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"An antineoplastic agent. It has significant activity against melanomas. (from Martindale, The Extra Pharmacopoeia, 31st ed, p564)" (MeSH 2013)

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Latest Research Publications

Web Resources: Dacarbazine (6 links)

Latest Research Publications

This list of publications is regularly updated (Source: PubMed).

Feng J, Yan PF, Zhao HY, et al.
Inhibitor of Nicotinamide Phosphoribosyltransferase Sensitizes Glioblastoma Cells to Temozolomide via Activating ROS/JNK Signaling Pathway.
Biomed Res Int. 2016; 2016:1450843 [PubMed] Free Access to Full Article Related Publications
Overcoming temozolomide (TMZ) resistance is a great challenge in glioblastoma (GBM) treatment. Nicotinamide phosphoribosyltransferase (NAMPT) is a rate-limiting enzyme in the biosynthesis of nicotinamide adenine dinucleotide and has a crucial role in cancer cell metabolism. In this study, we investigated whether FK866 and CHS828, two specific NAMPT inhibitors, could sensitize GBM cells to TMZ. Low doses of FK866 and CHS828 (5 nM and 10 nM, resp.) alone did not significantly decrease cell viability in U251-MG and T98 GBM cells. However, they significantly increased the antitumor action of TMZ in these cells. In U251-MG cells, administration of NAMPT inhibitors increased the TMZ (100 μM)-induced apoptosis and LDH release from GBM cells. NAMPT inhibitors remarkably enhanced the activities of caspase-1, caspase-3, and caspase-9. Moreover, NAMPT inhibitors increased reactive oxygen species (ROS) production and superoxide anion level but reduced the SOD activity and total antioxidative capacity in GBM cells. Treatment of NAMPT inhibitors increased phosphorylation of c-Jun and JNK. Administration of JNK inhibitor SP600125 or ROS scavenger tocopherol with TMZ and NAMPT inhibitors substantially attenuated the sensitization of NAMPT inhibitor on TMZ antitumor action. Our data indicate a potential value of NAMPT inhibitors in combined use with TMZ for GBM treatment.

Miyata H, Ashizawa T, Iizuka A, et al.
Combination of a STAT3 Inhibitor and an mTOR Inhibitor Against a Temozolomide-resistant Glioblastoma Cell Line.
Cancer Genomics Proteomics. 2017; 14(1):83-91 [PubMed] Free Access to Full Article Related Publications
BACKGROUND: Temozolomide-resistant (TMZ-R) glioblastoma is very difficult to treat, and a novel approach to overcome resistance is needed.
MATERIALS AND METHODS: The efficacy of a combination treatment of STAT3 inhibitor, STX-0119, with rapamycin was investigated against our established TMZ-resistant U87 cell line.
RESULTS: The growth-inhibitory effect of the combination treatment was significant against the TMZ-R U87 cell line (IC50: 78 μM for STX-0119, 30.5 μM for rapamycin and 11.3 μM for combination of the two). Western blotting analysis demonstrated that the inhibitory effect of STX-0119 on S6 and 4E-BP1 activation through regulation of YKL-40 expression occurred in addition to the inhibitory effect of rapamycin against the mTOR pathway.
CONCLUSION: These results suggest that the STAT3 pathway is associated with the mTOR downstream pathway mediated by YKL-40 protein, and the combination therapy of the STAT3 inhibitor and rapamycin could be worth developing as a novel therapeutic approach against TMZ-resistant relapsed gliomas.

Clark PA, Gaal JT, Strebe JK, et al.
The effects of tumor treating fields and temozolomide in MGMT expressing and non-expressing patient-derived glioblastoma cells.
J Clin Neurosci. 2017; 36:120-124 [PubMed] Article available free on PMC after 01/02/2018 Related Publications
A recent Phase 3 study of newly diagnosed glioblastoma (GBM) demonstrated the addition of tumor treating fields (TTFields) to temozolomide (TMZ) after combined radiation/TMZ significantly increased survival and progression free survival. Preliminary data suggested benefit with both methylated and unmethylated O-6-methylguanine-DNA methyl-transferase (MGMT) promoter status. To date, however, there have been no studies to address the potential interactions of TTFields and TMZ. Thus, the effects of TTFields and TMZ were studied in vitro using patient-derived GBM stem-like cells (GSCs) including MGMT expressing (TMZ resistant: 12.1 and 22GSC) and non-MGMT expressing (TMZ sensitive: 33 and 114GSC) lines. Dose-response curves were constructed using cell proliferation and sphere-forming assays. Results demonstrated a ⩾10-fold increase in TMZ resistance of MGMT-expressing (12.1GSCs: IC50=160μM; 22GSCs: IC50=44μM) compared to MGMT non-expressing (33GSCs: IC50=1.5μM; 114GSCs: IC50=5.2μM) lines. TTFields inhibited 12.1 GSC proliferation at all tested doses (50-500kHz) with an optimal frequency of 200kHz. At 200kHz, TTFields inhibited proliferation and tumor sphere formation of both MGMT GSC subtypes at comparable levels (12.1GSC: 74±2.9% and 38±3.2%, respectively; 22GSC: 61±11% and 38±2.6%, respectively; 33GSC: 56±9.5% and 60±7.1%, respectively; 114 GSC: 79±3.5% and 41±4.3%, respectively). In combination, TTFields (200kHz) and TMZ showed an additive anti-neoplastic effect with equal efficacy for TTFields in both cell types (i.e., ± MGMT expression) with no effect on TMZ resistance. This is the first demonstration of the effects of TTFields on cancer stem cells. The expansion of such studies may have clinical implications.

Pasi F, Fassina L, Mognaschi ME, et al.
Pulsed Electromagnetic Field with Temozolomide Can Elicit an Epigenetic Pro-apoptotic Effect on Glioblastoma T98G Cells.
Anticancer Res. 2016; 36(11):5821-5826 [PubMed] Related Publications
Treatment with pulsed electromagnetic fields (PEMFs) is emerging as an interesting therapeutic option for patients with cancer. The literature has demonstrated that low-frequency/low-energy electromagnetic fields do not cause predictable effects on DNA; however, they can epigenetically act on gene expression. The aim of the present work was to study a possible epigenetic effect of a PEMF, mediated by miRNAs, on a human glioblastoma cell line (T98G). We tested a PEMF (maximum magnetic induction, 2 mT; frequency, 75 Hz) that has been demonstrated to induce autophagy in glioblastoma cells. In particular, we studied the effect of PEMF on the expression of genes involved in cancer progression and a promising synergistic effect with temozolomide, a frequently used drug to treat glioblastoma multiforme. We found that electromagnetic stimulation in combination with temozolomide can elicit an epigenetic pro-apoptotic effect in the chemo- and radioresistant T98G glioblastoma cell line.

Alexiou GA, Gerogianni P, Vartholomatos E, Kyritsis AP
Deferiprone Enhances Temozolomide Cytotoxicity in Glioma Cells.
Cancer Invest. 2016; 34(10):489-495 [PubMed] Related Publications
Glioblastoma is the most malignant primary brain tumor with a median survival of 15 months. Temozolomide (TMZ) is the standard of care for these patients. Iron chelators have been shown to have anti-tumor activity; however, deferiprone (DFP), an orally administered iron chelator, has not been previously evaluated in gliomas. In the present study, we found that combination treatment in glioma cells with TMZ and DFP significantly reduced cell viability, produced cell cycle arrest at G2/M phase, and enhanced apoptosis. TMZ and DFP might be a potent new combination treatment for glioblastoma.

Lin L, Wang G, Ming J, et al.
Analysis of expression and prognostic significance of vimentin and the response to temozolomide in glioma patients.
Tumour Biol. 2016; 37(11):15333-15339 [PubMed] Related Publications
Gliomas are the most common primary intracranial malignant tumors in adults. Surgical resection followed by optional radiotherapy and chemotherapy is the current standard therapy for glioma patients. Vimentin, a protein of intermediate filament family, could maintain the cellular integrity and participate in several cell signal pathways to modulate the motility and invasion of cancer cells. The purpose of the present research was to identify the relationship between vimentin expression and clinical characteristics and detect the prognostic and predictive ability of vimentin in patients with glioma. To determine the expression of vimentin in glioma tissues, paraffin-embedded blocks from glioma patients by surgical resection were obtained and evaluated by immunohistochemistry. To further investigate the association of vimentin expression with survival, we employed mRNA expression of vimentin genes from the Chinese Glioma Genome Atlas (CGGA) and the GSE 16011 dataset. Kaplan-Meier analysis and Cox regression model were used to statistical analysis. We detected positive vimentin straining in 84 % of high-grade compared to 47 % in low-grade glioma patients. Additionally, vimentin mRNA expression was correlated with glioma grade in both CGGA and GSE16011 dataset. Patients with low vimentin expression have longer survival than high expression. In multivariate analysis, vimentin was an independent significant prognostic factor for high-grade glioma patients. We also identified that glioblastoma patients with low vimentin expression had a better response to temozolomide therapy. Vimentin expression has a significant association with tumor grade and overall survival of high-grade glioma patients. Low vimentin expression may benefit from temozolomide therapy.

Wu Y, Dong L, Bao S, et al.
FK228 augmented temozolomide sensitivity in human glioma cells by blocking PI3K/AKT/mTOR signal pathways.
Biomed Pharmacother. 2016; 84:462-469 [PubMed] Related Publications
Temozolomide is a novel cytotoxic agent currently used as first-line chemotherapy for glioblastoma multiforme (GBM). Romidepsin (FK228), a histone deacetylase inhibitor, is a promising new class of antineoplastic agent with the capacity to induce growth arrest and/or apoptosis of cancer cells. However, combination of the two drugs in glioma remains largely unknown. In the present study, we evaluated the combinatory effects of FK228 with TMZ in glioma, and its molecular mechanisms responsible for these effects. Glioma cell lines were treated with TMZ, FK228 or the combination of drugs. The resistance effect including cytotoxicity and apoptosis was determined in glioma cells, respectively. We further evaluated the effects of FK228 in the PI3K/Akt-signaling pathway in vitro. Mice engrafted with 5×10(6) LN382 cells were treated with TMZ, FK228 or the combination of two drugs, and tumor weights and volumes were measured, respectively. FK228 enhanced the cytotoxic effects of TMZ in glioma cells compared to vehicle-treated controls or each drug alone. The combination of FK228 and TMZ-induced apoptosis was demonstrated by increased expression of cleaved-Caspase 3, Bax, cleaved-PARP, and decreased Bcl-2 expression. Furthermore, the expression of key components of the PI3K/Akt-signaling pathway showed that combination of FK228 and TMZ block PI3K/Akt pathways in vitro. This block effect was also confirmed in vivo in mice models. Mice treated with both FK228 and TMZ drugs showed significantly reduced tumor weights and volumes, compared to each drug alone. Our results suggested that FK228 augmented temozolomide sensitivity in human glioma cells partially by blocking PI3K/AKT/mTOR signal pathways. It thus may provide a promising target for improving the therapeutic outcome of TMZ-resistant gliomas, although further studies will be needed.

Shah BK, Bista A, Sharma S
Survival Trends in Elderly Patients with Glioblastoma in the United States: a Population-based Study.
Anticancer Res. 2016; 36(9):4883-6 [PubMed] Related Publications
BACKGROUND/AIM: Concomitant and adjuvant temozolomide along with radiotherapy following surgery (the Stupp regimen) is the preferred therapy for young patients with glioblastoma as well as for elderly (>70 years) ones with favorable risk factors. This study investigated the survival trend since the introduction of the use of the Stupp regimen in elderly patients in a population-based setting.
MATERIALS AND METHODS: Surveillance, Epidemiology, and End Results 18 database was used to identify patients aged ≥70 years with glioblastoma as the first primary cancer diagnosed from 1999 to 2010. Chi-square test, Kaplan-Meier analysis with log-rank test and Cox proportional hazard method were used for analysis.
RESULT: A total of 5,575 patients were included in the survival analysis. Survival in Stupp era (year of diagnosis ≥2005) was significantly better compared to the pre-Stupp era with p<0.001 by log-rank test, with 1-, 2- and 3-year overall survival of 18.8% vs. 12.9%, 6.5% vs. 2.1% and 3.1% vs. 0.9% respectively, and hazard ratio for death in 3 years in the Stupp era was 0.87 (95% confidence interval=0.82-0.92; p<0.001) when compared with the pre-Stupp era. Factors such as younger age (<85 years), female sex, married status, Caucasian race and total resection favored better survival compared to their counterparts.
CONCLUSION: This study shows that the survival of elderly patients with glioblastoma has improved since the introduction of the Stupp regimen. However, there are significant differences in survival rates among various cohorts.

Uto M, Mizowaki T, Ogura K, et al.
Feasibility evaluation of hypofractionated radiotherapy with concurrent temozolomide in elderly patients with glioblastoma.
Int J Clin Oncol. 2016; 21(6):1023-1029 [PubMed] Related Publications
BACKGROUND: Although hypofractionated radiotherapy (HFRT) is preferred to conventionally fractionated radiotherapy when treating elderly patients with glioblastoma, the benefits and tolerability of HFRT with concurrent temozolomide (TMZ) remain unknown for such patients. We assessed the feasibility and outcomes of elderly patients with glioblastoma treated with HFRT and concurrent TMZ.
METHODS: We retrospectively reviewed the medical records of 11 patients aged ≥70 years who were treated with HFRT and concurrent TMZ. All patients had newly diagnosed and histologically confirmed glioblastoma and were treated at our institution between October 2011 and April 2015. The median age was 74 years (range, 70-85 years). Total resection/subtotal resection/biopsy were performed in 2/5/4 patients, respectively. The planning target volume included the T1-enhancing tumor and the resection cavity plus 2-cm margins, and all surrounding edema. The median prescription dose was 35 Gy (range, 35-42.5 Gy), delivered in 10 fractions. Seven patients received TMZ at 150 mg/m(2) for 5 days and 4 received TMZ at 75 mg/m(2) during HFRT. Overall survival (OS) was defined as the time from surgery to death or the last follow-up.
RESULTS: The median follow-up period was 13.2 months. The median OS and progression-free survival (PFS) times were 13.2 and 7.0 months, respectively. One patient experienced grade 4 neutropenia, lymphocytopenia, and thrombocytopenia. No grade 3 or higher nonhematological adverse event was noted.
CONCLUSION: Our analysis demonstrated the feasibility of HFRT with concurrent TMZ used to treat elderly patients with glioblastoma. Further prospective clinical trials are needed to define therapies that balance efficacy with tolerability.

Ignarro RS, Facchini G, Vieira AS, et al.
Sulfasalazine intensifies temozolomide cytotoxicity in human glioblastoma cells.
Mol Cell Biochem. 2016; 418(1-2):167-78 [PubMed] Related Publications
Temozolomide (TMZ) is an alkylating agent used to treat glioblastoma. This tumor type synthesizes the antioxidant glutathione through system X c (-) , which is inhibited by sulfasalazine (SAS). We exposed A172 and T98G human glioblastoma cells to a presumably clinically relevant concentration of TMZ (25 µM) and/or 0.5 mM SAS for 1, 3, or 5 days and assessed cell viability. For both cell lines, TMZ alone did not alter viability at any time point, while the coadministration of TMZ and SAS significantly reduced cell viability after 5 days. The drug combination exerted a synergistic effect on A172 cells after 3 and 5 days. Therefore, this particular lineage was subjected to complementary analyses on the genetic (transcriptome) and functional (glutathione and proliferating cell nuclear antigen (PCNA) protein) levels. Cellular pathways containing differentially expressed genes related to the cell cycle were modified by TMZ alone. On the other hand, SAS regulated pathways associated with glutathione metabolism and synthesis, irrespective of TMZ. Moreover, SAS, but not TMZ, depleted the total glutathione level. Compared with the vehicle-treated cells, the level of PCNA protein was lower in cells treated with TMZ alone or in combination with SAS. In conclusion, our data showed that the association of TMZ and SAS is cytotoxic to T98G and A172 cells, thus providing useful insights for improving TMZ clinical efficacy through testing this novel drug combination. Moreover, the present study not only reports original information on differential gene expression in glioblastoma cells exposed to TMZ and/or SAS but also describes an antiproliferative effect of TMZ, which has not yet been observed in A172 cells.

Moiseeva NI, Susova OY, Mitrofanov AA, et al.
Connection between Proliferation Rate and Temozolomide Sensitivity of Primary Glioblastoma Cell Culture and Expression of YB-1 and LRP/MVP.
Biochemistry (Mosc). 2016; 81(6):628-35 [PubMed] Related Publications
Glioblastomas (GBL) are the most common and aggressive brain tumors. They are distinguished by high resistance to radiation and chemotherapy. To find novel approaches for GBL classification, we obtained 16 primary GBL cell cultures and tested them with real-time PCR for mRNA expression of several genes (YB-1, MGMT, MELK, MVP, MDR1, BCRP) involved in controlling cell proliferation and drug resistance. The primary GBL cultures differed in terms of proliferation rate, wherein a group of GBL cell cultures with low proliferation rate demonstrated higher resistance to temozolomide. We found that GBL primary cell cultures characterized by high proliferation rate and lower resistance to temozolomide expressed higher mRNA level of the YB-1 and MDR1 genes, whereas upregulated expression of MVP/LRP mRNA was a marker in the group of GBL with low proliferation rate and high resistance. A moderate correlation between expression of YB-1 and MELK as well as YB-1 and MDR1 was found. In the case of YB-1 and MGMT expression, no correlation was found. A significant negative correlation was revealed between mRNA expression of MVP/LRP and MELK, MDR1, and BCRP. No correlation in expression of YB-1 and MVP/LRP genes was observed. It seems that mRNA expression of YB-1 and MVP/LRP may serve as a marker for GBL cell cultures belonging to distinct groups, each of which is characterized by a unique pattern of gene activity.

Stavrovskaya AA, Shushanov SS, Rybalkina EY
Problems of Glioblastoma Multiforme Drug Resistance.
Biochemistry (Mosc). 2016; 81(2):91-100 [PubMed] Related Publications
Glioblastoma multiforme (GBL) is the most common and aggressive brain neoplasm. A standard therapeutic approach for GBL involves combination therapy consisting of surgery, radiotherapy, and chemotherapy. The latter is based on temozolomide (TMZ). However, even by applying such a radical treatment strategy, the mean patient survival time is only 14.6 months. Here we review the molecular mechanisms underlying the resistance of GBL cells to TMZ including genetic and epigenetic mechanisms. Present data regarding a role for genes and proteins MGMT, IDH1/2, YB-1, MELK, MVP/LRP, MDR1 (ABCB1), and genes encoding other ABC transporters as well as Akt3 kinase in developing resistance of GBL to TMZ are discussed. Some epigenetic regulators of resistance to TMZ such as microRNA and EZH2 are reviewed.

Lasolle H, Raverot G
Therapeutic innovations in endocrine diseases - part 3 : temozolomide and future therapeutics for aggressive pituitary tumors and carcinomas.
Presse Med. 2016; 45(6 Pt 2):e211-6 [PubMed] Related Publications
Pituitary tumors are the most frequent intracranial tumor and classically considered as benign. However, clinical evidence and recent advances in pathological and molecular analyses suggest that these tumors should be considered as more than a simple endocrine disorder. Descriptions of aggressive pituitary tumors and pituitary carcinomas have increased notably over the last decade following the first report on the successful treatment of pituitary carcinomas using temozolomide. This alkylating agent, widely used to treat glioblastoma, is now the first-line treatment for pituitary tumors resistant to conventional therapies. However, only 40 to 50% of pituitary tumors are sensitive to this treatment. Here, we review results of temozolomide treatment in this indication and discuss the interest of different prognostic markers and perspectives for new therapeutics.

Kaul D, Florange J, Badakhshi H, et al.
Accelerated hyperfractionation plus temozolomide in glioblastoma.
Radiat Oncol. 2016; 11:70 [PubMed] Article available free on PMC after 01/02/2018 Related Publications
INTRODUCTION: Hyperfractionated (HFRT) or accelerated hyperfractionated radiotherapy (AHFRT) have been discussed as a potential treatment for glioblastoma based on a hypothesized reduction of late radiation injury and prevention of repopulation. HFRT and AHFRT have been examined extensively in the pre-Temozolomide era with inconclusive results. In this study we examined the role of accelerated hyperfractionation in the Temozolomide era.
MATERIALS AND METHODS: Sixty-four patients who underwent AHFRT (62 of which received Temozolomide) were compared to 67 patients who underwent normofractionated radiotherapy (NFRT) (64 of which received TMZ) between 02/2009 and 10/2014. Follow-up data were analyzed until 01/2015.
RESULTS: Median progression-free survival (PFS) was 6 months for the entire cohort. For patients treated with NFRT median PFS was 7 months, for patients treated with AHFRT median PFS was 6 months. Median overall survival (OS) was 13 months for all patients. For patients treated with NFRT median OS was 15 months, for patients treated with AHFRT median OS was 10 months. The fractionation regimen was not a predictor of PFS or OS in univariable- or multivariable analysis. There was no difference in acute toxicity profiles between the two treatment groups.
CONCLUSIONS: Univariable and multivariable analysis did not show significant differences between NFRT and AHFRT fractionation regimens in terms of PFS or OS. The benefits are immanent: the regimen does significantly shorten hospitalization time in a patient collective with highly impaired life expectancy. We propose that the role of AHFRT + TMZ should be further examined in future prospective trials.

Wang Q, Du J, Xu B, et al.
Silence of bFGF enhances chemosensitivity of glioma cells to temozolomide through the MAPK signal pathway.
Acta Biochim Biophys Sin (Shanghai). 2016; 48(6):501-8 [PubMed] Article available free on PMC after 01/06/2017 Related Publications
Basic fibroblast growth factor (bFGF) is a multifunctional growth factor in glioma cells and has been proved to be associated with the grade malignancy of glioma and prognosis of patients. Although there is evidence showing that bFGF plays an important role in proliferation, differentiation, angiogenesis, and survival of glioma cells, the effect of bFGF on chemosensitivity of glioma has not been verified. In this study, we analyzed the relationship between bFGF and chemotherapy resistance, with the objective of offering new strategy for chemotherapy of glioma patients. Here, siRNA was used to silence the expression of bFGF in glioma cell lines including U87 and U251 followed by chemotherapy of temozolomide (TMZ). Then, the characters of glioma including proliferation, apoptosis, migration, and cell cycle were studied in U87 and U251 cell lines. Our results demonstrated that silencing bFGF enhanced the effect of TMZ by inhibiting proliferation and migration, blocking cell cycle in G0/G1, and promoting apoptosis. In addition, the phosphorylation level of MAPK was measured to explore the mechanism of chemosensitization. The results showed that bFGF could promote the activation of the MAPK signal pathway. Our data indicated that bFGF might be a potential target for chemotherapy through the MAPK signal pathway.

Lee D, Porter J, Hertel N, et al.
Modelling Comparative Efficacy of Drugs with Different Survival Profiles: Ipilimumab, Vemurafenib and Dacarbazine in Advanced Melanoma.
BioDrugs. 2016; 30(4):307-19 [PubMed] Related Publications
BACKGROUND: In the absence of head-to-head data, a common method for modelling comparative survival for cost-effectiveness analysis is estimating hazard ratios from trial publications. This assumes that the hazards of mortality are proportional between treatments and that outcomes are not polluted by subsequent therapy use. Newer techniques that compare treatments where the proportional hazards assumption is violated and adjust for use of subsequent therapies often require patient-level data, which are rarely available for all treatments.
OBJECTIVE: The objective of this study was to provide a comparison of overall survival data for ipilimumab, vemurafenib and dacarbazine using data from three trials lacking a common comparator arm and confounded by the use of subsequent treatment.
METHODS: We compared three estimated overall survival curves for vemurafenib and the difference compared to ipilimumab and dacarbazine. We performed a naïve comparison and adjusted it for heterogeneity between the ipilimumab and vemurafenib trials, including differences in prognostic characteristics and subsequent therapy using a published hazard function for the impact of prognostic characteristics in melanoma and trial data on the impact of second-line use of ipilimumab.
RESULTS: The mean incremental life-years gained for patients receiving ipilimumab compared with vemurafenib were 0.34 (95 % confidence interval [CI] -0.24 to 0.84) using the naïve comparison and 0.51 (95 % CI -0.08 to 0.99) using the covariate-adjusted survival curve.
CONCLUSIONS: The analyses estimated the comparative efficacy of ipilimumab and vemurafenib in the absence of head-to-head patient-level data for all trials and proportional hazards in overall survival.

Yeh PS, Wu SJ, Hung TY, et al.
Evidence for the Inhibition by Temozolomide, an Imidazotetrazine Family Alkylator, of Intermediate-Conductance Ca2+-Activated K+ Channels in Glioma Cells.
Cell Physiol Biochem. 2016; 38(5):1727-42 [PubMed] Related Publications
BACKGROUND: Temozolomide (TMZ), an oral alkylator of the imidazotetrazine family, is used to treat glioma. Whether this drug has any ionic effects in glioma cells remains largely unclear.
METHODS: With the aid of patch-clamp technology, we investigated the effects of TMZ on the ionic currents in U373 glioma cells. The mRNA expression of KCNN4 (KCa3.1) in U373 glioma cells and TMZ's effect on K+ currents in these KCNN4 siRNA-transfected U373 cells were investigated.
RESULTS: In whole-cell recordings, TMZ decreased the amplitude of voltage-dependent K+ currents (IK) in U373 cells. TMZ-induced IK inhibition was reversed by ionomycin or 1-ethyl-2-benzimidazolinone (1-EBIO). In cell-attached configuration, TMZ concentration-dependently reduced the activity of intermediate-conductance Ca2+-activated K+ (IKCa) channels with an IC50 value of 9.2 µM. Chlorzoxazone or 1-EBIO counteracted the TMZ-induced inhibition of IKCa channels. Although TMZ was unable to modify single-channel conductance, its inhibition of IKCa channels was weakly voltage-dependent and accompanied by a significant prolongation in the slow component of mean closed time. However, neitherlarge-conductance Ca2+-activated (BKCa) nor inwardly rectifying K+ (Kir) channels were affected by TMZ. In current-clamp mode, TMZ depolarized the cell membrane and 1-EBIO reversed TMZ-induced depolarization. TMZ had no effect on IK in KCNN4 siRNA-transfected U373 cells.
CONCLUSION: In addition to the DNA damage it does, its inhibitory effect on IKCa channels accompanied by membrane depolarization could be an important mechanism underlying TMZ-induced antineoplastic actions.

Vandraas K, Tjønnfjord GE, Johannesen TB, Brandal P
Persistent bone marrow depression following short-term treatment with temozolomide.
BMJ Case Rep. 2016; 2016 [PubMed] Related Publications
Temozolomide (TMZ) is, in combination with radiotherapy (RT), the treatment of choice for glioblastoma multiforme. Although generally well tolerated, haematological side effects are observed in approximately 1-10% of patients receiving TMZ. We report a case of a patient who developed severe bone marrow failure (BMF) after only 3 weeks of concomitant TMZ. The BMF was grave with no signs of improvement for 12 months, resulting in more than 100 transfusions of blood cells.

Truc G, Bernier V, Mirjolet C, et al.
A phase I dose escalation study using simultaneous integrated-boost IMRT with temozolomide in patients with unifocal glioblastoma.
Cancer Radiother. 2016; 20(3):193-8 [PubMed] Related Publications
PURPOSE: To evaluate the maximum tolerated dose of simultaneous integrated-boost intensity-modulated radiotherapy (SIB-IMRT) associated with temozolomide in patients with glioblastoma.
PATIENTS AND METHODS: Between November 2009 and January 2012, nine patients with malignant glioma were enrolled in this phase I clinical trial. Radiotherapy was delivered using fractions of 2.5Gy on the planning target volume b and of 1.9Gy on the planning target volume a. Volumes were defined as follow: gross tumour volume b: tumour taking up contrast on T1 weighted MRI images; clinical target volume b: gross tumour volume b+0.5cm (adapted to the anatomical structures) and lastly planning target volume b: clinical target volume b+0.5cm; gross tumour volume a: tumour (gross tumour volume b)+2cm and including oedema outlined on T2Flair MRI sequences; clinical target volume a gross tumour volume a+0.5cm (adapted to the anatomical structures); planning target volume a: clinical target volume a+0.5cm. Three patients were enrolled at each of the three levels of dose (70, 75 and 80Gy prescribed on the planning target volume b and 56, 60 and 60.8Gy on the planning target volume a). Radiotherapy was delivered with temozolomide according to the standard protocol. Dose-limiting toxicities were defined as any haematological toxicities at least grade 4 or as any radiotherapy-related non-haematological acute toxicities at least grade 3, according to the Common Terminology Criteria for Adverse Events, version 3.0.
RESULTS: Until the last dose level of 80Gy, no patient showed dose-limiting toxicity.
CONCLUSIONS: SIB-IMRT, at least until a dose of 80Gy in 32 daily fractions, associated with temozolomide is feasible and well tolerated.

Gramatzki D, Roth P, Felsberg J, et al.
Chemotherapy for intracranial ependymoma in adults.
BMC Cancer. 2016; 16:287 [PubMed] Article available free on PMC after 01/06/2017 Related Publications
BACKGROUND: Ependymal tumors in adults are rare, accounting for less than 4% of primary tumors of the central nervous system in this age group. The low prevalence of intracranial ependymoma in adults limits the ability to perform clinical trials. Therefore, treatment decisions are based on small, mostly retrospective studies and the role of chemotherapy has remained unclear.
METHODS: We performed a retrospective study on 17 adult patients diagnosed with intracranial World Health Organisation grade II or III ependymoma, who were treated with chemotherapy at any time during the disease course. Benefit from chemotherapy was estimated by applying Macdonald criteria. Progression-free (PFS) and overall survival (OS) were calculated from start of chemotherapy, using the Kaplan-Meier method.
RESULTS: Eleven patients had supratentorial and 6 infratentorial tumors. Ten patients were treated with temozolomide (TMZ), 3 with procarbazine/lomustine/vincristine (PCV), 3 with platinum-based chemotherapy and 1 patient received epirubicin/ifosfamide. Response rates were as follows: TMZ 8/10 stable disease; PCV 3/3 stable disease; platinum-based chemotherapy 1/3 partial response; epirubicin/ifosfamide 1/1 complete response. PFS rates at 6, 12 and 24 months were 52.9, 35.3 and 23.5%. OS rates at 6, 12 and 24 months were 82.4, 82.4 and 70.1%. There was no indication for a favourable prognostic role of O(6)-methylguanyl-DNA-methyltransferase (MGMT) promoter methylation which was detected in 3/12 investigated tumors.
CONCLUSIONS: Survival outcomes in response to chemotherapy in adult intracranial ependymoma patients vary substantially, but individual patients may respond to any kind of chemotherapy. There were too few patients to compare survival data between chemotherapeutic subgroups.

Xin Y, Huang Q, Zhang P, et al.
Meta-Analysis of the Safety and Efficacy of Interferon Combined With Dacarbazine Versus Dacarbazine Alone in Cutaneous Malignant Melanoma.
Medicine (Baltimore). 2016; 95(16):e3406 [PubMed] Article available free on PMC after 01/06/2017 Related Publications
The aim of this study was to compare the efficacy and safety of interferon (IFN) combined with dacarbazine (DTIC) (experimental group) versus DTIC alone (control group) in cutaneous malignant melanoma. After searching all available databases, eligible articles were identified and subjected to quality assessment. Meta-analysis was performed using RevMan 5.3; combined relative risk (RR) and 95% confidence intervals (95% CIs) were calculated for survival rates, response rates, and adverse events. Eight randomized controlled trials published between 1990 and 2014 involving 795 patients were included in the meta-analysis. Compared with DTIC alone, IFN combined with DTIC significantly increased the overall response rate (RR = 1.59, 95% CI 1.21-2.08, P = 0.0008),the complete response rate (RR = 3.30, 95% CI 1.89-5.76, P < 0.0001), 2-year survival (RR = 1.59, 95% CI 0.99-2.54, P = 0.050) grade ≥3 hematologic toxicity (RR = 2.30, 95% CI 1.32-4.02, P = 0.003), neurotoxicity (RR = 18.15, 95% CI 5.34-61.74, P < 0.00001), and flu-like symptoms (RR = 6.31, 95% CI 1.95-20.39, P = 0.002). The partial response rate, grade ≥3 nausea and vomiting, treatment-related, and 1- and 3-year survival were not significantly different between IFN combined with DTIC and DTIC alone. IFN combined with DTIC may moderately improve the complete response rate, but increases the incidence of adverse events and has no significant effect on 1- and 3-year survival in cutaneous malignant melanoma.

Yu G, Wu F, Wang E
KLF8 Promotes Temozolomide Resistance in Glioma Cells via β-Catenin Activation.
Cell Physiol Biochem. 2016; 38(4):1596-604 [PubMed] Related Publications
BACKGROUND/AIMS: The transcription factor Krüppel-like factor (KLF) 8 plays important roles in tumorigenesis and tumor metastasis. However, the relationship between KLF8 and glioma cell chemoresistance is not known.
METHODS: The effects of KLF8 on glioma cell proliferation, apoptosis and chemosensitivity to temozolomide (TMZ) were analyzed by Cell Counting Kit 8 assay and flow cytometry assay. A xenograft model was used to study the effect of KLF8 on tumor growth and sensitivity to TMZ.
RESULTS: We found that in the absence of KLF8, glioma cells showed greater sensitivity to TMZ, resulting in the inhibition of cell growth and enhanced apoptosis. KLF8 overexpression had the opposite effect; that is, cell resistance to TMZ was increased, which was associated with β-catenin activation.
CONCLUSION: Taken together, these data suggest that KLF8 modulates glioma cell resistance to TMZ via activation of β-catenin; therefore, therapies that inhibit KLF8 levels in glioma can enhance the efficacy of TMZ treatment.

Nanegrungsunk D, Apaijai N, Yarana C, et al.
Bevacizumab is superior to Temozolomide in causing mitochondrial dysfunction in human brain tumors.
Neurol Res. 2016; 38(4):285-93 [PubMed] Related Publications
OBJECTIVE: Current chemotherapy treatments available for treating high-grade brain tumors, Temozolomide (TMZ) or Bevacizumab (BEV), not only have specific anti-tumor mechanisms, but also have an effect on mitochondria. However, effects of both drugs on mitochondria isolated from human brain tumors have not been thoroughly investigated. This study determined the direct effects of TMZ and BEV as well as the neurotoxic condition (calcium overload), on the function of mitochondria and compared these effects on mitochondria isolated from low- and high-grade human brain tumors.
METHODS: Mitochondria were isolated from either low- or high-grade human primary brain tumors. Calcium overload conditions (100 or 200 μM), TMZ (300 μM), and BEV (2 mg/mL) were applied to isolated mitochondria from low- and high-grade brain tumors. Following the treatment, mitochondrial function, including reactive oxygen species production, membrane potential changes, and swelling, were determined. The mitochondrial morphology was also examined.
RESULTS: In calcium overload conditions, mitochondrial dysfunction was only found to have occurred in low-grade tumors. In TMZ and BEV treatment, BEV, rather than TMZ, caused greater membrane depolarization and mitochondrial swelling in both grades of brain tumors.
CONCLUSIONS: TMZ and BEV can directly cause the dysfunction of mitochondria isolated from human brain tumors. However, BEV has a greater ability to disturb mitochondrial function in mitochondria isolated from human brain tumors than either TMZ or calcium overload conditions.

Baritchii A, Jurj A, Soritau O, et al.
Sensitizer drugs for the treatment of temozolomide-resistant glioblastoma.
J BUON. 2016 Jan-Feb; 21(1):199-207 [PubMed] Related Publications
PURPOSE: Glioblastoma multiforme (GBM) is the most aggressive primary brain tumor. Despite maximal cytoreductive surgery followed by chemoradiotherapy the prognosis is still poor. Although surgery and radiotherapy may have reached maximal effectiveness, chemotherapy has the potential to improve survival. The aim of this study was to evaluate in vitro the antitumor efficacy of tamoxifen (TAM), raloxifen (RAL), pyrimethamine (PYR) and alphanizomenon flos-aquae (AFA) in combination with temozolomide (TMZ) plus ionizing radiation against cultured glioblastoma stem-like cells and primary glioblastoma cells , as possible way to increase the treatment options in patients with therapy-refractory GBM.
METHODS: Stem-like tumor cells and glioblastoma cells isolated from two GBM biopsies were established by cell proliferation assays. TAM, RAL, PYR and AFA were added prior to TMZ and ionizing irradiation.
RESULTS: All tested drugs enhanced the cytotoxic effect of TMZ and sensitized cancer cells to radiotherapy as demonstrated by MTT assay and different staining reagents (TMRE, Hoechst dye and Annexin V) used for monitoring of several events in apoptosis.
CONCLUSION: The administration of certain selective estrogen receptor modulators (SERMs) (TAM and RAL), PYR and AFA before conventional postoperative chemo radiotherapy for glioblastoma might increase therapy efficiency compared to standard oncological treatment. These results need to be extended in vivo on laboratory animals in order to test the encouraging results obtained in vitro.

Li Q, Chen B, Cai J, et al.
Comparative Analysis of Matrix Metalloproteinase Family Members Reveals That MMP9 Predicts Survival and Response to Temozolomide in Patients with Primary Glioblastoma.
PLoS One. 2016; 11(3):e0151815 [PubMed] Article available free on PMC after 01/06/2017 Related Publications
BACKGROUND: Glioblastoma multiform (GBM) is the most common malignant primary brain tumor in adults. Radiotherapy plus concomitant and adjuvant TMZ chemotherapy is the current standard of care for patients with GBM. Matrix metalloproteinases (MMPs), a family of zinc-dependent endopeptidases, are key modulators of tumor invasion and metastasis due to their ECM degradation capacity. The aim of the present study was to identify the most informative MMP member in terms of prognostic and predictive ability for patients with primary GBM.
METHOD: The mRNA expression profiles of all MMP genes were obtained from the Chinese Glioma Genome Atlas (CGGA), the Repository for Molecular Brain Neoplasia Data (REMBRANDT) and the GSE16011 dataset. MGMT methylation status was also examined by pyrosequencing. The correlation of MMP9 expression with tumor progression was explored in glioma specimens of all grades. Kaplan-Meier analysis and Cox proportional hazards regression models were used to investigate the association of MMP9 expression with survival and response to temozolomide.
RESULTS: MMP9 was the only significant prognostic factor in three datasets for primary glioblastoma patients. Our results indicated that MMP9 expression is correlated with glioma grade (p<0.0001). Additionally, low expression of MMP9 was correlated with better survival outcome (OS: p = 0.0012 and PFS: p = 0.0066), and MMP9 was an independent prognostic factor in primary GBM (OS: p = 0.027 and PFS: p = 0.032). Additionally, the GBM patients with low MMP9 expression benefited from temozolomide (TMZ) chemotherapy regardless of the MGMT methylation status.
CONCLUSIONS: Patients with primary GBMs with low MMP9 expression may have longer survival and may benefit from temozolomide chemotherapy.

Miller K, Dixit S, Bredlau AL, et al.
Delivery of a drug cache to glioma cells overexpressing platelet-derived growth factor receptor using lipid nanocarriers.
Nanomedicine (Lond). 2016; 11(6):581-95 [PubMed] Related Publications
AIM: Glioblastoma multiforme is a devastating disease with no curative options due to the difficulty in achieving sufficient quantities of effective chemotherapies into the tumor past the blood-brain barrier. Micelles loaded with temozolomide (TMZ) were designed to increase the delivery of this drug into the brain.
MATERIALS & METHODS: pH-responsive micelles composed of distearoyl phosphoethanolamine-PEG-2000-amine and N-palmitoyl homocysteine were surface-functionalized with PDGF peptide and Dylight 680 fluorophore.
RESULTS & CONCLUSION: PDGF-micelles containing TMZ have specific uptake and increased killing in glial cells compared with untargeted micelles. In vivo studies demonstrated selective accumulation of PDGF-micelles containing TMZ in orthotopic gliomas implanted in mice. Targeted micelle-based drug carrier systems hold potential for delivery of a wide variety of hydrophobic drugs thereby reducing its systemic toxicity.

Riva G, Butta V, Cilibrasi C, et al.
Epigenetic targeting of glioma stem cells: Short-term and long-term treatments with valproic acid modulate DNA methylation and differentiation behavior, but not temozolomide sensitivity.
Oncol Rep. 2016; 35(5):2811-24 [PubMed] Related Publications
Glioblastoma (GBM) is the most aggressive tumor of the central nervous system. GBM is a fatal tumor, incurable by conventional therapies. One of the factors underlying tumor recurrence and poor long-term survival is the presence of a cancer stem-like cell population, termed glioma stem cells (GSCs), which is particularly resistant to chemotherapy and radiotherapy and supports tumor self-renewal. The aim of the present study was to evaluate the impact and difference in effects of short-term and long‑term treatments with valproic acid (VPA), a histone deacetylase inhibitor, on seven GSC lines. We investigated for the first time the changes in the genome-wide DNA methylation profile and the differentiation behavior of GSCs induced by short-term and long-term VPA treatments. Moreover, we verified VPA sensitivity after long-term VPA pretreatment and, notably, the results provide evidence of a subpopulation more resistant to further VPA treatments. Finally, since short-term VPA treatment induced a reversal of the MGMT methylation status, we aimed to sensitize GSCs to temozolomide, the drug commonly used for this tumor, using this regimen. The overall data highlighted the heterogeneous behavior of GSC lines that is representative of tumor heterogeneity in GBM. The VPA effects were variable among these cell lines in terms of pro‑differentiating ability and DNA methylation switch. Here, we attempted to identify a suitable therapy for the eradication of the stem cell subpopulation, which is mandatory to achieve an effective treatment for this tumor. Differentiation-inducing and epigenetic therapies are the most promising approaches to affect the multiple properties of GSCs and, finally, defeat GBM.

Ferguson SD, Srinivasan VM, Ghali MG, Heimberger AB
Cytomegalovirus-targeted immunotherapy and glioblastoma: hype or hope?
Immunotherapy. 2016; 8(4):413-23 [PubMed] Related Publications
Malignant gliomas, including glioblastoma (GBM), are the most common primary brain tumors. Despite extensive research only modest gains have been made in long-term survival. Standard of care involves maximizing safe surgical resection followed by concurrent chemoradiation with temozolomide. Immunotherapy for GBM is an area of intense research in recent years. New immunotherapies, although promising, have not been integrated into standard practice. Human cytomegalovirus (HCMV) is a DNA virus of the family Herpesviridae. Human seroprevalence is approximately 80%, and in most cases, is associated with asymptomatic infection. HCMV may be an important agent in the initiation, promotion and/or progression of tumorigenesis. Regardless of a possible etiologic role in GBM, interest has centered on exploiting this association for development of immunomodulatory therapies.

Kitange GJ, Mladek AC, Schroeder MA, et al.
Retinoblastoma Binding Protein 4 Modulates Temozolomide Sensitivity in Glioblastoma by Regulating DNA Repair Proteins.
Cell Rep. 2016; 14(11):2587-98 [PubMed] Article available free on PMC after 01/06/2017 Related Publications
Here we provide evidence that RBBP4 modulates temozolomide (TMZ) sensitivity through coordinate regulation of two key DNA repair genes critical for recovery from TMZ-induced DNA damage: methylguanine-DNA-methyltransferase (MGMT) and RAD51. Disruption of RBBP4 enhanced TMZ sensitivity, induced synthetic lethality to PARP inhibition, and increased DNA damage signaling in response to TMZ. Moreover, RBBP4 silencing enhanced TMZ-induced H2AX phosphorylation and apoptosis in GBM cells. Intriguingly, RBBP4 knockdown suppressed the expression of MGMT, RAD51, and other genes in association with decreased promoter H3K9 acetylation (H3K9Ac) and increased H3K9 tri-methylation (H3K9me3). Consistent with these data, RBBP4 interacts with CBP/p300 to form a chromatin-modifying complex that binds within the promoter of MGMT, RAD51, and perhaps other genes. Globally, RBBP4 positively and negatively regulates genes involved in critical cellular functions including tumorigenesis. The RBBP4/CBP/p300 complex may provide an interesting target for developing therapy-sensitizing strategies for GBM and other tumors.

Peng C, Chen Z, Wang S, et al.
The Error-Prone DNA Polymerase κ Promotes Temozolomide Resistance in Glioblastoma through Rad17-Dependent Activation of ATR-Chk1 Signaling.
Cancer Res. 2016; 76(8):2340-53 [PubMed] Related Publications
The acquisition of drug resistance is a persistent clinical problem limiting the successful treatment of human cancers, including glioblastoma (GBM). However, the molecular mechanisms by which initially chemoresponsive tumors develop therapeutic resistance remain poorly understood. In this study, we report that Pol κ, an error-prone polymerase that participates in translesion DNA synthesis, was significantly upregulated in GBM cell lines and tumor tissues following temozolomide treatment. Overexpression of Pol κ in temozolomide-sensitive GBM cells conferred resistance to temozolomide, whereas its inhibition markedly sensitized resistant cells to temozolomide in vitro and in orthotopic xenograft mouse models. Mechanistically, depletion of Pol κ disrupted homologous recombination (HR)-mediated repair and restart of stalled replication forks, impaired the activation of ATR-Chk1 signaling, and delayed cell-cycle re-entry and progression. Further investigation of the relationship between Pol κ and temozolomide revealed that Pol κ inactivation facilitated temozolomide-induced Rad17 ubiquitination and proteasomal degradation, subsequently silencing ATR-Chk1 signaling and leading to defective HR repair and the reversal of temozolomide resistance. Moreover, overexpression of Rad17 in Pol κ-depleted GBM cells restored HR efficiency, promoted the clearance of temozolomide-induced DNA breaks, and desensitized cells to the cytotoxic effects of temozolomide observed in the absence of Pol κ. Finally, we found that Pol κ overexpression correlated with poor prognosis in GBM patients undergoing temozolomide therapy. Collectively, our findings identify a potential mechanism by which GBM cells develop resistance to temozolomide and suggest that targeting the DNA damage tolerance pathway may be beneficial for overcoming resistance. Cancer Res; 76(8); 2340-53. ©2016 AACR.

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