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Introduction One of the most used regimens to treat breast cancer is the dose-dense ACT protocol, a combination of anthracycline doxorubicin (DOX) with cyclophosphamide and paclitaxel (PCTX). However, many tumors show resistance to the protocols applied. It is known that the nucleotide excision repair (NER) pathway acts by removing the DOX-generated lesions, and this, together with other DNA repair pathways, can modulate the response to treatment. Aims To evaluate the in vitro growth profile of breast cancer cells (MCF7), and the modulation of DNA repair genes, submitted to a protocol using DOX and PCTX in a similar regimen to what is used in clinical practice. Main methods MCF7 cells were treated with repeated cycles of DOX and PCTX and followed-up during and after each of the treatments. The population doubling of the remaining cells was calculated during the complete protocol and DNA repair gene expression was evaluated at different time-points. Key findings An increase in all NER genes analyzed after the DOX treatment was observed, but not after the PCTX treatment. MRE11was overexpressed at all evaluated time-points. There was a resumption of NER genes overexpression profile when cells were maintained for follow-up and retook their growth pattern, indicating that DNA repair pathways can modulate their expression during the chemotherapy exposure.

Fabry disease (FD) is a lysosomal disorder caused by mutations leading to a deficient activity α-galactosidase A with progressive and systemic accumulation of its substrates. Substrates deposition is related to tissue damage in FD, but the underlying molecular mechanisms remain not completely understood. DNA damage has been associated with disease progression in chronic diseases and was recently described in high levels in Fabry patients. Once renal complications are major morbidity causes in FD, we investigated the effects of the latest biomarker for FD – globotriaosylsphingosine (lyso-Gb3) in a cultured renal lineage – human embryonic kidney cells (HEK-293 T) – on DNA damage. In concentrations found in Fabry patients, lyso-Gb3 induced DNA damage (by alkaline comet assay) with oxidative origin in purines and pyrimidines (by comet assay with endonucleases). These data provide new information about a deleterious effect of lyso-Gb3 and could be useful to studies looking for new therapeutic strategies to FD.

A new series of Cu(II) complexes [bis[{(μ

Mitoxantrone (MXT) is an anticancer drug structurally related to anthracyclines, such as doxorubicin (DOX). Here we report that cells deficient in nucleotide excision repair (NER) are very sensitive to MXT. However, cells deficient in each of the NER sub-pathways - transcription coupled repair (deficient in CSB protein) and global genome repair (deficient in XPC protein) - demonstrate a difference in sensitivity from each other and also show different responses in cell cycle profile, DNA synthesis and topo II DNA complex formation upon MXT treatment. XPC-deficient cells are slightly more resistant than CSB-deficient cells, and in the same way as MRC5 NER-proficient cells, show G2/M arrest, normal DNA synthesis rate and a pattern of formation of complexes similar to proficient cells, whereas CSB-deficient cells show accumulation in S phase, reduced DNA synthesis and a more intense signal of topo II DNA complexes, indicating that they remain longer in these cells. Complementation of CSB mutant cells with CSB rescue MXT-induced sensitivity and also a decrease in the signal intensity of the complexes, suggest that resolution of these lesions would take place. Taken together, our results indicate that NER proteins are implicated in the response to MXT and that CSB protein has a key role in processing MXT-induced topo II DNA complexes.

In cancer treatment, chemotherapy is one of the main strategies used. The knowledge of the cellular and molecular characteristics of tumors allows the use of more specific drugs, making the removal of tumors more efficient. Among the drugs of choice in these treatments, topoisomerase inhibitors are widely used against different types of tumors. Topoisomerases are enzymes responsible for maintaining the structure of DNA, altering its topological state temporarily during the processes of replication and transcription, in order to avoid supercoiling and entanglements at the double helix. The DNA damage formed as a result of topoisomerase inhibition can be repaired by DNA repair mechanisms. Thus, DNA repair pathways can modulate the effectiveness of chemotherapy. Homologous recombination (HR) and non-homologous end joining (NHEJ) are the main pathways involved in the removal of double strand breaks (DSBs); while nucleotide excision repair (NER) is mainly characterized by the removal of lesions that lead to significant structural distortions in the DNA double helix. Evidence has shown that DSBs are the main type of damage resulting from the inhibition of the DNA topoisomerase II enzyme, and therefore the involvement of HR and NHEJ pathways in the repair process is well established. However, some topoisomerase II inhibitors induce other types of lesions, like DNA adducts, interstrand crosslinks and reactive oxygen species, and studies have shown that other DNA repair pathways might be participating in removing injury induced by these drugs. This review aims to correlate the involvement of proteins from different DNA repair pathways in response to these drugs, with an emphasis on NER.

A new series of Cu(II) complexes [bis[{(μ2-chloro)-2-MeO-Ph-CH2-(N=CH)-2,4-tert-butyl-2-OC6H2)}Cu(II)] (Cu1); bis[{(μ2-chloro)-2-MeS-Ph-CH2-(N=CH)-2,4-tert-butyl-2-(OC6H2)}Cu(II)] (Cu2); bis[{(μ2-chloro)-2-MeO-Ph-CH2-(N=CH)-2-(OC10H6)} Cu(II)] (Cu3); bis[{(μ2-chloro)-2-MeS-Ph-CH2-(N=CH)-2-(OC10H6)}Cu(II)] complex (Cu4); bis[{2-MeS-Ph-CH2-(N=CH)-2,4-tert-butyl-2-(OC6H2)}Cu(II)] (Cu5)] have been synthesized and characterized by elemental analysis, IR, UV–Visible and by X-ray crystallography for Cu1, Cu4 and Cu5. In the solid state, Cu1 features of a chloro-bridged dimer complex with κ2 coordination of the monoanionic phenoxy-imine ligand onto the copper center. On the other hand, the molecular structure of Cu4 reveals the naphthoxy-imine ligand with pendant S-group coordinated to the copper atom in tridentate meridional fashion. Treatment of [Cu(OAc)2·H2O] with two equiv. of [2-MeS-Ph-CH2-(N=CH)-2,4-tert-butyl-2-(HOC6H2)] led to a monomeric complex Cu5, with the ONS-donor Schiff base acting as a bidentate ligand. The redox behavior was explored by cyclic voltammetry. The reduction/oxidation potential of Cu(II) complexes depends on the structure and conformation of the central atom in the coordination compounds. Antioxidant activities of the complexes, Cu1 - Cu5, were determined by in vitro assays such as 1,1-diphenyl-2-picryl-hydrazyl free radicals (DPPH ) and 2,2′-azino-bis(3-ethylbenzthiazoline-6-sulfonic acid) radicals (ABTS+). The dinuclear compounds Cu1-Cu4, from the concentration of 5 μM, presented a good activity in scavenging DPPH radical. In addition, most of the Cu(II) complexes showed ABTS.+ radical-scavenging activity. The monomeric complex Cu5 at all concentrations tested showed antioxidant inability. The cytotoxicity of the Cu1 and Cu3 was determined in V79 cell line by reduction of 3(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-tetrazolium bromide (MTT) assay.

A series of 12 organosilanes exhibiting different steric and electronic properties were employed in the synthesis of hybrid silicas by the Stober sol-gel process. The resulting materials were characterized by a set of complementary techniques (nitrogen adsorption, dynamic light scattering, small-angle X-ray scattering, transmission electron microscopy, and carbon content analysis).. Hybrid silicas bearing polyethylene glycol (PEG), zwitterion (ZWT), and methyl (C1) moieties improved the physical-chemical properties of the nanoparticles for biological applications. Toxicological safety tests were performed on the fibroblast cell line (MRC-5), which showed that the functionalization of silica nanoparticles with PEG and ZWT increased cell viability, 111 ± 8.5% and 114 ± 6.3%, respectively, when compared to that of nanomaterials without functionalization, 98 ± 8.8%. Both functionalized and non-functionalized silica nanoparticles did not cause any damage to the DNA of the cells, even at the highest doses.

Predicting the individual response to chemotherapy is a crucial challenge in cancer treatment. DNA damage caused by antitumor therapies evokes different repair mechanisms responses, such as Nucleotide Excision Repair (NER), whose components are being studied as prognosis biomarkers and target therapies. However, few reports have addressed DNA damages in pediatric Acute Lymphoid Leukemia (ALL). Hence, we conducted an observational follow-up study with pediatric patients to assess DNA damage (by Comet Assay) and gene expression from NER pathway during chemotherapy induction. Bone marrow samples from diagnosis, 15th(D15) and 35th (D35) days of the treatment were collected from 28 patients with ALL. There was no increase in damage index. However, there was a reduction of cells with low damages on D35 compared with diagnosis. NER pathway expression remained the same, however, in a single patient, a significant decrease was observed, maybe due to silencing or downregulation of repair pathways. DNA damage levels and repair may influence the clinical outcome, being involved in drug resistance and risk of relapse. In pediatric ALL, we analyzed for the first time DNA damage and repair behavior in BM samples. Monitoring patient’s outcomes will help to access the implication of our findings in survival and relapse rates.

Fabry disease (FD) is a lysosomal disorder caused by mutations leading to a deficient activity α-galactosidase A with progressive and systemic accumulation of its substrates. Substrates deposition is related to tissue damage in FD, but the underlying molecular mechanisms remain not completely understood. DNA damage has been associated with disease progression in chronic diseases and was recently described in high levels in Fabry patients. Once renal complications are major morbidity causes in FD, we investigated the effects of the latest biomarker for FD - globotriaosylsphingosine (lyso-Gb3) in a cultured renal lineage - human embryonic kidney cells (HEK-293 T) - on DNA damage. In concentrations found in Fabry patients, lyso-Gb3 induced DNA damage (by alkaline comet assay) with oxidative origin in purines and pyrimidines (by comet assay with endonucleases). These data provide new information about a deleterious effect of lyso-Gb3 and could be useful to studies looking for new therapeutic strategies to FD.