Glioblastoma Multiforme Relapse Research Articles

Implantable Microneedle-Mediated Eradication of Postoperative Tumor Foci Mitigates Glioblastoma Relapse.

Glioblastoma multiforme (GBM) remains incurable despite multimodal treatments after surgical debulking. Almost all patients with GBM relapse within a narrow margin (2-3cm) of the initial resected lesion due to the unreachable residual cancerous cells. Here, a completely biodegradable microneedle for surgical cavity delivery glioblastoma-associated macrophages (GAMs)-activating immune nano-stimulator that mitigates glioblastoma relapse is reported. The residual tumor lesion-directed biocompatible microneedle releases the nano-stimulator and toll-like receptor 9 agonist in a controlled manner until the microneedles completely degrade over 1 week, efferently induce in situ phonotypic shifting of GAMs from anti- to pro-inflammatory and the tumor recurrence is obviously inhibited. The implantable microneedles offer a significant improvement over conventional transdermal ones, as they are 100% degradable, ensuring safe application within surgical cavities. It is also revealed that the T cells are recruited to the tumor niche as the GAMs initiate anti-tumor response and eradicate residual GBM cells. Taken together, this work provides a potential strategy for immunomodulating the postoperative tumor niche to mitigate tumor relapse in GBM patients, which may have broad applications in other malignancies with surgical intervention.

Immunotherapy for children with malignant brain tumors

The incidence of high-grade malignant gliomas (MG) ranges from 35 to 46% of all central nervous system tumors. Despite combined therapy including surgery, radiation treatment and chemotherapy, overall five-year survival does not exceed 10%. The advent of novel immunotherapeutic strategies has promoted a renewed hopes for the treatment of MG. The aim of the present study was to improve the survival rates of glioma patients. Our study included 5 pediatric patients at the median age of 7.6 years (2-16). Three pts had anaplastic astrocytoma (AA) (1st relapse, 1 pt; 2nd relapse, in 2 pts), One patient was diagnosed with glioblastoma multiforme (GBM) (3rd recurrence), and 1 child had diffuse brainstem glioma (BSG). The median time to the first relapse was 12 months (4 to 16), the second relapse occurred at a median of 5 months (1 to 8). The protocol of immunotherapy included combined administration of autologous dendritic cell-based vaccine (DV) and repeated intrathecal/intraventricular injections of donor allogeneic immunocompetent cells (alloIC) for at least 2 years. Two of 3 pts with AA experienced a progression-free interval of 67 and 71 months. One patient with 3rd GBM relapse is alive without any treatment for 13.3 years after starting the immunotherapy. The median time of follow-up was 67 months, with the 2-year overall survival rate of 58%. Two pts died from the disease progression within 6 and 7 months from the beginning of immunotherapy. Over the period of treatment, the patients received a median of 20 alloIC injections (8 to 60), and 18 DV administrations (8 to 44). No serious side-effects were observed. Immunotherapy could be an promising option for treating patients with high-grade malignant gliomas refractory to conventional therapy and, therefore, deserves further investigations.

Stimulation of tumoricidal immunity via bacteriotherapy inhibits glioblastoma relapse.

Glioblastoma multiforme (GBM) is a highly aggressive brain tumor characterized by invasive behavior and a compromised immune response, presenting treatment challenges. Surgical debulking of GBM fails to address its highly infiltrative nature, leaving neoplastic satellites in an environment characterized by impaired immune surveillance, ultimately paving the way for tumor recurrence. Tracking and eradicating residual GBM cells by boosting antitumor immunity is critical for preventing postoperative relapse, but effective immunotherapeutic strategies remain elusive. Here, we report a cavity-injectable bacterium-hydrogel superstructure that targets GBM satellites around the cavity, triggers GBM pyroptosis, and initiates innate and adaptive immune responses, which prevent postoperative GBM relapse in male mice. The immunostimulatory Salmonella delivery vehicles (SDVs) engineered from attenuated Salmonella typhimurium (VNP20009) seek and attack GBM cells. Salmonella lysis-inducing nanocapsules (SLINs), designed to trigger autolysis, are tethered to the SDVs, eliciting antitumor immune response through the intracellular release of bacterial components. Furthermore, SDVs and SLINs administration via intracavitary injection of the ATP-responsive hydrogel can recruit phagocytes and promote antigen presentation, initiating an adaptive immune response. Therefore, our work offers a local bacteriotherapy for stimulating anti-GBM immunity, with potential applicability for patients facing malignancies at a high risk of recurrence.

JAK3 Inhibition Regulates Stemness and Thereby Controls Glioblastoma Pathogenesis.

Glioblastoma multiforme (GBM) is the most deadly brain tumor, effective treatment options for which still remain elusive. The current treatment procedure of maximal resection followed by chemotherapy has proved to be grossly insufficient to prevent disease progression and death. Despite best efforts, the maximum survival post-diagnosis is a mere 1.5 years. Therefore, there is a huge unmet clinical need to find effective therapeutic procedures to prevent the pathogenesis and relapse of GBM. Small-molecule inhibitors of signaling pathways are an attractive option to prevent various types of tumors. However, no effective small-molecule inhibitors have been successful against GBM in clinical trials. Various signaling pathways are altered and an array of signaling molecules, transcription factors (TFs), and epigenetic modifying factors have been implicated in the pathogenesis of GBM. JAK-STAT pathway alteration is an important contributor to GBM pathogenesis and relapse. Many small-molecule inhibitors of JAKs, or STAT TFs, especially JAK2 and STAT3, have been assessed for their anti-tumor activity in GBM. However, no definitive success so far has been achieved. Herein, by using two small-molecule inhibitors of JAK3, we show that they are quite effective in inhibiting GBM cell proliferation and neurosphere formation, downregulating their stemness character, and inducing differentiation into neuronal origin cells. The effect of a single treatment with the drugs, both in a serum-containing differentiation medium and in a proliferation medium containing EGF and FGF, was really strong in limiting GBM cell growth, suggesting a potential therapeutic application for these JAK inhibitors in GBM therapy.

Fractionated Radiosurgery in Large Volume Relapsed Glioblastoma Multiforme

Relapse is part of the natural history in glioblastoma (GBM) and there are limited advances in surgical, alternating electric field therapy (TTF), chemotherapy (CTX), immunotherapy or radiotherapeutic treatments. Radiosurgery (SRS) and Fractionated Stereotactic Radiosurgery (FSRS) may be an option, but remains controversial. We performed a review of our patients with recurrent large volume glioblastoma treated with FSRS over the last 5 years. Since January 2017 to December 2021, we reviewed our experience with large volume FSRS for the treatment of selected patients with large volume GBM recurrence. Indications and treatment planning were done according RANO criteria MR images. Overall survival (OS) and progression-free survival (PFS) after salvage FSRS were the primary endpoints evaluated. Response to FSRS was assessed with clinical evaluation and using brain MR. A total of 15 patients with GBM recurrence were treated in our institution after surgery plus adjuvant radio-chemotherapy treatment with Stupp regimen. Median age was 58 (53-74) years old. Prescription dose was 24 Gy in 4 fractions in consecutive days. Selected patients for FSRS had a good PS with large volume relapse and edema. The target volume (CTV) was the enhanced volume in MR T2 classically known has edema and the relapsed T1 volume with gadolinium uptake. The median PTV was 118.5 cc (50-244cc). 33% of the patients received concurrent chemotherapy or biological therapy with or after FSRS. No patient developed G3 symptomatic adverse radiation effect. Median follow-up was 28.6 (10-82) months from diagnosis. PFS after salvage FSRS was 11 (4-55) months. Median overall survival was 12.4 months after FSRS. Our experience and results suggest that reirradiation provides encouraging disease control and survival rates in GBM relapsed patients. The large volume FSRS associated or not with systemic treatment had good tolerance and can improve survival of patients with relapsed large volume GBM. Randomized controlled trials are needed to establish the optimal management strategy for recurrent GBM.

Experience in the use of dendritic vaccines in the treatment of patients with recurrent gliomas

Purpose of the study. To substantiate the expediency of cellular immunotherapy in the treatment of patients with relapses of high-grade gliomas and evaluate the safety of injecting allogeneic cells directly into the cerebrospinal fluid.Materials and methods. Our study included 5 patients, median age 7,6 years (2–16). Three patients had anaplastic astrocytoma (AA) (1st recurrence – 1 patient, 2nd recurrence – 2 patients), 1 patient had glioblastoma multiforme (GBM) (3rd recurrence) and 1 had diffuse brainstem glioma (BSG). The median time to the first relapse was 12 months (4 to 16), to the second one was 5 months (1 to 8). The protocol of immunotherapy included combined administration of autologous dendritic cell-based vaccine (DV) and repeated intrathecal/intraventricular injections of donor allogenic immunocompetent cells (alloIC) for at least 2 years.Results. Two of 3 patients with AA experienced a progression-free interval of 67 and 71 months One patient with 3rd GBM relapse is alive without any therapy 13.3 years after immunotherapy start. The median time of follow-up was 67 months with the 2‑years overall survival was 58 %. Two patients died from disease progression within 6 and 7 months from the start of immunotherapy. Over the period of treatment the patients received a median of 20 (8 to 60) alloIC injections and 18 (8 to 44) DV administrations. No serious side-effect was observed.Conclusion. Immunotherapy could be an attractive option for treating patients with high-grade malignant gliomas irresponsible to conventional therapy and is worthy of further investigation.

Intracavity generation of glioma stem cell-specific CAR macrophages primes locoregional immunity for postoperative glioblastoma therapy.

Glioblastoma multiforme (GBM) remains incurable despite aggressive implementation of multimodal treatments after surgical debulking. Almost all patients with GBM relapse within a narrow margin around the initial resected lesion due to postsurgery residual glioma stem cells (GSCs). Tracking and eradicating postsurgery residual GSCs is critical for preventing postoperative relapse of this devastating disease, yet effective strategies remain elusive. Here, we report a cavity-injectable nanoporter-hydrogel superstructure that creates GSC-specific chimeric antigen receptor (CAR) macrophages/microglia (MΦs) surrounding the cavity to prevent GBM relapse. Specifically, we demonstrate that the CAR gene-laden nanoporter in the hydrogel can introduce GSC-targeted CAR genes into MΦ nuclei after intracavity delivery to generate CAR-MΦs in mouse models of GBM. These CAR-MΦs were able to seek and engulf GSCs and clear residual GSCs by stimulating an adaptive antitumor immune response in the tumor microenvironment and prevented postoperative glioma relapse by inducing long-term antitumor immunity in mice. In an orthotopic patient-derived glioblastoma humanized mouse model, the combined treatment with nanoporter-hydrogel superstructure and CD47 antibody increased the frequency of positive immune responding cells and suppressed the negative immune regulating cells, conferring a robust tumoricidal immunity surrounding the postsurgical cavity and inhibiting postoperative glioblastoma relapse. Therefore, our work establishes a locoregional treatment strategy for priming cancer stem cell-specific tumoricidal immunity with broad application in patients suffering from recurrent malignancies.

356P Redo surgery in relapsed glioblastoma multiforme: A comparative cohort analysis of a single institution experience

Glioblastoma multiforme (GBM) is the most common intracranial primary malignant brain tumour. Concurrent chemo-radiation as definitive treatment after maximal debulking is established as first-line treatment standard but recurrences are treated based on institutional experiences with or without surgery before second and susequent line of chemotherapy. In this study we look at our tertiary centre institution experience of recurrent Glioblastoma who underwent redo surgery for first recurrence.

Chemotherapy-Induced Degradation of Glycosylated Components of the Brain Extracellular Matrix Promotes Glioblastoma Relapse Development in an Animal Model.

Adjuvant chemotherapy with temozolomide (TMZ) is an intrinsic part of glioblastoma multiforme (GBM) therapy targeted to eliminate residual GBM cells. Despite the intensive treatment, a GBM relapse develops in the majority of cases resulting in poor outcome of the disease. Here, we investigated off-target negative effects of the systemic chemotherapy on glycosylated components of the brain extracellular matrix (ECM) and their functional significance. Using an elaborated GBM relapse animal model, we demonstrated that healthy brain tissue resists GBM cell proliferation and invasion, thereby restricting tumor development. TMZ-induced [especially in combination with dexamethasone (DXM)] changes in composition and content of brain ECM proteoglycans (PGs) resulted in the accelerated adhesion, proliferation, and invasion of GBM cells into brain organotypic slices ex vivo and more active growth and invasion of experimental xenograft GBM tumors in SCID mouse brain in vivo. These changes occurred both at core proteins and polysaccharide chain levels, and degradation of chondroitin sulfate (CS) was identified as a key event responsible for the observed functional effects. Collectively, our findings demonstrate that chemotherapy-induced changes in glycosylated components of brain ECM can impact the fate of residual GBM cells and GBM relapse development. ECM-targeted supportive therapy might be a useful strategy to mitigate the negative off-target effects of the adjuvant GBM treatment and increase the relapse-free survival of GBM patients.

Long Noncoding RNA NONHSAT079852.2 Contributes to GBM Recurrence by Functioning as a ceRNA for has-mir-10401-3p to Facilitate HSPA1A Upregulation.

Glioblastoma multiforme (GBM) is the most common brain malignancy and major cause of high mortality in patients with GBM, and its high recurrence rate is its most prominent feature. However, the pathobiological mechanisms involved in recurrent GBM remain largely unknown. Here, whole-transcriptome sequencing (RNA-sequencing, RNA-Seq) was used in characterizing the expression profile of recurrent GBM, and the aim was to identify crucial biomarkers that contribute to GBM relapse. Differentially expressed RNAs in three recurrent GBM tissues compared with three primary GBM tissues were identified through RNA-Seq. The function and mechanism of a candidate long noncoding RNA (lncRNA) in the progression and recurrence of GBM were elucidated by performing comprehensive bioinformatics analyses, such as functional enrichment analysis, protein–protein interaction prediction, and lncRNA–miRNA–mRNA regulatory network construction, and a series of in vitro assays. As the most significantly upregulated gene identified in recurrent GBM, HSPA1A is mainly related to antigen presentation and the MAPK signaling pathway, as indicated by functional enrichment analysis. HSPA1A was predicted as the target gene of the lncRNA NONHSAT079852.2. qRT-PCR revealed that NONHSAT079852.2 was significantly elevated in recurrent GBM relative to that in primary GBM, and high NONHSAT079852.2 expression was associated with the poor overall survival rates of patients with GBM. The knockdown of NONHSAT079852.2 successfully induced tumor cell apoptosis, inhibited the proliferation, migration, invasion and the expression level of HSPA1A in glioma cells. NONHSAT079852.2 was identified to be a sponge for hsa-miR-10401-3p through luciferase reporter assay. Moreover, HSPA1A was targeted and regulated by hsa-miR-10401-3p. Collectively, the results suggested that NONHSAT079852.2 acts as a sponge of hsa-mir-10401-3p and thereby enhances HSPA1A expression, promotes tumor cell proliferation and invasion, and leads to the progression and recurrence of GBM. This study will provide new insight into the regulatory mechanisms of NONHSAT079852.2-mediated competing endogenous RNA in the pathogenesis of recurrent GBM and evidence of the potential of lncRNAs as diagnostic biomarkers or potential therapeutic targets.

Rapid tumor recurrence in a novel murine GBM surgical model is associated with Akt/PD-L1/vimentin signaling

Glioblastoma multiforme (GBM) is the most common primary malignant brain tumor without curable therapy. Surgical resection remains the first choice of patients with GBM but tumors relapse rapidly even combined with conventional chemoradiotherapy. The mechanism of GBM rapid recurrence is poorly understood, which is largely due to the lack of an appropriate animal model, thus heavily impedes the improvement of postoperative therapy. Here we established a highly reproducible mouse GBM surgical model by using the syngeneic G422TN-GBM cells, which faithfully recapitulates the features of rapid recurrence of human GBM after surgery. Implanting 2 × 103–5 × 104 of G422TN-GBM cells in mouse cerebral cortex caused death in all animal within 23 days, while surgery was an effective therapy but not curable. After complete removal of visible tumors on day 5–9 of tumor growth, the tumors recurred macroscopically within 5 days accompanied by increasing infiltrative cancer foci. Mechanistically, the rapid recurrence of resected tumors was positively correlated to early Akt activation, which subsequently upregulated PD-L1/Vimentin and promoted proliferation/migration of cancer cells. In addition, environmental astrocytic activation with strong PD-L1 signal was prominent. Taken together, we provided a novel GBM surgical recurrence model for preclinical studies and suggested complicated recurring mechanisms involving in strong oncogenic signaling as well as immune inhibitory signals from both GBM cells and their neighboring astrocytes.

MTOR Modulates Intercellular Signals for Enlargement and Infiltration in Glioblastoma Multiforme

Simple SummaryGlioblastoma multiforme (GBM) is the most aggressive and lethal primary brain tumor. Emerging evidence indicate the multi-faceted role of extracellular vesicles (EVs) in GBM growth and proliferation. In fact, GBM-derived EVs can alter the phenotype of GBM-associated parenchymal cells; thus, promoting tumor growth, angiogenesis, and immune evasion. Remarkably, among several pathways that are frequently deregulated in GBM, mammalian Target of Rapamycin (mTOR) up-regulation, and subsequent autophagy (ATG) depression are considered hallmarks of GBM. In fact, mTOR-dependent ATG inhibition strongly correlates with the presence of EVs, which in turn promotes glioblastoma cancer stem cells (GSCs) self-renewal, proliferation, and infiltration. ATG and exosome release are reciprocally regulated. In detail, a failure in ATG enhances exosomal release. Therefore, strategies aimed at targeting on mTOR-dependent extracellular vesicles could be a promising approach for GBM prevention and treatment.Recently, exosomal release has been related to the acquisition of a malignant phenotype in glioblastoma cancer stem cells (GSCs). Remarkably, intriguing reports demonstrate that GSC-derived extracellular vesicles (EVs) contribute to glioblastoma multiforme (GBM) tumorigenesis via multiple pathways by regulating tumor growth, infiltration, and immune invasion. In fact, GSCs release tumor-promoting macrovesicles that can disseminate as paracrine factors to induce phenotypic alterations in glioma-associated parenchymal cells. In this way, GBM can actively recruit different stromal cells, which, in turn, may participate in tumor microenvironment (TME) remodeling and, thus, alter tumor progression. Vice versa, parenchymal cells can transfer their protein and genetic contents to GSCs by EVs; thus, promoting GSCs tumorigenicity. Moreover, GBM was shown to hijack EV-mediated cell-to-cell communication for self-maintenance. The present review examines the role of the mammalian Target of Rapamycin (mTOR) pathway in altering EVs/exosome-based cell-to-cell communication, thus modulating GBM infiltration and volume growth. In fact, exosomes have been implicated in GSC niche maintenance trough the modulation of GSCs stem cell-like properties, thus, affecting GBM infiltration and relapse. The present manuscript will focus on how EVs, and mostly exosomes, may act on GSCs and neighbor non tumorigenic stromal cells to modify their expression and translational profile, while making the TME surrounding the GSC niche more favorable for GBM growth and infiltration. Novel insights into the mTOR-dependent mechanisms regulating EV-mediated intercellular communication within GBM TME hold promising directions for future therapeutic applications.

Personalized therapy and stem cell transplantation for pro-inflammatory modulation of cancer stem cells microenvironment in glioblastoma: Review.

Glioblastoma multiforme (GBM) is one of the most aggressive types of brain tumor in humans. The prognosis for patients with GBM is unfavorable and treatment is largely ineffective, where modern treatment regimens typically increase survival by 15 months. GBM relapse and progression are associated with cancer stem cells (CSCs). The present review provides a critical analysis of the primary reasons underlying the lack of effectiveness of modern CSC management methods. An emphasis is placed on the role of the blood-brain barrier in the development of treatment resistance. The existing methods for increasing the efficiency of antitumor genotoxic therapy are also described, and a strategy for personalized regulation of CSC based on post-genome technologies is suggested. The hypothesis that GBM cells employ a special mechanism for DNA repair based on their interactions with normal stem cells, is presented and the function of the tumor microenvironment in fulfilling the antitumor potential of normal stem cells is explained. Additionally, the mechanisms by which cancer stem cells regulate glioblastoma progression and recurrence are described based on novel biomedical technologies.

Prion Protein in Glioblastoma Multiforme.

The cellular prion protein (PrPc) is an evolutionarily conserved cell surface protein encoded by the PRNP gene. PrPc is ubiquitously expressed within nearly all mammalian cells, though most abundantly within the CNS. Besides being implicated in the pathogenesis and transmission of prion diseases, recent studies have demonstrated that PrPc contributes to tumorigenesis by regulating tumor growth, differentiation, and resistance to conventional therapies. In particular, PrPc over-expression has been related to the acquisition of a malignant phenotype of cancer stem cells (CSCs) in a variety of solid tumors, encompassing pancreatic ductal adenocarcinoma (PDAC), osteosarcoma, breast cancer, gastric cancer, and primary brain tumors, mostly glioblastoma multiforme (GBM). Thus, PrPc is emerging as a key in maintaining glioblastoma cancer stem cells’ (GSCs) phenotype, thereby strongly affecting GBM infiltration and relapse. In fact, PrPc contributes to GSCs niche’s maintenance by modulating GSCs’ stem cell-like properties while restraining them from differentiation. This is the first review that discusses the role of PrPc in GBM. The manuscript focuses on how PrPc may act on GSCs to modify their expression and translational profile while making the micro-environment surrounding the GSCs niche more favorable to GBM growth and infiltration.

Glioblastoma cancer stem cell biology: Potential theranostic targets.

Glioblastoma multiforme (GBM) is among the most incurable cancers. GBMs survival rate has not markedly improved, despite new radical surgery protocols, the introduction of new anticancer drugs, new treatment protocols, and advances in radiation techniques. The low efficacy of therapy, and short interval between remission and recurrence, could be attributed to the resistance of a small fraction of tumorigenic cells to treatment. The existence and importance of cancer stem cells (CSCs) is perceived by some as controversial. Experimental evidences suggest that the presence of therapy-resistant glioblastoma stem cells (GSCs) could explain tumor recurrence and metastasis. Some scientists, including most of the authors of this review, believe that GSCs are the driving force behind GBM relapses, whereas others however, question the existence of GSCs. Evidence has accumulated indicating that non-tumorigenic cancer cells with high heterogeneity, could undergo reprogramming and become GSCs. Hence, targeting GSCs as the "root cells" initiating malignancy has been proposed to eradicate this devastating disease. Most standard treatments fail to completely eradicate GSCs, which can then cause the recurrence of the disease. To effectively target GSCs, a comprehensive understanding of the biology of GSCs as well as the mechanisms by which these cells survive during treatment and develop into new tumor, is urgently needed. Herein, we provide an overview of the molecular features of GSCs, and elaborate how to facilitate their detection and efficient targeting for therapeutic interventions. We also discuss GBM classifications based on the molecular stem cell subtypes with a focus on potential therapeutic approaches.

RECURRENT GLIOBLASTOMA MANAGEMENT USING STEREOTACTIC RADIOSURGERY AND SYSTEMIC TREATMENT

Glioblastoma multiforme (GBM) is the most common primary malignant tumor of the central nervous system in adults. Dismal survival rates and poor prognosis for recurrent GBM patients still remains a challenging problem. Despite aggressive initial treatment, above 100 % GBM patients have development of recurrent diseases. Management of GBM recurrence is still debatable. The multimodality approaches using combination of stereotactic radiosurgery (SRS), cytostatic agents (Тemozolomide (TMZ)) and antiangiogenic therapy (bevacizumab (BEV)) are often beneficial for such patients and may achieve survival improving. Aim of research: to assess the efficacy and toxicity of combination therapy approach using stereotactic radiosurgery (SRS) and systemic treatment (chemotherapy and antiangiogenic therapy) in glioblastoma multiforme recurrence treatment. Materials and methods: at the State Institution “Institute of Neurosurgery named after acad. A.P. Romodanov of NAMS of Ukraine” (Kyiv, Ukraine) 21 patients (pts) with GBM recurrence were treated (8 females and 11 men; median age at time of diagnosis 52.4 (29.7–69.3) from January 2014 till December 2017. The initial surgical treatment as gross total tumor resection was performed in 12 pts (57.1 %), subtotal resection – 5 pts (23.9 %), biopsy – 4 pts (19 %). 12 pts (57.1 %) were MGMT methylated and 9 pts (42.9 %) were MGMT unmethylated. In all cases adjuvant radiation therapy (60 Gy in 30 fractions) were used, 12 pts of them (57.1 %) – in combination with TMZ followed by 6-12 courses of chemotherapy (TMZ) according Stupp protocol. Recurrent disease was treated by SRS followed by TMZ + BEV. SRS was performed by means of “Trilogy” LINAC (“Varian”, USA) with a median dose and fractions of 19.2 Gy (range, 12.0–36.0) in 1 to 5 fractions. Results: median survival after initial diagnosis was 18.3 months, and 1- and 2-year survival rates of 85.7 % (18 from 21 pts) and 38.1 % (8 from 21 pts) respectively. The median survival from the time of recurrence treatment was 8.3 months. The 6‐ and 12‐months overall survival from SRS were 95.2 % (20 from 21 pts) and 23.8 % (5 from 21 pts), respectively. Adverse radiation effects were noted in 6 (28.6 %) pts and were controlled with corticosteroids. Adverse events grade 1-2 related to the systemic therapy included hematological complications, fatigue, hypertension and proteinuria were observed in 23.8 % (5 from 21 pts) without the occurrence of grade 3 events. Conclusion: recurrent GBM management using combination of SRS, chemotherapy and antiangiogenic therapy is a promising multimodal treatment approach providing survival improving whereas appropriate toxicity ratio. Further studies of combined treatment of GBM relapse are needed.

Radiosurgery Outcome Related to Chemotherapy Association in Relapsed Glioblastoma Multiforme

Radiosurgery Outcome Related to Chemotherapy Association in Relapsed Glioblastoma Multiforme

Relapse pathway of glioblastoma revealed by single-cell molecular analysis.

Glioblastoma multiforme (GBM) remains an incurable brain tumor. The highly malignant behavior of GBM may, in part, be attributed to its intraclonal genetic and phenotypic diversity (subclonal evolution). Identifying the molecular pathways driving GBM relapse may provide novel, actionable targets for personalized diagnosis, characterization of prognosis and improvement of precision therapy. We screened single-cell transcriptomes, namely RNA-seq data of primary and relapsed GBM tumors from a patient, to define the molecular profile of relapse. Characterization of hundreds of individual tumor cells identified three mutated genes within single cells, involved in the RAS/GEF GTP-dependent signaling pathway. The identified molecular pathway was further verified by meta-analysis of RNA-seq data from more than 3000 patients. This study showed that single-cell molecular analysis overcomes the inherent heterogeneity of bulk tumors with respect to defining tumor subclonal evolution relevant to GBM relapse.

PP242 Counteracts Glioblastoma Cell Proliferation, Migration, Invasiveness and Stemness Properties by Inhibiting mTORC2/AKT.

Glioblastoma multiforme (GBM) is the most malignant brain tumor and is associated with poor prognosis due to its thorny localization, lack of efficacious therapies and complex biology. Among the numerous pathways driving GBM biology studied so far, PTEN/phosphatidylinositol-4,5-bisphosphate 3-kinase (PI3K)/AKT/mechanistic target of rapamycin (mTOR) signaling plays a pivotal role, as it controls cell survival, proliferation and metabolism and is involved in stem cell maintenance. In front of recent and numerous evidences highlighting mTOR upregulation in GBM, all the strategies developed to inhibit this pathway have been substantially unsuccessful. Our study focused on mTOR complex 2 (mTORC2) to understand its involvement in GBM cell growth, proliferation, migration and invasiveness. We utilized an in vitro model, characterized by various genetic alterations (i.e., GL15, U257, U87MG and U118MG cell lines) in order to achieve the clonal heterogeneity observed in vivo. Additionally, being the U87MG cell line endowed with glioblastoma stem cells (GSCs), we also investigated the role of the PTEN/PI3K/AKT/mTOR pathway in this specific cell population, which is responsible for GBM relapse. We provide further insights that explain the reasons for the failure of numerous clinical trials conducted to date targeting PI3K or mTOR complex 1 (mTORC1) with rapamycin and its analogs. Additionally, we show that mTORC2 might represent a potential clinically valuable target for GBM treatment, as proliferation, migration and GSC maintenance appear to be mTORC2-dependent. In this context, we demonstrate that the novel ATP-competitive mTOR inhibitor PP242 effectively targets both mTORC1 and mTORC2 activation and counteracts cell proliferation via the induction of high autophagy levels, besides reducing cell migration, invasiveness and stemness properties.

Temozolomide-induced increase of tumorigenicity can be diminished by targeting of mitochondria in in vitro models of patient individual glioblastoma

Glioblastoma multiforme (GBM) is a highly heterogeneous and aggressive brain tumor with a dismal prognosis. Development of resistance towards cytostatic drugs like the GBM standard drug temozolomide is a severe problem in GBM treatment. One potential source of GBM relapse could be so called cancer stem like cells (CSCs). These represent an undifferentiated subpopulation of cells with high potential for tumor initiation. Furthermore, it has been shown that differentiated GBM cells can regain CSC properties when exposed to continuous temozolomide treatment in vitro. In this study, treatment of several primary GBM cell lines with clinically relevant doses of temozolomide increased their tumorigenicity as determined by colony formation assays in soft agar. Increased tumorigenicity is a known property of CSCs. Hence, therapy options that specifically target CSCs are under investigation. CSCs appear to be particularly dependent on mitochondria biogenesis which may represent a useful target for CSC elimination. Toxicity towards mitochondria is a known side effect of several antibiotics. Thus, addition of antibiotics like doxycycline may represent a useful tool to inhibit CSCs in GBM. Here, we show that combining temozolomide treatment of primary GBM cells with doxycycline could counteract the increase of tumorigenicity induced by temozolomide treatment.