Temozolomide Monotherapy Research Articles

Apatinib combined with temozolomide in diffuse midline glioma: a novel and effective therapy

PurposeDiffuse midline glioma (DMG), H3 K27M-mutant is a type of diffuse high-grade glioma that occurs in the brain midline carrying an extremely poor prognosis under the best efforts of surgery, radiation, and other therapies. For better therapy, we explored the efficacy and toxicity of a novel therapy that combines apatinib and temozolomide in DMG.MethodsA retrospective analysis of 32 patients with DMG who underwent apatinib plus temozolomide treatment was performed. Apatinib was given 500 mg in adults, 250 mg in pediatric patients once daily. Temozolomide was administered at 200 mg/m2/d according to the standard 5/28 days regimen. The main clinical data included basic information of patients, radiological and pathological characteristics of tumors, treatment, adverse reactions, prognosis.ResultsThe objective response rate was 24.1%, and the disease control rate was 79.3%. The median PFS of all patients was 5.8 months, and median OS was 10.3 months. A total of 236 cycles of treatment were available for safety assessment and the toxicity of the combination therapy was relatively well tolerated. The most common grade 3 toxicities were myelosuppression including leukopenia (5.08%), neutropenia (4.24%), lymphopenia (2.12%), thrombocytopenia (1.69%) and anemia (1.27%). Grade 4 toxicities included neutropenia (2.12%), thrombocytopenia (2.12%) and proteinuria (1.69%). All the adverse events were relieved after symptomatic treatment or dose reduction.ConclusionsApatinib plus temozolomide could be an effective regimen with manageable toxicities and favorable efficacy and may outperform temozolomide monotherapy, particularly in newly diagnosed adults with tumors located outside the pons. The novel therapy deserves further investigation in adult DMG patients.

Abstract 7593: Photodynamic therapy improves therapeutic management of glioblastoma

Abstract Glioblastoma (GBM) remains a formidable challenge in the realm of oncology, primarily due to the limitations of the standard of care therapies. Photodynamic therapy (PDT), which exploits the light-activated potential of 5-aminolevulinic acid (5-ALA), emerges as a promising avenue to combat GBM. In this study, primary patient-derived cell lines, Ox5 core, and G7, served as critical subjects, exposed to light excitation at wavelengths of 410 nm, 528 nm, and 810 nm, both with and without 5-ALA (protoporphyrin IX). The central objective was to rigorously assess the efficacy of PDT, either with or without 5-ALA, in reducing cell viability and curtailing clonogenic expansion. This evaluation was performed within the context of the existing standard of care for GBM, encompassing Temozolomide (TMZ) and Radiotherapy. Our results unveiled striking insights into the potential of PDT as an innovative therapeutic strategy. Notably, Ox5 cells exhibited a remarkable reduction in viability, exceeding 70%, following exposure to PDT with 410 nm light and 5-ALA at a concentration of 50μM. A similar, albeit slightly less profound, effect was observed in G7 cells, with a viability decrease of more than 53%. These outcomes, meticulously quantified through the MTT viability assay (n=4), were reinforced by statistical significance, as indicated by p-values falling below 0.05 and, lower 0.001. Furthermore, clonogenic assays employing G7 cells provided an additional layer of evidence, demonstrating a substantial inhibition of clonogenic potential following PDT treatment with 410 nm light and 5-ALA. Immunohistochemistry techniques, particularly focusing on the cleaved caspase-3 marker, in both Ox5 core and G7 cells, underscoring the mechanistic basis of the observed cell death. In stark contrast, the conventional standard of care, involving TMZ monotherapy, was tested, and the results across four biological replicates were less significant. The relative viability of Ox5 and G7 cells exhibited no statistical significance, with p-values exceeding 0.05, implying a limited impact of this regimen on cell viability. Moreover, clonogenic assays conducted under the standard of care protocol (TMZ+/-Radiotherapy) unveiled the persistence of colonies, even at higher radiation doses of 4 and 6 Gy.In summary, PDT, specifically when implemented with 410 nm light and 5-ALA, represents a breakthrough strategy that leads to substantial cell death in both Ox5 and G7 cells. This compelling alternative therapy shines a hopeful light on the horizon of GBM treatment, providing a potentially transformative approach that can augment the current standard of care. Citation Format: Nazar Vasyliv, Karin Williams. Photodynamic therapy improves therapeutic management of glioblastoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 7593.

Abstract B018: Epigenetic targeting improves glioblastoma cell sensitivity to chemotherapy

Abstract B018: Epigenetic targeting improves glioblastoma cell sensitivity to chemotherapy

Aggressive pituitary tumors and carcinomas: medical treatment beyond temozolomide.

Aggressive pituitary tumors are a subset of pituitary neoplasms, characterized by unusually fast growth rate, invasiveness and overall resistance to optimized standard treatment. When metastases are present, the term pituitary carcinoma is employed. After failure of standard treatments, current guidelines recommend first-line temozolomide monotherapy. However, a significant number of patients do not respond to temozolomide, or experience disease progression following its discontinuation; in these latter cases, re-challenge with temozolomide is generally advised, although the reported outcomes have been less satisfactory. Although no alternative therapies have been formally recommended after temozolomide failure, growing evidence regarding potential second- or third-line therapeutic strategies has emerged. In the present work, we reviewed the available evidence published up to April 2023 involving the most relevant therapies employed so far, namely immune checkpoint inhibitors, bevacizumab, peptide radionuclide receptor therapy, tyrosine kinase inhibitors and mTOR inhibitors. For each treatment, we report efficacy and safety outcomes, along with data regarding potential predictors of response. Overall, immune checkpoint inhibitors and bevacizumab are showing the most promise as therapeutic options after temozolomide failure. The former showed better responses in pituitary carcinomas. Peptide radionuclide receptor therapy has also showed some efficacy in these tumors, while tyrosine kinase inhibitors and mTOR inhibitors have exhibited so far limited or no efficacy. Further studies, as well as an individualized, patient-tailored approach, are clearly needed. In addition, we report an unpublished case of a silent corticotroph pituitary carcinoma that progressed under dual immunotherapy, and then showed stable disease under a combination of lomustine and bevacizumab.

CTNI-31. TREATMENT BENEFIT IN PATIENTS AGED 80 YEARS OR OLDER WITH BIOPSY-PROVEN AND NON-RESECTED GLIOBLASTOMA IS DEPENDENT ON MGMT PROMOTER METHYLATION STATUS

Abstract PURPOSE Glioblastoma is associated with especially poor outcome in the elderly. It is unclear if patients aged ≥ 80 years benefit from tumor-specific therapy as opposed to receiving best supportive care (BSC) only. METHODS Patients with IDH-wildtype glioblastoma (WHO 2021), aged ≥ 80 years, and diagnosed by biopsy between 2010 and 2022 were included. Patient characteristics and clinical parameters were assessed. Uni- and multivariate analyses were performed. RESULTS 76 patients with a median age of 82 (range 80–89) and a median initial KPS of 80 (range 50–90) were included. Tumor-specific therapy was initiated in 52 patients (68%). 22 patients (29%) received temozolomide monotherapy, 23 patients (30%) were treated with radiotherapy (RT) alone and 7 patients (9%) received combination therapies. In 24 patients (32%), tumor-specific therapy was omitted in lieu of BSC. Overall survival (OS) was longer in patients receiving tumor-specific therapy (5.4 vs. 3.3 months, p<0.001). Molecular stratification showed that the survival benefit was owed to patients with MGMT promoter methylation (MGMTpos) who received tumor-specific therapy as opposed to BSC (6.2 vs. 2.6 months, p<0.001), especially to those with better clinical status and no initial polypharmacy. Patients with unmethylated MGMT promoter (MGMTneg) did not benefit from tumor-specific therapy (3.6 vs. 3.7 months, p=0.18). In multivariate analyses, better clinical status and MGMT promoter methylation were associated with prolonged survival (p<0.01 and p=0.01). CONCLUSION Benefit from tumor-specific treatment in patients with newly diagnosed glioblastoma aged ≥ 80 years might be restricted to MGMTpos patients, especially to those with good clinical status and no polypharmacy.

Responses to systemic therapy in metastatic pheochromocytoma/paraganglioma: a retrospective multicenter cohort study.

The therapeutic options for metastatic pheochromocytomas/paragangliomas (mPPGLs) include chemotherapy with cyclophosphamide/vincristine/dacarbazine (CVD), temozolomide monotherapy, radionuclide therapies, and tyrosine kinase inhibitors such as sunitinib. The objective of this multicenter retrospective study was to evaluate and compare the responses of mPPGLs including those with pathogenic variants in succinate dehydrogenase subunit B (SDHB), to different systemic treatments. This is a retrospective analysis of treatment responses of mPPGL patients (n = 74) to systemic therapies. Patients with mPPGLs treated at 6 specialized national centers were selected based on participation in the ENSAT registry. Survival until detected progression (SDP) and disease-control rates (DCRs) at 3 months were evaluated based on imaging reports. For the group of patients with progressive disease at baseline (83.8% of 74 patients), the DCR with first-line CVD chemotherapy was 75.0% (n = 4, SDP 11 months; SDHB [n = 1]: DCR 100%, SDP 30 months), with somatostatin peptide receptor-based radionuclide therapy (PPRT) 85.7% (n = 21, SDP 17 months; SDHB [n = 10]: DCR 100%, SDP 14 months), with 131I-meta-iodobenzylguanidine (131I-MIBG) 82.6% (n = 23, SDP 43 months; SDHB [n = 4]: DCR 100%, SDP 24 months), with sunitinib 100% (n = 7, SDP 18 months; SDHB [n = 3]: DCR 100%, SDP 18 months), and with somatostatin analogs 100% (n = 4, SDP not reached). The DCR with temozolomide as second-line therapy was 60.0% (n = 5, SDP 10 months; SDHB [n = 4]: DCR 75%, SDP 10 months). We demonstrate in a real-life clinical setting that all current therapies show reasonable efficacy in preventing disease progression, and this is equally true for patients with germline SDHB mutations.

THU520 Successful Treatment Of Ectopic ACTH From Metastatic Gastrinoma With Temozolomide Monotherapy

Abstract Disclosure: A. Syeda: None. A. Khan: None. D. Larosa: None. P. Kunz: None. B. Esayag-Tendler: None. Background: Temozolomide is a promising therapeutic agent for the treatment of refractory ACTH-secreting pituitary tumors. However, its role in the management of ectopic ACTH secretion due to neuro endocrine tumors (NETs) has not been well elucidated. Case: A 46-year-old man with a refractory functional pancreatic NET/ high grade metastatic gastrinoma, post distal pancreatectomy and splenectomy, briefly on everolimus therapy, presented with altered mentation and worsening edema. Clinically he had proximal muscle weakness, anasarca and hypokalemia with a potassium of 2.8mmol/L (n:3.6-5.1 mmol/L). Further work up revealed AM cortisol 79.6 ug/dL (n:7-23 ug/dL), 24-hour urine cortisol was 1820 ug/d (n: < 60 ug/d), ACTH 807 pg/mL (n:7.2-63.3 pg/mL) and gastrin level >10,000 pg/mL (n:0-100 pg/mL). Imaging studies of the brain, chest, abdomen, and pelvis were unremarkable. Octreotide infusion at 100 mg/hour was started with a goal to decrease gastrin and ectopic ACTH production. There was no response to Octreotide even after 5 days of continuous infusion, hence it was switched to subcutaneous injection form to control diarrhea. Lutathera/Peptide receptor radionuclide therapy was considered but held off due to the patient's delirium. As hypercortisolism is associated with multiple risks including thromboembolic events, rapid reduction of cortisol biosynthesis was achieved with Ketoconazole. Other options to inhibit steroidogenesis were available; the goal was to decrease both ACTH and Gastrin levels and for this reason Temozolomide was started. It crosses the blood-brain-barrier and hence was a preferred agent in this patient as he was noted to have atypical cells in the CSF. He received Temozolomide 150 mg/m² for 5 days of a 28-day cycle. Subsequently, AM cortisol decreased to 3.4 ug/dL, ACTH and gastrin started to trend down to 144 pg/mL and 3505 pg/mL respectively. Thereafter, the patient was given steroids and ketoconazole as part of a block and replace strategy to avoid adrenal insufficiency and hypercortisolism respectively. Temozolomide was very well tolerated; there were different reasons to hold Capecitabine including severe thrombocytopenia. Bilateral adrenalectomy was discussed but deferred as the ACTH levels decreased. Clinically, the patient reported improved muscle strength, edema and weight decreased significantly. The hospital stay was complicated by several other comorbidities which were managed appropriately by a multidisciplinary approach. Conclusion: Temozolomide should be considered in ACTH producing NETs refractory to conventional treatment strategies. Presentation: Thursday, June 15, 2023

Effectiveness and Safety of Different Postoperative Adjuvant Regimens in Patients with Low-Grade Gliomas: A Network Meta-Analysis

This study aimed to investigate the effectiveness and safety of various adjuvant regimens in patients with low-grade gliomas and to further explore the optimal adjuvant treatment for patients with low-grade gliomas and the differences in the efficacy of each treatment regimens in different tumor types. A comprehensive search of the PubMed, Cochrane Library, Ovid, Embase, and Web of Science databases was conducted to screen randomized and nonrandomized controlled trials related to adjuvant therapy in patients with low-grade gliomas. The Cochrane quality assessment method and the Newcastle-Ottawa Scale were used to assess the quality of the included randomized and nonrandomized controlled trials, respectively. The data from previous studies were extracted using Excel and GetData Graph Digitizer 2.26 software, and network meta-analysis was performed using RevMan 5.3 and Stata 16.0 statistical software. The specific ranking of 5-year progression-free survival (5-year PFS) for each treatment regimen from the best to the worst in patients with low-grade gliomas was surgery (S) combined with procarbazine, lomustine, and vincristine (S+PCV); surgery combined with standard radiotherapy and PCV multidrug chemotherapy (S+RT+PCV); surgery combined with standard radiotherapy and temozolomide monotherapy (S+RT+TMZ); surgery combined with enhanced radiotherapy (S+H-RT); surgery combined with standard radiotherapy (S+RT); surgery combined with TMZ (S+TMZ); and S. The 5-year overall survival (OS) ranking was S+RT+TMZ, S+RT+PCV, surgery combined with enhanced radiotherapy and TMZ monotherapy (S+H-RT+TMZ), S+H-RT, S+RT, and S. The 2-year progression-free survival ranking was S+RT+TMZ, S+PCV, S+RT, S+RT+PCV, S+TMZ, S+H-RT, and S. The 2-year overall survival ranking was S+RT+TMZ, S+H-RT+TMZ, S+RT, S+RT+PCV, S+H-RT, and S. The incidence of adverse events (≥3) was ranked from highest to lowest as follows: S+RT+PCV, S+RT+TMZ, S+PCV, S+H-RT, S+TMZ, and S+RT. In the isocitrate dehydrogenase 1/2 mutation nonchromosome 1p and 19q chromosome whole arm codeletion (IDHmt/noncoder) group, the S+RT+PCV and S+H-RT regimens had better 5-year PFS and 5-year OS. In the isocitrate dehydrogenase 1/2 mutation and chromosome 1p and 19q chromosome whole arm codeletion (IDHmt/coder) group, the 5-year PFS of each treatment regimen ranked from the best to the worst was S+RT+TMZ, S+RT+PCV, S+H-RT, S+RT, S+TMZ, and S. The order of 5-year OS from the best to the worst was S+H-RT, S+RT+TMZ, S+RT+PCV, S+RT, and S. In the isocitrate dehydrogenase 1/2 wild-type (IDHwt) group, the S+H-RT and S+TMZ regimens had better 5-year PFS. This study revealed that both the S+RT+TMZ and S+RT+PCV regimens might be effective therapies for treating patients with low-grade gliomas. Among these, the S+RT+TMZ regimen seemed to be safer but might lead to tumor deterioration. In the IDHmt/coder type, the S+RT+TMZ scheme might have a significant advantage. In the IDHmt/noncoder type, the S+RT+PCV scheme might be more dominant, while in the IDHwt type, the S+H-RT and S+TMZ schemes also might be good treatment options.

Co-administration of temozolomide (TMZ) and the experimental therapeutic targeting miR-10b, profoundly affects the tumorigenic phenotype of human glioblastoma cells.

Introduction: Recent studies have shown that miRNA-10b is highly expressed in high-grade glioblastoma multiforme (GBM), and its inhibition leads to deregulation of multiple pathways in tumorigenesis, resulting in repression of tumor growth and increased apoptosis. Thus, we hypothesized that suppressing miR-10b could enhance the cytotoxicity of conventional GBM chemotherapy with temozolomide (TMZ). Methods: Inhibition of miR-10b in glioblastoma cells was achieved using an experimental therapeutic consisting of anti-miR10b antagomirs conjugated to iron oxide nanoparticles (termed MN-anti-miR10b). The nanoparticles serve as delivery vehicles for the antagomirs as well as imaging reporters guiding the delivery in future animal studies. Results: Treatment of U251 and LN229 human glioblastoma cells with MN-anti-miR10b led to inhibition of miR-10b accompanied by repression of growth and increase in apoptosis. We next explored whether MN-anti-miR10b could enhance the cytotoxic effect of TMZ. During these studies, we unexpectedly found that TMZ monotherapy increased miR-10b expression and changed the expression of corresponding miR-10b targets. This discovery led to the design of a sequence-dependent combination treatment, in which miR-10b inhibition and induction of apoptosis by MN-anti-miR10b was followed by a sub-therapeutic dose of TMZ, which caused cell cycle arrest and ultimately cell death. This combination was highly successful in significant enhancement of apoptosis and decrease in cell migration and invasiveness. Discussion: Considering the unexpected effects of TMZ on miR-10b expression and possible implications on its clinical application, we reasoned that comprehensive in vitro studies were warranted before embarking on studies in animals. These intriguing findings serve as a solid foundation for future in vivo studies and offer promise for the successful treatment of GBM.

A multicenter retrospective study of the duration of adjuvant temozolomide in IDH-mutant gliomas.

e14048 Background: Gliomas with isocitrate dehydrogenase (IDH) mutations have improved prognosis and are more treatment responsive compared to IDH wild-type gliomas. For glioblastoma (IDH wild-type glioma), Stupp protocol has demonstrated superiority with 6 cycles of adjuvant temozolomide (TMZ). However, recommended duration of TMZ for IDH mutant gliomas is not well-defined, with studies such as RTOG 0424, CATNON, and CODEL extending treatment up to 12 cycles. Prolonged TMZ duration following radiation therapy (RT) is associated with increased toxicity including both financial (cost of drug, lab work, and visits) and drug side effects including cytopenias. We aimed to evaluate for any differences in survival between patients treated with more than 6 cycles of TMZ and those treated with 6 or fewer. Methods: We conducted a multicenter retrospective study of patients treated at the University of Washington and Stanford Medical Center for oligodendrogliomas (oligo) and IDH mutated astrocytomas (astro) using World Health Organization 2016 molecular diagnostic criteria including IDH mutation. Other inclusion criteria were grades 2 and 3, as well as treatment with RT (with or without concurrent TMZ) followed by adjuvant TMZ monotherapy with number of cycles documented. Survival probability, mean overall survival (mOS) and mean progression-free survival (mPFS), were calculated using Kaplan-Meier method with distributions compared using log-rank test in Prism GraphPad comparing >6 cycles of adjuvant TMZ and ≤6 cycles. Results: Of 153 patients treated with both XRT and adjuvant TMZ, 88 were treated with between 1 and 6 cycles of adjuvant TMZ, while 91 were treated with >6 cycles Treatment duration ranged from 1-12 cycles for oligos, 4-12 cycles for grade 2 astros, and 1-14 cycles for grade 3 astros. mOS of oligos was undefined for those treated with 1-6 cycles and 84 months (m) for those treated with >6 cycles (p=0.1448). mOS of grade 2 astros was 154m for those treated with 1-6 cycles and 162.9m for those treated with >6 cycles (p=0.8864). mOS of grade 3 astros was undefined for those treated with 1-6 cycles and 117m for those treated with >6 cycles (p=0.8003). mPFS of oligos was 93m for those treated with 1-6 cycles and undefined for those treated with >6 cycles (p=0.584). mPFS of grade 2 astros was 79.6m for those treated with 1-6 cycles and 144.56m for those treated with >6 cycles (p=0.610). mPFS of grade 3 astros was 72m for those treated with 1-6 cycles and 79.4m for those treated with >6 cycles (p=0.9596). Conclusions: While this study is limited by power, there was no difference in mOS or mPFS with greater than 6 cycles of TMZ among patients with oligodendrogliomas and IDH mutant astrocytomas. More data is needed to evaluate the optimal treatment duration to maximize survival without over-exposing these patients to toxicities.[Table: see text]

Treatment benefit in patients aged 80 years or older with biopsy-proven and non-resected glioblastoma is dependent on MGMT promoter methylation status

PurposeGlioblastoma is associated with especially poor outcome in the elderly. It is unclear if patients aged ≥80 years benefit from tumor-specific therapy as opposed to receiving best supportive care (BSC) only.MethodsPatients with IDH-wildtype glioblastoma (WHO 2021), aged ≥80 years, and diagnosed by biopsy between 2010 and 2022 were included. Patient characteristics and clinical parameters were assessed. Uni- and multivariate analyses were performed.Results76 patients with a median age of 82 (range 80–89) and a median initial KPS of 80 (range 50–90) were included. Tumor-specific therapy was initiated in 52 patients (68%). 22 patients (29%) received temozolomide monotherapy, 23 patients (30%) were treated with radiotherapy (RT) alone and 7 patients (9%) received combination therapies. In 24 patients (32%), tumor-specific therapy was omitted in lieu of BSC. Overall survival (OS) was longer in patients receiving tumor-specific therapy (5.4 vs. 3.3 months, p < 0.001). Molecular stratification showed that the survival benefit was owed to patients with MGMT promoter methylation (MGMTpos) who received tumor-specific therapy as opposed to BSC (6.2 vs. 2.6 months, p < 0.001), especially to those with better clinical status and no initial polypharmacy. Patients with unmethylated MGMT promoter (MGMTneg) did not benefit from tumor-specific therapy (3.6 vs. 3.7 months, p = 0.18). In multivariate analyses, better clinical status and MGMT promoter methylation were associated with prolonged survival (p < 0.01 and p = 0.01).ConclusionBenefit from tumor-specific treatment in patients with newly diagnosed glioblastoma aged ≥80 years might be restricted to MGMTpos patients, especially to those with good clinical status and no polypharmacy.

MODL-27. PRECLINICAL INTERROGATION OF IMMUNOTHERAPY TREATMENT STRATEGIES IN GLIOBLASTOMA (GBM) USING A CLINICALLY RELEVANT DISEASE MODEL

Abstract Clinically faithful pre-clinical models are essential for screening therapies and studying resistance mechanisms. Historically models have failed to predict response in the clinical setting. Current models seldom incorporate surgical resection, and commonly use young animals whose immune contexture differs from older patients. Here, we have established an orthotopic model, employing the syngeneic, mesenchymal-NFpp10a-cell line, in both young and aged mice. We have characterised the model's response to standard of care resection and temozolomide (TMZ) treatment. We have further studied response to anti-PD1 therapy (adjuvant and neoadjuvant). NFpp10a-Luc2 expressing cells were orthotopically implanted into C57BL/6 mice (aged { &amp;gt; 18months} and young {6-8weeks}) and weekly bioluminescence imaging (BLI) performed to monitor tumour growth. Several therapeutic interventions were assessed to study tumour growth and survival: (1)surgical resection, (2)TMZ, (3)anti-PD1 (4)neoadjuvant anti-PD1. RNAseq, murine microenvironment cell population (mMCP) counter and gene ontology analyses characterised treatment related changed in the TME. We demonstrated survival advantage in aged mice undergoing resection (Resection:33.5 days vs Non-Resection:18 days;p=0.0166). Subsequently, we observed that TMZ and anti-PD1 monotherapy had no impact on NFpp10a-Luc2 growth (TMZ-overall:p=0.9001, and anti-PD1-overall:p = 0.7933) or survival (TMZ-overall:p = 0.3035, anti-PD1-overall:p= 0.6328). Neoadjuvant anti-PD1 treated mice demonstrated no survival advantage compared to IgG control (33-days vs 35-days:p = 0.9429). or BLI signal (p = 0.1703). NFpp10a-Luc2 forms immune-cold TME relative to commonly employed models. mMCP counter analysis demonstrates neoadjuvant anti-PD1 induced influx of CD8+-T cells, B cells, and monocytes into the TME compared to IgG control, and was associated with significantly upregulated CXCR3 chemokine receptor binding pathway on gene ontology analysis (p = 0.0045). Overall, we have, for the first time established and characterised response of the NFpp10a-Luc2-C57BL/6 model to resection, TMZ and anti-PD1 therapies. NFpp10a-Luc2 tumours demonstrate similar therapeutic resistance and TME profile compared to human mesenchymal GBM. The model may therefore be employed in future pre-clinical studies to guide clinical trials in mesenchymal GBM.

The Impact of Chemoradiotherapy on Biophysical Properties of Glioblastoma Utilizing a Novel Murine Model

<h3>Purpose/Objective(s)</h3> Glioblastoma, historically viewed as a single disease entity, is now known to be composed of various subtypes. Here, we present our work evaluating the effects of chemoradiotherapy on cellular biophysical processes using a novel murine model of glioblastoma developed by our group. <h3>Materials/Methods</h3> Primary tumor cell lines were established from a murine glioma model generated from a synthetic DNA transposon system delivered oncogenic drivers SV40-LgTA and either NRASV12 or PDGFB. We have previously shown these cell lines, termed NRAS and PDGF, respectively, recapitulate the mesenchymal and proneural tumor subtypes. Treatment was administered with temozolomide (TMZ) to a maximum of 100µM, single fraction radiation therapy (RT) to a maximum of 10 Gy, or both. Cells were stained with Hoechst dye, imaged with an epifluorescence microscope with 10X objective lens, and counted with an image segmentation algorithm daily for 4 days to estimate cell survival and proliferation. On post-treatment day 4, surviving cells were plated on Matrigel coated 9.3kPa polyacrylamide gel and imaged with an inverted, transmitted light microscope with 10X objective lens every 5 minutes for 4 hours. Single cell mean squared displacement (MSD) was measured from time lapse images via an image segmentation algorithm. The random motility coefficient (µ) was calculated by the relationship MSD(t) = 4µt, where t is time. Data was compared via the Kruskal-Wallis test with Bonferroni correction for multiple comparisons when appropriate. <h3>Results</h3> There was no significant difference in cellular death or proliferation between treatment and control arms for the PDGF cell lines. In the NRAS cell lines, TMZ alone did not induce cell death while RT (P < 0.01) and combined modality therapy (P < 0.01) yielded cellular killing in a dose dependent manner. Furthermore, RT-treated NRAS cells proliferated more slowly than non-treated cells (0.05 vs. 0.20 hr-1, P=0.04). Control NRAS cell lines migrated faster than their PDGF counterparts at baseline (3.82 vs. 0.73 µm2/hr, P<1E-5). Within each cell line, the use of combined modality therapy significantly reduced cellular motility (PDGF: 0.73 vs. 0.21 µm2/hr, P=0.008; NRAS: 0.65 vs. 3.82 µm2/hr, P<1E-5). RT monotherapy additionally reduced motility in NRAS cell lines (1.07 vs. 3.82 µm2/hr, P<1E-5) while no difference was observed in PDGF cells. TMZ monotherapy did not affect motility within either cell line. <h3>Conclusion</h3> We evaluated biophysical properties of a novel murine glioma model utilizing oncogenic drivers overexpressing NRASV12 or PDGFB which we have previously shown recapitulates the mesenchymal and proneural subtypes of human glioblastoma, respectively. Here, we observed phenotypic differences in cellular migration following RT and TMZ regimens which could have subtype-specific ramifications for radiotherapy dose and target volume delineation.

Temozolomide Sensitivity of Malignant Glioma Cell Lines – A Systematic Review Assessing Consistencies Between In Vitro Studies

Abstract AIMS Malignant glioma cell line models are integral to pre-clinical testing of novel potential therapies. Accurate prediction of likely efficacy in the clinic requires that these models are reliable and consistent. We assessed this by examining the reporting of experimental conditions and sensitivity to temozolomide in glioma cells lines. METHOD We searched Medline and Embase (Jan 1994-Jan 2021) for studies evaluating the effect of temozolomide monotherapy on cell viability of at least one malignant glioma cell line. Key data items included type of cell lines, temozolomide exposure duration in hours (hr), and cell viability measure (IC50). RESULTS We included 212 studies from 2789 non-duplicate records that reported 248 distinct cell lines. The commonest cell line was U87 (60.4%). Only 10.4% studies used a patient-derived cell line. The proportion of studies not reporting each experimental condition ranged from 8.0–27.4%, including base medium (8.0%), serum supplementation (9.9%) and number of replicates (27.4%). In studies reporting IC50, the median value for U87 at 24 h, 48 h and 72 h was 123.9 μM (IQR 75.3–277.7 μM), 223.1 μM (IQR 92.0–590.1 μM) and 230.0 μM (IQR 34.1–650.0 μM), respectively. The median IC50 at 72 h for patient-derived cell lines was 220 μM (IQR 81.1–800.0 μM). CONCLUSION Temozolomide sensitivity reported in comparable studies was not consistent between or within malignant glioma cell lines. Drug discovery science performed on these models cannot reliably inform clinical translation. A consensus model of reporting can maximise reproducibility and consistency among in vitro studies.

P11.51.B Initial temozolomide monotherapy without radiotherapy might be of limited benefit in the treatment of astrocytoma, IDH-mutant, CNS WHO grade 2 and 3

Abstract Background The role of temozolomide chemotherapy alone in isocitrate dehydrogenase (IDH-) mutant astrocytomas has not been conclusively determined. Radiotherapy might be superior to temozolomide alone. Recent studies have linked temozolomide therapy with poor clinical course and induction of hypermutation in IDH-mutant gliomas. Material and Methods In this retrospective, single-center study, 183 patients with astrocytoma, IDH-mutant, CNS WHO grade 2 or 3 according to WHO 2021 and diagnosed between 2000 and 2019 were included. Patients initially monitored by means of a wait-and-scan strategy, or treated with radiotherapy alone, or receiving temozolomide alone after histological sampling through biopsy or tumor resection were studied. Patient-related, clinical and imaging data were correlated with progression-free and overall survival. A matched-pair analysis accounting for post-surgical tumor volume was conducted. Results No significant differences in median age and clinical status at diagnosis was seen. WHO grades were balanced between patients treated with radiotherapy and temozolomide, but the proportion of WHO grade 2 gliomas was higher in the wait-and-scan cohort. Radiotherapy was associated with significantly longer overall survival than temozolomide (in years, 14.4 vs 10.7; p=0.02) and longer progression-free survival than temozolomide (in years, 6.2 vs 3.4, p=0.02) and wait-and-scan strategies (in years, 6.2 vs 4; p=0.03). Comparing wait-and-scan with temozolomide, survival was significantly longer in the wait-and-scan cohort (in years, not reached vs 10.7, p&amp;lt;0.0001). An analysis of WHO grade 2 astrocytomas only also showed superior survival in the wait-and-scan cohort as compared to temozolomide (p=0.02). Of note PFS was similar overall and in WHO grade 2 astrocytomas. Conclusion The results suggest superiority of radiotherapy alone over temozolomide alone or wait-and-scan strategies in IDH-mutant WHO grade 2 and 3. Recent study results indicating that temozolomide might compromise prognosis in some IDH-mutant gliomas might be supported by our data, although caution in interpretation of retrospective data is required. The potential negative effects may only be apparent in the long-term.

EP14.05-004 Temozolomide and Atezolizumab as Second Line Treatment for Extensive Stage Small Cell Lung Cancer: A Randomized, Multi-Cohort Phase 2 Trial

Treatment options are limited for patients with extensive stage small cell lung cancer (ES-SCLC) after progression on first line chemo-immunotherapy (CIT). Temozolomide (TEM) is active in ES-SCLC and has been shown to have an immunomodulatory effect for patients with advanced cancers. Immune checkpoint inhibitor (ICI) therapy combined with TEM has demonstrated promising activity among patients in 2nd and 3rd line after CIT (NCT03728361, reported at this meeting). Two different dosing regimens of TEM monotherapy have been explored in ES-SCLC but the objective response rate among patients treated after first line CIT remains unknown.

Abstract 5362: Targeting PIK3CB in glioblastoma

Abstract Background: Glioblastoma (GBM) is the most common and one of the most lethal malignant brain tumors in existence. The poor prognosis of this disease is due in part to tumor recurrence and temozolomide (TMZ) resistance, for which PI3K/AKT pathway overactivation has been implicated. Our work is to demonstrate that p110β inhibition could represent a therapeutic target in sensitizing recurrent tumors to TMZ therapy, and demonstrate the utility of personalized GBM treatments. Objective: We aim to develop a more effective treatment for TMZ resistant GBM patients. We hypothesize that a p110β inhibitor will sensitize resistant GBM cell lines to TMZ therapy. We intend to support this hypothesis by demonstrating that the p110β inhibitor TGX-221 in combination with TMZ will provide a significantly greater level of cytotoxicity on TMZ resistant GBM cell lines than TGX-221 or TMZ monotherapy alone. We also intend to provide further evidence for this therapy by utilizing it to overcome TMZ resistance in glioblastoma stem cells (GSC’s). Methods: We compared the cytotoxicity of TMZ, TGX-221, and a TMZ/TGX-221 combination therapy on p110β-high/TMZ resistant and p110β-low/TMZ sensitive GBM cell lines. Cell viability was determined using the MTS assay. We then tested these reagents on normal human astrocytes to determine any potential dose-limiting off-target effects. Lastly, we tested these reagents using human-derived GSC’s. Results: A statistically significant difference (p &amp;lt; 0.01) in cell viability was found using the TMZ/TGX-221 combination therapy as compared to either TMZ or TGX-221 alone in our TMZ resistant SF295 cells, and a significant different was found between the combination therapy and TMZ monotherapy in our TMZ resistant U87MG cells. No significant difference was found between treatments in our TMZ sensitive A172 cells or normal human astrocytes. Conclusions: The results of our GBM cell line experiments provide support that combination TMZ/TGX-211 is superior in cytotoxicity to either monotherapy alone in TMZ resistant cell lines. This indicates that TGX-211, through p110β inhibition, is able to sensitize resistant cell lines to TMZ therapy. More experiments are ongoing to determine if this effect will also be demonstrated in human-derived GSC’s. Citation Format: Marc R. Fromherz, Kevin J. Pridham, Zhi Sheng. Targeting PIK3CB in glioblastoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 5362.

Regorafenib Reverses Temozolomide-Induced CXCL12/CXCR4 Signaling and Triggers Apoptosis Mechanism in Glioblastoma.

Temozolomide (TMZ) monotherapy is known to be insufficient for resistant/relapsed glioblastoma (GBM), thus seeking a sensitization agent for TMZ is necessary. It was found that regorafenib may improve the overall survival of relapsed GBM patients. We aimed to discover whether regorafenib can enhance the anti-GBM effects of TMZ, and elucidate underlying mechanism. Our analysis of The Cancer Genome Atlas database revealed that the increased expression of CXCR4 is linked to poor survival of GBM patients. Additionally, TMZ treatment may trigger CXCR4/CXCL12 axis of GBM. We used two GBM cell lines, two primary GBM cells, and animal model to identify underlying mechanism and treatment efficacy of regorafenib combined with TMZ by cytotoxicity, apoptosis, reporter gene and invasion/migration assays, chemokine array, Western blotting, MRI, microarray, and immunohistochemistry. We observed that the chemokine CXCL-12 and its receptor CXCR4 regulate the resistance to TMZ, whereas the inhibition of CXCL-12/CXCR4 signaling sensitizes GBM cells to TMZ. The TMZ-induced CXCL-12/CXCR4 signaling, phosphor-extracellular signal-regulated kinases 1 and 2 (ERK1/2) and nuclear factor kappa light chain enhancer of activated B cells (NF-κB), and NF-κB-related proteins can effectively diminish when combining with regorafenib. Regorafenib significantly enhanced the TMZ-induced extrinsic/intrinsic apoptotic pathways, and facilitated the suppression of invasion and migration potential in GBM. Orthotopic tumor experiments demonstrated tumor size reduction and prolonged survival in combination group even with half-dose of TMZ. Our findings provide promising evidence that regorafenib may sensitize GBM to TMZ treatment through inhibition of the CXCL12/CXCR4/ERK/NF-κB signaling.

Growth suppression of glioblastoma multiforme cell line response to the combination of Temozolomide and Nimotuzumab

Background: Researches towards Glioblastoma multiforme therapy (GBM) has been performed, especially in finding the tumor’s genetic cellular expression. The overexpression of EGFR, frequently found in human malignancies, is known to significantly impact cancer cells hallmark traits, such as increased cell survival, proliferation and invasion. This research is performed to figure out the synergistic effect of temozolomide, the main chemotherapy regimen used, and the monoclonal antibody anti-EGFR nimotuzumab in inhibiting the growth of GBM cells in vitro.Methods: We performed cell cultures using GBM U87MG cells and administered nimotuzumab 1000µg/ml and temozolomide 20 µg/ml in different sequences and timings. Inhibition of GBM cell growth is evaluated by measuring Ki-67 and ?H2AX levels using flowcytometry and tested with one-way ANOVA. Data were analyzed using SPSS version 21 for Windows.Results: Levels of Ki-67 were in the control group (23.17±1.72), nimotuzumab monotherapy (15.43±1.70), temozolomide monotherapy (14.80±1.37), simultaneous therapy (10.73±1.19), nimotuzumab 24 hours before temozolomide (10.57±1.05), and nimotuzumab 48 hours before temozolomide (14.47±1.37). The level of ?H2AX is measured in the control group (11.90±1.25), nimotuzumab monotherapy (29.33±1.91), temozolomide monotherapy (28.13±1.58), simultaneous therapy (41.53±3.51), nimotuzumab 24 hours before temozolomide (39.56±2.06), and nimotuzumab 48 hours before temozolomide (35.93±3.56).Conclusion: This research shows that administration of nimotuzumab simultaneously with temozolomide and nimotuzumab 24 hours before temozolomide effectively inhibits the growth of U87MG GBM cells. Inhibition of EGFR expression before temozolomide administration is able to increase DNA damage and inhibit the proliferation of glioma cells.

Temozolomide sensitivity of malignant glioma cell lines \u2013 a systematic review assessing consistencies between in vitro studies

BackgroundMalignant glioma cell line models are integral to pre-clinical testing of novel potential therapies. Accurate prediction of likely efficacy in the clinic requires that these models are reliable and consistent. We assessed this by examining the reporting of experimental conditions and sensitivity to temozolomide in glioma cells lines.MethodsWe searched Medline and Embase (Jan 1994-Jan 2021) for studies evaluating the effect of temozolomide monotherapy on cell viability of at least one malignant glioma cell line. Key data items included type of cell lines, temozolomide exposure duration in hours (hr), and cell viability measure (IC50).ResultsWe included 212 studies from 2789 non-duplicate records that reported 248 distinct cell lines. The commonest cell line was U87 (60.4%). Only 10.4% studies used a patient-derived cell line. The proportion of studies not reporting each experimental condition ranged from 8.0–27.4%, including base medium (8.0%), serum supplementation (9.9%) and number of replicates (27.4%). In studies reporting IC50, the median value for U87 at 24 h, 48 h and 72 h was 123.9 μM (IQR 75.3–277.7 μM), 223.1 μM (IQR 92.0–590.1 μM) and 230.0 μM (IQR 34.1–650.0 μM), respectively. The median IC50 at 72 h for patient-derived cell lines was 220 μM (IQR 81.1–800.0 μM).ConclusionTemozolomide sensitivity reported in comparable studies was not consistent between or within malignant glioma cell lines. Drug discovery science performed on these models cannot reliably inform clinical translation. A consensus model of reporting can maximise reproducibility and consistency among in vitro studies.