Temozolomide Chemotherapy Research Articles

CTIM-10. PHASE 1 TRIAL OF PERSONALIZED NEOANTIGEN VACCINES IN COMBINATION WITH STANDARD CARE TO TREAT GLIOBLASTOMA

Abstract The tumor microenvironment (TME) of glioblastoma (GBM) is populated by cells that foster immunosuppression. Reversing immunosuppression and promoting tumor surveillance by T cells that recognize the antigens generated by tumor-specific mutations (neoantigens) is critical to eliminating the tumor cells. In a phase 1 clinical trial of newly diagnosed GBM (NCT03223103), patients were treated with personalized neoantigen vaccines (PNV) combined with standard of care (resection, radiotherapy, temozolomide chemotherapy, and TTFields). The neoantigens were identified using the OpenVax computational pipeline. Primary endpoints included safety and feasibility, and the secondary endpoints included PFS, OS, TME analysis, and immunogenicity assays. The study enrolled 12 patients, ages 32-84, between December 2017 - July 2020. With a feasibility endpoint of one successful PNV administration, all patients got at least 6. All developed PNV-related injection site reactions, and flu-like symptoms grade 1-2. Concomitant use with TTFields did not increase toxicity. None of the patients exhibited dose-limiting toxicity within 30 days of receiving the PNV. However, one developed grade 3 SAE, consisting of seizures, neck pain, and progressive neurological deficits, after vaccine 10, culminating in a grade 5 SAE and brain demyelination 10 months later. Assays performed on this subject showed induction of neoantigen-specific responses with PNV. PNV induced CD4+ and CD8+ T cells reactive against multiple vaccine peptide sequences with CD8+ T cell cross-reactivity against one wild-type epitope. Other patients had immunogenicity against the vaccinated peptides. Overall, the 6 months PFS was 100%, with 67% 2-year and 58% 3-year survival. Although the mutation burden is low in GBM, neoantigens were detected in all tumors, and PNV were manufactured for all patients. PNV with synthetic long peptides combined with standard care treatment may help improve outcomes in GBM. Cross-reactivity may potentially be responsible for post-vaccination T-cell demyelination. Further evidence is needed to substantiate a direct effect. Funding: CRI - V Foundation CLIP (#3680)

EXTH-15. AN EGFRVIII RNA-LNP VACCINE PROTOTYPE ACHIEVES TUMOUR CLEARANCE IN A GBM MOUSE MODEL

Abstract Glioblastoma (GBM) is an aggressive high-grade glioma that is fatal despite standard-of-care therapy. Recurrent somatic alterations that form neoantigens represent opportunities for targeted therapeutic intervention. Using human EGFRvIII as a prototypical structural alteration and neoantigen, we tested the potential of a mRNA-LNP vaccine approach to improve the survival of mice with EGFRvIII-driven GBM. To generate the model, we used in vivo electroporation to introduce genetic alterations (EGFRvIII-OE/CDKN2A-KO/PTEN-KO) into periventricular cells of early postnatal C3H mice, then propagated cells from the subsequent tumours to create implantable cell lines. Following orthotopic implantation, the resulting syngeneic tumours faithfully recapitulate histologic features of GBM with infiltrative growth, mitoses, necrosis, and vascular proliferation. Also like human GBM, the models are sensitive to but not cured by temozolomide chemotherapy and are resistant to immune checkpoint blockade. We delivered mRNA-LNP vaccines against EGFRvIII into the thigh muscle of tumour-bearing mice on days 7, 10, 14, 21, and 36 after tumour cell implant. We observed no tumour in vaccine-treated mice compared to significant tumour burden in control vector-treated animals by MR imaging at day 30 post-tumour cell implant. By day 37, all control-treated mice had died, whereas vaccine-treated mice cleared their tumours with no tumour burden detectable by histology at day 150 (N= 5 per group, **p= 0.0023). In a follow-up experiment with vaccine or control treatment on days 10, 14, 18, and 25 post-cell implants, all control mice had died by day 39. Further, vaccine-treated surviving animals were re-challenged with tumour cell implant into the contralateral hemisphere on day 42 and remain alive as of day 90. Our ongoing proof-of-principle work demonstrates that neoantigen driver mutations in high-grade glioma models can be targeted with an mRNA lipid vaccine. We hope this pre-clinical work will lead to early-phase clinical trials.

CTNI-31. AI-GUIDED PERSONALIZED PRECISION RADIATION THERAPY WITH TARGETED DOSE ESCALATION FOR NEWLY DIAGNOSED GLIOBLASTOMA: A MATCHED-CONTROL STUDY

Abstract BACKGROUND The purpose of this study was to assess the feasibility and effectiveness of AI-guided personalized precision radiation therapy (PPRT) with targeted dose escalation in enhancing outcomes for patients with newly diagnosed glioblastoma. METHODS An open-label trial was conducted at the University of Pennsylvania (NCT03477513) from August 2018 to April 2023, enrolling 20 patients with IDH-wildtype glioblastoma who underwent maximal safe resection. They were matched with a contemporaneous cohort of glioblastoma patients based on age, sex, extent of resection (EOR), O6-methylguanine-DNA methyltransferase promoter (MGMTp) methylation status, and IDH status. Propensity score matching (PSM) was employed to select the control group, utilizing one-to-four nearest neighbor matching. One patient was excluded due to concurrent treatment with tumor treating fields (TTFields). The PPRT group received personalized radiation dose escalation to 75 Gy in 30 fractions guided by AI-based predictive modeling of recurrence, along with temozolomide chemotherapy. The control group received standard-of-care chemoradiotherapy, 60 Gy in 30 fractions. A previously published and evaluated (retrospectively and prospectively) predictive AI model, which has demonstrated high predictive value for neoplastic cell infiltration and future tumor recurrence using preoperative, multi-parametric MRIs, was utilized. RESULTS Median overall survival was 24.3 months in the PPRT-temozolomide group compared to 17.5 months in the standard-of-care treatment group (hazard ratio [HR]=0.30; 95% CI: 0.16-0.57; p<0.001). Excluding two patients with leptomeningeal disease and bone marrow metastasis, the median survival was 35.4 months (HR=0.25; 95% CI: 0.12-0.51; p<0.001). CONCLUSION AI-guided PPRT for newly diagnosed glioblastoma patients demonstrated feasibility in routine clinical practice and significantly improved overall survival compared to matched controls receiving standard-of-care treatment. These findings underscore the potential of personalized precision radiation therapy, with focused dose escalation, in improving outcomes for glioblastoma patients and emphasize the need for prospective validation in a randomized controlled clinical trial.

DNAR-09. GB13 IS A POTENT NEOADJUVANT TREATMENT OPTION FOR IL13RA2-EXPRESSING GBM AND IMPROVES STANDARD-OF-CARE THERAPY

Abstract Glioblastoma (GBM) is the most common primary adult brain cancer and is uniformly fatal. Despite maximum safe surgical resection followed by radiation and temozolomide chemotherapy, current median survival is 14-18 months. GB13 is a novel therapy for treatment of GBM and received Orphan Drug Designation by the Food and Drug Administration (FDA) for treatment of malignant gliomas. GB13 specifically targets the tumor-restricted IL13Ra2 receptor that is highly expressed in GBM, among other cancers, but not on non-cancerous cells. IL13Ra2 represents a clinically viable target for directed therapies and is being explored by numerous approaches. Previous data demonstrate that GB13 potently kills GBM and diffuse midline glioma (DMG) cells and tumors, IL13Ra2 correlates to GB13 sensitivity and, GB13 can significantly improve the cytotoxic effects of ionizing radiation (IR) when tested in models of pediatric diffuse midline glioma. In the current studies, the ability of GB13 to enhance the effects of IR were explored using IL13Ra2-positive and negative GBM models. Major findings demonstrate that neoadjuvant GB13 treatment increases cytotoxic effects of IR, enhances cell apoptosis and decreases cell viability. These results were not observed in IL13Ra2-negative settings, demonstrating the necessity for this clinical target. Mechanistically, increased cell death was caused by sustained apoptotic signaling through caspase-mediated pathways. Preclinical models support the use of GB13 prior to radiation for decreased tumor proliferation. Using multiple models, our results identify a temporal benefit for treating GBM tumors prior to IR and this should be tested in future clinical studies.

DDDR-46. TARGETING TRANSGLUTAMINASE 2 (TGM2) ENHANCES SENSITIVITY OF GLIOBLASTOMA CELL LINES TO RADIOTHERAPY AND TEMOZOLOMIDE

Abstract Glioblastoma (GBM), the most aggressive and common primary brain tumor in adults, remains highly resistant to conventional therapeutics, including radiation therapy (RT), largely due to its molecular heterogeneity. Few biomarkers have been identified that successfully guide or predict treatment response. Transglutaminase 2 (TGM2), a ubiquitous multifunctional enzyme involved in numerous signal transduction pathways related to tumorigenesis, has recently been suggested to drive chemoradioresistance. Here, we investigate the effects of disrupting TGM2 by pharmacologic inhibition or CRISPR knockout (TGM2-KO) on GBM cell’s response to RT and Temozolomide (TMZ) chemotherapy. Using western blotting and clonogenic assays, we show that the allosteric TGM2 inhibitor, GK921, stabilizes p53 expression and impedes reproductive ability at IC50 and IC25 concentrations. TGM2-KO and GK921 (at IC10 and lower) sensitized GBM cell lines to RT with almost equivalent efficacy, resulting in a 2- to 3-fold suppression of clonal expansion compared to scramble controls or irradiation alone. We also demonstrate increased sensitivity of GBM cell lines to TMZ upon inhibition of TGM2 by GK921. Our findings indicate that the use of TGM2 inhibitors, such as GK921, could enhance the efficacy of RT and the potency of TMZ, positioning TGM2 as a promising therapeutic target that may improve standard treatment of GBM cells expressing TGM2.

QLTI-22. TEMOZOLOMIDE CHEMOTHERAPY EFFECTS ON GLIOMA PATIENT FERTILITY AND THEIR OFFSPRING: A RETROSPECTIVE REVIEW

Abstract Gliomas represent ~30% of primary brain tumors. Temozolomide (TMZ) chemotherapy with concurrent radiation or following radiation is the main course of treatment. Avoidance of pregnancy in female patients and partner of male patients is strongly encouraged due to unknown teratogenic and long-term effects to the health and development of fetus. Patients of childbearing age must wrestle with receiving TMZ treatment, potentially impacting fertility, and the desire for biological children in the future. Gamete preservation prior to TMZ induction is the current solution, which is often financially prohibitive, leaving patients to consider natural conception after completion of TMZ. We intend to identify potential difficulties in conception, pregnancy complications, birth abnormalities, and childhood developmental deficiencies that may be correlated to TMZ exposure prior to conception. Included patients conceived and delivered one or two children after completing treatment with TMZ. All patients received antiepileptic drugs (range = 1-4) which have variable known teratogenic effects during pregnancy. We identified 13 patients (7 male, 6 female; median age of 29) with diagnoses of astrocytoma (n=5), oligodendroglioma (n=5), oligoastrocytoma (n=2; diagnosed prior to 2021 WHO classification), and glioblastoma (n=1). Two reported issues with conceiving (1 male and 1 female) and 17 children were born. One child had developmental abnormalities (6%), and all other 16 children were healthy per parental assessment. Complete results of pregnancy complication and childhood development data will be updated at the meeting. Information on teratogenic and developmental effects of TMZ in humans is largely unknown. Animal studies have shown an increase in fetal malformations when exposed to TMZ during pregnancy. Despite the limitations of a retrospective study, our findings suggest that natural conception after the conclusion of TMZ treatment may be safer than suspected. Given the limited sample size, future comprehensive studies are warranted to corroborate these observations.

NCOG-41. COMPARATIVE ANALYSIS OF MORTALITY AND SHORT-TERM SIDE EFFECTS IN PATIENTS WITH GLIOBLASTOMA MULTIFORME TREATED WITH TEMOZOLOMIDE VERSUS TEMOZOLOMIDE PLUS BEVACIZUMAB CHEMOTHERAPY

Abstract INTRODUCTION Glioblastoma multiforme (GBM) is a highly aggressive primary brain tumor in adults with limited treatment options and poor prognosis. Temozolomide (TMZ) chemotherapy is the standard treatment for GBM, but alternative therapies have shown limited success. Bevacizumab (BEV), a monoclonal antibody targeting vascular endothelial growth factor (VEGF), is used to restrict GBM growth and spread. This study evaluates the efficacy of combining TMZ with BEV compared to TMZ alone in managing GBM. METHODS A retrospective cohort study was conducted using TriNetX database data, focusing on patients diagnosed with GBM and receiving chemotherapy. Cohorts were defined by treatment: TMZ plus BEV versus TMZ alone. Propensity-score matching balanced baseline characteristics, including demographics and health conditions. Primary outcomes included mortality rates and short-term side effects within the first year of treatment, such as cognitive communication deficits, headache, dizziness, insomnia, and nausea/vomiting. RESULTS After matching, 922 patients were included in each cohort. There were no significant demographic differences post-matching. The mortality rate was higher in the TMZ plus BEV group compared to TMZ alone (51.30% vs. 36.98%, RR: 1.387, 95% CI: 1.249-1.541). However, TMZ plus BEV was associated with a lower incidence of cognitive communication deficits (1.95% vs. 4.34%, RR: 0.45, 95% CI: 0.26-0.779) and dizziness (7.27% vs. 10.52%, RR: 0.691, 95% CI: 0.513-0.93). No significant differences were found in headache, insomnia, or nausea/vomiting rates between the groups. CONCLUSION This study indicates that combining bevacizumab with temozolomide may increase mortality in GBM patients but reduce certain side effects such as cognitive deficits and dizziness. These findings emphasize the need to carefully consider the benefits and risks of different chemotherapy regimens for GBM and highlight the necessity for further research to optimize treatment strategies and improve patient outcomes.

CSIG-04. ANTI-TUMOR RESPONSE OF ONCOMAGNETIC MONOTHERAPY IN GLIOBLASTOMA

Abstract BACKGROUND Glioblastoma (GBM) is the most lethal primary malignant brain tumor with a median survival of 15–20 months. Concurrent temozolomide (TMZ) chemotherapy and radiation (XRT) remain the current standard of care (SOC) treatment for newly diagnosed GBM. The addition of tumor treating fields (TTFs) improves median survival for newly diagnosed GBM from 16 to 20.9 months. This modest improvement underscores the urgent need to identify a new treatment modality as a safe and effective therapy. PURPOSE The noninvasive Oncomagnetic device developed in our laboratory selectively kills glioblastoma (GBM) in vitro. We studied the cellular and molecular effects of Oncomagnetic monotherapy (OMT) on GBM cell lines and investigated immune response in a syngeneic mouse model. RESULTS OMT significantly reduces cell proliferation and cell survival in vitro. OMT induces persistent ROS primarily by increasing superoxide level in cancer cells and reduces mitochondrial-membrane potential in GBM cells. It also induces DNA damage and arrests cells in G1-phase of the cell cycle. Whole-body Oncomagnetic stimulation caused a substantial retardation of tumor growth and reduction of the contrast-enhanced tumor volume in 9.4T MRI scans. OMT showed significant increase in overall survival in treated mice. We also observed upregulated immune response indicated by RNA sequencing data obtained from OMT-treated GBM cells as well as in treated GBM mouse tumor sections by imaging mass cytometry analysis. The tSNE analysis of various immune clusters suggests significant increase in immune response by activating CD4+, CD8+, murine-macrophages and M1-macrophages located at tumor site in the treated group. CONCLUSION The obtained data indicate significant anti-tumor response by inhibiting cancer signaling pathways and an increased immune response. Our findings suggest unique mechanism of action for OMT stimulation and provide a strong rationale for standalone OMT for GBM.

INNV-27. TEMOZOLOMIDE FOR PATIENTS WITH AGGRESSIVE PITUITARY TUMORS: A CASE SERIES

Abstract BACKGROUND Pituitary adenomas are often effectively managed with medical therapy, surgery, and radiation therapy. However, up to 15% of pituitary neoplasms exhibit rapid growth, invasive behavior, or, rarely, metastasize despite optimal standard treatments. Temozolomide is associated with a survival benefit for patients with these aggressive pituitary tumors. METHODS We present a case series of 8 patients with an aggressive pituitary tumor (APT) or pituitary carcinoma (PC) treated with temozolomide. RESULTS Eight patients (3 female, median age at diagnosis 44) with APT (n=6) or PC (n=2) were treated. A variety of pituitary tumor types were represented (1 prolactinoma, 5 corticotroph adenomas, 1 gonadotroph adenoma, 1 thyrotropinoma). Prior to temozolomide initiation, patients underwent a median 5 treatments including medical management (n=4), surgery (n=7), radiation therapy (n=7). Temozolomide was started at median 3.5 recurrence. Median treatment duration was 6 cycles (n=6, 150-200 mg/m2 days 1-5, 28-day cycles; n=1, 75 mg/m2, days 1-21, 28-day cycles). Seven patients experienced progression after temozolomide treatment, median progression-free survival (PFS) was 4 months. One patient remains on treatment, progression-free at 5 months. MGMT methylation status was assessed for 3 tumors. Among 2 patients with MGMT promoter methylated tumors, PFS was 4 months for one patient, the other remains on treatment. For one patient with MGMT promoter unmethylated corticotroph adenoma, PFS was 9 months. No ≥ grade 4 toxicities were noted. Most common toxicities were nausea (n=5), thrombocytopenia (n=3), and fatigue (n=2). CONCLUSION In this group of heavily pretreated patients, temozolomide monotherapy was well-tolerated and associated with median PFS of 4 months. Interestingly, PC patients had longer PFS at 9 months and 24 months. Our findings support use of single-agent temozolomide chemotherapy for patients with APT/PC, but further prospective analysis is needed to identify patients more likely to benefit from treatment and optimal timing of chemotherapy initiation.

EXTH-81. A RARE CASE OF RELENTLESSLY PROGRESSIVE METASTATIC PINEOCYTOMA MANAGED WITH SEQUENTIAL MULTIMODAL THERAPY

Abstract BACKGROUND Pineocytoma is a rare pineal parenchymal WHO grade 1 tumor, typically well-managed with surgical resection alone. With gross total resection (GTR), 91% 1-year and 84% 5-year survival rates have been reported. Recurrent pineocytoma is rare and optimal management in that setting is unknown, in part owing to the rarity of the condition. METHODS We report an atypical course of pineocytoma in a 58-year-old male involving metastatic disease. RESULTS A pineal mass was identified upon MRI of the brain obtained for vision changes. Patient underwent GTR, pathology was consistent with pineocytoma, WHO grade 1. Ki-67 labeling index was low at 1-2%. Despite low-grade pathology, two years later, surveillance imaging demonstrated recurrence in the pineal region and a second lesion in the right thalamus. The patient underwent gamma knife surgery (GKRS) to both lesions. Three years later, he developed three new lesions in the right cerebellum and again underwent GKRS. Subsequent surveillance imaging identified new lesions in the right cerebellum and along ventricular walls, treated with further GKRS. Nine years after initial diagnosis, focal nodular leptomeningeal metastases were discovered, along with progression at the primary tumor site. Patient was treated with GKRS to the nodular deposits followed by pembrolizumab. Further disease progression as noted despite immunotherapy. Patient was treated with 6 cycles of temozolomide chemotherapy and at further progression 3 cycles of lomustine. Upon additional progression, further radiation therapy was administered with bevacizumab to reduce risk of radiation necrosis. Patient remains on surveillance 13 years after initial diagnosis with visual changes and mild headache representing only clinical issues. CONCLUSIONS Although exceedingly rare, pineocytoma is capable of metastasizing to brain parenchyma and the leptomeninges, as demonstrated in our patient. However, our case demonstrates prolonged survival is possible even in the setting of relentlessly progressive metastatic disease with utilization of multimodality treatment.

RADT-09. CHEMORADIOTHERAPY WITH TEMOZOLOMIDE VS. RADIOTHERAPY ALONE IN PATIENTS WITH IDH WILD-TYPE AND TERT PROMOTER MUTATION HISTOLOGICAL GRADE 2/3 GLIOMAS: A POSTHOC ANALYSIS OF A RANDOMIZED CONTROLLED TRIAL

Abstract PURPOSE In 2016, we initiated a signal center prospective randomized trial to compare chemoradiotherapy (CRT) with temozolomide (TMZ) to radiotherapy (RT) alone in patients with IDH wild-type and TERT promoter mutation histological grade 2/3 gliomas. This study demonstrated patients who received CRT had a longer median OS than those who received RT alone and found no statistical difference in PFS between the two groups. Now, we recruited more patients in the CRT group to further explore whether there were differences in PFS between patients treated with CRT and RT. Besides, we explored the effect of MGMT promoter (MGMTp) methylation status on OS and PFS in patients receiving CRT therapy in the STUPP schedule. METHODS We expanded the scope by enrolling 21 participants in the CRT group and extending the follow-up period. OS and PFS were analyzed using the log-rank test, and high-risk factors were explored through Cox regression analysis. RESULTS Patients’ median follow-up is 21.9 months. CRT group has a longer median OS (25.3 vs 17.2 months; P = 0.029, HR = 0.443) and PFS (14.6 vs 8.3 months; P = 0.0008, HR = 0.387) than the RT group. Multivariate analysis identified CRT as a favorable prognostic variable for both OS (P = 0.003) and PFS (P = 0.002). The status of MGMTp methylation did not affect OS (P = 0.560, HR = 1.30) and PFS (P = 0.75, HR = 0.88) in patients with IDH-wt/TERTp-mut receiving TMZ chemotherapy. CRT with TMZ did not significantly increase grade 3 or higher toxicities. CONCLUSIONS The long-term results confirmed that the OS and PFS benefits of the RT plus TMZ regimen exceeded those of the RT alone group in patients with IDH-wt/TERTp-mut gliomas.

β-Ketoenamine covalent organic framework nanoplatform combined with immune checkpoint blockade via photodynamic immunotherapy inhibit glioblastoma progression

The synergistic approach of combining photodynamic immunotherapy with endogenous clearance of PD-L1 immune checkpoint blockade therapy holds promise for enhancing survival outcomes in glioblastoma (GBM) patients. The observed upregulation of O-GlcNAc glycolysis in tumors may contribute to the stabilization of endogenous PD-L1 protein, facilitating tumor immune evasion. This study presents a pH-adapted excited state intramolecular proton transfer (ESIPT)-isomerized β-ketoamide-based covalent organic framework (COF) nanoplatform (denoted as OT@COF-RVG). Temozolomide (TMZ) and OSMI-4 (O-GlcNAc transferase inhibitor) were integrated into COF cavities, then modified on the surface with polyethylene glycol and the rabies virus peptide RVG-29, showing potential for sensitizing TMZ chemotherapy and initiating photodynamic therapy (PDT). By inhibiting O-GlcNAc and promoting lysosomal degradation of PD-L1, OT@COF-RVG enhanced the effectiveness of immune checkpoint blockade (ICB) therapy. Additionally, treatment with OT@COF-RVG led to a notable elevation in reactive oxygen species (ROS) levels, thereby re-establishing an immunostimulatory state, inducing immunogenic cell death (ICD). In summary, our research unveiled a correlation between O-GlcNAc in GBM and the evasion of immune responses by tumors, while showcasing the potential of OT@COF-RVG in reshaping the immunosuppressive microenvironment of GBM and offering a more effective approach to immunotherapy in clinical settings.

One-carbon-mediated purine synthesis underlies temozolomide resistance in glioblastoma

Glioblastoma accounts for nearly half of all primary malignant brain tumors in adults, and despite an aggressive standard of care, including excisional surgery and adjuvant chemoradiation, recurrence remains universal, with an overall median survival of 14.6 months. Recent work has revealed the importance of passenger mutations as critical mediators of metabolic adaptation in cancer progression. In our previous work, we identified a role for the epigenetic modifier ID-1 in temozolomide resistance in glioblastoma. Here, we show that ID-1-mediated glioblastoma tumourigenesis is accompanied by upregulation of one-carbon (1-C) mediated de novo purine synthesis. ID-1 knockout results in a significant reduction in the expression of 1-C metabolism and purine synthesis enzymes. Analysis of glioblastoma surgical specimens at initial presentation and recurrence reveals that 1-C purine synthesis metabolic enzymes are enriched in recurrent glioblastoma and that their expression correlates with a shorter time to tumor recurrence. Further, we show that the 1-C metabolic phenotype underlies proliferative capacity and temozolomide resistance in glioblastoma cells. Supplementation with exogenous purines restores proliferation in ID-1-deficient cells, while inhibition of purine synthesis with AICAR sensitizes temozolomide-resistant glioblastoma cells to temozolomide chemotherapy. Our data suggest that the metabolic phenotype observed in treatment-resistant glioma cells is a potential therapeutic target in glioblastoma.

Role of Non-coding RNAs in the Response of Glioblastoma to Temozolomide.

Chemotherapy and radiotherapy are widely used in clinical practice across the globe as cancer treatments. Intrinsic or acquired chemoresistance poses a significant problem for medical practitioners and researchers, causing tumor recurrence and metastasis. The most dangerous kind of malignant brain tumor is called glioblastoma multiforme (GBM) that often recurs following surgery. The most often used medication for treating GBM is temozolomide chemotherapy; however, most patients eventually become resistant. Researchers are studying preclinical models that accurately reflect human disease and can be used to speed up drug development to overcome chemoresistance in GBM. Non-coding RNAs (ncRNAs) have been shown to be substantial in regulating tumor development and facilitating treatment resistance in several cancers, such as GBM. In this work, we mentioned the mechanisms of how different ncRNAs (microRNAs, long non-coding RNAs, circular RNAs) can regulate temozolomide chemosensitivity in GBM. We also address the role of these ncRNAs encapsulated inside secreted exosomes.

Enhancing Therapeutic Approaches in Glioblastoma with Pro-Oxidant Treatments and Synergistic Combinations: In Vitro Experience of Doxorubicin and Photodynamic Therapy.

Glioblastoma (GBM) is an aggressive brain cancer characterized by significant molecular and cellular heterogeneity, which complicates treatment efforts. Current standard therapies, including surgical resection, radiation, and temozolomide (TMZ) chemotherapy, often fail to achieve long-term remission due to tumor recurrence and resistance. A pro-oxidant environment is involved in glioma progression, with oxidative stress contributing to the genetic instability that leads to gliomagenesis. Evaluating pro-oxidant therapies in brain tumors is crucial due to their potential to selectively target and eradicate cancer cells by exploiting the elevated oxidative stress levels inherent in these malignant cells, thereby offering a novel and effective strategy for overcoming resistance to conventional therapies. This study investigates the therapeutic potential of doxorubicin (DOX) and photodynamic therapy (PDT) with Me-ALA, focusing on their effects on redox homeostasis. Basal ROS levels and antioxidant gene expression (NFE2L2, CAT, GSR) were quantitatively assessed across GBM cell lines, revealing significant variability probably linked to genetic differences. DOX and PDT treatments, both individually and in combination, were analyzed for their efficacy in inducing oxidative stress and cytotoxicity. An in silico analysis further explored the relationship between gene mutations and oxidative stress in GBM patients, providing insights into the molecular mechanisms underlying treatment responses. Our findings suggest that pro-oxidant therapies, such as DOX and PDT in combination, could selectively target GBM cells, highlighting a promising avenue for improving therapeutic outcomes in GBM.

How to sensitize glioblastomas to temozolomide chemotherapy: a gap-centered view.

Temozolomide (TMZ) is a methylating agent used as the first-line drug in the chemotherapy of glioblastomas. However, cancer cells eventually acquire resistance, necessitating the development of TMZ-potentiating therapy agents. TMZ induces several DNA base adducts, including O 6 -meG, 3-meA, and 7-meG. TMZ cytotoxicity stems from the ability of these adducts to directly (3-meA) or indirectly (O 6 -meG) impair DNA replication. Although TMZ toxicity is generally attributed to O 6 -meG, other alkylated bases can be similarly important depending on the status of various DNA repair pathways of the treated cells. In this mini-review we emphasize the necessity to distinguish TMZ-sensitive glioblastomas, which do not express methylguanine-DNA methyltransferase (MGMT) and are killed by the futile cycle of mismatch repair (MMR) of the O 6 -meG/T pairs, vs. TMZ-resistant MGMT-positive or MMR-negative glioblastomas, which are selected in the course of the treatment and are killed only at higher TMZ doses by the replication-blocking 3-meA. These two types of cells can be TMZ-sensitized by inhibiting different DNA repair pathways. However, in both cases, the toxic intermediates appear to be ssDNA gaps, a vulnerability also seen in BRCA-deficient cancers. PARP inhibitors (PARPi), which were initially developed to treat BRCA1/2-deficient cancers by synthetic lethality, were re-purposed in clinical trials to potentiate the effects of TMZ. We discuss how the recent advances in our understanding of the genetic determinants of TMZ toxicity might lead to new approaches for the treatment of glioblastomas by inhibiting PARP1 and other enzymes involved in the repair of alkylation damage (e.g., APE1).

Cavitation monitoring, treatment strategy, and acoustic simulations of focused ultrasound blood-brain barrier disruption in patients with glioblastoma

PurposeWe report our experience disrupting the blood-brain barrier (BBB) to improve drug delivery in glioblastoma patients receiving temozolomide chemotherapy. The goals of this retrospective analysis were to compare MRI-based measures of BBB disruption and vascular damage to the exposure levels, acoustic emissions data, and acoustic simulations. We also simulated the cavitation detectors. MethodsMonthly BBB disruption (BBBD) was performed using a 220 kHz hemispherical phased array focused ultrasound system (Exablate Neuro, InSightec) and Definity microbubbles (Lantheus) over 38 sessions in nine patients. Exposure levels were actively controlled via the cavitation dose obtained by monitoring subharmonic acoustic emissions. The acoustic field and sensitivity profile of the cavitation detection system were simulated. Exposure levels and cavitation metrics were compared to the level of BBBD evident in contrast-enhanced MRI and to hypointense regions in T2*-weighted MRI. ResultsOur treatment strategy evolved from using a relatively high cavitation dose goal to a lower goal and longer sonication duration and ultimately resulted in BBBD across the treatment volume with minimal petechiae. Subsonication-level feedback control of the exposure using acoustic emissions also improved consistency. Simulations of the acoustic field suggest that reflections and standing waves appear when the focus is placed near the skull, but their effects can be mitigated with aberration correction. Simulating the cavitation detectors suggest variations in the sensitivity profile across the treatment volume and between patients. A correlation was observed with the cavitation dose, BBBD and petechial hemorrhage in 8/9 patients, but substantial variability was evident. Analysis of the cavitation spectra found that most bursts did not contain wideband emissions, a signature of inertial cavitation, but biggest contribution to the cavitation dose – the metric used to control the procedure – came from bursts with wideband emissions. ConclusionUsing a low subharmonic cavitation dose with a longer duration resulted in BBBD with minimal petechiae. The correlation between cavitation dose and outcomes demonstrates the benefits of feedback control based on acoustic emissions, although more work is needed to reduce variability. Acoustic simulations could improve focusing near the skull and inform our analysis of acoustic emissions. Monitoring additional frequency bands and improving the sensitivity of the cavitation detection could provide signatures of microbubble activity associated with BBB disruption that were undetected here and could improve our ability to achieve BBB disruption without vascular damage.

HGG-43. DIFFUSE PEDIATRIC HIGH GRADE GLIOMA SUCCESSFULLY TREATED WITH MULTIMODAL THERAPY

Abstract BACKGROUND Pediatric high grade glioma (HGG) have a dismal prognosis despite aggressive treatment. In this report, we discuss a patient with HGG successfully treated with combination of resection, radiotherapy, chemotherapy, and biologic therapy. RESULTS An 8-year-old male presented with intermittent headaches, vomiting and fatigue. Imaging demonstrated four solid/cystic enhancing intra-axial lesions within the left cerebral hemisphere- two within the left frontotemporal region, one in the superior parietal region, and one in the temporal lobe, all with perilesional edema and resultant subfalcine herniation with midline shift. The patient underwent subtotal resection of the frontotemporal and parietal lesions. Histopathology was consistent with glioblastoma. Whole exome sequencing revealed alterations in TP53, ATRX, PTEN, TSC2 as well as subclonal mutation in NF1. The tumor was unable to be further classified by DNA methylation. However histopathologic and molecular findings support the diagnosis of diffuse pediatric-high grade glioma, H3-wildtype and IDH-wildtype. The patient received adjuvant 59.4 Gy focal proton therapy with concurrent temozolomide and maintenance chemotherapy with temozolomide and lomustine for 6 cycles. End of therapy imaging demonstrated complete resolution of all sites of disease. Due to high likelihood of recurrence, the patient was subsequently started on targeted therapy with everolimus and ribociclib which continue to be well tolerated without dose adjustments. The patient remains stable and without recurrence 2.5 years since diagnosis, and 15 months since initiation of biologic therapy. Additionally, the patient underwent testing for cancer predisposition which revealed presence of TP53 heterozygous mutation consistent with Li-Fraumeni syndrome. The patient remains without other malignancies on surveillance imaging per LFS guidelines. CONCLUSION Our case report illustrates the value of both chemotherapy and biologic therapy in treatment of HGG. In addition to this, it emphasizes the importance of germline testing for cancer predisposition in patients with high grade tumors.

Alterations of the tumor microenvironment (TME) in recurrent glioblastoma following apatinib in combination with temozolomide.

e14018 Background: Glioblastoma (GBM) is the highly malignant primary central nervous system tumor. The standard treatment for glioblastoma is maximal surgical resection followed by concomitant radiotherapy and temozolomide chemotherapy, but patient’s survival still remains poor. At present, apatinib in combination with temozolomide (TMZ) has achieved reasonable clinical efficacy in the treatment of recurrent glioblastoma (rGBM), however, there are currently no clear biomarkers related to clinical efficacy or prognosis. Methods: This retrospective study was enrolled 22 rGBMs treated with apatinib in combination with TMZ and 6 patients who received standard radiotherapy combined with TMZ and experienced recurrence. At the same time, we collected their tissue samples for RNA transcriptome analysis by the Nanostring nCounter platform. In prognosis analysis, long survival benefit is defined as a PFS≥4.2 months, and short survival benefit is defined as a PFS<4.2 months. This PFS threshold was primarily referenced from a Phase III study of bevacizumab combined with chemotherapy for rGBM. The study was approved by the institutional ethics committee of Sanbo Brain Hospital, Capital Medical University (SBNK-YJ-2021-010-02) and informed consent was also obtained from the patients. Results: The differential gene of pre and post standard chemoradiotherapy results suggest that standard treatment has reduced the expression of genes associated with tumor proliferation and up-regulated the expression of the genes associated with the immune response in rGBM. In apatinib combined TMZ patients, compared to the non-response group, the response group had significantly up-regulated expression of genes related to endothelial cells and apoptosis. Enrichment analysis revealed that signaling pathways related to cell proliferation were down-regulated in the response group. In terms of prognosis, compared with the short-survival benefit group (< 4.2 months), four tumor progression-associated genes were down-regulated in response group (≥4.2 months). Hypoxia related-genes was significantly up-regulated in the long survival benefit group. Enrichment analysis showed that genes related to cell proliferation were also down-regulated in the long-survival benefit group, while the expression of signaling pathway genes related to cell activation, and immune response was significantly up-regulated. Conclusions: Our study suggests that the combination of apatinib and TMZ may potentially provide clinical benefits in treating rGBM by modulating genes associated with cell proliferation, promoting apoptosis, regulating hypoxia, and enhancing immune response within the tumor microenvironment. Clinical trial information: NCT04814329 .

Diffuse midline gliomas in children: Does changing strategies change results?

10045 Background: The prognosis of children with diffuse intrinsic pontine gliomas (DIPG)/diffuse midline glioma (DMG) is dismal. Radiotherapy (RT) is considered the standard of treatment. We previously published results of our center, where patients receiving temozolomide or other chemotherapy after radiotherapy (RT) had a better survival than those receiving RT alone (1). This study aims to evaluate a larger cohort of children with DMG in a single center. Methods: We retrospectively reviewed demographic, clinical characteristics and treatment outcome of children with DMG diagnosed and treated at Istanbul University, Oncology Institute between Feb1999-Feb 2023. We compared the groups that received only radiotherapy (Group 1, only RT, n=19), the ones that received RT with concomitant and adjuvant temozolomide po (Group 2-n= 38 TMZ 75 mg/m2/day for 6 weeks concomitant (c.) with RT, followed by TMZ (200 mg/m2/day) for 5 days every 28 days until progression or for 12 cycles), and the ones that received RT with c. TMZ, followed by other systemic agents (Group 3 n= 18 RT c.TMZ, followed by nimotuzumab containing regimens; Group 4 the rest 26 received other agents such as bevacizumab, CCNU, ONC201 and other). The ones that progressed on group 2, received nimotuzumab containing or other regimens. Results: 114 children (49 female, 65 male) with a mean age of 7± 4 years (6 months-16 years) were analyzed. The most frequent clinical findings were ataxia, strabismus and motor weakness. 108 had diffuse intrinsic pontine gliomas (DIPG). In total 106 patients received RT, 54-60 Gy to the tumor site. The overall survival (OS) in all patients at 2 years, 3 years and 5 years were 25.6%,15% and 11.5% respectively. The 2 years, 3 years and 5 years OS in group1 were 0.79%, 0% ,0% respectively; in group 2 they were 38.4%, 27.9%, 16%respectively ; in group 3 they were 17.6% , 0 % ,0% respectively, in Group 4 they were 10.3%, 0.34%, 0% respectively, The OS in Group 2 or3 or 4 were significantly higher than group 1 (only RT) (P =0.002, p=0.004, p<0.001,respectively). There was no major side effect due to TMZ, nor nimotuzumab. Seven patients were re-irradiated at progression. The number of patients undergoing biopsies and molecular testing increased to 50% of the patients after 2016 versus only in two patients previously. Conclusions: In our series, the overall survival was significantly superior in patients who received RT with concurrent and adjuvant temozolomide and/or adjuvant nimotuzumab containing regimens or other adjuvant systemic treatment in comparison to patients that received RT alone, suggesting that adding systemic treatment after RT (poTMZ or iv nimotuzumab containing regimens or other) may help extend survival. Oral temozolomide may be easier to use as first line treatment after radiotherapy especially in resource limited settings, switching to nimotuzumab containing or other chemotherapy and/or re-radiotherapy at progression. 1. Kebudi R, 2013.