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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 -
Future Medicinal Chemistry Aug 2018The DNA repair protein, O-methylguanine DNA methyltransferase (MGMT), can confer resistance to guanine O-alkylating agents. Therefore, inhibition of resistant MGMT... (Review)
Review
The DNA repair protein, O-methylguanine DNA methyltransferase (MGMT), can confer resistance to guanine O-alkylating agents. Therefore, inhibition of resistant MGMT protein is a practical approach to increase the anticancer effects of such alkylating agents. Numerous small molecule inhibitors were synthesized and exhibited potential MGMT inhibitory activities. Although they were nontoxic alone, they also inhibited MGMT in normal tissues, thereby enhancing the side effects of chemotherapy. Therefore, strategies for tumor-specific MGMT inhibition have been proposed, including local drug delivery and tumor-activated prodrugs. Over-expression of MGMT in hematopoietic stem cells to protect bone marrow from the toxic effects of chemotherapy is also a feasible selection. The future prospects and challenges of MGMT inhibitors in cancer chemotherapy were also discussed.
Topics: Animals; Antineoplastic Agents, Alkylating; Drug Resistance, Neoplasm; Enzyme Inhibitors; Guanine; Humans; Neoplasms; O(6)-Methylguanine-DNA Methyltransferase
PubMed: 30001630
DOI: 10.4155/fmc-2018-0069 -
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 -
CNS & Neurological Disorders Drug... 2023Chemotherapy with the oral alkylating agent temozolomide still prevails as a linchpin in the therapeutic regimen of glioblastoma alongside radiotherapy. Because of the... (Review)
Review
BACKGROUND
Chemotherapy with the oral alkylating agent temozolomide still prevails as a linchpin in the therapeutic regimen of glioblastoma alongside radiotherapy. Because of the impoverished prognosis and sparse chemotherapeutic medicaments associated with glioblastoma, the burgeoning resistance to temozolomide has made the whole condition almost irremediable.
OBJECTIVE
The present review highlights the possible mechanisms of drug resistance following chemotherapy with temozolomide.
METHODS
The review summarizes the recent developments, as published in articles from Scopus, PubMed, and Web of Science search engines.
DESCRIPTION
One of the prime resistance mediators, O-6-methylguanine-DNA methyltransferase, upon activation, removes temozolomide-induced methyl adducts bound to DNA and reinstates genomic integrity. In the bargain, neoteric advances in the conception of temozolomide resistance have opened the door to explore several potential mediators like indirect DNA repair systems, efflux mechanisms, epigenetic modulation, microenvironmental influences, and autophagy-apoptosis processes that constantly lead to the failure of chemotherapy.
CONCLUSION
This review sheds light on recent discoveries, proposed theories, and clinical developments in the field of temozolomide resistance to summarize the complex and intriguing involvement of oncobiological pathways.
Topics: Humans; Temozolomide; Glioblastoma; O(6)-Methylguanine-DNA Methyltransferase; Dacarbazine; Antineoplastic Agents, Alkylating; DNA; Cell Line, Tumor; Brain Neoplasms
PubMed: 35379142
DOI: 10.2174/1871527321666220404180944 -
Analytical Chemistry Nov 2022Apurinic/apyrimidinic (AP) sites, that is, abasic sites, are among the most frequently induced DNA lesions. Spontaneous or DNA glycosylase-mediated β-elimination of the...
Apurinic/apyrimidinic (AP) sites, that is, abasic sites, are among the most frequently induced DNA lesions. Spontaneous or DNA glycosylase-mediated β-elimination of the 3'-phosphoryl group can lead to strand cleavages at AP sites to yield a highly reactive, electrophilic 3'-phospho-α,β-unsaturated aldehyde (3'-PUA) remnant. The latter can react with amine or thiol groups of biological small molecules, DNA, and proteins to yield various damaged 3'-end products. Considering its high intracellular concentration, glutathione (GSH) may conjugate with 3'-PUA to yield 3-glutathionyl-2,3-dideoxyribose (GS-ddR), which may constitute a significant, yet previously unrecognized endogenous lesion. Here, we developed a liquid chromatography tandem mass spectroscopy method, in combination with the use of a stable isotope-labeled internal standard, to quantify GS-ddR in genomic DNA of cultured human cells. Our results revealed the presence of GS-ddR in the DNA of untreated cells, and its level was augmented in cells upon exposure to an alkylating agent, -methyl--nitrosourea (MNU). In addition, inhibition of AP endonuclease (APE1) led to an elevated level of GS-ddR in the DNA of MNU-treated cells. Together, we reported here, for the first time, the presence of appreciable levels of GS-ddR in cellular DNA, the induction of GS-ddR by a DNA alkylating agent, and the role of APE1 in modulating its level in human cells.
Topics: Humans; Animals; DNA-(Apurinic or Apyrimidinic Site) Lyase; DNA Repair; Methylnitrosourea; DNA Damage; DNA; Alkylating Agents; Mammals
PubMed: 36332130
DOI: 10.1021/acs.analchem.2c02003 -
Cancer Chemotherapy and Pharmacology Oct 2022The DNA alkylating agent temozolomide (TMZ), is the first-line therapeutic for the treatment of glioblastoma (GBM). However, its use is confounded by the occurrence of...
PURPOSE
The DNA alkylating agent temozolomide (TMZ), is the first-line therapeutic for the treatment of glioblastoma (GBM). However, its use is confounded by the occurrence of drug resistance and debilitating adverse effects. Previously, we observed that letrozole (LTZ), an aromatase inhibitor, has potent activity against GBM in pre-clinical models. Here, we evaluated the effect of LTZ on TMZ activity against patient-derived GBM cells.
METHODS
Employing patient-derived G76 (TMZ-sensitive), BT142 (TMZ-intermediately sensitive) and G43 and G75 (TMZ-resistant) GBM lines we assessed the influence of LTZ and TMZ on cell viability and neurosphere growth. Combination Index (CI) analysis was performed to gain quantitative insights of this interaction. We then assessed DNA damaging effects by conducting flow-cytometric analysis of ˠH2A.X formation and induction of apoptotic signaling pathways (caspase3/7 activity). The effects of adding estradiol on LTZ-induced cytotoxicity and DNA damage were also evaluated.
RESULTS
Co-treatment with LTZ at a non-cytotoxic concentration (40 nM) reduced TMZ IC by 8, 37, 240 and 640 folds in G76, BT-142, G43 and G75 cells, respectively. The interaction was deemed to be synergistic based on CI analysis. LTZ co-treatment also significantly increased DNA damaging effects of TMZ. Addition of estradiol abrogated these LTZ effects.
CONCLUSIONS
LTZ increases DNA damage and synergistically enhances TMZ activity in TMZ sensitive and TMZ-resistant GBM lines. These effects are abrogated by the addition of exogenous estradiol underscoring that the observed effects of LTZ may be mediated by estrogen deprivation. Our study provides a strong rationale for investigating the clinical potential of combining LTZ and TMZ for GBM therapy.
Topics: Antineoplastic Agents, Alkylating; Aromatase Inhibitors; Brain Neoplasms; Cell Line, Tumor; Drug Resistance, Neoplasm; Estradiol; Glioblastoma; Humans; Letrozole; Temozolomide
PubMed: 36050497
DOI: 10.1007/s00280-022-04469-5 -
Nucleic Acids Research Apr 2020Alkylation is one of the most ubiquitous forms of DNA lesions. However, the motif preferences and substrates for the activity of the major types of alkylating agents...
Alkylation is one of the most ubiquitous forms of DNA lesions. However, the motif preferences and substrates for the activity of the major types of alkylating agents defined by their nucleophilic substitution reactions (SN1 and SN2) are still unclear. Utilizing yeast strains engineered for large-scale production of single-stranded DNA (ssDNA), we probed the substrate specificity, mutation spectra and signatures associated with DNA alkylating agents. We determined that SN1-type agents preferably mutagenize double-stranded DNA (dsDNA), and the mutation signature characteristic of the activity of SN1-type agents was conserved across yeast, mice and human cancers. Conversely, SN2-type agents preferably mutagenize ssDNA in yeast. Moreover, the spectra and signatures derived from yeast were detectable in lung cancers, head and neck cancers and tumors from patients exposed to SN2-type alkylating chemicals. The estimates of mutation loads associated with the SN2-type alkylation signature were higher in lung tumors from smokers than never-smokers, pointing toward the mutagenic activity of the SN2-type alkylating carcinogens in cigarettes. In summary, our analysis of mutations in yeast strains treated with alkylating agents, as well as in whole-exome and whole-genome-sequenced tumors identified signatures highly specific to alkylation mutagenesis and indicate the pervasive nature of alkylation-induced mutagenesis in cancers.
Topics: Adenine; Alkylating Agents; Animals; DNA Glycosylases; DNA, Fungal; DNA, Single-Stranded; Humans; Mice; Mutagenesis; Mutation; Neoplasms; Yeasts
PubMed: 32133535
DOI: 10.1093/nar/gkaa150 -
Drug Metabolism and Disposition: the... Dec 2016Pyrrolobenzodiazepine (PBD)-dimer is a DNA minor groove alkylator, and its CD22 THIOMAB antibody drug conjugate (ADC) demonstrated, through a disulfide linker, an...
Pyrrolobenzodiazepine (PBD)-dimer is a DNA minor groove alkylator, and its CD22 THIOMAB antibody drug conjugate (ADC) demonstrated, through a disulfide linker, an efficacy in tumor reduction for more than 7 weeks with minimal body weight loss in xenograft mice after a single 0.5-1 mg/kg i.v. dose. The DNA alkylation was investigated here in tumors and healthy organs of mice to understand the sustained efficacy and tolerability. The experimental procedures included the collection of tumors and organ tissues of xenograft mice treated with the ADC followed by DNA isolation/hydrolysis/quantitation and payload recovery from reversible DNA alkylation. PBD-dimer formed a considerable amount of adducts with tissue DNA, representing approximately 98% (at 24 hours), and 99% (at 96 hours) of the total PBD-dimer in tumors, and 78-89% in liver and lung tissues, suggesting highly efficient covalent binding of the released PBD-dimer to tissue DNA. The amount of PBD-DNA adducts in tumor tissues was approximately 24-fold (at 24 hours) and 70-fold (at 96 hours) greater than the corresponding amount of adducts in liver and lung tissues. In addition, the DNA alkylation levels increased 3-fold to 4-fold from 24 to 96 hours in tumors [41/10 base pairs (bp) at 96 hours] but remained at the same level (1/10 bp) in livers and lungs. These results support the typical target-mediated cumulative uptake of ADC into tumors and payload release that offers an explanation for its sustained antitumor efficacy. In addition, the low level of DNA alkylation in normal tissues is consistent with the tolerability observed in mice.
Topics: Alkylation; Animals; Antibodies; Benzodiazepines; DNA; DNA Adducts; Heterografts; Immunoconjugates; Liver; Lung; Mice; Neoplasms; Pyrroles
PubMed: 27683653
DOI: 10.1124/dmd.116.073031 -
Cells Oct 2022The tumor suppressor PTEN mainly inhibits the PI3K/Akt pathway in the cytoplasm and maintains DNA stability in the nucleus. The status of PTEN remains therapeutic...
The tumor suppressor PTEN mainly inhibits the PI3K/Akt pathway in the cytoplasm and maintains DNA stability in the nucleus. The status of PTEN remains therapeutic effectiveness for chemoresistance of the DNA alkylating agent temozolomide (TMZ) in glioblastoma (GB). However, the underlying mechanisms of PTEN's interconnected role in the cytoplasm and nucleus in TMZ resistance are still unclear. In this study, we report that TMZ-induced PTEN nuclear import depends on PTEN ubiquitylation modification by Smurf1. The Smurf1 suppression decreases the TMZ-induced PTEN nuclear translocation and enhances the DNA damage. In addition, Smurf1 degrades cytoplasmic PTEN K289E (the nuclear-import-deficient PTEN mutant) to activate the PI3K/Akt pathway under TMZ treatment. Altogether, Smurf1 interconnectedly promotes PTEN nuclear function (DNA repair) and cytoplasmic function (activation of PI3K/Akt pathway) to resist TMZ. These results provide a proof-of-concept demonstration for a potential strategy to overcome the TMZ resistance in PTEN wild-type GB patients by targeting Smurf1.
Topics: Humans; Temozolomide; Glioblastoma; Proto-Oncogene Proteins c-akt; Phosphatidylinositol 3-Kinases; Cell Line, Tumor; Drug Resistance, Neoplasm; Alkylating Agents; PTEN Phosphohydrolase; Ubiquitin-Protein Ligases
PubMed: 36291166
DOI: 10.3390/cells11203302 -
Mutation Research. Reviews in Mutation... 2015In genetic toxicology, risk assessment has traditionally adopted linear dose-responses for any compound that causes genotoxic effects. Increasing evidence of non-linear... (Review)
Review
In genetic toxicology, risk assessment has traditionally adopted linear dose-responses for any compound that causes genotoxic effects. Increasing evidence of non-linear dose-responses, however, suggests potential cellular tolerance to low levels of many genotoxicants with diverse modes of action. Such putative non-linear dose-responses need to be substantiated by strong mechanistic data that identifies the mechanisms responsible for the tolerance to low doses. This can be achieved by experimental demonstration of cytoprotective mechanisms and by providing experimental support for the existence of tolerance mechanisms against low dose effects. By highlighting key experiments into low dose mechanisms, this review aims to clarify which mechanistic data are required to support the use of non-linear dose-response models in risk assessment. Such key experiments are presented and discussed for alkylating agents, oxidants, particulate matter, nucleoside analogues, topoisomerase inhibitors and aneugens and exemplify the use of gene knockout models or transgenic models as well as chemical modulators of key effectors of relevant pathways and their impact on dose-response relationships. In vitro studies are particularly valuable to elucidate mechanisms of low-dose protection or lack thereof, while in vivo experiments are most appropriate for deriving a safe dose. In order to evaluate the existence of non-linear dose-response relationships for genotoxicants, we suggest that careful attention should be given to the mode of genotoxic action, relevant biomarkers of exposure, as well as to the existence and impact of potential cytoprotective mechanisms like detoxifying metabolism and DNA repair.
Topics: Alkylating Agents; Aneugens; Animals; DNA Damage; Dose-Response Relationship, Drug; Humans; Models, Chemical; Mutagenicity Tests; Mutagens; Nucleosides; Oxidants; Particulate Matter; Risk Assessment; Topoisomerase Inhibitors
PubMed: 25795120
DOI: 10.1016/j.mrrev.2014.11.001