Chemotherapy Of Malignant Gliomas Research Articles

Bioinspired Adaptive Microdrugs Enhance the Chemotherapy of Malignant Glioma: Beyond Their Nanodrugs.

Solid nanoparticle-mediated drug delivery systems are usually confined to nanoscale due to the enhanced permeability and retention effect. However, they remain a great challenge for malignant glioma chemotherapy because of poor drug delivery efficiency and insufficient tumor penetration resulting from the blood-brain barrier/blood-brain tumor barrier (BBB/BBTB). Inspired by biological microparticles (e.g., cells) with excellent adaptive deformation, it is demonstrated that the adaptive microdrugs (even up to 3.0µm in size) are more efficient than their nanodrugs (less than 200nm in size) to cross BBB/BBTB and penetrate into tumor tissues, achieving highly efficient chemotherapy of malignant glioma. The distinct delivery of the adaptive microdrugs is mainly attributed to the enhanced interfacial binding and endocytosis via adaptive deformation. As expected, the obtained adaptive microdrugs exhibit enhanced accumulation, deep penetration, and cellular internalization into tumor tissues in comparison with nanodrugs, significantly improving the survival rate of glioblastoma mice. It is believed that the bioinspired adaptive microdrugs enable them to efficiently cross physiological barriers and deeply penetrate tumor tissues for drug delivery, providing an avenue for the treatment of solid tumors.

Basic principles of contemporary chemotherapy of malignant gliomas of the brain

The modern view on the place of antiblastic chemotherapy in clinical neuro-oncology based on NCCN 2021 clinical guidelines (The National Comprehensive Cancer Network), EANO recommendations (The European Association for Neuro-Oncology), cIMPACT-NOW (The Consortium for Inform Molecular and Practical Approaches to CNS Tumor Taxonomy) and many years of experience of the department of adjuvant treatment for the central nervous system tumors of the State Institution "Romodanov Neurosurgery Institute, Ukraine" is presented and the basic principles of its application in the complex treatment of malignant gliomas of the brain are substantiated. Malignant gliomas are a heterogeneous group of the most numerous primary tumors of the central nervous system, differing in both the grade of malignancy and the prognosis of the disease. The latest WHO tumors classification 2021 defines this group of tumors as "diffuse gliomas" of the brain, that is, the term itself indicates infiltrative nature of their growth, that limits the possibility of surgical removal and requires a multimodal approach to their treatment in order to maximize the reduction of tumor tissue. The new era of chemotherapy in neuro-oncology, as well as in general oncology, began with the study of the molecular profile of tumors, which is important both for predicting the course of the disease and for choosing tactics of chemotherapeutic treatment of malignant gliomas. It’s enough to give the following example: in the absence of IDH gene mutation and co-deletion of chromosome 1p/19q loci in grade 2 of anaplasia diffuse gliomas, the prognosis of the disease does not differ from that in glioblastoma multiforme. For the same reason, in modern neuro-oncology, the designation of molecular genetic markers in malignant gliomas is essential for the personification of the treatment of pathology is essential to personalize the treatment of this pathology.

Elastin-like Polypeptide Hydrogels for Tunable, Sustained Local Chemotherapy in Malignant Glioma.

Glioblastoma (GBM) is a primary brain tumor that carries a dismal prognosis, which is primarily attributed to tumor recurrence after surgery and resistance to chemotherapy. Since the tumor recurrence appears near the site of surgical resection, a concept of immediate and local application of chemotherapeutic after initial tumor removal could lead to improved treatment outcome. With the ultimate goal of developing a locally-applied, injectable drug delivery vehicle for GBM treatment, we created elastin-like polypeptide (ELP) hydrogels. The ELP hydrogels can be engineered to release anti-cancer drugs over an extended period. The purpose of this study was to evaluate the biomechanical properties of ELP hydrogels, to characterize their ability to release doxorubicin over time, and to investigate, in vitro, the anti-proliferative effect of Dox-laden ELP hydrogels on GBM. Here, we present microstructural differences, swelling ratio measurements, drug release characteristics, and in vitro effects of different ELP hydrogel compositions. We found that manipulation of the ELP–collagen ratio allows for tunable drug release, that the released drug is taken up by cells, and that incubation with a small volume of ELP-Dox hydrogel drastically reduced survival and proliferation of GBM cells in vitro. These results underscore the potential of ELP hydrogels as a local delivery strategy to improve prognosis for GBM patients after tumor resection.

Cerebral Edema Due to Chemotherapeutic Wafer Implantation for Malignant Glioma: Registry Study of Correlation with Perioperative Epileptic Seizures

Factors predicting adverse events following implantation with wafers containing 1,3-bis(2-chloroethyl)-1-nitrosourea (carmustine, BCNU), which is used in local chemotherapy for malignant gliomas (MGs), are unknown. The association between cerebral edema (CE), which often occurs after implantation, and perioperative seizures, which are often observed in MG cases, is under debate. This study investigated risk factors for CE associated with BCNU wafer implantation and their relationship with perioperative seizures. A total of 31 surgical cases involving 28 adult patients who underwent BCNU wafer implantation for MGs were investigated and classified into those with and without postoperative transient CE. We assessed the correlations between CE caused by BCNU implantation and various factors, including postoperative epileptic seizures. World Health Organization (WHO) grade III MGs significantly affected postoperative CE (p = 0.003) and the occurrence of seizures (p = 0.0004). Factors predictive of postoperative seizures were WHO grade III MGs (p = 0.0026), increased postoperative CE (p = 0.0272), and history of preoperative seizures (p = 0.0316). Postoperative CE, WHO grade III MGs, and a history of preoperative seizures might predict the postoperative occurrence of seizures, necessitating stringent management of seizures and CE in the affected patients.

MGMT-Methylation in Non-Neoplastic Diseases of the Central Nervous System.

Quantifying O6-methylguanine-DNA methyltransferase (MGMT) promoter methylation plays an essential role in assessing the potential efficacy of alkylating agents in the chemotherapy of malignant gliomas. MGMT promoter methylation is considered to be a characteristic of subgroups of certain malignancies but has also been described in various peripheral inflammatory diseases. However, MGMT promoter methylation levels have not yet been investigated in non-neoplastic brain diseases. This study demonstrates for the first time that one can indeed detect slightly enhanced MGMT promoter methylation in individual cases of inflammatory demyelinating CNS diseases such as multiple sclerosis and progressive multifocal leucencephalopathy (PML), as well as in other demyelinating diseases such as central pontine and exptrapontine myelinolysis, and diseases with myelin damage such as Wallerian degeneration. In this context, we identified a reduction in the expression of the demethylase TET1 as a possible cause for the enhanced MGMT promoter methylation. Hence, we show for the first time that MGMT hypermethylation occurs in chronic diseases that are not strictly associated to distinct pathogens, oncogenic viruses or neoplasms but that lead to damage of the myelin sheath in various ways. While this gives new insights into epigenetic and pathophysiological processes involved in de- and remyelination, which might offer new therapeutic opportunities for demyelinating diseases in the future, it also reduces the specificity of MGMT hypermethylation as a tumor biomarker.

STMO-01 Cerebral edema and perioperative epilepsy due to placement of BCNU wafer for malignant glioma

Introduction: Cerebral edema is the most frequent adverse event of BCNU wafer, which is used as local chemotherapy of malignant glioma. However, predictive factor of this event is unknown. Moreover, there is no consensus about cerebral edema and perioperative seizure, which is often observed in glioma. Here, we report risk factor of cerebral edema with BCNU placement and relationship with perioperative seizure in malignant glioma cases.Material and Method: Thirty-one case of adult malignant glioma who underwent BCNU placement in our institute between March 2013 to March 2019 were investigated. The patients were dichotomized to two groups; patient with postoperative transient cerebral edema (CE+ group) and patient without postoperative transient cerebral edema (CE- group).Result: Postoperative cerebral edema associated with placement of BCNU was observed in 9 out of 31 patients (29%). Tumor malignancy was significant parameter for postoperative cerebral edema (p=0.003). Other factors such as, age, gender, laterality, tumor location, primary or recurrent, number of BCNU wafers, duration of recurrence were not significant for postoperative cerebral edema. Seizure was seen in 14 patients (45%), and cerebral edema was not significant parameter for seizure. Tumor malignancy was significant parameters for postoperative cerebral edema. Tumor malignancy was significant parameters for seizure (p=0.0004). Although postoperative seizure was observed in 4 patients (44%) with CE+ group, neither maximum volume (mean 61.1 ml) nor change ratio (mean 354%) of FLAIR-high-intensity region were not related with postoperative seizure.Conclusions: Tumor malignancy was important factor for patients who underwent placement of BCNU wafer with postoperative cerebral edema and seizure. On the other hand, there were no relationship between postoperative cerebral edema and perioperative seizure in patients treated with BCNU wafer.

Abstract 6436: A potential treatment for malignant glioblastoma: Silver nanoparticles and low-level laser combination

Abstract Glioblastomamultiforme (GBM) is a dreadful primary brain tumor characterized with extremely poor prognosis and survival rate, despite available treatments. The failure of current therapies to eliminate specific subpopulations within heterogeneous GBM has been considered a key factor contributing to the inevitable recurrence after treatments. To address this concern, it is necessary to develop novel treatments, which can kill all the GBM cells or at least convert the heterogeneous GBM population to homogeneous populations, which can be easily targeted. In this study, we investigated the effects of Ag-PMMA-PAA nanoparticles (Silver np's) on human malignant glioma(U251) cells and Silver np's role in combinational use with low-level He-Ne laser (632.8nm) against U251 cells.The Silver np's were synthesized using a green chemistry approach and were then characterized using spectroscopic methods. Dose and time dependent studies revealed that the maximum killing (81%) of U251 cells occurred at 225μM Silver np's over 6 hours. Moreover, combined HeNe laser exposure resulted in overall cell death of 92%. Western analysis suggests caspase family members, other than caspase 9, are involved in killing Silver np treated U251 cells or the combination treatment. Thus, our Silver np and low-level laser combination treatment could have a potential application in enhancing chemotherapy for malignant glioma. Citation Format: Rohini Atluri, Daniel Korir, Nishant Tyagi, Eunyoung Kim, Tae-Youl Choi, Denise P. Simmons. A potential treatment for malignant glioblastoma: Silver nanoparticles and low-level laser combination [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 6436.

Temozolomide desensitization followed by metronomic dosing in patients with hypersensitivity.

Temozolomide is the most effective chemotherapy for malignant glioma. Hypersensitivity requiring interruption of therapy may significantly impact patient survival. We have successfully employed temozolomide desensitization followed by metronomic dosing of temozolomide. Our purpose was to report patient characteristics and outcomes in patients with glioma (Grade 2-4) and temozolomide hypersensitivity managed by desensitization and metronomic dosing. We performed an observational study of 15 patients at Mayo Clinic (Rochester) with a diagnosis of glioma who underwent temozolomide desensitization with subsequent metronomic dosing from May 2012 to January 2017. We calculated overall and progression-free survival using the Kaplan-Meier method, and log-rank analyses to assess for differences in survival by WHO Grade or treatment initiation. Median age at time of desensitization was 49.3years (26.8-64.7years). Median follow-up after desensitization was 35.5months. One patient (6.7%) was unable to resume temozolomide due to recurrent allergy. The median time from first desensitization to discontinuation of metronomic temozolomide was 4.2months (0-15.2months). Median OS and PFS for the whole sample were 181.7months and 44.9months. For Grade 4, OS was 100% at 1year, 40% at 3years, 20% at 5years; and PFS was 60% at 1year, 40% at 3years, and 20% at 5years. Our results suggest that rapid-desensitization followed by metronomic temozolomide should be considered in patients with glioma who experience hypersensitivity. This strategy provides comparable outcomes to therapy with standard protocols, with the majority of patients able to tolerate temozolomide after desensitization with favorable disease control.

Assessment of the Prognostic Value of Radiomic Features in 18F-FMISO PET Imaging of Hypoxia in Postsurgery Brain Cancer Patients: Secondary Analysis of Imaging Data from a Single-Center Study and the Multicenter ACRIN 6684 Trial.

Hypoxia is associated with resistance to radiotherapy and chemotherapy in malignant gliomas, and it can be imaged by positron emission tomography with 18F-fluoromisonidazole (18F-FMISO). Previous results for patients with brain cancer imaged with 18F-FMISO at a single center before conventional chemoradiotherapy showed that tumor uptake via T/Bmax (tissue SUVmax/blood SUV) and hypoxic volume (HV) was associated with poor survival. However, in a multicenter clinical trial (ACRIN 6684), traditional uptake parameters were not found to be prognostically significant, but tumor SUVpeak did predict survival at 1 year. The present analysis considered both study cohorts to reconcile key differences and examine the potential utility of adding radiomic features as prognostic variables for outcome prediction on the combined cohort of 72 patients with brain cancer (30 University of Washington and 42 ACRIN 6684). We used both 18F-FMISO intensity metrics (T/Bmax, HV, SUV, SUVmax, SUVpeak) and assessed radiomic measures that determined first-order (histogram), second-order, and higher-order radiomic features of 18F-FMISO uptake distributions. A multivariate model was developed that included age, HV, and the intensity of 18F-FMISO uptake. HV and SUVpeak were both independent predictors of outcome for the combined data set (P < .001) and were also found significant in multivariate prognostic models (P < .002 and P < .001, respectively). Further model selection that included radiomic features showed the additional prognostic value for overall survival of specific higher order texture features, leading to an increase in relative risk prediction performance by a further 5%, when added to the multivariate clinical model..

Effectiveness of team medical care in the management of pressure ulcers with a pocket during chemotherapy for malignant glioma

Effectiveness of team medical care in the management of pressure ulcers with a pocket during chemotherapy for malignant glioma

DRES-02. PARYLATION OF MGMT BY PARP IS REQUIRED FOR MGMT MEDIATED TEMOZOLOMIDE-INDUCED O6-METHYLGUANINE REPAIR: A NOVEL MECHANISM OF MGMT ACTION

Abstract Temozolomide (TMZ) is the standard chemotherapy for malignant gliomas (MG), and resistance to this drug is mediated by the DNA repair protein O6-methylguanine-DNA methyltransferase (MGMT). Epigenetic silencing of the MGMT gene by promoter methylation in about 40% patients is associated with loss of MGMT expression that compromises DNA repair leading to favorable response to TMZ therapy. Understanding the mechanism of MGMT mediated repair and modulating MGMT activity will enhance TMZ activity in MGMT unmethylated MG. Here we report a novel mode of regulation of MGMT protein activity by Poly-ADP-ribose polymerase (PARP). We found that PAPR physically interacts with MGMT and PARylates MGMT in response to TMZ treatment. We further showed PARylation of MGMT by PAPR is required for MGMT binding to DNA and to remove O6-methylguanine adducts in damaged DNA induced by TMZ. All 4 PARP inhibitors (trapping and non-trapping) tested (Talazoparib, Pamiparib, Veliparib, Olaparib) can inhibit PARP-MGMT binding, PARylation of MGMT, binding to DNA and subsequent removal of O6 - lesions in damaged DNA. We showed combination of PARP inhibitor with TMZ potentiated TMZ cytotoxicity in both MGMT methylated and unmethylated Glioma stem cell lines, but more profoundly in unmethylated group in vitro and in vivo. PARP inhibition acted as a double-edged sword in MGMT unmethylated MG: blocking BER/SSBR pathway to repair TMZ induced N7-MetG and O3-MetA, and more importantly, suppressing PARP-mediated PARylation of MGMT and thus silencing MGMT activity to repair O6-MetG, resulting in augmented cytotoxicity. This is the first study to show that PARylation of MGMT by PARP is required for repairing TMZ-induced O6-methylguanine adducts, and inhibition of MGMT PARylation abolishes MGMT function and renders sensitization to TMZ treatment. This finding provides a rationale for combining TMZ/CCNU and PARP inhibitors in MGMT unmethylated MG patients to enhance the benefit of adjuvant chemotherapy.

Impact of predictive impact of MGMT promoter methylation in malignant astrocytomas depends on the methylation subgroup.

2013 Background: O6-methylguanine DNA-methyl transferase (MGMT) status is predictive for alkylating chemotherapy in most series, but there are non-benefitting subgroups. Despite multiple attempts, MGMT has not been unambiguously established as a predictive biomarker for patients with malignant gliomas. Further, these tumors are to be better classified according to global methylation profiles. Methods: Long-term efficacy data of the NOA-08 trial (NCT01502241) that compared efficacy and safety of radiotherapy (RT, n= 176) to temozolomide (TMZ, n= 193) in patients &gt; 65 years with anaplastic astrocytoma (AA) or GB as well as genome-wide DNA methylation patterns and copy number variations assessed by methylation arrays in a biomarker subset ( n= 104) and an independent cohort ( n= 380) have been used to assess the interaction between MGMT status and methylation subgroups. Results: In the long-term update of NOA-08 patients with MGMT methylated tumors had longer OS and EFS when treated with TMZ (18.4 [13.9-24.4] months and 8.5 [6.9-13.3] months) versus RT (9.6 [6.4-13.7] months and 4.8 [4.3-6.2] months, HR 0.44 [0.27-0.70], p &lt; 0.001 for OS and 0.46 [0.29-0.73], p = 0.001 for EFS). These data compared favorably with recently published data from patients treated with chemoradiation (Perry et al. NEJM 2017). Importantly, only patients with glioblastomas of the methylation class receptor tyrosine kinase II (RTKII) and mesenchymal but not RTK I demonstrated the predictive impact of MGMT in the NOA and the independent validation cohort. Conclusions: MGMT promoter methylation as a strong but methylation subclass-dependent predictive biomarker for the use of alkylating chemotherapy in malignant gliomas. The data call for embedding of MGMT tests into global methylation analyses for all patients with malignant gliomas potentially treated with alkylating chemotherapy.

Inhibition of NF-κB results in anti-glioma activity and reduces temozolomide-induced chemoresistance by down-regulating MGMT gene expression

The introduction of temozolomide (TMZ) has improved chemotherapy for malignant gliomas. However, many gliomas are refractory to TMZ, so there is a pressing need for more effective therapeutic options. Here we demonstrated that glioma specimens and cell lines have constitutively high levels of nuclear factor κB (NF-κB) activity. Notably, the expression levels of this transcription factor correlated with malignant grades in glioblastoma multiforme (GBM) and inversely correlated with overall survival. Conversely, knockdown of NF-κB inhibits glioma cell proliferation and treating a panel of established glioma cell lines with pharmacological NF-κB inhibitors markedly decreased glioma viability, led to S cell cycle arrest, and induced apoptosis. We also found a significant correlation between NF-κB expression and O6-methylguanine-DNA methyltransferase (MGMT) expression in gliomas with different origins, and immunohistochemistry confirmed these findings. Genetic or pharmacological (especially parthenolide) inhibition of NF-κB activity down-regulated MGMT gene expression and substantially restored TMZ chemosensitivity in vitro and in vivo. Importantly, the TMZ sensitizing effect of siNF-κB(p65) or parthenolide were rescued by MGMT cDNA expression. These findings suggest that NF-κB is a potential target for inducing cell death in gliomas. A targeted combination strategy in which the response to TMZ is synergistically enhanced by the addition of parthenolide which may be useful, especially in chemoresistant gliomas with high MGMT expression.

Liposome-Based Systemic Glioma-Targeted Drug Delivery Enabled by All-d Peptides.

As the most aggressive brain tumor, chemotherapy of malignant glioma remains to be extremely challenging in clinic. The blood-brain barrier (BBB) and blood-brain tumor barrier (BBTB) are physiological and pathological barriers preventing therapeutic drugs from reaching the glioma region. In addition, vasculogenic mimicry (VM) formed by invasive glioma cells instead of endothelial cells and angiogenesis are very common in glioma, leading to the poor prognosis and recurrence of glioma. An ideal drug delivery system for glioma chemotherapy needs to traverse the BBB and BBTB and then target VM, angiogenesis, and glioma cells. Herein we developed a liposome-based drug delivery system with the modification of proteolytically stable d-peptide ligands (dCDX/dA7R-LS). dCDX is a d-peptide ligand of nicotine acetylcholine receptors (nAChRs) capable of circumventing the BBB, and dA7R is a d-peptide ligand of vascular endothelial growth factor receptor 2 (VEGFR2) and neuropilin-1 (NRP-1) overexpressed on angiogenesis, VM, and glioma, presenting excellent glioma-homing property. dCDX/dA7R-LS could efficiently internalize into the brain capillary endothelial cells, glioma cells, tumor neovascular endothelial cells, and tumor spheroids and cross the in vitro BBB and BBTB models. Ex vivo imaging and in vivo immunofluorescence assays confirmed the superiority of dCDX/dA7R-LS in targeting intracranial glioma in comparison to plain liposomes or liposomes modified with an individual d-peptide ligand (either dCDX or dA7R). When loaded with doxorubicin, dCDX/dA7R-LS achieved the best antiglioma, antiangiogenesis, and anti-VM effects among all tested formulations. These results suggested that systemic glioma-targeted drug delivery enabled by all-d peptide ligands was promising for the antiglioma therapy.

OS1.6 Tumor Microtubes contribute to resistance against surgical lesions, and chemotherapy in malignant glioma

AbstractBackground:The current standard for the treatment of astrocytomas, including glioblastomas, consists of tumor resection, followed by radio- and chemotherapy. As we could recently demonstrate, a dense multicellular tumor network formed by intercellular tumor microtubes (TMs) greatly contributes to radioresistance. The neuronal growth-associated protein 43 (GAP-43) is involved in this mechanism. Here we asked whether similar resistance mechanisms can be found with respect to surgical lesions, and chemotherapy.Methods:Cranial windows were implanted into 8–10 weeks old male NMRI nude mice. Human glioblastoma stem-like cells (GBMSCs; stably transduced with GFP, RFP, YFP, shRNA for GAP-43, control vector, and/or H2B-GFP to label tumor cell nuclei) were stereotactically injected into the mouse’s brain. In established tumors, 100mg/kg temozolomide (TMZ) was applied to mice p.o. for three consecutive days (day 0,1,2). For surgical lesion experiments, a regional injury was set to the brain by a 26 gauge Hamilton syringe.Results:Similar to radiotherapy, GBMSCs that were not part of the TM-connected tumor cell network died in relevant numbers 7 days after chemotherapy, while TM-connected tumor cells survived. The number of TM-connected tumor cells even increased twofold after chemotherapy, which speaks for an adapative resistance mechanism. It is currently under investigation whether knock down of GAP-43 increases overall efficacy of TMZ therapy. After surgical resection, the lesioned area was rapidly re-colonized with TM-extending tumor cells, with a striking increase in tumor cells at the site of lesion that by far extended the tumor cell densitiy in unlesioned tumor areas. Qantification revealed that the tumor cell nuclear density increased to numbers five-fold above values before surfical intervention in this area, evident as early as five days (488.3%; P=0.033; 95% CI, 50.3–726.4), and extending to 14 days (523.9%; P=0.03; 95% CI, 66.7–781.1) after surgical procedure. This apparent,,repair response” gradually diminished with increasing distance to the surgical lesion site. Finally, while dexamethasone did not relevantly change these reponses, GAP-43 knock down reduced them significantly.Conclusion:TMs convey primary and adaptive resistance to TMZ chemotherapy, in accordance to what we have shown before for radiotherapy. They are also involved in a strong repair response at the very site of a surgical lesion. Reducing the ability of gliomas to repair themselves, and to resist genotoxic stress by interfering with TM formation and function appears as a promising avenue to improve treatment efficacies in these callenging diseases.

Concurrent Chemotherapy of Malignant Glioma in Rats by Using Multidrug-Loaded Biodegradable Nanofibrous Membranes.

Glioblastoma multiforme has a poor prognosis and is highly chemoresistant. In this study, we implanted biodegradable 1,3-bis[2-chloroethyl]-1-nitroso-urea-, irinotecan-, and cisplatin-eluting poly[(d,l)-lactide-co-glycolide] (BIC/PLGA) and virgin nanofibrous membranes on the brain surface of C6 glioma-bearing rats in concurrent and virgin groups, respectively. The concentrations of all applied drugs were significantly higher in the brain than in the blood for more than 8 weeks in all studied rats. Tumor growth was more rapid in the vehicle-treated group, and tumor volumes were significantly higher in the vehicle-treated group. Moreover, the average survival time was significantly shorter in the vehicle-treated group (P = 0.026), and the BIC/PLGA nanofibrous membranes significantly reduced the risk of mortality (P < 0.001). Furthermore, the results suggested that the BIC/PLGA nanofibers reduced the malignancy of C6 glioma. The experimental findings indicate that the multianticancer drug (i.e., BIC)-eluting PLGA nanofibers are favorable candidates for treating malignant glioma.

Temozolomide in combination with metformin act synergistically to inhibit proliferation and expansion of glioma stem-like cells.

Glioblastoma is the most common and most aggressive brain tumor in adults. The introduction of temozolomide (TMZ) has advanced chemotherapy for malignant gliomas, but it is not curative. The difficulties in treating glioblastoma may be as a result of the presence of glioma stem cells (GSCs), which are a source of relapse and chemoresistance. Another reason may be that endogenous Akt kinase activity may be activated in response to clinically relevant concentrations of TMZ. Akt activation is correlated with the increased tumorigenicity, invasiveness and stemness of cancer cells and overexpression of an active form of Akt increases glioma cell resistance to TMZ. Mounting evidence has demonstrated that cancer stem cells are preferentially sensitive to an inhibitor of Akt and down-regulation of the PI3K/Akt pathway may enhance the cytotoxicity of TMZ. Metformin (MET), the first-line drug for treating diabetes, it has been proved that it reduces AKT activation and selectively kills cancer stem cells, but whether it can potentiate the cytotoxicity of TMZ for GSCs remains unknown. In the present study, the GSCs isolated from human glioma cell line U87 and Rat glioma cell line C6, in vitro treatment with TMZ either alone or with MET. The present study demonstrates that MET acts synergistically with TMZ in inhibiting GSCs proliferation and generating the highest apoptotic rates when compared to either drug alone. These findings implicate that GSCs cytotoxicity mediated by TMZ may be stimulated by MET, have a synergistic effect, but the definite mechanisms remain elusive.

Low c-Met expression levels are prognostic for and predict the benefits of temozolomide chemotherapy in malignant gliomas.

Aberrant c-Met has been implicated in the development of many cancers. The objective of this study was to identify an unfavorable prognostic marker that might guide decisions regarding clinical treatment strategies for high-grade gliomas. C-Met expression was measured using immunohistochemistry in 783 gliomas, and we further analyzed c-Met mRNA levels using the Agilent Whole Genome mRNA Microarray in 286 frozen samples. In vitro, we performed cell migration and invasion assays. Cell sensitivity to temozolomide (TMZ) chemotherapy was determined using MTT assays. Both mRNA and protein levels of c-Met were significantly associated with tumor grade progression and inversely correlated with overall and progression-free survival in high-grade gliomas (all P < 0.0001). These findings were nearly consistent at the mRNA level across 3 independent cohorts. Multivariable analysis indicated that c-Met was an independent prognostic marker after adjusting for age, preoperative Karnofsky Performance Status (KPS) score, the extent of resection, radiotherapy, TMZ chemotherapy, and O6-methylguanine-DNA methyltransferase (MGMT) promoter methylation status. Further analysis in vitro revealed that downregulating the expression of c-Met dramatically inhibited cell migration and invasion capacities, enhanced sensitivity to TMZ chemotherapy in H4 and U87 glioma cells. Our results suggest that c-Met may serve as a potential predictive maker for clinical decision making.

NVP-BEZ235, a novel dual PI3K–mTOR inhibitor displays anti-glioma activity and reduces chemoresistance to temozolomide in human glioma cells

Glioblastoma multiforme (GBM) is the most frequent and most aggressive brain tumor in adults. The introduction of temozolomide (TMZ) has advanced chemotherapy for malignant gliomas. However, a considerable number of GBM cases are refractory to TMZ, the need for more effective therapeutic options is overwhelming. Mounting evidence shows that endogenous AKT (protein kinase B) activity can be activated in response to clinically relevant concentrations of TMZ. AKT activation correlated with the increased tumorigenicity, invasiveness and stemness and overexpression of an active form of AKT increases glioma cell resistance to TMZ. Previous studies also show that TMZ contributes to glioma cell apoptosis by inhibiting mTOR signaling. Thus, we hypothesized that the dual PI3K–mTOR inhibitor NVP-BEZ235 may act as antitumor agent against gliomas and potentiate the cytotoxicity of TMZ. In the present study, we found that NVP-BEZ235 treatment of glioma cell lines led to G1 cell cycle arrest, and induced apoptosis. Combination treatment with both TMZ and NVP-BEZ235 resulted in synergistically inhibited glioma cell growth and induced apoptosis (combination index CI<1) in a subset of glioma cell lines, as shown in the increased levels of Bax, and active Caspase-3, and decreased level of Bcl-2. Furthermore, NVP-BEZ235 treatment reversed p-AKT levels enhanced by TMZ. Inhibition of mTOR (p70S6K) signaling with the combination of TMZ and NVP-BEZ235 can be augmented beyond that achieved using each agent individually. In vivo xenograft models in mice, the combinatorial treatment with TMZ and NVP-BEZ235 significantly reduced tumor growth rates and prolonged median survival of tumor-bearing mice. These findings exhibit that TMZ in combination with NVP-BEZ235 act synergistically to inhibit proliferation of glioma cells by down–regulating of the PI3K–AKT–mTOR pathway, suggesting TMZ and NVP-BEZ235 combination therapy may be an option for GBM treatment.

Micheliolide derivative DMAMCL inhibits glioma cell growth in vitro and in vivo.

BackgroundThere is no highly effective chemotherapy for malignant gliomas to date. We found that dimethylaminomicheliolide (DMAMCL), a selective inhibitor of acute myeloid leukemia (AML) stem/progenitor cells, inhibited the growth of glioma cells.MethodsThe distribution of DMAMCL in brain was analyzed by an ultraperformance liquid chromatography-mass spectrometry (UPLC-MS/MS) system. The anti-tumor evaluations of DMAMCL in vitro were performed by MTT, FACS and RT-PCR. In vivo, the mixture of C6 cells and matrigel was injected into caudatum, and the anti-tumor activity of DMAMCL was evaluated by tumor growth and rat survival. The toxicity of DMAMCL was evaluated by body weight, daily food intake, hematological or serum biochemical analyses, and histological appearance of tissues.ResultsThe IC50 values of DMAMCL against the C6 and U-87MG cell lines in vitro were 27.18 ± 1.89 μM and 20.58 ± 1.61 μM, respectively. DAMMCL down-regulated the anti-apoptosis gene Bcl-2 and increased apoptosis in C6 and U-87MG cells in a dose-dependent manner. In a C6 rat tumor model, daily administration of DMAMCL for 21 days reduced the burden of C6 tumors by 60% to 88% compared to controls, and more than doubled the mean lifespan of tumor-bearing rats. Distribution analysis showed that the DMAMCL concentration was higher in the brain than in plasma. Evaluations for toxicity revealed that oral administration of DMAMCL at 200 or 300 mg/kg once a day for 21 days did not result in toxicity.ConclusionsThese results suggest that DMAMCL is highly promising for the treatment of glioma.