drug-DNA Adducts Research Articles

An evaluation of the interaction of pixantrone with formaldehyde-releasing drugs in cancer cells.

Pixantrone is a synthetic aza-anthracenedione currently used in the treatment of non-Hodgkin's lymphoma. The drug is firmly established as a poison of the nuclear enzyme topoisomerase II, however, pixantrone can also generate covalent drug-DNA adducts following activation by formaldehyde. While pixantrone-DNA adducts form proficiently in vitro, little evidence is presently at hand to indicate their existence within cells. The molecular nature of these lesions within cancer cells exposed to pixantrone and formaldehyde-releasing prodrugs was characterized along with the cellular responses to their formation. In vitro crosslinking assays, [14C] scintillation counting analyses and alkaline comet assays were applied to characterize pixantrone-DNA adducts. Flow cytometry, cell growth inhibition and clonogenic assays were used to measure cancer cell kill and survival. Pixantrone-DNA adducts were not detectable in MCF-7 breast cancer cells exposed to [14C] pixantrone (10-40µM) alone, however the addition of the formaldehyde-releasing prodrug AN9 yielded readily measurable levels of the lesion at ~ 1 adduct per 10kb of genomic DNA. Co-administration with AN9 completely reversed topoisomerase II-associated DNA damage induction by pixantrone yet potentiated cell kill by the drug, suggesting that pixantrone-DNA adducts may promote a topoisomerase II-independent mechanism of cell death. Pixantrone-DNA adduct-forming treatments generally conferred mild synergism in multiple cell lines in various cell death and clonogenic assays, while pixantrone analogues either incapable or relatively defective in forming DNA adducts demonstrated antagonism when combined with AN9. The features unique to pixantrone-DNA adducts may be leveraged to enhance cancer cell kill and may be used to guide the design of pixantrone analogues that generate adducts with more favorable anticancer properties.

Oxaliplatin-DNA Adducts as Predictive Biomarkers of FOLFOX Response in Colorectal Cancer: A Potential Treatment Optimization Strategy.

FOLFOX is one of the most effective treatments for advanced colorectal cancer. However, cumulative oxaliplatin neurotoxicity often results in halting the therapy. Oxaliplatin functions predominantly via the formation of toxic covalent drug-DNA adducts. We hypothesize that oxaliplatin-DNA adduct levels formed in vivo in peripheral blood mononuclear cells (PBMC) are proportional to tumor shrinkage caused by FOLFOX therapy. We further hypothesize that adducts induced by subtherapeutic "diagnostic microdoses" are proportional to those induced by therapeutic doses and are also predictive of response to FOLFOX therapy. These hypotheses were tested in colorectal cancer cell lines and a pilot clinical study. Four colorectal cancer cell lines were cultured with therapeutically relevant (100 μmol/L) or diagnostic microdose (1 μmol/L) concentrations of [14C]oxaliplatin. The C-14 label enabled quantification of oxaliplatin-DNA adduct level with accelerator mass spectrometry (AMS). Oxaliplatin-DNA adduct formation was correlated with oxaliplatin cytotoxicity for each cell line as measured by the MTT viability assay. Six colorectal cancer patients received by intravenous route a diagnostic microdose containing [14C]oxaliplatin prior to treatment, as well as a second [14C]oxaliplatin dose during FOLFOX chemotherapy, termed a "therapeutic dose." Oxaliplatin-DNA adduct levels from PBMC correlated significantly to mean tumor volume change of evaluable target lesions (5 of the 6 patients had measurable disease). Oxaliplatin-DNA adduct levels were linearly proportional between microdose and therapeutically relevant concentrations in cell culture experiments and patient samples, as was plasma pharmacokinetics, indicating potential utility of diagnostic microdosing.

Formaldehyde-activated WEHI-150 induces DNA interstrand crosslinks with unique structural features

Mitoxantrone is an anticancer anthracenedione that can be activated by formaldehyde to generate covalent drug-DNA adducts. Despite their covalent nature, these DNA lesions are relatively labile. It was recently established that analogues of mitoxantrone featuring extended side-chains terminating in primary amino groups typically yielded high levels of stable DNA adducts following their activation by formaldehyde. In this study we describe the DNA sequence-specific binding properties of the mitoxantrone analogue WEHI-150 which is the first anthracenedione to form apparent DNA crosslinks mediated by formaldehyde. The utility of this compound lies in the versatility of the covalent binding modes displayed. Unlike other anthracenediones described to date, WEHI-150 can mediate covalent adducts that are independent of interactions with the N-2 of guanine and is capable of adduct formation at novel DNA sequences. Moreover, these covalent adducts incorporate more than one formaldehyde-mediated bond with DNA, thus facilitating the formation of highly lethal DNA crosslinks. The versatility of binding observed is anticipated to allow the next generation of anthracenediones to interact with a broader spectrum of nucleic acid species than previously demonstrated by the parent compounds, thus allowing for more diverse biological activities.

Antibody-Drug Conjugates with Indolinobenzodiazepine Dimer Payloads: DNA-Binding Mechanism of Indolinobenzodiazepine Dimer Catabolites in Target Cancer Cells.

DNA-targeting indolinobenzodiazepine dimer (IGN) payloads are used in several clinical-stage antibody-drug conjugates. IGN drugs alkylate DNA through the single imine moiety present in the dimer in contrast to the pyrrolobenzodiazepine dimer drugs, such as talirine and tesirine, which contain two imine moieties per dimer and cross-link DNA. This study explored the mechanism of binding of IGN to DNA in cells and to synthetic duplex and hairpin oligonucleotides. New, highly sensitive IGN-DNA binding enzyme-linked immunosorbent assay methods were developed using biotinylated IGN analogues (monoimine, diimine, and diamine IGNs) and digoxigenin-labeled duplex oligonucleotides, which allowed the measurement of drug-DNA adducts in viable cells at concentrations below IC50. Furthermore, the release of free drug from the IGN-DNA adduct upon treatment with nuclease ex vivo was tested under physiological conditions. The monoimine IGN drug formed a highly stable adduct with DNA in cells, with stability similar to that of the diimine drug analogue. Both monoimine and diimine IGN-DNA adducts released free drugs upon DNA cleavage by nuclease at 37 °C, although more free drug was released from the monoimine compared to the diimine adduct, which presumably was partly cross-linked. The strong binding of the monoimine IGN drug to duplex DNA results from both the noncovalent IGN-DNA interaction and the covalent bond formation between the 2-amino group of a guanine residue and the imine moiety in IGN.

Abstract CT055: Microdose induced oxaliplatin-DNA adducts as a predictive biomarker of response in colorectal cancer

Abstract Background Combination 5-FU and oxaliplatin (FOLFOX) is standard therapy for colorectal cancer (CRC) in neoadjuvant, adjuvant, and metastatic settings. However, oxaliplatin neuropathy is the main dose-limiting toxicity that often necessitates dose reduction or discontinuation before progression. Prediction of oxaliplatin sensitivity in tumor cells would be valuable for dose optimization to maximize anti-tumorigenic effect and limit sensory neuropathy. Oxaliplatin functions via the formation of covalent drug-DNA adducts which ultimately inhibit cell replication and promote apoptosis. Detection of these drug-DNA adducts could serve as a biomarker of oxaliplatin efficacy. We therefore hypothesized that drug-DNA adduct levels induced by sub-therapeutic "diagnostic microdoses" are proportional to those induced by therapeutic doses and are predictive of tumor responses. Methods The feasibility of this predictive diagnostic microdosing approach was assessed in CRC cell culture and a pilot clinical trial of six CRC patients. Four CRC cell lines were cultured with therapeutically relevant (100 µM) or diagnostic microdose (1 µM) concentrations of [14C]oxaliplatin. The C-14 label enabled quantification of oxaliplatin-DNA adduct levels with accelerator mass spectrometry, an ultrasensitive isotope analysis technique. Adduct formation was correlated with oxaliplatin cytotoxicity as measured by the MTT viability assay. In a pilot clinical trial (NCT02569723), six CRC patients received an intravenous diagnostic microdose containing [14C]oxaliplatin prior to treatment and a second [14C]oxaliplatin dose during FOLFOX chemotherapy. Adduct levels from peripheral blood mononuclear cells (PBMC), used as surrogates for tumor cells, were correlated to mean tumor volume change of evaluable target lesions. Results Drug-DNA adduct levels were linearly proportional between microdoses and therapeutically relevant concentrations in cell culture (R2 = 0.91, p < 0.0001) and patient samples (R2 = 0.63, p < 0.0001). Plasma pharmacokinetics of microdoses were consistent with those of therapeutic dosing. No microdose-associated toxicity was observed in this patient population. PBMC adduct levels significantly correlated with tumor shrinkage (microdose: R2 = 0.82, p = 0.033; therapeutic dose: R2=0.65, p = 0.099). Conclusion Diagnostic microdosing with oxaliplatin is feasible and is predictive of oxaliplatin sensitivity in CRC patients. Citation Format: Justin Chen, May Cho, Maike Zimmermann, Thomas Semrad, Chun-Yi Wu, Aiming Yu, Chong-Xian Pan, Paul T. Henderson, Edward J. Kim. Microdose induced oxaliplatin-DNA adducts as a predictive biomarker of response in colorectal cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr CT055.

Radiocarbon Tracers in Toxicology and Medicine: Recent Advances in Technology and Science.

This review summarizes recent developments in radiocarbon tracer technology and applications. Technologies covered include accelerator mass spectrometry (AMS), including conversion of samples to graphite, and rapid combustion to carbon dioxide to enable direct liquid sample analysis, coupling to HPLC for real-time AMS analysis, and combined molecular mass spectrometry and AMS for analyte identification and quantitation. Laser-based alternatives, such as cavity ring down spectrometry, are emerging to enable lower cost, higher throughput measurements of biological samples. Applications covered include radiocarbon dating, use of environmental atomic bomb pulse radiocarbon content for cell and protein age determination and turnover studies, and carbon source identification. Low dose toxicology applications reviewed include studies of naphthalene-DNA adduct formation, benzo[a]pyrene pharmacokinetics in humans, and triclocarban exposure and risk assessment. Cancer-related studies covered include the use of radiocarbon-labeled cells for better defining mechanisms of metastasis and the use of drug-DNA adducts as predictive biomarkers of response to chemotherapy.

Correlation of Platinum Cytotoxicity to Drug-DNA Adduct Levels in a Breast Cancer Cell Line Panel.

Platinum drugs, including carboplatin and oxaliplatin, are commonly used chemotherapy drugs that kill cancer cells by forming toxic drug-DNA adducts. These drugs have a proven, but modest, efficacy against several aggressive subtypes of breast cancer but also cause several side effects that can lead to the cessation of treatment. There is a clinical need to identify patients who will respond to platinum drugs in order to better inform clinical decision making. Diagnostic microdosing involves dosing patients or patient samples with subtherapeutic doses of radiolabeled platinum followed by measurement of platinum-DNA adducts in blood or tumor tissue and may be used to predict patient response. We exposed a panel of six breast cancer cell lines to 14C-labeled carboplatin or oxaliplatin at therapeutic and microdose (1% therapeutic dose) concentrations for a range of exposure lengths and isolated DNA from the cells. The DNA was converted to graphite, and measurement of radiocarbon due to platinum-DNA adduction was quantified via accelerator mass spectrometry (AMS). We observed a linear correlation in adduct levels between the microdose and therapeutic dose, and the level of platinum-DNA adducts corresponded to cell line drug sensitivity for both carboplatin and oxaliplatin. These results showed a clear separation in adduct levels between the sensitive and resistant groups of cell lines that could not be fully explained or predicted by changes in DNA repair rates or mutations in DNA repair genes. Further, we were able to quantitate oxaliplatin-DNA adducts in the blood and tumor tissue of a metastatic breast cancer patient. Together, these data support the use of diagnostic microdosing for predicting patient sensitivity to platinum. Future studies will be aimed at replicating this data in a clinical feasibility trial.

Toward Predicting Acute Myeloid Leukemia Patient Response to 7 + 3 Induction Chemotherapy via Diagnostic Microdosing.

Acute myeloid leukemia (AML) is a rare yet deadly cancer of the blood and bone marrow. Presently, induction chemotherapy with the DNA damaging drugs cytarabine (ARA-C) and idarubicin (IDA), known as 7 + 3, is the standard of care for most AML patients. However, 7 + 3 is a relatively ineffective therapy, particularly in older patients, and has serious therapy-related toxicities. Therefore, a diagnostic test to predict which patients will respond to 7 + 3 is a critical unmet medical need. We hypothesize that a threshold level of therapy-induced 7 + 3 drug-DNA adducts determines cytotoxicity and clinical response. We further hypothesize that in vitro exposure of AML cells to nontoxic diagnostic microdoses enables prediction of the ability of AML cells to achieve that threshold during treatment. Our test involves dosing cells with very low levels of 14C-labeled drug followed by DNA isolation and quantification of drug-DNA adducts via accelerator mass spectrometry. Here, we have shown proof of principle by correlating ARA-C- and DOX-DNA adduct levels with cellular IC50 values of paired sensitive and resistant cancer cell lines and AML cell lines. Moreover, we have completed a pilot retrospective trial of diagnostic microdosing for 10 viably cryopreserved primary AML samples and observed higher ARA-C- and DOX-DNA adducts in the 7 + 3 responders than nonresponders. These initial results suggest that diagnostic microdosing may be a feasible and useful test for predicting patient response to 7 + 3 induction chemotherapy, leading to improved outcomes for AML patients and reduced treatment-related morbidity and mortality.

Doxorubicin-DNA adduct entrenched and motif tethered artificial virus encased in pH-responsive polypeptide complex for targeted cancer therapy

Doxorubicin is a broad spectrum anticancer antibiotic that possesses toxic effects such as cardiomyopathy, that even lead to congestive heart failure. Thus, the development of a new bio-inspired system is required, that retain the advantageous effect of doxorubicin while retarding the side effects. Hence, a system was developed that we describe ‘doxorubicin-DNA adduct entrenched artificial virus encased in polypeptide complex’. The drug-DNA adduct (DDA) was prepared by a formaldehyde mediated reaction. A simple chloroform extraction method for the separation of DDA was developed. DDA was employed to self-assemble the folate tethered bovine serum albumin to form the protein coat in the proposed artificial virus. The folate tethered albumin provides an artificial virus concept, with tumor tissue targeting due to the presence of folate. The whole system was then encased in a pH-responsive polypeptide complex that dissolves in acidic pH, but not in basic pH. DDA was evaluated by UV–Vis spectrophotometry, spectrofluorimetry and high-performance liquid chromatography (HPLC). A promising drug release at physiological condition was observed from DDA. The developed system was evaluated by a developed and validated artificial cell apparatus that mimic the features of a cancer cell. The drug delivery system displayed a considerable amount of drug release within 24 h. Moreover, the developed artificial virus system reduced angiogenesis caused by tumor cells in chick chorioallantoic membrane. Histopathology of treated chicken heart slices demonstrated that the developed artificial virus system reduces the tissue deformation and apoptosis in heart tissue slices, thus providing a new approach to prevent Dox-induced cardiomyopathy.

Drug-DNA adducts as biomarkers for metabolic activation of the nitro-aromatic nitrogen mustard prodrug PR-104A

PR-104A is a clinical-stage nitrogen mustard prodrug that is activated for DNA alkylation by reduction of a nitro group to the corresponding hydroxylamine (PR-104H) or amine (PR-104M). Metabolic reduction is catalysed by flavoreductases such as cytochrome P450 oxidoreductase (POR) under hypoxia, or by aldo-ketoreductase 1C3 (AKR1C3) independently of hypoxia. The unstable reduced metabolites are challenging to measure in biological samples, and biomarkers of the metabolic activation of PR-104A have not been used in the clinical evaluation of PR-104 to date. Here, we employ a selected reaction monitoring mass spectrometry assay for DNA crosslinks to assess the capacity of human cancer cells to bioactivate PR-104A. We also test whether the more abundant DNA monoadducts could be used for the same purpose. DNA monoadducts and crosslinks from PR-104A itself, and from its reduced metabolites, accumulated over 4 h in AKR1C3-expressing TF1 erythroleukaemia cells under hypoxia, whereas intracellular concentrations of unstable PR-104H and PR-104M reached steady state within 1 h. We then varied rates of PR-104A reduction by manipulating hypoxia or reductase expression in a panel of cell lines, in which AKR1C3 and POR were quantified by targeted proteomics. Hypoxia or reductase overexpression induced large increases in PR-104A sensitivity (inhibition of proliferation), DNA damage response (γH2AX formation), steady-state concentrations of PR-104H/M and formation of reduced drug-DNA adducts but not DNA adducts retaining the dinitro groups of PR-104A. The fold-change in the sum of PR-104H and PR-104M correlated with the fold-change in reduced crosslinks or monoadducts (R2 = 0.87 for both), demonstrating their potential for assessing the capacity of cancer cells to bioactivate PR-104A.

Hybrid Gd3+/cisplatin cross-linked polymer nanoparticles enhance platinum accumulation and formation of DNA adducts in glioblastoma cell lines.

Glioblastoma is the most frequent and aggressive primary malignant tumor of the central nervous system with a gloomy prognosis. Platinum derivatives and one among them, cisplatin, exhibited promising results when locally administered into the brain of glioblastoma bearing rats. Nanovectorization of anticancer agents through polymeric nanoparticles may even promote drug accumulation within cells, thus concentrating the drug efficiently at its target. Anchorage of gadolinium complexes on the corona of such smart drug delivery systems could further allow magnetic resonance imaging (MRI) monitoring of the nanoplatform biodistribution in the damaged parenchyma and its therapeutic benefit. For this purpose, a biocompatible amphiphilic triblock copolymer, made of degradable polyester and polycarbonate and bioeliminable polyethylene oxide (PEO), was synthesized by successive ring-opening polymerizations. After micellization in water, gadolinium complexes were grafted onto the PEO micelle corona and the carboxylate functions, located at the surface of the micelle's core, were able to cross-link with Pt(ii) complexes. A macromolecular prodrug was therefore recovered in which more than one third of the carboxylate functions were linked to a platinum atom. By this strategy, stable cisplatin cross-linked nanoparticles were formulated with a mean size in the range of 100.63 ± 12.04 nm consistent with biological investigations. Relaxometry measurements both in water and in plasma at 7 T, 25 °C, confirmed the intrinsic potential of these hybrid nanoparticles as alternative MRI contrast agents with a substantial increase in the r2/r1 ratio by a factor of 3.3 and 2.7, respectively, compared to the conventional low molar mass Gd-DTPA. As a result, their infusion within the striatum of glioblastoma-bearing mice resulted in a hypersignal on T2-weighted MR images that persisted over time. Ultimately, the formulated prodrug exhibited up to 50-fold increased accumulation in human glioblastoma cell lines and up to 32-fold enhanced subsequent Pt-DNA adduct formation in comparison with free cisplatin, thus supporting the potential of this innovative bimodal tool for further applications.

Microdose-Induced Drug-DNA Adducts as Biomarkers of Chemotherapy Resistance in Humans and Mice.

We report progress on predicting tumor response to platinum-based chemotherapy with a novel mass spectrometry approach. Fourteen bladder cancer patients were administered one diagnostic microdose each of [14C]carboplatin (1% of the therapeutic dose). Carboplatin-DNA adducts were quantified by accelerator mass spectrometry in blood and tumor samples collected within 24 hours, and compared with subsequent chemotherapy response. Patients with the highest adduct levels were responders, but not all responders had high adduct levels. Four patient-derived bladder cancer xenograft mouse models were used to test the possibility that another drug in the regimen could cause a response. The mice were dosed with [14C]carboplatin or [14C]gemcitabine and the resulting drug-DNA adduct levels were compared with tumor response to chemotherapy. At least one of the drugs had to induce high drug-DNA adduct levels or create a synergistic increase in overall adducts to prompt a corresponding therapeutic response, demonstrating proof-of-principle for drug-DNA adducts as predictive biomarkers. Mol Cancer Ther; 16(2); 376-87. ©2016 AACR.

Highlights of This Issue

The pharmacological inhibition of lysine specific demethylase 1 (LSD1, also known as KDM1A) has recently drawn attention as a novel therapeutic option against acute myeloid leukemia (AML). Here, Ishikawa, Gamo, and colleagues demonstrated that a novel irreversible LSD1 inhibitor, T-3775440, exhibited anti-leukemic efficacy in GFI1B-expressing acute erythroleukemia (AEL) and acute megakaryoblastic leukemia (AMKL) cells. T-3775440 exerts anti-AML effects through a mechanism involving disruption of the LSD1/GFI1B complex and consequent AML cell transdifferentiation. Given that several LSD1 inhibitors have entered clinical trials for treating patients with AML, these results provide new perspectives in the therapeutic strategy of AEL and AMKL.The mechanism of acquired resistance against afatinib is still unclear. Here, Kobayashi and colleagues established a panel of resistant clones from Ba/F3 cells transduced with mutated EGFR genes (Del18, G719A, Del19 or L858R). Among 84 resistant clones, secondary C797S mutation was found in subsets of Del18, G719A or L858R but not in Del19 clones. A novel L792F was present in Del18 clones while the majority had a common T790M. Clones with C797S and L792F exhibit sensitivity to erlotinib and dacomitinib, respectively. In conclusion, afatinib resistance could be driven by L792F or C797S mutations and therefore testing novel combinations of EGFR-TKIs might benefit patients with these minor mutations.Common cytotoxic chemotherapy regimens currently lack diagnostic tests that predict response. Zimmermann and colleagues demonstrated the feasibility of using microdose-induced drug-DNA adducts as predictive biomarkers of response to gemcitabine and cisplatin or carboplatin in a pilot clinical study and several mouse models of bladder cancer. Patients with the highest carboplatin-DNA adduct levels were responders, but not all responders had high adduct levels. In mice bearing patient-derived tumor xenografts, at least one of the drugs in the regimen had to induce high drug-DNA adduct levels or a synergistic increase in overall adducts to prompt a corresponding therapeutic response.The potential of epigenetic drugs to synergize with other drugs against colon cancer cells remains to be uncovered. To identify new drug interactions, high-throughput screening was performed on cancer cells treated with DNA methylation or histone deacetylase inhibitors in combination with FDA-approved drug libraries. The screening model measured reporter gene expression level, as a surrogate for tumor suppressor gene reactivation. This study revealed new combinations of epigenetic drugs and FDA-approved drugs producing epigenetic synergy, which can be rapidly implemented into clinical trials against colon cancer.

Liquid chromatography-mass spectrometry as a general approach for investigating covalent binding of drugs to DNA.

This paper aims at developing a general strategy to study the detection of adducts of drugs with DNA. In particular, ethacrynic acid has been chosen as a model reactive drug that could be able to bind covalently to DNA bases. Such interactions were detected by ultra-high performance liquid chromatography-high resolution mass spectrometry (UHPLC-HRMS). Principal component analysis (PCA) was applied as an unsupervised method to try to find the potential candidate adduct from MS features. The occurrence of adducts was investigated preliminarily using deoxynucleosides of the guanine, cytosine, adenine, and thymine separately as a way to optimize both separation and detection conditions. Interpretations of MS and MS/MS spectra provided tentative structures of the compounds formed. Conclusions extracted from such simple nucleoside models were further extended to the analysis of DNA adducts. For such a purpose, DNA was incubated in the presence of ethacrynic acid under appropriate experimental conditions and its further enzymatic hydrolysis released the corresponding nucleosides. UHPLC-MS analysis of the resulting test samples under the SRM detection mode confirmed the presence of ethacrynic acid derivatives of nucleosides occurring at very low concentration levels, thus proving the overall performance of the method. Graphical Abstract General approach for investigating drug-DNA adduct formation.

Molecular Dissection of Induced Platinum Resistance through Functional and Gene Expression Analysis in a Cell Culture Model of Bladder Cancer.

We report herein the development, functional and molecular characterization of an isogenic, paired bladder cancer cell culture model system for studying platinum drug resistance. The 5637 human bladder cancer cell line was cultured over ten months with stepwise increases in oxaliplatin concentration to generate a drug resistant 5637R sub cell line. The MTT assay was used to measure the cytotoxicity of several bladder cancer drugs. Liquid scintillation counting allowed quantification of cellular drug uptake and efflux of radiolabeled oxaliplatin and carboplatin. The impact of intracellular drug inactivation was assessed by chemical modulation of glutathione levels. Oxaliplatin- and carboplatin-DNA adduct formation and repair was measured using accelerator mass spectrometry. Resistance factors including apoptosis, growth factor signaling and others were assessed with RNAseq of both cell lines and included confirmation of selected transcripts by RT-PCR. Oxaliplatin, carboplatin, cisplatin and gemcitabine were significantly less cytotoxic to 5637R cells compared to the 5637 cells. In contrast, doxorubicin, methotrexate and vinblastine had no cell line dependent difference in cytotoxicity. Upon exposure to therapeutically relevant doses of oxaliplatin, 5637R cells had lower drug-DNA adduct levels than 5637 cells. This difference was partially accounted for by pre-DNA damage mechanisms such as drug uptake and intracellular inactivation by glutathione, as well as faster oxaliplatin-DNA adduct repair. In contrast, both cell lines had no significant differences in carboplatin cell uptake, efflux and drug-DNA adduct formation and repair, suggesting distinct resistance mechanisms for these two closely related drugs. The functional studies were augmented by RNAseq analysis, which demonstrated a significant change in expression of 83 transcripts, including 50 known genes and 22 novel transcripts. Most of the transcripts were not previously associated with bladder cancer chemoresistance. This model system and the associated phenotypic and genotypic data has the potential to identify some novel details of resistance mechanisms of clinical importance to bladder cancer.

Synthesis, structural characterization, in vitro bioactivities, interaction with SS-DNA and DFT study of 4-chloro-3-ferrocenylaniline

We report here the synthesis, characterization (FT-IR, multinuclear (1H and 13C) NMR, Raman, AAS, elemental analysis and single-crystal XRD), DNA binding (cyclic voltammetry, UV–Vis spectroscopy and viscometry) and in vitro biological screening of 4-chloro-3-ferrocenylaniline (CFA). The crystallographic analysis revealed a supramolecular structure mediated by secondary non-covalent interactions (π⋯H and π⋯π). The DNA binding studies performed by cyclic voltammetry and UV–Vis spectroscopy produced results that are in close agreement with one another for the binding constants (K), 1.64×104M−1 and 2.39×104M−1, respectively, and an electrostatic mode of interaction was observed. The diffusion coefficient of the drug-DNA adduct (1.02×10−6cm2s−1) is lower than that for the free drug (1.31×10−6cm2s−1) indicating slow diffusion of the comparatively high molecular weight drug towards the electrode in the cyclic voltammetric study. The binding site size of 0.309 base pairs is also consistent with electrostatic interactions. The nature and the extent of interaction with DNA was also investigated by viscometry. DFT/B3LYP method was used to determine the charge distribution and HOMO/LUMO energies of the optimized structure. The CFA compound exhibited good free radical scavenging activity against DPPH with an IC50 value of 160μM. CFA was also screened for antimicrobial, cytotoxic and protein kinase inhibition potential and proved to be good candidate in terms of microbial growth and protein kinase inhibition. These properties may prove valuable in the future design of new anticancer and antimicrobial drugs.

Photoactivatable platinum(II) compounds: in search of novel anticancer drugs

Photoactivated chemotherapy is a promising clinical alternative to focus the action of a drug in a tumoral region while sparing undamaged tissues. However, the phototherapeutic window is rather narrow (620–850 nm), so that any novel photoactivatable drug needs to be excited within that range. In the present work, we asses the potential performances of several novel photoactivatable platinum-based anticancer drugs by means of calculations. Indeed, a panel of theoretical levels, including molecular dynamics simulations, density functional theory and its time-dependent counterpart, are used to determine drug–DNA adduct structures as well as to compute their optical properties. The reported data provide comprehensive insights into the design of improved platinum(II) drugs able to induce a direct reaction of the metallic center with DNA upon irradiation in the phototherapeutic window.

A Synthetic Aptamer-Drug Adduct for Targeted Liver Cancer Therapy.

AS1411 (previously known as AGRO100) is a 26 nucleotide guanine-rich DNA aptamer which forms a guanine quadruplex structure. AS1411 has shown promising utility as a treatment for cancers in Phase I and Phase II clinical trials without causing major side-effects. AS1411 inhibits tumor cell growth by binding to nucleolin which is aberrantly expressed on the cell membrane of many tumors. In this study, we utilized a simple technique to conjugate a widely-used chemotherapeutic agent, doxorubicin (Dox), to AS1411 to form a synthetic Drug-DNA Adduct (DDA), termed as AS1411-Dox. We demonstrate the utility of AS1411-Dox in the treatment of hepatocellular carcinoma (HCC) by evaluating the targeted delivery of Dox to Huh7 cells in vitro and in a murine xenograft model of HCC.

Bioactivity of new ferrocene incorporated N,N′-disubstituted ureas: Synthesis, structural elucidation and DFT study

We report here the synthesis, structural characterization and biological assessment of three new ferrocene incorporated ureas (1–3). The synthesis of these complexes was accomplished by the deprotection of ferrocene-based thioureas to the corresponding oxo analogues using NaOH(aq) and mercuric chloride. The new ferrocenyl ureas were characterized by FT-IR, multinuclear (1H and 13C) NMR, AAS and elemental analysis. Furthermore, the single-crystal X-ray structure of compound 2 was also determined. The DNA binding potency of these ureas was evaluated by UV–Vis spectroscopy and cyclic voltammetry (CV). The three complexes interact electrostatically with DNA and have impressive binding constants ranging from 3.42×104 to 8.15×104M−1. The diffusion coefficients of the drug–DNA adducts are lower than is that for the free drug indicating the formation of a high molecular weight complex that diffuses slowly towards the electrode. The small binding site size of 0.509 (1), 0.528 (2) and 0.473 (3) base pairs is also indicative of an electrostatic mode of interaction. The DFT calculated HOMO and LUMO energies correlate well with the experimentally determined redox potential values. The synthesized ureas (1–3) were screened for their antibacterial, antifungal and protein kinase inhibition potency. These compounds play a significant role in arresting microbial growth and are potent protein kinase inhibitors.

Synthesis, structural characterization, DNA binding and antioxidant potency of new ferrocene incorporated acyl ureas

In this article, we have reported the synthesis of three new ferrocene incorporated ureas namely; 1-(4-Chlorobenzoyl)-3-(4-ferrocenylphenyl)urea (P4Cl), 1-(3-Chlorobenzoyl)-3-(4-ferrocenyl phenyl)urea (P3Cl) and 1-(2-Chlorobenzoyl)-3-(4-ferrocenylphenyl)urea (P2Cl). All new compounds were unambiguously characterized by common analytical techniques (NMR, FT-IR, AAS, CHNS and molecular docking). Furthermore, single crystal XRD analysis was done for 1-(3-Chlorobenzoyl)-3-(4-ferrocenylphenyl)urea. DNA binding is a pre-requisite for a compound to be used as an antitumor agent. The DNA binding study was done by cyclic voltammetry, UV–vis spectroscopy and viscometry. The drug–DNA binding constant was found to vary in the sequence: KP2Cl (6.056 × 104 M−1) > KP4Cl (5.713 × 104 M−1) > KP3Cl (4.631 × 104 M−1). Diffusion coefficient of the drug–DNA adduct for all the compounds is lower than the free drug, indicating that drug–DNA adduct is of higher molecular weight and slow diffusing as compared to the free drug. Small binding site size of 0.440 (P3Cl), 0.585 (P4Cl) and 0.673 (P2Cl) base pairs is consistent with electrostatic interaction. All the compounds exhibited good antioxidant activities with IC50 values of 82, 136 and 54 μM for P4Cl, P3Cl and P2Cl respectively, against DPPH.