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Science (New York, N.Y.) Jul 2022Approximately half of glioblastoma and more than two-thirds of grade II and III glioma tumors lack the DNA repair protein O-methylguanine methyl transferase (MGMT)....
Approximately half of glioblastoma and more than two-thirds of grade II and III glioma tumors lack the DNA repair protein O-methylguanine methyl transferase (MGMT). MGMT-deficient tumors respond initially to the DNA methylation agent temozolomide (TMZ) but frequently acquire resistance through loss of the mismatch repair (MMR) pathway. We report the development of agents that overcome this resistance mechanism by inducing MMR-independent cell killing selectively in MGMT-silenced tumors. These agents deposit a dynamic DNA lesion that can be reversed by MGMT but slowly evolves into an interstrand cross-link in MGMT-deficient settings, resulting in MMR-independent cell death with low toxicity in vitro and in vivo. This discovery may lead to new treatments for gliomas and may represent a new paradigm for designing chemotherapeutics that exploit specific DNA repair defects.
Topics: Antineoplastic Agents, Alkylating; Brain Neoplasms; Cell Line, Tumor; DNA Methylation; DNA Modification Methylases; DNA Repair; DNA Repair Enzymes; Dacarbazine; Drug Design; Drug Resistance, Neoplasm; Glioblastoma; Humans; Temozolomide; Tumor Suppressor Proteins
PubMed: 35901163
DOI: 10.1126/science.abn7570 -
International Journal of Molecular... Feb 2023Nitrosamines occur widespread in food, drinking water, cosmetics, as well as tobacco smoke and can arise endogenously. More recently, nitrosamines have been detected as... (Review)
Review
Nitrosamines occur widespread in food, drinking water, cosmetics, as well as tobacco smoke and can arise endogenously. More recently, nitrosamines have been detected as impurities in various drugs. This is of particular concern as nitrosamines are alkylating agents that are genotoxic and carcinogenic. We first summarize the current knowledge on the different sources and chemical nature of alkylating agents with a focus on relevant nitrosamines. Subsequently, we present the major DNA alkylation adducts induced by nitrosamines upon their metabolic activation by CYP450 monooxygenases. We then describe the DNA repair pathways engaged by the various DNA alkylation adducts, which include base excision repair, direct damage reversal by MGMT and ALKBH, as well as nucleotide excision repair. Their roles in the protection against the genotoxic and carcinogenic effects of nitrosamines are highlighted. Finally, we address DNA translesion synthesis as a DNA damage tolerance mechanism relevant to DNA alkylation adducts.
Topics: Nitrosamines; DNA Damage; Alkylation; DNA Repair; Alkylating Agents; DNA Adducts
PubMed: 36902118
DOI: 10.3390/ijms24054684 -
Journal of Zhejiang University.... Jan 2021Alkylated DNA lesions, induced by both exogenous chemical agents and endogenous metabolites, represent a major form of DNA damage in cells. The repair of alkylation... (Review)
Review
Alkylated DNA lesions, induced by both exogenous chemical agents and endogenous metabolites, represent a major form of DNA damage in cells. The repair of alkylation damage is critical in all cells because such damage is cytotoxic and potentially mutagenic. Alkylation chemotherapy is a major therapeutic modality for many tumors, underscoring the importance of the repair pathways in cancer cells. Several different pathways exist for alkylation repair, including base excision and nucleotide excision repair, direct reversal by methyl-guanine methyltransferase (MGMT), and dealkylation by the AlkB homolog (ALKBH) protein family. However, maintaining a proper balance between these pathways is crucial for the favorable response of an organism to alkylating agents. Here, we summarize the progress in the field of DNA alkylation lesion repair and describe the implications for cancer chemotherapy.
Topics: AlkB Homolog 1, Histone H2a Dioxygenase; Alkylating Agents; Alkylation; DNA Adducts; DNA Damage; DNA Glycosylases; DNA Mismatch Repair; DNA Modification Methylases; DNA Repair; DNA Repair Enzymes; Humans; Models, Biological; Neoplasms; Tumor Suppressor Proteins
PubMed: 33448187
DOI: 10.1631/jzus.B2000344 -
Neuro-oncology Jul 2023Efficient DNA repair in response to standard chemo and radiation therapies often contributes to glioblastoma (GBM) therapy resistance. Understanding the mechanisms of...
BACKGROUND
Efficient DNA repair in response to standard chemo and radiation therapies often contributes to glioblastoma (GBM) therapy resistance. Understanding the mechanisms of therapy resistance and identifying the drugs that enhance the therapeutic efficacy of standard therapies may extend the survival of GBM patients. In this study, we investigated the role of KDM1A/LSD1 in DNA double-strand break (DSB) repair and a combination of KDM1A inhibitor and temozolomide (TMZ) in vitro and in vivo using patient-derived glioma stem cells (GSCs).
METHODS
Brain bioavailability of the KDM1A inhibitor (NCD38) was established using LS-MS/MS. The effect of a combination of KDM1A knockdown or inhibition with TMZ was studied using cell viability and self-renewal assays. Mechanistic studies were conducted using CUT&Tag-seq, RNA-seq, RT-qPCR, western blot, homologous recombination (HR) and non-homologous end joining (NHEJ) reporter, immunofluorescence, and comet assays. Orthotopic murine models were used to study efficacy in vivo.
RESULTS
TCGA analysis showed KDM1A is highly expressed in TMZ-treated GBM patients. Knockdown or knockout or inhibition of KDM1A enhanced TMZ efficacy in reducing the viability and self-renewal of GSCs. Pharmacokinetic studies established that NCD38 readily crosses the blood-brain barrier. CUT&Tag-seq studies showed that KDM1A is enriched at the promoters of DNA repair genes and RNA-seq studies confirmed that KDM1A inhibition reduced their expression. Knockdown or inhibition of KDM1A attenuated HR and NHEJ-mediated DNA repair capacity and enhanced TMZ-mediated DNA damage. A combination of KDM1A knockdown or inhibition and TMZ treatment significantly enhanced the survival of tumor-bearing mice.
CONCLUSIONS
Our results provide evidence that KDM1A inhibition sensitizes GBM to TMZ via attenuation of DNA DSB repair pathways.
Topics: Animals; Mice; Temozolomide; Glioblastoma; Lysine; DNA Breaks, Double-Stranded; Tandem Mass Spectrometry; Cell Line, Tumor; Glioma; DNA Repair; DNA; Histone Demethylases; Drug Resistance, Neoplasm; Antineoplastic Agents, Alkylating; Brain Neoplasms; Xenograft Model Antitumor Assays
PubMed: 36652263
DOI: 10.1093/neuonc/noad018 -
Molecules (Basel, Switzerland) Sep 2022DNA-alkylating natural products play an important role in drug development due to their significant antitumor activities. They usually show high affinity with DNA... (Review)
Review
DNA-alkylating natural products play an important role in drug development due to their significant antitumor activities. They usually show high affinity with DNA through different mechanisms with the aid of their unique scaffold and highly active functional groups. Therefore, the biosynthesis of these natural products has been extensively studied, especially the construction of their pharmacophores. Meanwhile, their producing strains have evolved corresponding self-resistance strategies to protect themselves. To further promote the functional characterization of their biosynthetic pathways and lay the foundation for the discovery and rational design of DNA alkylating agents, we summarize herein the progress of research into DNA-alkylating antitumor natural products, including their biosynthesis, modes of action, and auto-resistance mechanisms.
Topics: Alkylating Agents; Biological Products; Biosynthetic Pathways; DNA
PubMed: 36234921
DOI: 10.3390/molecules27196387 -
Trends in Biochemical Sciences Mar 2017Alkylation chemotherapy is one of the most widely used systemic therapies for cancer. While somewhat effective, clinical responses and toxicities of these agents are... (Review)
Review
Alkylation chemotherapy is one of the most widely used systemic therapies for cancer. While somewhat effective, clinical responses and toxicities of these agents are highly variable. A major contributing factor for this variability is the numerous distinct lesions that are created upon alkylation damage. These adducts activate multiple repair pathways. There is mounting evidence that the individual pathways function cooperatively, suggesting that coordinated regulation of alkylation repair is critical to prevent toxicity. Furthermore, some alkylating agents produce adducts that overlap with newly discovered methylation marks, making it difficult to distinguish between bona fide damaged bases and so-called 'epigenetic' adducts. Here, we discuss new efforts aimed at deciphering the mechanisms that regulate these repair pathways, emphasizing their implications for cancer chemotherapy.
Topics: Alkylation; Antineoplastic Agents, Alkylating; DNA Damage; DNA Repair; DNA, Neoplasm; Humans; Neoplasms
PubMed: 27816326
DOI: 10.1016/j.tibs.2016.10.001 -
Critical Reviews in Biochemistry and... Apr 2021DNA damaging agents have been a cornerstone of cancer therapy for nearly a century. The discovery of many of these chemicals, particularly the alkylating agents, are... (Review)
Review
DNA damaging agents have been a cornerstone of cancer therapy for nearly a century. The discovery of many of these chemicals, particularly the alkylating agents, are deeply entwined with the development of poisonous materials originally intended for use in warfare. Over the last decades, their anti-proliferative effects have focused on the specific mechanisms by which they damage DNA, and the factors involved in the repair of such damage. Due to the variety of aberrant adducts created even for the simplest alkylating agents, numerous pathways of repair are engaged as a defense against this damage. More recent work has underscored the role of RNA damage in the cellular response to these agents, although the understanding of their role in relation to established DNA repair pathways is still in its infancy. In this review, we discuss the chemistry of alkylating agents, the numerous ways in which they damage nucleic acids, as well as the specific DNA and RNA repair pathways which are engaged to counter their effects.
Topics: Alkylating Agents; Alkylation; Animals; DNA; DNA Damage; DNA Repair; Humans; RNA
PubMed: 33430640
DOI: 10.1080/10409238.2020.1869173 -
Current Oncology Reports Mar 2022Elderly patients with newly diagnosed glioblastoma (eGBM) carry a worse prognosis compared with their younger counterparts. eGBM garners special attention due to the... (Review)
Review
PURPOSE OF REVIEW
Elderly patients with newly diagnosed glioblastoma (eGBM) carry a worse prognosis compared with their younger counterparts. eGBM garners special attention due to the unique challenges, including increased treatment-associated toxicity, less relative benefit from aggressive therapy, medical comorbidities, and immunosuppression. The pivotal GBM trials excluded patients > 70 years old and the optimal treatment approach remains unsettled for eGBM. In this review, we analyze the historical evidence-based data for treating eGBM and discuss the future direction for managing this vulnerable population.
RECENT FINDINGS
Treatment for eGBM continues to evolve. Therapy choice is guided by performance status and presence of O6-methylguanine-DNA-methyltransferase (MGMT) promoter methylation. For eGBM with good performance status, combinatorial hypofractionated radiation therapy (hRT) and temozolomide should be recommended. For those with poor performance status, further stratification based on MGMT promoter methylation test result is recommended. Single-agent temozolomide is a viable treatment option for MGMT methylated tumors (mMGMT); in particular, those classified with receptor tyrosine kinase II methylation. hRT alone can be considered in MGMT unmethylated (uMGMT) eGBM patients. As precision oncology continues to advance, effective targeted and immunotherapy may emerge as new treatment options for eGBM. Management of elderly patients with newly diagnosed GBM carries a unique set of challenges. Progress has been made in defining the optimal therapeutic approach for these patients, but many questions remain to be answered.
Topics: Aged; Antineoplastic Agents, Alkylating; Brain Neoplasms; DNA Methylation; Glioblastoma; Humans; Precision Medicine; Prognosis; Temozolomide
PubMed: 35122621
DOI: 10.1007/s11912-022-01201-7 -
Mutation Research. Reviews in Mutation... 2016From a risk assessment perspective, DNA-reactive agents are conventionally assumed to have genotoxic risks at all exposure levels, thus applying a linear extrapolation... (Review)
Review
From a risk assessment perspective, DNA-reactive agents are conventionally assumed to have genotoxic risks at all exposure levels, thus applying a linear extrapolation for low-dose responses. New approaches discussed here, including more diverse and sensitive methods for assessing DNA damage and DNA repair, strongly support the existence of measurable regions where genotoxic responses with increasing doses are insignificant relative to control. Model monofunctional alkylating agents have in vitro and in vivo datasets amenable to determination of points of departure (PoDs) for genotoxic effects. A session at the 2013 Society of Toxicology meeting provided an opportunity to survey the progress in understanding the biological basis of empirically-observed PoDs for DNA alkylating agents. Together with the literature published since, this review discusses cellular pathways activated by endogenous and exogenous alkylation DNA damage. Cells have evolved conserved processes that monitor and counteract a spontaneous steady-state level of DNA damage. The ubiquitous network of DNA repair pathways serves as the first line of defense for clearing of the DNA damage and preventing mutation. Other biological pathways discussed here that are activated by genotoxic stress include post-translational activation of cell cycle networks and transcriptional networks for apoptosis/cell death. The interactions of various DNA repair and DNA damage response pathways provide biological bases for the observed PoD behaviors seen with genotoxic compounds. Thus, after formation of DNA adducts, the activation of cellular pathways can lead to the avoidance of a mutagenic outcome. The understanding of the cellular mechanisms acting within the low-dose region will serve to better characterize risks from exposures to DNA-reactive agents at environmentally-relevant concentrations.
Topics: Alkylating Agents; Alkylation; Apoptosis; DNA Adducts; DNA Damage; DNA Repair; Dose-Response Relationship, Drug; Humans; Mutagenicity Tests
PubMed: 27036068
DOI: 10.1016/j.mrrev.2015.11.001 -
Chemistry (Weinheim An Der Bergstrasse,... Feb 2021Hairpin pyrrole-imidazole polyamides (hPIPs) and their chlorambucil (Chb) conjugates (hPIP-Chbs) can alkylate DNA in a sequence-specific manner, and have been studied as...
Hairpin pyrrole-imidazole polyamides (hPIPs) and their chlorambucil (Chb) conjugates (hPIP-Chbs) can alkylate DNA in a sequence-specific manner, and have been studied as anticancer drugs. Here, we conjugated Chb to a cyclic PIP (cPIP), which is known to have a higher binding affinity than the corresponding hPIP, and investigated the DNA alkylation properties of the resulting cPIP-Chb using the optimized capillary electrophoresis method and conventional HPLC product analysis. cPIP-Chb conjugate 3 showed higher alkylation activity at its binding sites than did hPIP-Chb conjugates 1 and 2. Subsequent HPLC analysis revealed that the alkylation site of conjugate 3, which was identified by capillary electrophoresis, was reliable and that conjugate 3 alkylates the N3 position of adenine as do hPIP-Chbs. Moreover, conjugate 3 showed higher cytotoxicity against LNCaP prostate cancer cells than did conjugate 1 and cytotoxicity comparable to that of conjugate 2. These results suggest that cPIP-Chbs could be novel DNA alkylating anticancer drugs.
Topics: Alkylation; Chlorambucil; DNA; Imidazoles; Nylons; Pyrroles
PubMed: 33145851
DOI: 10.1002/chem.202004421