scholarly journals Novel multi-drugs incorporating hybrid-structured nanofibers enhance alkylating agent activity in malignant gliomas

2019 ◽  
Vol 11 ◽  
pp. 175883591987555 ◽  
Author(s):  
Shih-Jung Liu ◽  
Shun-Tai Yang ◽  
Shu-Mei Chen ◽  
Yin-Chen Huang ◽  
Wei-Hwa Lee ◽  
...  

Background: Malignant gliomas (MGs) are highly chemotherapy-resistant. Temozolomide (TMZ) and carmustine (BiCNU) are alkylating agents clinically used for treating MGs. However, their effectiveness is restrained by overexpression of the DNA repair protein O6-methylguanine-DNA methyltransferase (MGMT) in tumors. O6-benzylguanine (O6-BG) is a nonreversible inhibitor of MGMT, it promotes the cytotoxicity of alkylating chemotherapy. The authors have developed a hybrid-structured nanofibrous membrane (HSNM) that sequentially delivers high concentrations of O6-BG, BiCNU, and TMZ in an attempt to provide an alternative to the current therapeutic options for MGs. Methods: The HSNMs were implanted onto the cerebral surface of pathogen-free rats following surgical craniectomy, while the in vivo release behaviors of O6-BG, TMZ, and BiCNU from the HSNMs were explored. Subsequently, the HSNMs were surgically implanted onto the brain surface of two types of tumor-bearing rats. The survival rate, tumor volume, malignancy of tumor, and apoptotic cell death were evaluated and compared with other treatment regimens. Results: The biodegradable HSNMs sequentially and sustainably delivered high concentrations of O6-BG, BiCNU, and TMZ for more than 14 weeks. The tumor-bearing rats treated with HSNMs demonstrated therapeutic advantages in terms of retarded and restricted tumor growth, prolonged survival time, and attenuated malignancy. Conclusion: The results demonstrated that O6-BG potentiates the effects of interstitially transported BiCNU and TMZ. Therefore, O6-BG may be required for alkylating agents to offer maximum therapeutic benefits for the treatment of MGMT-expressing tumors. In addition, the HSNM-supported chemoprotective gene therapy enhanced chemotherapy tolerance and efficacy. It can, therefore, potentially provide an improved therapeutic alternative for MGs.

2021 ◽  
Vol 22 (8) ◽  
pp. 3845
Author(s):  
Sarah Teuber-Hanselmann ◽  
Karl Worm ◽  
Nicole Macha ◽  
Andreas Junker

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.


Biomolecules ◽  
2020 ◽  
Vol 10 (1) ◽  
pp. 161 ◽  
Author(s):  
Terezia Kiskova ◽  
Peter Kubatka ◽  
Dietrich Büsselberg ◽  
Monika Kassayova

Despite intensive research, malignant brain tumors are among the most difficult to treat due to high resistance to conventional therapeutic approaches. High-grade malignant gliomas, including glioblastoma and anaplastic astrocytoma, are among the most devastating and rapidly growing cancers. Despite the ability of standard treatment agents to achieve therapeutic concentrations in the brain, malignant gliomas are often resistant to alkylating agents. Resveratrol is a plant polyphenol occurring in nuts, berries, grapes, and red wine. Resveratrol crosses the blood‒brain barrier and may influence the central nervous system. Moreover, it influences the enzyme isocitrate dehydrogenase and, more importantly, the resistance to standard treatment via various mechanisms, such as O6-methylguanine methyltransferase. This review summarizes the anticancer effects of resveratrol in various types of brain cancer. Several in vitro and in vivo studies have presented promising results; however, further clinical research is necessary to prove the therapeutic efficacy of resveratrol in brain cancer treatment.


2012 ◽  
Vol 2012 ◽  
pp. 1-6 ◽  
Author(s):  
Rajendra Pavan ◽  
Sapna Jain ◽  
Shraddha ◽  
Ajay Kumar

Bromelain belongs to a group of protein digesting enzymes obtained commercially from the fruit or stem of pineapple. Fruit bromelain and stem bromelainare prepared differently and they contain different enzymatic composition. “Bromelain” refers usually to the “stem bromelain.” Bromelain is a mixture of different thiol endopeptidases and other components like phosphatase, glucosidase, peroxidase, cellulase, escharase, and several protease inhibitors. In vitro and in vivo studies demonstrate that bromelain exhibits various fibrinolytic, antiedematous, antithrombotic, and anti-inflammatory activities. Bromelain is considerably absorbable in the body without losing its proteolytic activity and without producing any major side effects. Bromelain accounts for many therapeutic benefits like the treatment of angina pectoris, bronchitis, sinusitis, surgical trauma, and thrombophlebitis, debridement of wounds, and enhanced absorption of drugs, particularly antibiotics. It also relieves osteoarthritis, diarrhea, and various cardiovascular disorders. Bromelain also possesses some anticancerous activities and promotes apoptotic cell death. This paper reviews the important properties and therapeutic applications of bromelain, along with the possible mode of action.


2012 ◽  
Vol 56 (2) ◽  
pp. 211-216 ◽  
Author(s):  
Ján Bystriansky ◽  
Ján Burkuš ◽  
Štefan Juhás ◽  
Dušan Fabian ◽  
Juraj Koppel

Abstract High plasma urea nitrogen concentration has been proposed as an important factor contributing to the decline in reproductive parameters of domestic animals. The aim of this study was to evaluate the effect of urea on the development of preimplantation embryos in a mouse model. During in vivo tests, acute renal failure (ARF) accompanied by hyper-uraemia was induced by intramuscular administration of glycerol (50%) into hind limbs of fertilised dams. During in vitro tests, embryos collected from healthy dams were cultured in a medium with the addition of various concentrations of urea from the 4-cell stage to the blastocyst stage. Stereomicroscopic evaluation and fluorescence staining of embryos obtained from dams with ARF showed that high blood urea is connected with an increase in the number blastocysts containing at least one apoptotic cell and in the incidences of dead cells per blastocyst, but it did not affect their ability to reach the blastocyst stage. In vitro tests showed that culture of embryos with urea at concentration of 10 mM negatively affected the quality of obtained blastocysts. Blastocysts showed significantly lower numbers of cells and increased incidence of dead cells. An increase in apoptosis incidence was observed even in blastocysts obtained from cultures with 5 mM urea. Urea at concentrations 50 mM and higher negatively affected the ability of embryos to reach the blastocyst stage and the highest used concentrations (from 500 mM) caused overall developmental arrest of embryos at the 4- or 5- cell stage. These results show that elevated levels of urea may cause changes in the microenvironment of developing preimplantation embryos, which can negatively affect their quality. Embryo growth remains un-affected up to very high concentrations of urea.


2012 ◽  
Vol 30 (15_suppl) ◽  
pp. e12503-e12503
Author(s):  
Zhong-ping Chen ◽  
Dong Shen ◽  
Jie Wang ◽  
Qun-ying Yang

e12503 Background: O6-methylguanine DNA methyltranferase (MGMT) is one of the main mechanisms of chemoresistance for alkylating agents in malignant gliomas. Recent studies have showed that glioma stem-like cells (GSCs) could be the main reason for tumor recurrence and chemoresistance. In this study, we aimed to explore the effects of interferon-α/β against MGMT-positive glioma stem-like cells, and to investigate whether interferon-α/β can enhance the efficiency of temozolomide (TMZ) and the possible mechanism Methods: The growth inhibition effect of TMZ, with interferon-α or interferon-β, against the MGMT-positive GSCs from human glioma cell lines U251 and SKMG-4 (U251G and SKMG-4G) was evaluated by using Cell Counting Kit-8 (CCK-8) assay in vitro, and in xenograft models. MGMT and NF-κB expression in the tumor samples were determined by RT-PCR and Western blot analysis. Results: Our results revealed that the anti-tumor activity of TMZ was significantly enhanced by combined using interferon-α/β in vitro. In xenograft models, the tumor growth inhibit rate (IR) of TMZ to SKMG-4G and U251G was 35.2%±2.28% and 16.7%±1.96%, respectively. When TMZ combined with interferon-α or interferon-β, the IR to SKMG-4G was 58.4%±4.34% and 63.4%±1.08%; and to U251G was 41.1%±8.66% and 44.5%±1.90%, respectively(P<0.05). The expression of NF-κB and MGMT in MGMT-positive GSCs decreased significantly in both mRNA and protein levels after using interferon-α/β. Conclusions: Our results indicate that IFN-α/β can enhance the sensitivity of TMZ, possibly through down-regulate NF-κB expression resulting in lower MGMT transcription expression.


2013 ◽  
Vol 12 (5) ◽  
pp. 511-516 ◽  
Author(s):  
Sarah T. Garber ◽  
Robert J. Bollo ◽  
Jay K. Riva-Cambrin

Pediatric spinal pilomyxoid astrocytoma (PMA) is an extremely rare tumor that merits recognition as a specific, unique entity. The authors present the case of an intramedullary PMA in the thoracic spinal cord of an 11-year-old boy who presented with back pain, scoliosis, and multiple lung nodules. The patient underwent T5–11 laminoplasty and near-total resection of the spinal tumor. The final pathological diagnosis was WHO Grade II PMA. The patient did well for 14 months until the tumor progressed both clinically and radiographically. A literature review focusing on the clinical characteristics, histology, and treatment of PMAs provides a better understanding of these rare lesions. Because of the small number of cases optimal treatment guidelines have not been established, but gross-total resection and adjuvant chemotherapy with alkylating agents appear to confer a better long-term prognosis. Pediatric patients with PMAs can remain recurrence free at least 5 years after surgery, although these tumors may disseminate or dedifferentiate into more malignant gliomas. Recognition of intramedullary PMA as a unique entity in children is vital to the development of specific surgical and adjuvant treatment regimens.


2019 ◽  
Vol 21 (Supplement_6) ◽  
pp. vi71-vi72 ◽  
Author(s):  
Shaofang Wu ◽  
Feng Gao ◽  
Dimpy Koul ◽  
Alfred Yung

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.


Biomedicines ◽  
2019 ◽  
Vol 7 (4) ◽  
pp. 90 ◽  
Author(s):  
Bernd Kaina

Temozolomide, a DNA methylating drug, is currently being used first-line in glioblastoma therapy. Although the mode of action of this so-called SN1 alkylating agent is well described, including the types of induced DNA damage triggering the DNA damage response and survival and death pathways, some researchers expressed doubt that data mostly obtained by in vitro models can be translated into the in vivo situation. In experimental settings, high doses of the agent are often used, which are likely to activate responses triggered by base N-alkylations instead of O6-methylguanine (O6MeG), which is the primary cytotoxic lesion induced by low doses of temozolomide and other methylating drugs in O6-methylguanine-DNA methyltransferase (MGMT) repair incompetent cells. However, numerous studies provided compelling evidence that O6MeG is not only a mutagenic, but also a powerful toxic lesion inducing DNA double-strand breaks, apoptosis, autophagy and cellular senescence. MGMT, repairing the lesion through methyl group transfer, is a key node in protecting cells against all these effects and has a significant impact on patient’s survival following temozolomide therapy, supporting the notion that findings obtained on a molecular and cellular level can be translated to the therapeutic setting in vivo. This comment summarizes the current knowledge on O6MeG-triggered pathways, including dose dependence and the question of thresholds, and comes up with the conclusion that data obtained on cell lines using low dose protocols are relevant and apoptosis, autophagy and senescence are therapeutically important endpoints.


2017 ◽  
Vol 114 (16) ◽  
pp. 4129-4134 ◽  
Author(s):  
Timothy L. Sita ◽  
Fotini M. Kouri ◽  
Lisa A. Hurley ◽  
Timothy J. Merkel ◽  
Alexandra Chalastanis ◽  
...  

RNA interference (RNAi)-based gene regulation platforms have shown promise as a novel class of therapeutics for the precision treatment of cancer. Techniques in preclinical evaluation of RNAi-based nanoconjugates have yet to allow for optimization of their gene regulatory activity. We have developed spherical nucleic acids (SNAs) as a blood–brain barrier-/blood–tumor barrier-penetrating nanoconjugate to deliver small interfering (si) and micro (mi)RNAs to intracranial glioblastoma (GBM) tumor sites. To identify high-activity SNA conjugates and to determine optimal SNA treatment regimens, we developed a reporter xenograft model to evaluate SNA efficacy in vivo. Engrafted tumors stably coexpress optical reporters for luciferase and a near-infrared (NIR) fluorescent protein (iRFP670), with the latter fused to the DNA repair protein O6-methylguanine-DNA-methyltransferase (MGMT). Using noninvasive imaging of animal subjects bearing reporter-modified intracranial xenografts, we quantitatively assessed MGMT knockdown by SNAs composed of MGMT-targeting siRNA duplexes (siMGMT-SNAs). We show that systemic administration of siMGMT-SNAs via single tail vein injection is capable of robust intratumoral MGMT protein knockdown in vivo, with persistent and SNA dose-dependent MGMT silencing confirmed by Western blotting of tumor tissue ex vivo. Analyses of SNA biodistribution and pharmacokinetics revealed rapid intratumoral uptake and significant intratumoral retention that increased the antitumor activity of coadministered temozolomide (TMZ). Our study demonstrates that dual noninvasive bioluminescence and NIR fluorescence imaging of cancer xenograft models represents a powerful in vivo strategy to identify RNAi-based nanotherapeutics with potent gene silencing activity and will inform additional preclinical and clinical investigations of these constructs.


Sign in / Sign up

Export Citation Format

Share Document