.001), higher stone size (OR 1.06; 95% CI 1.02-1.1; p = 0.01) and density (OR 1.00; 95% CI 1.0-1.00; p = 0.02) were associated with bacteriuria; male gender and lower caliceal location were inversely related to it. Beyond expected risk factors, such as female gender, other parameters are seemingly favoring the presence of positive urine culture. The awareness of variables associated with bacteriuria allows to assess which individuals are at increased risk of presenting bacteriuria and reduce the rate of septic complications.

Comparison of right hemicolectomies with and without complete mesocolic excision (CME)

Objective

Since the concept of complete mesocolic excision (CME) in right hemicolectomies was introduced, it is still under debate if all patients require this radical technique.

Methods

Patients with adenocarcinoma of the colon undergoing right hemicolectomies at our hospital were retrospectively analyzed and stratified in a non-CME group (08/2014-04/2018) and a CME group (05/2018-11/2021). Patients were compared in regard to clinical, histopathological and prognostic parameters. CME were classified according to Benz et al.

Results

A total of 130 right hemicolectomies were performed, 33 (25.4%) patients were excluded due to other pathologies or emergency patients. Finally, 97 patients were included (53 in the CME group, 39 in the non-CME group). No difference in patient's characteristics were found except more male patients in the CME group (20 vs. 6; p=0.02). Tumors in the CME group were mainly located in the colon ascendens (66.0%), in the non-CME group in the coecum (48.7%; n.s.). In the CME group, 26 of 53 (49.1%) patients were operated laparoscopically compared to 10 of 39 (25.6%) patients in the non-CME group. Da Vinci system were used exclusively in the CME group (5 of 53 (9.4%); p=0.003). TNM classification, histology and UICC stadium showed no significant difference. In total, 50 (94.3%) surgical specimen were classification either as CME 0 or 1. In average, 35.2 lymph nodes (8.2% positive) were found in the CME group compared to 32.7 (16.2% positive) lymph nodes in the non-CME group (p=0.9). No relevant intraoperative complications occurred in both groups. Distance of the mesocolon were available in 39 (73.6%) patients in the CME group and 34 (37.1%) in the non-CME group; the distance tended to be longer in the CME group (mean 116.0 mm in CME group vs. 96.6 mm in non-CME group; p=0.09). Follow-up were 336.4 days in CME-group and 1210.4 days in the non-CME group. In the follow-up, 2 (5.1%) patients in the non-CME group developed a local recurrence in the smaller pelvis. No local recurrence occurred in the CME group (p=0.18). Distant metastasis occurred in 5 of 53 (9.4%) patients in the CME group and in 2 of 39 (5.4%) patients in the non-CME group (p=0.7).

Conclusion

This study shows that the benefit for CME in all performed right hemicolectomies is marginal and that the surgical standards was already high in the pre-CME era.

A multifactorial intervention to reduce use of antibiotics in acute uncomplicated diverticulitis – a single centre feasibility study

Objective

Standard treatment for uncomplicated diverticulitis in our institution consists of antibiotics. However, current evidence suggests that bacterial infection has a less predominant role than previously thought, and that uncomplicated acute diverticulitis may be a self-limiting condition in which inflammation can be managed without antibiotics. With the support of a multidisciplinary team we developed an intervention in order to reduce the use of antibiotics for patients with uncomplicated diverticular disease.

Methods

Standard practice and knowledge of current evidence were investigated with a structured survey sent to general practitioners and gastroenterologists with private practice in the area. A clinical process model for treatment of uncomplicated left-sided diverticulitis was created and exclusion criteria were selected in order to define patients with a high risk of developing complications. An educational intervention based on current evidence and the new treatment pathway was conducted on hospital staff as well as primary care physicians in the area in order to raise awareness about the possibility of avoiding antibiotics in uncomplicated diverticulitis. Patients were also involved and received an informative sheet about the rationale of the new treatment, the planned follow up and warning signs warranting further investigations and referral in case of outpatient treatment. All patients from May 2021 to December 2021 with a computed tomography-verified left-sided acute uncomplicated diverticulitis were included in the study and evaluated prospectively.

Results

Of 60 patients with acute uncomplicated diverticulitis, 23 (38%) were eligible for treatment without antibiotics. High inflammatory markers on presentation were the main reason (84%) for giving antibiotics. Adherence to the new policy was 74%. None of the 17 patients initially managed without antibiotics failed conservative treatment.

Conclusion

This project confirmed that treatment of uncomplicated diverticulitis without antibiotics can successfully be offered to a selected group of patients without altering the course of the disease. Further efforts are needed in order to overcome existing barriers to rational antimicrobial use such as lack of trust in new guidelines, general uncertainty and risk avoidance, patients’ expectations for antibiotic treatment, and fear of legal consequences.

CRISPR-based gene disruption and integration of high-avidity, WT1-specific T cell receptors improve antitumor T cell function

T cell receptor (TCR)-based therapy has the potential to induce durable clinical responses in patients with cancer by targeting intracellular tumor antigens with high sensitivity and by promoting T cell survival. However, the need for TCRs specific for shared oncogenic antigens and the need for manufacturing protocols able to redirect T cell specificity while preserving T cell fitness remain limiting factors. By longitudinal monitoring of T cell functionality and dynamics in 15 healthy donors, we isolated 19 TCRs specific for Wilms' tumor antigen 1 (WT1), which is overexpressed by several tumor types. TCRs recognized several peptides restricted by common human leukocyte antigen (HLA) alleles and displayed a wide range of functional avidities. We selected five high-avidity HLA-A*02:01-restricted TCRs, three that were specific to the less explored immunodominant WT1_37-45 and two that were specific to the noncanonical WT1_-78-64 epitopes, both naturally processed by primary acute myeloid leukemia (AML) blasts. With CRISPR-Cas9 genome editing tools, we combined TCR-targeted integration into the TCR α constant (TRAC) locus with TCR β constant (TRBC) knockout, thus avoiding TCRαβ mispairing and maximizing TCR expression and function. The engineered lymphocytes were enriched in memory stem T cells. A unique WT1_37-45-specific TCR showed antigen-specific responses and efficiently killed AML blasts, acute lymphoblastic leukemia blasts, and glioblastoma cells in vitro and in vivo in the absence of off-tumor toxicity. T cells engineered to express this receptor are being advanced into clinical development for AML immunotherapy and represent a candidate therapy for other WT1-expressing tumors.

mTORC1 promotes malignant large cell/anaplastic histology and is a targetable vulnerability in SHH-TP53 mutant medulloblastoma

Medulloblastoma (MB), one of the most malignant brain tumors of childhood, comprises distinct molecular subgroups, with p53 mutant sonic hedgehog-activated (SHH-activated) MB patients having a very severe outcome that is associated with unfavorable histological large cell/anaplastic (LC/A) features. To identify the molecular underpinnings of this phenotype, we analyzed a large cohort of MB developing in p53-deficient Ptch+/- SHH mice that, unexpectedly, showed LC/A traits that correlated with mTORC1 hyperactivation. Mechanistically, mTORC1 hyperactivation was mediated by a decrease in the p53-dependent expression of mTORC1 negative regulator Tsc2. Ectopic mTORC1 activation in mouse MB cancer stem cells (CSCs) promoted the in vivo acquisition of LC/A features and increased malignancy; accordingly, mTORC1 inhibition in p53-mutant Ptch+/- SHH MB and CSC-derived MB resulted in reduced tumor burden and aggressiveness. Most remarkably, mTORC1 hyperactivation was detected only in p53-mutant SHH MB patient samples, and treatment with rapamycin of a human preclinical model phenocopying this subgroup decreased tumor growth and malignancy. Thus, mTORC1 may act as a specific druggable target for this subset of SHH MB, resulting in the implementation of a stringent risk stratification and in the potentially rapid translation of this precision medicine approach into the clinical setting.

Conformable hierarchically engineered polymeric micromeshes enabling combinatorial therapies in brain tumours

The poor transport of molecular and nanoscale agents through the blood-brain barrier together with tumour heterogeneity contribute to the dismal prognosis in patients with glioblastoma multiforme. Here, a biodegradable implant (μMESH) is engineered in the form of a micrometre-sized poly(lactic-co-glycolic acid) mesh laid over a water-soluble poly(vinyl alcohol) layer. Upon poly(vinyl alcohol) dissolution, the flexible poly(lactic-co-glycolic acid) mesh conforms to the resected tumour cavity as docetaxel-loaded nanomedicines and diclofenac molecules are continuously and directly released into the adjacent tumour bed. In orthotopic brain cancer models, generated with a conventional, reference cell line and patient-derived cells, a single μMESH application, carrying 0.75 mg kg^-1 of docetaxel and diclofenac, abrogates disease recurrence up to eight months after tumour resection, with no appreciable adverse effects. Without tumour resection, the μMESH increases the median overall survival (∼30 d) as compared with the one-time intracranial deposition of docetaxel-loaded nanomedicines (15 d) or 10 cycles of systemically administered temozolomide (12 d). The μMESH modular structure, for the independent coloading of different molecules and nanomedicines, together with its mechanical flexibility, can be exploited to treat a variety of cancers, realizing patient-specific dosing and interventions.

POS1447 LOW-INTENSITY PULSED ELECTROMAGNETIC FIELDS IMPROVE PHYSICAL PERFORMANCE IN A DOSE-DEPENDENT MANNER: AN OBSERVATIONAL STUDY IN OLDER ADULTS WITH RHEUMATIC DISEASES

Background:

Low-intensity pulsed electromagnetic fields (PEMF) have been shown to improve gait parameters in frail older adults.1 Furthermore, the continuous exposure to PEMF (up to 1 year) have been demonstrated to produce progressive improvements in self-selected gait speed in older adults at risk of falling.2

Objectives:

To investigate the effects of two different treatment regimens of PEMF on physical performances in older adults presenting with rheumatoid arthritis (RA), osteoarthritis (OA) or severe osteoporosis (OP).

Methods:

Older adults presenting with RA, OA or OP, at increased risk of falls, evaluated in our Falls Prevention Clinic, were considered for a prospective observational study investigating the effects of PEMF on physical performances. PEMF were supplied by the THS 280 E device (THS-Therapeutic Solutions Srl, Milan, Italy). It provides a new therapeutic approach, named TEPS (Triple Energy Postural Stabilization), that represents an evolution of physical therapy.1,2 On the basis of the physician judgment, PEMF were administered following an intensive protocol, every 45 days (PEMF-45), or a standard validated protocol1,2, every 60 days (PEMF-60). All subjects were assessed at baseline and every 3 months with the following tests: 4 meters gait speed test [4MGS, seconds (sec)], timed up and go test (TUG, sec), chair stand test (CST, sec), short physical performance battery (SPPB, score), and hand grip strength (HGS) by hand dynamometer (Kg). Demographic, anthropometric and clinical characteristics, including pharmacological treatments and functional status were evaluated at baseline. Clinical and adverse events were assessed every 45 or 60 days after PEMF administration.

Results:

Overall, 94 patients were enrolled between January and December 2020. Of these, 43 subjects (N=33 PEMF-45, N=11 PEMF-60) with a valid 6-month follow-up assessment were considered for the current analysis. The two groups were comparable regarding the main baseline characteristics, and similar % of patients presented with RA, OA or OP. Mean age (±SE) was 78±7 in PEMF-45 and 77±7 in PEMF-60. As expected, all physical performance tests improved significantly from baseline to 6 months in both groups. Mean (±SE) 4MGS increased significantly more in PEMF-45 (from 3.24±0.12 sec to 2.83±0.18 sec) compared to PEMF-60 (from 3.22±0.21 sec to 3.02±0.30 sec, p=.018). Likewise, mean (±SE) CST improved more in PEMF-45 (from 12.4±0.9 sec to 8.7±0.4 sec) compared to PEMF-60 (from 11.1±1.5 sec to 9.8±0.7 sec, p=.002). No significant difference between groups was found for the other tests, although a trend toward better results in PEMF-45 was manifest: SPPB improved by 6.4% in PEMF-45 and by 3.0% in PEMF-60, and TUG decreased by 7.8% in PEMF-45 and by 6.1% in PEMF-60. During the 6 months observation period no adverse event was observed.

Conclusion:

Preliminary results of our ongoing prospective observational study suggest that a more frequent administration of PEMF produces greater improvements in some but not all physical performance parameters compared to a standard validated regimen1,2.

References:

[1]Giusti A et al., Geriatr Gerontol Int 2013. 2Giusti A et al., J Am Geriatr Soc 2014.

Disclosure of Interests:

Massimo Giovale: None declared, Giuseppina Tramontano: None declared, Rossana Galli: None declared, Simone Rando: None declared, Andrea Giusti Speakers bureau: UCB, Amgen, Kyowa Kirin, Abiogen Pharma, and Eli Lilly, outside the submitted work, Consultant of: EffRx and Abiogen Pharma, outside the submitted work, Lorenzo Bandi: None declared, Francesca Russo: None declared, Stefano Rampoldi Employee of: THS Therapeutic Solutions SRL, Luigi Carlo Bottaro: None declared, Gerolamo Bianchi Speakers bureau: Abbvie, Abiogen Pharma, Amgen, BMS, Celgene, Eli Lilly, GSK, Janssen-Cilag, Medac, MSD, Novartis, Pfizer, Roche, Sanofi, Genzyme and Servier, outside the submitted work

Imaging Metformin Efficacy as Add-On Therapy in Cells and Mouse Models of Human EGFR Glioblastoma

Glioblastoma (GBM) is a highly aggressive tumor of the brain. Despite the efforts, response to current therapies is poor and 2-years survival rate ranging from 6-12%. Here, we evaluated the preclinical efficacy of Metformin (MET) as add-on therapy to Temozolomide (TMZ) and the ability of [¹⁸F]FLT (activity of thymidine kinase 1 related to cell proliferation) and [¹⁸F]VC701 (translocator protein, TSPO) Positron Emission Tomography (PET) radiotracers to predict tumor response to therapy. Indeed, TSPO is expressed on the outer mitochondrial membrane of activated microglia/macrophages, tumor cells, astrocytes and endothelial cells. TMZ-sensitive (Gli36ΔEGFR-1 and L0627) or -resistant (Gli36ΔEGFR-2) GBM cell lines representative of classical molecular subtype were tested in vitro and in vivo in orthotopic mouse models. Our results indicate that in vitro, MET increased the efficacy of TMZ on TMZ-sensitive and on TMZ-resistant cells by deregulating the balance between pro-survival (bcl2) and pro-apoptotic (bax/bad) Bcl-family members and promoting early apoptosis in both Gli36ΔEGFR-1 and Gli36ΔEGFR-2 cells. In vivo, MET add-on significantly extended the median survival of tumor-bearing mice compared to TMZ-treated ones and reduced the rate of recurrence in the TMZ-sensitive models. PET studies with the cell proliferation radiopharmaceutical [¹⁸F]FLT performed at early time during treatment were able to distinguish responder from non-responder to TMZ but not to predict the duration of the effect. On the contrary, [¹⁸F]VC701 uptake was reduced only in mice treated with MET plus TMZ and levels of uptake negatively correlated with animals’ survival. Overall, our data showed that MET addition improved TMZ efficacy in GBM preclinical models representative of classical molecular subtype increasing survival time and reducing tumor relapsing rate. Finally, results from PET imaging suggest that the reduction of cell proliferation represents a common mechanism of TMZ and combined treatment, whereas only the last was able to reduce TSPO. This reduction was associated with the duration of treatment response. TSPO-ligand may be used as a complementary molecular imaging marker to predict tumor microenvironment related treatment effects.

MicroRNA Expression Profile Distinguishes Glioblastoma Stem Cells from Differentiated Tumor Cells

Glioblastoma (GBM) represents the most common and aggressive tumor of the brain. Despite the fact that several studies have recently addressed the molecular mechanisms underlying the disease, its etiology and pathogenesis are still poorly understood. GBM displays poor prognosis and its resistance to common therapeutic approaches makes it a highly recurrent tumor. Several studies have identified a subpopulation of tumor cells, known as GBM cancer stem cells (CSCs) characterized by the ability of self-renewal, tumor initiation and propagation. GBM CSCs have been shown to survive GBM chemotherapy and radiotherapy. Thus, targeting CSCs represents a promising approach to treat GBM. Recent evidence has shown that GBM is characterized by a dysregulated expression of microRNA (miRNAs). In this study we have investigated the difference between human GBM CSCs and their paired autologous differentiated tumor cells. Array-based profiling and quantitative Real-Time PCR (qRT-PCR) were performed to identify miRNAs differentially expressed in CSCs. The Cancer Genome Atlas (TCGA) data were also interrogated, and functional interpretation analysis was performed. We have identified 14 miRNAs significantly differentially expressed in GBM CSCs (p < 0.005). MiR-21 and miR-95 were among the most significantly deregulated miRNAs, and their expression was also associated to patient survival. We believe that the data provided here carry important implications for future studies aiming at elucidating the molecular mechanisms underlying GBM.

Patient-specific mental rehearsal with three-dimensional models before low anterior resection: randomized clinical trial

Background

It was hypothesized that preparing for a surgical procedure, taking into account individual patient characteristics, may facilitate the procedure and improve surgical quality. The aim of this study was to compare different case-specific, preoperative mental rehearsal methods before minimally invasive rectal cancer surgery.

Methods

In this RCT, patients were allocated in a 1 : 1 : 1 : 1 ratio to four groups: systematic mental rehearsal (SMR) using MRI scans; SMR and three-dimensional (3D) virtual models; SMR and synthetic 3D printed models; and routine practice (control group). Surgeons operating on all but the control group underwent mental rehearsal with the visual aids, including axial MRI scans of the pelvis, interactive 3D virtual models reconstructed from axial MRIs, and synthetic models, manufactured by 3D printing. Operations were video-recorded and assessed by two experts blinded to allocation using two validated scores, the Competency Assessment Tool (CAT) and Objective Clinical Human Reliability Analysis (OCHRA). The primary outcome of the study was surgical performance, measured by the CAT.

Results

Forty-nine patients were randomized and allocated to the four groups. There were 12 participants in each of the control, MRI and SMR, and virtual and SMR groups, whereas the SMR using physical models and simulation group included 13. No difference was observed between groups in median CAT scores (control 30.50, MRI 34.25, virtual 31.75, physical 34.00; P = 0.748, partial η² <0.001, where _pη² is indicative of effect size) or OCHRA scores (anterior, posterior, right and left lateral planes, transection P>0.200, _pη² =0.052–0.088). Time spent not performing dissection was significantly shorter for the SMR with MRI group than for the control (57.5 versus 42 respectively; P < 0.001, _pη² =0.212).

Conclusion

Mental rehearsal did not affect CAT and OCHRA scores of consultant surgeons. Reference number: ISRCTN 75603704 (https://www.isrctn.com).

A simplified integrated molecular and immunohistochemistry-based algorithm allows high accuracy prediction of glioblastoma transcriptional subtypes

Glioblastomas (GBM) can be classified into three major transcriptional subgroups (proneural, mesenchymal, classical), underlying different molecular alterations, prognosis, and response to therapy. However, transcriptional analysis is not routinely feasible and assessment of a simplified method for glioblastoma subclassification is required. We propose an integrated molecular and immunohistochemical approach aimed at identifying GBM subtypes in routine paraffin-embedded material. RNA-sequencing analysis was performed on representative samples (n = 51) by means of a "glioblastoma transcriptional subtypes (GliTS) redux" custom gene signature including a restricted number (n = 90) of upregulated genes validated on the TCGA dataset. With this dataset, immunohistochemical profiles, based on expression of a restricted panel of gene classifiers, were integrated by a machine-learning approach to generate a GliTS based on protein quantification that allowed an efficient GliTS assignment when applied to an extended cohort (n = 197). GliTS redux maintained high levels of correspondence with the original GliTS classification using the TCGA dataset. The machine-learning approach designed an immunohistochemical (IHC)-based classification, whose concordance was 79.5% with the transcriptional- based classification, and reached 90% for the mesenchymal subgroup. Distribution and survival of GliTS were in line with reported data, with the mesenchymal subgroup given the worst prognosis. Notably, the algorithm allowed the identification of cases with comparable probability to be assigned to different GliTS, thus falling within overlapping regions and reflecting an extreme heterogeneous phenotype that mirrors the underlying genetic and biological tumor heterogeneity. Indeed, while mesenchymal and classical subgroups were well segregated, the proneural types frequently showed a mixed proneural/classical phenotype, predicted as proneural by the algorithm, but with comparable probability of being assigned to the classical subtype. These cases, characterized by concomitant high expression of EGFR and proneural biomarkers, showed lower survival. Collectively, these data indicate that a restricted panel of highly sensitive immunohistochemical markers can efficiently predict GliTS with high accuracy and significant association with different clinical outcomes.

Galectin-3 in Prostate Cancer Stem-Like Cells Is Immunosuppressive and Drives Early Metastasis

Galectin-3 (Gal-3) is an extracellular matrix glycan-binding protein with several immunosuppressive and pro-tumor functions. The role of Galectin-3 in cancer stem-like cells (CSCs) is poorly investigated. Here, we show that prostate CSCs also colonizing prostate-draining lymph nodes of transgenic adenocarcinoma of the mouse prostate (TRAMP) mice overexpress Gal-3. Gal-3 contributes to prostate CSC-mediated immune suppression because either Gal-3 silencing in CSCs, or co-culture of CSCs and T cells in the presence of the Gal-3 inhibitor N-Acetyl-D-lactosamine rescued T cell proliferation. N-Acetyl-D-lactosamine also rescued the proliferation of T cells in prostate-draining lymph nodes of TRAMP mice affected by prostate intraepithelial neoplasia. Additionally, Gal-3 impacted prostate CSC tumorigenic and metastatic potential in vivo, as Gal-3 silencing in prostate CSCs reduced both primary tumor growth and secondary invasion. Gal-3 was also found expressed in more differentiated prostate cancer cells, but with different intracellular distribution as compared to CSCs, which suggests different functions of Gal-3 in the two cell populations. In fact, the prevalent nuclear and cytoplasmic distribution of Gal-3 in prostate CSCs made them less susceptible to apoptosis, when compared to more differentiated prostate cancer cells, in which Gal-3 was predominantly intra-cytoplasmic. Finally, we found Gal-3 expressed in human and mouse prostate intraepithelial neoplasia lesions and in metastatic lymph nodes. All together, these findings identify Gal-3 as a key molecule and a potential therapeutic target already in the early phases of prostate cancer progression and metastasis.

AB0958 LOW-ENERGY PULSED ELECTROMAGNETIC FIELD THERAPY REDUCES PAIN IN FIBROMYALGIA: A RANDOMIZED SINGLE-BLIND CONTROLLED PILOT STUDY

Background:

Fibromyalgia is a clinical condition characterized by diffuse chronic muscle-skeletal pain, fatigue, sleep/mood disorders and muscular stiffness. The pathogenesis of fibromyalgia remains poorly understood but numerous lines of evidence suggest a role for alterations of both the central and peripheral nervous systems leading to heightened pain sensitivity along with acorollariumof other symptoms1. Low-energy pulsed electromagnetic field (PEMF) has promising data in the prevention of falls in senior individuals and is believed to promote osteogenesis and angiogenesis thus proving promising to treat bone diseases with chronic pain2. No data is available in fibromyalgia.

Objectives:

To investigate the efficacy and safety of PEMF on fibromyalgia symptoms in a randomized single-blind pilot study.

Methods:

We enrolled 21 women (median age 59 years, IQR 16,5) affected by fibromyalgia according to the 2010 ACR classification criteria3not receiving chronic medical treatment for pain; patients were randomly allocated to receive PEMF TEPT (triple energy pain treatment) / New Sunrise 280 (THS - Therapeutic Solutions, Milan, Italy) on the selected points (10 agopuncture points) or scrambled points for 20 minutes at baseline (T0) and after 4 (T4) and 8 (T8) weeks. Outcome measures were recorded at T0, T4 and T8 and included FIQ (fibromyalgia impact questionnaire), WIP (widespread pain index), VAS pain, SS (symptom severity scale), and SF-36 (short form 36 health survey questionnaire).

Results:

Patients receiving the active treatment had a deep reduction of WIP from T0 to T8 (-76% vs -13% in placebo) with a statistically significant difference compared to the placebo group (p=0.0025) (Figure 1). In all endpoints, we observed a general reduction at T4 and T8 compared to T0 also for FIQ, VAS pain, SS, SF-36, regardless of the treatment arm and the decrease was higher in the active treatment arm compared to the placebo group, albeit not reaching statistical significance (Figure 2).

Conclusion:

The results of our pilot study show that PEMF is more effective than placebo in reducing widespread pain in fibromyalgia while confirming that a placebo effect is clear in this complex disease.

References:

[1]Targeting network hubs with noninvasive brain stimulation in patients with fibromyalgia Chelsea M. Kaplan, R.E. Harris, UnCheol Lee, Alexander F. DaSilva, George A. Mashour, Steven E. Harte. PAIN: January 2020 - Volume 161 - Issue 1 - p 43-46

[2]Yuan J, Xin F, Jiang W. Underlying Signaling Pathways and Therapeutic Applications of Pulsed Electromagnetic Fields in Bone Repair.Cell Physiol Biochem. 2018;46(4):1581-1594

[3]Wolfe F, Clauw DJ, Fitzcharles MA, et al. The American College of Rheumatology preliminary diagnostic criteria for fibromyalgia and measurement of symptom severity. Arthritis Care Res (Hoboken).2010;62:600-61

Disclosure of Interests:

Massimo Giovale: None declared, Lucia Novelli: None declared, Stefano Rampoldi: None declared, Rossana Galli: None declared, Patrizia Monteforte: None declared, Marica Doveri: None declared, Gerolamo Bianchi Grant/research support from: Celgene, Consultant of: Amgen, Janssen, Merck Sharp & Dohme, Novartis, UCB, Speakers bureau: Abbvie, Abiogen, Alfa-Sigma, Amgen, BMS, Celgene, Chiesi, Eli Lilly, GSK, Janssen, Medac, Merck Sharp & Dohme, Novartis, Pfizer, Roche, Sanofi Genzyme, Servier, UCB, Luigi Carlo Bottaro: None declared, Carlo Selmi Grant/research support from: AbbVie, Janssen, MSD, Novartis, Pfizer, Celgene, and Leo Pharma, Consultant of: Bristol-Myers Squibb, Celgene, Eli Lilly, Janssen, Novartis, Pfizer, Roche, and Sanofi-Regeneron, Speakers bureau: AbbVie, Aesku, Alfa-Wassermann, Bristol-Myers Squibb, Biogen, Celgene, Eli-Lilly, Grifols, Janssen, MSD, Novartis, Pfizer, Roche, Sanofi-Genzyme, UCB Pharma

Enhanced SPARCL1 expression in cancer stem cells improves preclinical modeling of glioblastoma by promoting both tumor infiltration and angiogenesis

Glioblastoma (GBM) is the most malignant brain tumor of adults and is characterized by extensive cell dissemination within the brain parenchyma and enhanced angiogenesis. Effective preclinical modeling of these key features suffers from several shortcomings. Aim of this study was to determine whether modulating the expression of extracellular matrix (ECM) modifiers in proneural (PN) and mesenchymal (MES) cancer stem cells (CSCs) and in conventional glioma cell lines (GCLs) might improve tumor invasion and vascularization. To this end, we selected secreted, acidic and rich in cysteine-like 1 (SPARCL1) as a potential mediator of ECM remodeling in GBM. SPARCL1 transcript and protein expression was assessed in PN and MES CSCs as well as GCLs, in their xenografts and in patient-derived specimens by qPCR, WB and IHC. SPARCL1 expression was then enforced in both CSCs and GCLs by lentiviral-based transduction. The effect of SPARCL1 gain-of-function on microvascular proliferation, microglia activation and advanced imaging features was tested in intracranial xenografts by IHC and MRI and validated by chorioallantoic membrane (CAM) assays. SPARCL1 expression significantly enhanced the infiltrative and neoangiogenic features of PN and MES CSC/GCL-induced tumors, with the concomitant activation of inflammatory responses associated with the tumor microenvironment, thus resulting in experimental GBMs that reproduced both the parenchymal infiltration and the increased microvascular density, typical of GBM. Overall, these results indicate that SPARCL1 overexpression might be instrumental for the generation of CSC-derived preclinical models of GBM in which the main pathognomonic hallmarks of GBMs are retrievable, making them suitable for effective preclinical testing of therapeutics.

Tuberous sclerosis complex-associated CNS abnormalities depend on hyperactivation of mTORC1 and Akt

Tuberous sclerosis complex (TSC) is a dominantly inherited disease caused by hyperactivation of the mTORC1 pathway and characterized by the development of hamartomas and benign tumors, including in the brain. Among the neurological manifestations associated with TSC, the tumor progression of static subependymal nodules (SENs) into subependymal giant cell astrocytomas (SEGAs) is one of the major causes of morbidity and shortened life expectancy. To date, mouse modeling has failed in reproducing these 2 lesions. Here we report that simultaneous hyperactivation of mTORC1 and Akt pathways by codeletion of Tsc1 and Pten, selectively in postnatal neural stem cells (pNSCs), is required for the formation of bona fide SENs and SEGAs. Notably, both lesions closely recapitulate the pathognomonic morphological and molecular features of the corresponding human abnormalities. The establishment of long-term expanding pNSC lines from mouse SENs and SEGAs made possible the identification of mTORC2 as one of the mediators conferring tumorigenic potential to SEGA pNSCs. Notably, in spite of concurrent Akt hyperactivation in mouse brain lesions, single mTOR inhibition by rapamycin was sufficient to strongly impair mouse SEGA growth. This study provides evidence that, concomitant with mTORC1 hyperactivation, sustained activation of Akt and mTORC2 in pNSCs is a mandatory step for the induction of SENs and SEGAs, and, at the same time, makes available an unprecedented NSC-based in vivo/in vitro model to be exploited for identifying actionable targets in TSC.

Brain tumor stem cell dancing

BACKGROUND

Issues regarding cancer stem cell (CSC) movement are important in neurosphere biology as cell-cell or cell-environment interactions may have significant impacts on CSC differentiation and contribute to the heterogeneity of the neurosphere.

AIMS

Despite the growing body of literature data on the biology of brain tumor stem cells, floating CSC-derived neurospheres have been scarcely characterized from a morphological and ultrastructural point of view.

RESULTS

Here we report a morphological and ultrastructural characterization performed by live imaging and scanning electron microscopy. Glioblastoma multiforme (GBM) CSC-derived neurospheres are heterogeneous and are constituted by cells, morphologically different, capable of forming highly dynamic structures. These dynamic structures are regulated by not serendipitous cell-cell interactions, and they synchronously pulsate following a cyclic course made of "fast" and "slow" alternate phases. Autocrine/paracrine non canonical Wnt signalling appears to be correlated with the association status of neurospheres.

CONCLUSIONS

The results obtained suggest that GBM CSCs can behave both as independents cells and as "social" cells, highly interactive with other members of its species, giving rise to a sort of "multicellular organism".

miR-135a Inhibits Cancer Stem Cell-Driven Medulloblastoma Development by Directly Repressing Arhgef6 Expression

microRNAs (miRNAs) are short noncoding RNAs, which regulate gene expression post-transcriptionally and play crucial roles in relevant biological and pathological processes. Here, we investigated the putative role of miRNAs in modulating the tumor-initiating potential of mouse medulloblastoma (MB)-derived cancer stem cells (CSCs). We first subjected bona fide highly tumorigenic (HT) CSCs as well as lowly tumorigenic MB CSCs and normal neural stem cells to miRNA profiling, which identified a HT CSC-specific miRNA signature. Next, by cross-checking CSC mRNA/miRNA profiles, we pinpointed miR-135a as a potential tumor suppressor gene, which was strongly downregulated in HT CSCs as well as in the highly malignant experimental tumors derived from them. Remarkably, enforced expression of miR-135a in HT CSCs strongly inhibited tumorigenesis by repressing the miR-135a direct target gene Arhgef6. Considering the upregulation of Arhgef6 in human MBs and its involvement in mediating experimental medulloblastomagenesis, its efficient suppression by miR-135a might make available an effective therapeutic strategy to selectively impair the tumorigenic potential of MB CSCs. Stem Cells 2015;33:1377-1389.

Tenascin-C Protects Cancer Stem-like Cells from Immune Surveillance by Arresting T-cell Activation

Precociously disseminated cancer cells may seed quiescent sites of future metastasis if they can protect themselves from immune surveillance. However, there is little knowledge about how such sites might be achieved. Here, we present evidence that prostate cancer stem-like cells (CSC) can be found in histopathologically negative prostate draining lymph nodes (PDLN) in mice harboring oncogene-driven prostate intraepithelial neoplasia (mPIN). PDLN-derived CSCs were phenotypically and functionally identical to CSC obtained from mPIN lesions, but distinct from CSCs obtained from frank prostate tumors. CSC derived from either PDLN or mPIN used the extracellular matrix protein Tenascin-C (TNC) to inhibit T-cell receptor-dependent T-cell activation, proliferation, and cytokine production. Mechanistically, TNC interacted with α5β1 integrin on the cell surface of T cells, inhibiting reorganization of the actin-based cytoskeleton therein required for proper T-cell activation. CSC from both PDLN and mPIN lesions also expressed CXCR4 and migrated in response to its ligand CXCL12, which was overexpressed in PDLN upon mPIN development. CXCR4 was critical for the development of PDLN-derived CSC, as in vivo administration of CXCR4 inhibitors prevented establishment in PDLN of an immunosuppressive microenvironment. Taken together, our work establishes a pivotal role for TNC in tuning the local immune response to establish equilibrium between disseminated nodal CSC and the immune system.

EGFR amplified and overexpressing glioblastomas and association with better response to adjuvant metronomic temozolomide

BACKGROUND

Lack of robust predictive biomarkers, other than MGMT promoter methylation, makes temozolomide responsiveness in newly diagnosed glioblastoma (GBM) patients difficult to predict. However, we identified patients with long-term survival (≥35 months) within a group of newly diagnosed GBM patients treated with standard or metronomic adjuvant temozolomide schedules. We thus investigated possible molecular profiles associated with longer survival following temozolomide treatment.

METHODS

We investigated the association of molecular features with progression-free (PFS) and overall survival (OS). Human-derived GBM cancer stem cells (CSCs) were used to investigate in vitro molecular mechanisms associated with temozolomide responsiveness. Surgically removed recurrences allowed investigation of molecular changes occurring during therapy in vivo. Statistical analyses included one- and two-way analysis of variance, Student's t test, Cox proportional hazards, and the Kaplan-Meier method. All statistical tests were two-sided.

RESULTS

No association was found between survival and gene classifiers associated with different molecular GBM subtypes in the standard-treated group, while in metronomic-treated patients robust association was found between EGFR amplification/overexpression and PFS and OS (OS, EGFR-high vs low: hazard ratiodeath = 0.22, 95% confidence interval = 0.09 to 0.55, P = .001). The result for OS remained statistically significant after Bonferroni correction (P interaction < .0005). Long-term survival following metronomic temozolomide was independent from MGMT and EGFRvIII status and was more pronounced in EGFR-overexpressing GBM patients with PTEN loss. In vitro findings confirmed a selective dose- and time-dependent decrease in survival of temozolomide-treated EGFR+ human-derived glioblastoma CSCs, which occurred through inhibition of NF-κB transcriptional activity. In addition, reduction in EGFR-amplified cells, along with a statistically significant decrease in NF-κB/p65 expression, were observed in specimens from recurrent metronomic-treated EGFR-overexpressing GBM patients.

CONCLUSIONS

EGFR-amplified/overexpressing glioblastomas strongly benefit from metronomic temozolomide-based therapies.

Sialidase NEU4 is involved in glioblastoma stem cell survival

The human sialidase, NEU4, has emerged as a possible regulator of neuronal differentiation and its overexpression has been demonstrated to promote the acquisition of a stem cell-like phenotype in neuroblastoma cells. In this paper, we demonstrated that glioblastoma stem cells (GSCs) isolated from glioblastoma multiforme (GBM) cell lines and patients' specimens as neurospheres are specifically marked by the upregulation of NEU4; in contrast, the expression of NEU4 is very low in non-neurosphere-differentiated GBM cells. We showed that NEU4 silencing by miRNA or a chemical inhibitor of its catalytic activity triggered key events in GSCs, including (a) the activation of the glycogen synthase kinase 3β, with the consequent inhibition of Sonic Hedgehog and Wnt/β-catenin signalling pathways; (b) the decrease of the stem cell-like gene expression and marker signatures, evidenced by the reduction of NANOG, OCT-4, SOX-2, CD133 expression, ganglioside GD3 synthesis, and an altered protein glycosylation profile; and (c) a significant decrease in GSCs survival. Consistent with this finding, increased NEU4 activity and expression induced in the more differentiated GBM cells by the NEU4 agonist thymoquinone increased the expression of OCT-4 and GLI-1. Thus, NEU4 expression and activity appeared to help to determine the molecular signature of GSCs and to be closely connected with their survival properties. Given the pivotal role played by GSCs in GBM lethality, our results strongly suggest that NEU4 inhibition could significantly improve current therapies against this tumour.

mTOR signaling in neural stem cells: from basic biology to disease

The mammalian target of rapamycin (mTOR) pathway is a central controller of growth and homeostasis, and, as such, is implicated in disease states where growth is deregulated, namely cancer, metabolic diseases, and hamartoma syndromes like tuberous sclerosis complex (TSC). Accordingly, mTOR is also a pivotal regulator of the homeostasis of several distinct stem cell pools in which it finely tunes the balance between stem cell self-renewal and differentiation. mTOR hyperactivation in neural stem cells (NSCs) has been etiologically linked to the development of TSC-associated neurological lesions, such as brain hamartomas and benign tumors. Animal models generated by deletion of mTOR upstream regulators in different types of NSCs reproduce faithfully some of the TSC neurological alterations. Thus, mTOR dysregulation in NSCs seems to be responsible for the derangement of their homeostasis, thus leading to TSC development. Here we review recent advances in the molecular dissection of the mTOR cascade, its involvement in the maintenance of stem cell compartments, and in particular the implications of mTOR hyperactivation in NSCs in vivo and in vitro.

Gene signatures distinguish stage-specific prostate cancer stem cells isolated from transgenic adenocarcinoma of the mouse prostate lesions and predict the malignancy of human tumors

The relevant social and economic impact of prostate adenocarcinoma, one of the leading causes of death in men, urges critical improvements in knowledge of the pathogenesis and cure of this disease. These can also be achieved by implementing in vitro and in vivo preclinical models by taking advantage of prostate cancer stem cells (PCSCs). The best-characterized mouse model of prostate cancer is the transgenic adenocarcinoma of the mouse prostate (TRAMP) model. TRAMP mice develop a progressive lesion called prostatic intraepithelial neoplasia that evolves into adenocarcinoma (AD) between 24 and 30 weeks of age. ADs often metastasize to lymph nodes, lung, bones, and kidneys. Eventually, approximately 5% of the mice develop an androgen-independent neuroendocrine adenocarcinoma. Here we report the establishment of long-term self-renewing PCSC lines from the different stages of TRAMP progression by application of the neurosphere assay. Stage-specific prostate cell lines were endowed with the critical features expected from malignant bona fide cancer stem cells, namely, self-renewal, multipotency, and tumorigenicity. Notably, transcriptome analysis of stage-specific PCSCs resulted in the generation of well-defined, meaningful gene signatures, which identify distinct stages of human tumor progression. As such, TRAMP-derived PCSCs represent a novel and valuable preclinical model for elucidating the pathogenetic mechanisms leading to prostate adenocarcinoma and for the identification of molecular mediators to be pursued as therapeutic targets.

Extracellular sphingosine-1-phosphate: a novel actor in human glioblastoma stem cell survival

Glioblastomas are the most frequent and aggressive intracranial neoplasms in humans, and despite advances and the introduction of the alkylating agent temozolomide in therapy have improved patient survival, resistance mechanisms limit benefits. Recent studies support that glioblastoma stem-like cells (GSCs), a cell subpopulation within the tumour, are involved in the aberrant expansion and therapy resistance properties of glioblastomas, through still unclear mechanisms. Emerging evidence suggests that sphingosine-1-phosphate (S1P) a potent onco-promoter able to act as extracellular signal, favours malignant and chemoresistance properties in GSCs. Notwithstanding, the origin of S1P in the GSC environment remains unknown. We investigated S1P metabolism, release, and role in cell survival properties of GSCs isolated from either U87-MG cell line or a primary culture of human glioblastoma. We show that both GSC models, grown as neurospheres and expressing GSC markers, are resistant to temozolomide, despite not expressing the DNA repair protein MGMT, a major contributor to temozolomide-resistance. Pulse experiments with labelled sphingosine revealed that both GSC types are able to rapidly phosphorylate the long-chain base, and that the newly produced S1P is efficiently degraded. Of relevance, we found that S1P was present in GSC extracellular medium, its level being significantly higher than in U87-MG cells, and that the extracellular/intracellular ratio of S1P was about ten-fold higher in GSCs. The activity of sphingosine kinases was undetectable in GSC media, suggesting that mechanisms of S1P transport to the extracellular environment are constitutive in GSCs. In addition we found that an inhibitor of S1P biosynthesis made GSCs sensitive to temozolomide (TMZ), and that exogenous S1P reverted this effect, thus involving extracellular S1P as a GSC survival signal in TMZ resistance. Altogether our data implicate for the first time GSCs as a pivotal source of extracellular S1P, which might act as an autocrine/paracrine signal contributing to their malignant properties.