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Cancer Biology & Therapy 2019Glioblastoma is the most invasive form of brain tumor. Although temozolomide chemotherapy has been shown to significantly improve survival in patients with GBM, this... (Review)
Review
Glioblastoma is the most invasive form of brain tumor. Although temozolomide chemotherapy has been shown to significantly improve survival in patients with GBM, this increase is only trivial. The underlying cause is that many GBMs do not respond to temozolomide, and the rest produces resistance. In the past two decades, many attempts have been made to understand resistance mechanisms and to combine other treatments with temozolomide to maximize patient benefit. Unfortunately, it seems to be a red queen game, and the speed of disease development is as fast as the progress in the field. In order to win this game, a comprehensive approach is needed to decipher the details of the resistance mechanism and to transfer the basic research to the clinic. This article reviews the following: temozolomide discovery, chemistry, and mechanism of action, and mechanisms of resistance, as well as combination therapy with other strategies.
Topics: Antineoplastic Agents, Alkylating; Antineoplastic Combined Chemotherapy Protocols; Clinical Trials as Topic; Combined Modality Therapy; DNA Repair; Drug Resistance, Neoplasm; Glioblastoma; Humans; Temozolomide; Treatment Outcome
PubMed: 31068075
DOI: 10.1080/15384047.2019.1599662 -
British Journal of Cancer Oct 2023Patient-derived glioma stem-like cells (GSCs) have become the gold-standard in neuro-oncological research; however, it remains to be established whether loss of in situ...
BACKGROUND
Patient-derived glioma stem-like cells (GSCs) have become the gold-standard in neuro-oncological research; however, it remains to be established whether loss of in situ microenvironment affects the clinically-predictive value of this model. We implemented a GSC monolayer system to investigate in situ-in vitro molecular correspondence and the relationship between in vitro and patient response to temozolomide (TMZ).
METHODS
DNA/RNA-sequencing was performed on 56 glioblastoma tissues and 19 derived GSC cultures. Sensitivity to TMZ was screened across 66 GSC cultures. Viability readouts were related to clinical parameters of corresponding patients and whole-transcriptome data.
RESULTS
Tumour DNA and RNA sequences revealed strong similarity to corresponding GSCs despite loss of neuronal and immune interactions. In vitro TMZ screening yielded three response categories which significantly correlated with patient survival, therewith providing more specific prediction than the binary MGMT marker. Transcriptome analysis identified 121 genes related to TMZ sensitivity of which 21were validated in external datasets.
CONCLUSION
GSCs retain patient-unique hallmark gene expressions despite loss of their natural environment. Drug screening using GSCs predicted patient response to TMZ more specifically than MGMT status, while transcriptome analysis identified potential biomarkers for this response. GSC drug screening therefore provides a tool to improve drug development and precision medicine for glioblastoma.
Topics: Humans; Temozolomide; Glioblastoma; Dacarbazine; Drug Evaluation, Preclinical; Glioma; Biomarkers; DNA; Brain Neoplasms; Drug Resistance, Neoplasm; Antineoplastic Agents, Alkylating; Cell Line, Tumor; Tumor Microenvironment
PubMed: 37620410
DOI: 10.1038/s41416-023-02402-y -
Journal of Neurochemistry Mar 2018Glioblastoma is a malignant brain tumor that inevitably develops resistance to standard of care drug temozolomide (TMZ) due to a population of cells called cancer stem...
Outlining involvement of stem cell program in regulation of O6-methylguanine DNA methyltransferase and development of temozolomide resistance in glioblastoma: An Editorial Highlight for 'Transcriptional control of O -methylguanine DNA methyltransferase expression and temozolomide resistance in...
Glioblastoma is a malignant brain tumor that inevitably develops resistance to standard of care drug temozolomide (TMZ) due to a population of cells called cancer stem cells (CSCs). These cells utilize progenitor cell signaling programs and develop robust DNA repair machinery. In this editorial highlight we focus on stem cell regulation of TMZ resistance and discuss findings of Happold et al. () that outline direct transcriptional regulation of DNA repair enzyme O6-methylguanine DNA methyltransferase (MGMT) in glioblastoma CSCs through NFkB activation. The authors found that cells cultured in CSC propagating conditions exhibit increase in MGMT expression when compared to adherent differentiated monolayer cells. This in turn increases resistance to standard of care drug temozolomide (TMZ) in these cells. NFkB activation was found to directly activate expression of MGMT in sphere cultured GBM CSC.
Topics: Antineoplastic Agents, Alkylating; DNA; Dacarbazine; Drug Resistance, Neoplasm; Glioblastoma; Guanine; Humans; Temozolomide
PubMed: 29644711
DOI: 10.1111/jnc.14280 -
Experimental Eye Research Nov 2020This review details the current understanding of the mechanism of action and corneal effects of mitomycin C (MMC) for prophylactic prevention of stromal fibrosis after... (Review)
Review
This review details the current understanding of the mechanism of action and corneal effects of mitomycin C (MMC) for prophylactic prevention of stromal fibrosis after photorefractive keratectomy (PRK), and includes discussion of available information on dosage and exposure time recommended for MMC during PRK. MMC is an alkylating agent, with DNA-crosslinking activity, that inhibits DNA replication and cellular proliferation. It acts as a pro-drug and requires reduction in the tissue to be converted to an active agent capable of DNA alkylation. Although MMC augments the early keratocyte apoptosis wave in the anterior corneal stroma, its most important effect responsible for inhibition of fibrosis in surface ablation procedures such as PRK is via the inhibition of mitosis of myofibroblast precursor cells during the first few weeks after PRK. MMC use is especially useful when treating eyes with higher levels of myopia (≥approximately 6 D), which have shown higher risk of developing fibrosis (also clinically termed late haze). Studies have supported the use of MMC at a concentration of 0.02%, rather than lower doses (such as 0.01% or 0.002%), for optimal reduction of fibrosis after PRK. Exposure times for 0.02% MMC longer than 40 s may be beneficial for moderate to high myopia (≥6D), but shorter exposures times appear to be equally effective for lower levels of myopia. Although MMC treatment may also be beneficial in preventing fibrosis after PRK treatments for hyperopia and astigmatism, more studies are needed. Thus, despite the clinical use of MMC after PRK for nearly twenty years-with limited evidence of harmful effects in the cornea-many decades of experience will be needed to exclude late long-term effects that could be noted after MMC treatment.
Topics: Alkylating Agents; Corneal Opacity; Corneal Stroma; Fibrosis; Humans; Lasers, Excimer; Mitomycin; Myopia; Photorefractive Keratectomy; Postoperative Complications; Visual Acuity
PubMed: 32905844
DOI: 10.1016/j.exer.2020.108218 -
Pharmacological Research Jan 2024Resistance to temozolomide (TMZ), the frontline chemotherapeutic agent for glioblastoma (GBM), has emerged as a formidable obstacle, underscoring the imperative to...
Resistance to temozolomide (TMZ), the frontline chemotherapeutic agent for glioblastoma (GBM), has emerged as a formidable obstacle, underscoring the imperative to identify alternative therapeutic strategies to improve patient outcomes. In this study, we comprehensively evaluated a novel agent, O6-methyl-2'-deoxyguanosine-5'-triphosphate (O6-methyl-dGTP) for its anti-GBM activity both in vitro and in vivo. Notably, O6-methyl-dGTP exhibited pronounced cytotoxicity against GBM cells, including those resistant to TMZ and overexpressing O6-methylguanine-DNA methyltransferase (MGMT). Mechanistic investigations revealed that O6-methyl-dGTP could be incorporated into genomic DNA, disrupting nucleotide pools balance, and inducing replication stress, resulting in S-phase arrest and DNA damage. The compound exerted its anti-tumor properties through the activation of AIF-mediated apoptosis and the parthanatos pathway. In vivo studies using U251 and Ln229 cell xenografts supported the robust tumor-inhibitory capacity of O6-methyl-dGTP. In an orthotopic transplantation model with U87MG cells, O6-methyl-dGTP showcased marginally superior tumor-suppressive activity compared to TMZ. In summary, our research, for the first time, underscores the potential of O6-methyl-dGTP as an effective candidate against GBM, laying a robust scientific groundwork for its potential clinical adoption in GBM treatment regimens.
Topics: Humans; Glioblastoma; Antineoplastic Agents, Alkylating; Nucleosides; Caspases; Cell Line, Tumor; Temozolomide; Nucleotides; O(6)-Methylguanine-DNA Methyltransferase; Deoxyguanosine; DNA; Drug Resistance, Neoplasm; Polyphosphates
PubMed: 37984506
DOI: 10.1016/j.phrs.2023.106990 -
Bioorganic Chemistry Jun 2022While interstrand crosslinks (ICLs) have been considered as one type of DNA damage in the past, there is mounting evidence suggesting that these highly cytotoxic lesions...
While interstrand crosslinks (ICLs) have been considered as one type of DNA damage in the past, there is mounting evidence suggesting that these highly cytotoxic lesions are processed differently by the cellular machinery depending upon the ICL structure. In this study, we examined the crosslinking ability of three mitomycins, the structure of the ICLs they produce and the cytotoxicity of the drugs toward three different cell lines. The drugs are: mitomycin C (1), decarbamoylmitomycin C (2), and a mitomycin-conjugate (3) whose mitosane moiety is linked to a N-methylpyrrole carboxamide. We found that, overall, both MC and compound 3 show strong similarities regarding their alkylation of DNA, while DMC alkylating behavior is markedly different. To gain further insight into the mode of action of these drugs, we performed high throughput gene expression and gene ontology analysis to identify gene expression and cellular pathways most impacted by each drug treatment in MCF-7 cell lines. We observed that the novel mitomycin derivative (3) specifically causes changes in the expression of genes encoding proteins involved in cell integrity and tissue structure. Further analysis using bioinformatics (IPA) indicated that the new derivative (3) displays a stronger downregulation of major signaling networks that regulate the cell cycle, DNA damage response and cell proliferation when compared to MC and DMC. Collectively, these findings demonstrate that cytotoxic mechanisms of all three drugs are complex and are not solely related to their crosslinking abilities or the structure of the ICLs they produce.
Topics: Alkylation; DNA; DNA Adducts; DNA Damage; Humans; Mitomycin; Mitomycins
PubMed: 35349830
DOI: 10.1016/j.bioorg.2022.105744 -
Bioorganic & Medicinal Chemistry Jun 2019Quinone methides (QMs) are transient reactive species that can be efficiently generated from stable precursors under a variety of biocompatible conditions. Due to their... (Review)
Review
Quinone methides (QMs) are transient reactive species that can be efficiently generated from stable precursors under a variety of biocompatible conditions. Due to their electrophilic nature, QMs have been widely explored as cross-linking agents of DNA and proteins under physiological conditions. However, QMs also have a diene character and can irreversibly react via Diels-Alder reaction with electron-rich dienophiles. This particular reactivity has been recently exploited to label biomolecules with fluorophores in living cells. QMs are characterised by two unique properties that make them ideal candidates for chemical biology applications: i) they can be efficiently generated in situ from very stable precursors by means of bio-orthogonal protocols ii) they are reversible cross-linking agents, making them suitable for "catch and release" target-enrichment experiments. Nevertheless, there are only few examples reported to date that truly take advantage of QMs unique chemistry in the context of chemical-biology assay development. In this review, we will examine the most relevant examples that illustrate the benefit of using QMs for chemical biology purposes and we will anticipate novel approaches to further their applications in biologically relevant contexts.
Topics: Alkylation; Click Chemistry; Cycloaddition Reaction; DNA; Humans; Indolequinones; Microscopy, Fluorescence; Proteins; RNA Interference; Ultraviolet Rays
PubMed: 30955994
DOI: 10.1016/j.bmc.2019.04.001 -
Cancer Biology & Therapy Dec 2017Glioblastoma is a lethal form of brain tumour usually treated by surgical resection followed by radiotherapy and an alkylating chemotherapeutic agent. Key to the success... (Review)
Review
Glioblastoma is a lethal form of brain tumour usually treated by surgical resection followed by radiotherapy and an alkylating chemotherapeutic agent. Key to the success of this multimodal approach is maintaining apoptotic sensitivity of tumour cells to the alkylating agent. This initial treatment likely establishes conditions contributing to development of drug resistance as alkylating agents form the O-methylguanine adduct. This activates the mismatch repair (MMR) process inducing apoptosis and mutagenesis. This review describes key juxtaposed drivers in the balance between alkylation induced mutagenesis and apoptosis. Mutations in MMR genes are the probable drivers for alkylation based drug resistance. Critical to this interaction are the dose-response and temporal interactions between adduct formation and MMR mutations. The precision in dose interval, dose-responses and temporal relationships dictate a role for alkylating agents in either promoting experimental tumour formation or inducing tumour cell death with chemotherapy. Importantly, this resultant loss of chemotherapeutic selective pressure provides opportunity to explore novel therapeutics and appropriate combinations to minimise alkylation based drug resistance and tumour relapse.
Topics: Antineoplastic Agents, Alkylating; Apoptosis; DNA Adducts; DNA Mismatch Repair; DNA Repair; Drug Resistance, Neoplasm; Glioblastoma; Guanine; Humans; Mutation; Neoplasm Recurrence, Local
PubMed: 29020502
DOI: 10.1080/15384047.2017.1385680 -
Chemical Research in Toxicology Nov 2020The reversible generation and capture of certain electrophilic quinone methide intermediates support dynamic reactions with DNA that allow for migration and transfer of...
The reversible generation and capture of certain electrophilic quinone methide intermediates support dynamic reactions with DNA that allow for migration and transfer of alkylation and cross-linking. This reversibility also expands the possible consequences that can be envisioned when confronted by DNA repair processes and biological machines. To begin testing the response to such an encounter, quinone methide-based modification of DNA has now been challenged with a helicase (T7 bacteriophage gene protein four, T7gp4) that promotes 5' to 3' translocation and unwinding. This model protein was selected based on its widespread application, well characterized mechanism and detailed structural information. Little over one-half of the cross-linking generated by a bisfunctional quinone methide remained stable to T7gp4 and did not suppress its activity. The helicase likely avoids the topological block generated by this fraction of cross-linking by its ability to shift from single- to double-stranded translocation. The remaining fraction of cross-linking was destroyed during T7gp4 catalysis. Thus, this helicase is chemically competent to promote release of the quinone methide from DNA. The ability of T7gp4 to act as a Brownian ratchet for unwinding DNA may block recapture of the QM intermediate by DNA during its transient release from a donor strand. Most surprisingly, T7gp4 releases the quinone methide from both the translocating strand that passes through its central channel and the excluded strand that was typically unaffected by other lesions. The ability of T7gp4 to reverse the cross-link formed by the quinone methide does not extend to that formed irreversibly by the nitrogen mustard mechlorethamine.
Topics: Alkylation; Cross-Linking Reagents; DNA; Indolequinones; Molecular Structure
PubMed: 33147957
DOI: 10.1021/acs.chemrestox.0c00413 -
Analytical Chemistry Aug 2023Temozolomide (TMZ) is considered a first line chemotherapy drug for glioblastoma (GBM). Unfortunately, the GBM without methylation of O-methylguanine-DNA...
Temozolomide (TMZ) is considered a first line chemotherapy drug for glioblastoma (GBM). Unfortunately, the GBM without methylation of O-methylguanine-DNA methyltransferase (MGMT), accounting for about 70% of all GBM, shows an inherent resistance to TMZ treatment. Aberrant accumulation of neutral lipids, primarily triglycerides (TGs) and cholesteryl esters (CEs), in lipid droplets (LDs) has been recognized as metabolic vulnerability for GBM therapy. However, it is not known whether MGMT methylation affects lipid accumulation in GBM. Herein, we employed label-free Raman spectromicroscopy, which integrated stimulated Raman scattering (SRS) microscopy and confocal Raman spectroscopy, to quantitatively analyze both the amount and composition of intracellular LDs in intact GBM tissues obtained from patients who had undergone resection surgery. Our results showed significant reductions in both the LD amount and the CE percentage in MGMT unmethylated GBMs (MGMT methylation < 15%) compared to MGMT methylated ones (MGMT methylation ≥ 15%). Due to a big variation of lipid accumulation in the MGMT methylated GBMs, these patients were further divided into hypermethylated group (MGMT methylation ≥ 50%) and intermediate-methylated group (MGMT methylation 15∼50%), according to the significantly different median survival rates of these two groups. Remarkable differences in LD amount, CE percentage, and also lipid saturation degree were found between the hypermethylated group and the other two groups, but not between the unmethylated and intermediate-methylated groups. To elucidate the possible underlying mechanism, we analyzed the differential expression of lipid metabolism-related genes in GBM with different levels of MGMT methylation using The Cancer Genome Atlas Program (TCGA) dataset. It was shown that the genes related to lipid oxidation and lipid efflux were upregulated, and the genes related to lipid synthesis were downregulated in unmethylated group. These findings unravel the relationship between MGMT methylation and lipid accumulation in GBM, which may offer new opportunities for the diagnosis and treatment of TMZ-resistant GBM.
Topics: Humans; Glioblastoma; Antineoplastic Agents, Alkylating; Dacarbazine; DNA Methylation; Brain Neoplasms; Temozolomide; DNA Modification Methylases; DNA Repair Enzymes; Lipids; Tumor Suppressor Proteins
PubMed: 37417930
DOI: 10.1021/acs.analchem.3c00967