Evaluation of doxorubicin and ß-lapachone analogs as anticancer agents, a biological and computational study.

We have conducted an experimental and computational evaluation of new doxorubicin (4a-c) and ß-lapachone (5a-c) analogs. These novel anticancer analogs were previously synthesized, but had not been tested or characterized until now. We have evaluated their antiproliferative and DNA cleavage inhibition properties using breast (MCF-7 and MDA-MB-231) and prostate (PC3) cancer cell lines. Additionally, cell cycle analysis was performed using flow cytometry. Computational studies, including molecular docking, pharmacokinetic properties, and an analysis of DFT and QTAIM chemical descriptors, were performed to gain insights into the electronic structure and elucidate the molecular binding of the new ß-lapachone and doxorubicin analogs with a DNA sequence and Topoisomerase II (Topo II)α. Our results show that 4a analog displays the highest antiproliferative activity in cancer cell lines by inducing cell death. We observed that stacking interactions and hydrogen bonding are essential to stabilize the molecule-DNA-Topo IIα complex. Moreover, 4a and 5a analogs inhibited Topo's DNA cleavage activity. Pharmacodynamic results indicated that studied molecules have favorable adsorption and permeability properties. The calculated chemical descriptors indicate that electron accumulation in quinone rings is relevant to the reactivity and biological activity. Based on our results, 4a is a strong candidate for becoming an anticancer drug.

Interaction study with DNA/HSA, anti-topoisomerase IIα, cytotoxicity and in vitro antiproliferative evaluations and molecular docking of indole-thiosemicarbazone compounds.

In this work we will discuss the antiproliferative evaluation and the possible mechanisms of action of indole-thiosemicarbazone compounds LTs with anti-inflammatory activity, previously described in the literature. In this perspective, some analyzes were carried out, such as the study of binding to human serum albumin (HSA) and to biological targets: DNA and human topoisomerase IIα (topo). Antiproliferative study was performed with DU-145, Jukart, MCF-7 and T-47D tumor lines and J774A.1, besides HepG2 macrophages and hemolytic activity. In the HSA interaction tests, the highest binding constant was 3.70 × 106 M-1, referring to LT89 and in the fluorescence, most compounds, except for LT76 and LT87, promoted fluorescent suppression with the largest Stern-Volmer constant for the LT88 3.55 × 104. In the antiproliferative assay with DU-145 and Jurkat strains, compounds LT76 (0.98 ± 0.10/1.23 ± 0.32 µM), LT77 (0.94 ± 0.05/1.18 ± 0.08 µM) and LT87 (0.94 ± 0.12/0.84 ± 0.09 µM) stood out, due to their IC50 values mentioned above. With the MCF-7 and T-47D cell lines, the lowest IC50 was presented by LT81 with values of 0.74 ± 0.12 µM and 0.68 ± 0.10 µM, respectively, followed by the compounds LT76 and LT87. As well as the positive control amsacrine, the compounds LT76, LT81 and LT87 were able to inhibit the enzymatic action of human Topoisomerase IIα.

Topoisomerase Enzyme Inhibitors as Potential Drugs Against Cancer: What Makes Them Selective or Dual? - A Review.

Topoisomerase inhibitors are extensively used in cancer chemotherapy. In the process of identifying novel anticancer compounds, biological evaluations are crucial and include, among others, the use of in silico and in vitro approaches. This work aimed to present recent research involving the obtainment and in silico and in vitro evaluation of topoisomerase I, II, and double inhibitors, of synthetic and natural origin, as potential compounds against tumor cells, in addition to proposing the construction of a desirable enzyme catalytic site. Therefore, it was observed that most Topoisomerase I inhibitors presented medium to large structures, with a rigid portion and a flexible region. In contrast, Topoisomerase IIα inhibitors showed medium and large structural characteristics, in addition to the planarity of the aromatic rings, which are mitigated due to flexible rings but may also present elements that restrict conformation. Most compounds that exhibit dual inhibitory activity had relatively long chains, in addition to a flat and rigid portion suggestive of affinity for Topo I and a flexible region characteristic of selective drugs for Topo II. Besides, it is noticed that most compounds that exhibit dual inhibitory showed similarities in the types of interactions and amino acids when compared to the selective compounds of Topo I and II. For instance, selective Topoisomerase I inhibitors interact with Arginine364 residues, and selective Topoisomerase II inhibitors interact with Arginine487 residues, as both residues are targets for dual compounds.

Inhibition of Aedes aegypti DNA topoisomerase II by etoposide: Impact on survival and morphology of larvae and pupae.

DNA topoisomerase II enzymes maintain DNA stability during vital processes, such as genome replication, transcription and chromosomal segregation during mitosis and meiosis. In the present work, we analyzed functional aspects of the DNA topoisomerase II (AeTopII) enzyme of the mosquito Aedes aegypti. Here, we show that AeTopII mRNA is expressed at all stages of mosquito development. By in situ hybridization, we found that the AeTopII mRNA is concentrated along the ovarian follicular cells as well as in the region of the follicles. The observed expression profiles likely reflect increased topoisomerase II cellular requirements due to the intense ovarian growth and egg production following blood feeding in Ae. aegypti females. The drug etoposide, a classic inhibitor of topoisomerase II, was used for in vivo testing with 2nd stage larvae, in order to investigate the functional importance of this enzyme in Ae. aegypti survival and development. Inhibition of topoisomerase II activity with etoposide concentrations ranging from 10 to 200 µM did not leads to the immediate death of larvae. However, after 10 days of observation, etoposide treatments resulted in 30-40% decrease in survival, in a dose dependent manner, with persisting larvae and pupae presenting incomplete development, as well as morphological abnormalities. Also, approximately 50% of the treated larvae did not reach the pupal stage. Thus, we conclude that AeTopII is a vital enzyme in the development of Ae. aegypti and its sensitivity to inhibitors should be explored for potential chemical agents to be used in vector control.

Ursolic and betulinic semisynthetic derivatives show activity against CQ-resistant Plasmodium falciparum isolated from Amazonia.

ACT's low levels of Plasmodium parasitemia clearance are worrisome since it is the last treatment option against P. falciparum. This scenario has led to investigations of compounds with different mechanisms of action for malaria treatment. Natural compounds like ursolic acid (UA) and betulinic acid (BA), distinguished by their activity against numerous microorganisms, including P. falciparum, have become relevant. This study evaluated the antiplasmodial activity of imidazole derivatives of UA and BA against P. falciparum in vitro. Eight molecules were obtained by semisynthesis and tested against P. falciparum strains (NF54 and CQ-resistant 106/cand isolated in Porto Velho, Brazil); 2a and 2b showed activity against NF54 and 106/cand strains with IC50  < 10 µM. They presented high selectivity indexes (SI > 25) and showed synergism when combined with artemisinin. 2b inhibited the parasite's ring and schizont forms regardless of when the treatment began. In silico analysis presented a tight bind of 2b in the topoisomerase II-DNA complex. This study demonstrates the importance of natural derivate compounds as new candidates for malarial treatment with new mechanisms of action. Semisynthesis led to new triterpenes that are active against P. falciparum and may represent new alternatives for malaria drug development.

TOP2A/MCM2, p16INK4a, and cyclin E1 expression in liquid-based cytology: a biomarkers panel for progression risk of cervical premalignant lesions.

BACKGROUND: To improve the efficiency of early diagnosis systems for cervical cancer, the use of cellular and viral markers for identifying precancerous lesions with a greater probability to progress to cancer has been proposed. Several cellular proteins and markers of oxidative DNA damage have been suggested as possible biomarkers of cervical carcinogenesis; however, they have not been evaluated together. In this study, we analyzed the expression of the cellular markers p16INK4a, Ki-67, CyclinE1, TOP2A/MCM2, and telomerase, as well as the DNA oxidative damage markers ROS and 8-OHdG. The analyses were performed in liquid-based cervical cytology samples or biopsies with premalignant lesions or cervical cancer diagnosis, with the purpose of selecting a panel of biomarkers that allow the identification of precursor lesions with greater risk of progression to cervical cancer. METHODS: We analyzed 1485 liquid-based cytology samples, including 239 non-squamous intraepithelial lesions (NSIL), 901 low-grade squamous intraepithelial lesions (LSIL), 54 high-grade squamous intraepithelial lesions (HSIL), and 291 cervical cancers (CC). The biomarkers were analyzed by immunocytochemistry and Human Papilloma Virus (HPV) genotyping with the INNO-LiPA genotyping Extra kit. RESULTS: We found that all tested cellular biomarkers were overexpressed in samples with high risk-HPV infection, and the expression levels increased with the severity of the lesion. TOP2A/MCM2 was the best biomarker for discriminating between LSIL and HSIL, followed by p16INK4a and cyclinE1. Statistical analysis showed that TOP2A/MCM2 provided the largest explanation of HSIL and CC cases (93.8%), followed by p16INK4a (91%), cyclin E1 (91%), Ki-67 (89.3%), and telomerase (88.9%). CONCLUSIONS: We propose that the detection of TOP2A/MCM2, p16INK4a and cyclin E1 expression levels is useful as a panel of biomarkers that allow identification of cervical lesions with a higher risk for progression to CC with high sensitivity and precision; this can be done inexpensively, in a single and non-invasive liquid-based cytology sample.

Novel 4-quinoline-thiosemicarbazone derivatives: Synthesis, antiproliferative activity, in vitro and in silico biomacromolecule interaction studies and topoisomerase inhibition.

Twelve 2-(quinolin-4-ylmethylene) hydrazinecarbothioamide derivatives were synthetized and their biological properties were investigated, among which, the ability to interact with DNA and BSA through UV-Vis absorption, fluorescence, Circular Dichroism, molecular docking and relative viscosity, antiproliferative activity against MCF-7 and T-47D mammary tumor cells and RAW-264.7 macrophages and inhibitory capacity of the enzyme topoisomerase IIα. In the binding study with DNA and BSA, all the compounds displayed affinity for interaction with both biomolecules, especially JF-92 (p-ethyl-substituted), with binding constant of 1.62 × 106 and 1.43 × 105, respectively, and DNA binding mode by intercalation. The IC50 values were obtained between 0.81 and 1.48 µM and topoisomerase inhibition results in 10 µM. Thus, we conclude that the reduction of the acridine to quinoline ring did not disrupt the antitumor action and that substitution patterns are important for biomolecule interaction affinity as they demonstrate the potential of these compounds for anticancer therapy.

Topoisomerase inhibition and albumin interaction studies of acridine-thiosemicarbazone derivatives.

In the present study, acridine-thiosemicarbazones (ATD) derivatives were tested for their interaction properties with BSA through UV-Vis absorption and fluorescence spectroscopic studies. Both hyperchromic and hypochromic effects, as well as red or blue shifts were demonstrated after the derivatives were added to the BSA. Values for the binding constant (Kb) ranged from 1.62 × 104 to 8.71 × 105 M-1 and quenching constant (KSV) from 3.46 × 102 to 7.83 × 103 M-1 indicating a good affinity to BSA protein. Complementary, two compounds were selected to assess their inhibition activity against topoisomerase IIα enzyme, of which derivative 3a presented the best result. Moreover, to evaluate protein-ligand interactions, as well as the antitopoisomerase potential of these compounds, tests of molecular modeling were performed between all compounds using the albumin and Topoisomerase IIα/DNA complex. Finally, in silico studies showed that all derivatives used in this research displayed good oral bioavailability potential.

5-Nitro-Thiophene-Thiosemicarbazone Derivatives Present Antitumor Activity Mediated by Apoptosis and DNA Intercalation.

BACKGROUND: Considering the need for the development of new antitumor drugs, associated with the great antitumor potential of thiophene and thiosemicarbazonic derivatives, in this work we promote molecular hybridization approach to synthesize new compounds with increased anticancer activity. OBJECTIVE: Investigate the antitumor activity and their likely mechanisms of action of a series of N-substituted 2-(5-nitro-thiophene)-thiosemicarbazone derivatives. METHODS: Methods were performed in vitro (cytotoxicity, cell cycle progression, morphological analysis, mitochondrial membrane potential evaluation and topoisomerase assay), spectroscopic (DNA interaction studies), and in silico studies (docking and molecular modelling). RESULTS: Most of the compounds presented significant inhibitory activity; the NCIH-292 cell line was the most resistant, and the HL-60 cell line was the most sensitive. The most promising compound was LNN-05 with IC50 values ranging from 0.5 to 1.9 µg.mL-1. The in vitro studies revealed that LNN-05 was able to depolarize (dose-dependently) the mitochondrial membrane, induceG1 phase cell cycle arrest noticeably, promote morphological cell changes associated with apoptosis in chronic human myelocytic leukaemia (K-562) cells, and presented no topoisomerase II inhibition. Spectroscopic UV-vis and molecular fluorescence studies showed that LNN compounds interact with ctDNA forming supramolecular complexes. Intercalation between nitrogenous bases was revealed through KI quenching and competitive ethidium bromide assays. Docking and Molecular Dynamics suggested that 5-nitro-thiophene-thiosemicarbazone compounds interact against the larger DNA groove, and corroborating the spectroscopic results, may assume an intercalating interaction mode. CONCLUSION: Our findings highlight 5-nitro-thiophene-thiosemicarbazone derivatives, especially LNN-05, as a promising new class of compounds for further studies to provide new anticancer therapies.

NEK5 interacts with topoisomerase IIß and is involved in the DNA damage response induced by etoposide.

Cells are daily submitted to high levels of DNA lesions that trigger complex pathways and cellular responses by cell cycle arrest, apoptosis, alterations in transcriptional response, and the onset of DNA repair. Members of the NIMA-related kinase (NEK) family have been related to DNA damage response and repair and the first insight about NEK5 in this context is related to its role in centrosome separation resulting in defects in chromosome integrity. Here we investigate the potential correlation between NEK5 and the DNA damage repair index. The effect of NEK5 in double-strand breaks caused by etoposide was accessed by alkaline comet assay and revealed that NEK5-silenced cells are more sensitive to etoposide treatment. Topoisomerase IIß (TOPIIß) is a target of etoposide that leads to the production of DNA breaks. We demonstrate that NEK5 interacts with TOPIIß, and the dynamics of this interaction is evaluated by proximity ligation assay. The complex NEK5/TOPIIß is formed immediately after etoposide treatment. Taken together, the results of our study reveal that NEK5 depletion increases DNA damage and impairs proper DNA damage response, pointing out NEK5 as a potential kinase contributor to genomic stability.

Determination of in vitro absorption in Caco-2 monolayers of anticancer Ru(II)-based complexes acting as dual human topoisomerase and PARP inhibitors.

Due to their unique and versatile biochemical properties, ruthenium-based compounds have emerged as promising anticancer agents. Previous studies showed that three ruthenium(II) compounds: [Ru(pySH)(bipy)(dppb)]PF6 (1), [Ru(HSpym)(bipy)(dppb)]PF6 (2) and Ru[(SpymMe2)(bipy)(dppb)]PF6 (3) presented anticancer properties higher than doxorubicin and cisplatin and acted as human topoisomerase IB (Topo I) inhibitors. Here, we focused our studies on in vitro intestinal permeability and anticancer mechanisms of these three complexes. Caco-2 permeation studies showed that 1 did not permeate the monolayer of intestinal cells, suggesting a lack of absorption on oral administration, while 2 and 3 permeated the cells after 60 and 120 min, respectively. Complexes 2 and 3 fully inhibited Topo II relaxation activity at 125 µM. In previously studies, 3 was the most potent inhibitor of Topo I, here, we concluded that it is a dual topoisomerase inhibitor. Moreover, it presented selectivity to cancer cells when evaluated by clonogenic assay. Thus, 3 was selected to gene expression assay front MDA-MB-231 cells from triple-negative breast cancer (TNBC), which represents the highly aggressive subgroup of breast cancers with poor prognosis. The analyses revealed changes of 27 out of 84 sought target genes. PARP1 and PARP2 were 5.29 and 1.83 times down-regulated after treatment with 3, respectively. PARPs have been attractive antitumor drug targets, considering PARP inhibition could suppress DNA damage repair and sensitize tumor cells to DNA damage agents. Recent advances in DNA repair studies have shown that an approach that causes cell lethality using synthetic PARP-inhibiting drugs has produced promising results in TNBC.

Synthesis, DNA and protein interactions and human topoisomerase inhibition of novel Spiroacridine derivatives.

Nine new spiroacridine derivatives were synthetized by introducing cyano-N-acylhydrazone group between the acridine and phenyl-substituted rings followed by spontaneous cyclization. The new compounds were assayed for their DNA binding properties, human topoisomerase IIα inhibition and bovine serum albumin (BSA) interaction. Besides, docking analysis were performed in order to better understanding the biomolecule-compounds interactions. All compounds interacted with BSA which was demonstrated by the fluorescence suppression constant of 104 M-1. Compounds with chloro and NO2 substituents at that para-position on phenyl ring demonstrated the best results for BSA interaction. DNA binding constant determined by UV-vis data demonstrated high values for AMTAC-11 and AMTAC-14, 1.1 × 108 M-1 and 4.8 × 106 M-1, respectively, and all others presented constant values of 105 M-1. AMTAC-06 with chloro at para-position on phenyl ring presented a topoisomerase II inhibition of 84.34% in comparison to the positive controls used. Docking studies indicated that AMTAC-06 is able to intercalate the DNA base pairs at topoisomerase IIα active site, preventing DNA connection after break, in a process known as poisoning. Topoisomerase enzyme inhibition result was correlated to BSA interaction profile, since AMTAC-06 showed the best results in both analysis. The findings obtained here proved that methoxy or chloro substitution on phenyl ring at para-position is fundamental for in vitro activity of new spiroacridine derivatives, and indicates that AMTAC-06 is a promising entity and should serve as a lead compound in the development of new DNA and protein binders, as well as human topoisomerase II inhibitors.

Measurement of Drug-Stabilized Topoisomerase II Cleavage Complexes by Flow Cytometry.

The poisoning of Topoisomerase II (Top2) has been found to be useful as a therapeutic strategy for the treatment of several tumors. The mechanism of Top2 poisons involves a drug-mediated stabilization of a Top2-DNA complex, termed Top2 cleavage complex (Top2cc), which maintains a 5' end of DNA covalently bound to a tyrosine from Top2 through a phosphodiester group. Drug-stabilized Top2cc leads to Top2-linked-DNA breaks, which are believed to mediate their cytotoxicity. Several time-consuming or cell type-limiting assays have been used in the past to study drug-stabilized Top2cc. Here, we describe a flow cytometry-based method that allows a rapid assessment of drug-induced Top2cc, which is suitable for high throughput analysis in almost any kind of human cell. The analyses of the drug-induced Top2cc in the cell cycle context and the possibility to track its removal are additional benefits from this methodology. © 2017 by John Wiley & Sons, Inc.

Thiosemicarbazones and 4-thiazolidinones indole-based derivatives: Synthesis, evaluation of antiproliferative activity, cell death mechanisms and topoisomerase inhibition assay.

In this study, we report the synthesis and structural characterization of a series of thiosemicarbazone and 4-thiazolidinones derivatives, as well as their in vitro antiproliferative activity against eight human tumor cell lines. For the most potent compound further studies were performed evaluating cell death induction, cell cycle profile, ctDNA interaction and topoisomerase IIα inhibition. A synthetic three-step route was established for compounds (2a-e and 3a-d) with yields ranging from 32 to 95%. Regarding antiproliferative activity, compounds 2a-e and 3a-d showed mean GI50 values ranging between 1.1 µM (2b) - 84.65 µM (3d). Compound 2b was the most promising especially against colorectal adenocarcinoma (HT-29) and leukemia (K562) cells (GI50 = 0.01 µM for both cell lines). Mechanism studies demonstrated that 24 h-treatment with compound 2b (5 µM) induced phosphatidylserine residues exposition and G2/M arrest on HT-29 cells. Moreover, 2b (50 µM) was able to interact with ctDNA and inhibited topoisomerase IIα activity. These results demonstrate the importance of thiosemicarbazone, especially the derivative 2b, as a promising candidate for anticancer therapy.

Overexpression of p53 protein is a marker of poor prognosis in Mexican women with breast cancer.

Breast cancer (BC) is a disease with different clinical, histological and molecular characteristics, frequently presenting mutated tumour-suppressing genes and oncogenes. P53 is a known tumour suppressor that is often mutated in BC; several mutations in p53 inhibit its role as a transcriptional repressor of several oncogenes. Topoisomerase 2α (TOP2α) is a gene target of p53, and it is also a known target for anthracyclines. The aim of the present study, was to analyse the genetic alterations of p53 and TOP2α genes and their levels of protein expression, as well as their association with survival in Mexican women with BC. A total of 102 biopsies were collected (tumour and adjacent tissues) from patients with BC. To identify point mutations and deletions in the p53 gene, the Sanger sequencing method was carried out. Deletions or amplifications for TOP2α gene were determined using quantitative polymerase chain reaction (qPCR). In addition, the expression of the TOP2α and p53 proteins was evaluated by western blotting. Furthermore, p53 protein expression was analysed by proximity ligation assay (PLA)-qPCR. Only 28.5% of the patients were found to have triple-negative breast cancer (TNBC); the average age at the time of diagnosis of these patients was 50 years, and Scarff-Bloom-Richardson (SBR) histological grade III (p=0.0089). No differences in point mutations or deletions in p53, and deletions or amplifications as well as protein expression level of TOP2α were observed between patients with TNBC and non-TNBC patients. However, patients with TNBC showed p53 protein overexpression as determined by PLA-qPCR and western blotting (p<0.0001). Furthermore, we found an association between TOP2α amplification and overexpression of its protein in patients with TNBC (p<0.0001). Concerning p53, overexpression resulted in a lower survival in patients with BC.

Pathways of cardiac toxicity: comparison between chemotherapeutic drugs doxorubicin and mitoxantrone.

Anthracyclines, e.g., doxorubicin (DOX), and anthracenediones, e.g., mitoxantrone (MTX), are drugs used in the chemotherapy of several cancer types, including solid and non-solid malignancies such as breast cancer, leukemia, lymphomas, and sarcomas. Although they are effective in tumor therapy, treatment with these two drugs may lead to side effects such as arrhythmia and heart failure. At the same clinically equivalent dose, MTX causes slightly reduced cardiotoxicity compared with DOX. These drugs interact with iron to generate reactive oxygen species (ROS), target topoisomerase 2 (Top2), and impair mitochondria. These are some of the mechanisms through which these drugs induce late cardiomyopathy. In this review, we compare the cardiotoxicities of these two chemotherapeutic drugs, DOX and MTX. As described here, even though they share similarities in their modes of toxicant action, DOX and MTX seem to differ in a key aspect. DOX is a more redox-interfering drug, while MTX induces energy imbalance. In addition, DOX toxicity can be explained by underlying mechanisms that include targeting of Top2 beta, mitochondrial impairment, and increases in ROS generation. These modes of action have not yet been demonstrated for MTX, and this knowledge gap needs to be filled.

Immunocytochemical study of TOP2A and Ki-67 in cervical smears from women under routine gynecological care.

BACKGROUND: Cervical cancer is one of the most common female cancers and is caused by human papillomavirus (HPV). Viral infection leads to cell cycle deregulation by inactivating p53 and retinoblastoma protein by viral oncoproteins E6 and E7, respectively. Then, nuclear proteins such as DNA topoisomerase type IIa (TOP2A) and Ki-67 show increased expression because of increased cell division. These molecules are used as biomarkers for immunohistochemistry analysis of cervical tissue. METHODS: In this cross-sectional study, we recruited 110 women receiving regular gynecological surveillance at public health centers in Olinda - PE, Brazil. Cervicovaginal cells were collected to determine the presence of cytological abnormalities and HPV infection. Pap smear slides were used to evaluate the expression of TOP2A and Ki-67 using immunocytochemistry techniques. RESULTS: Of the 110 women, 75.4 % showed HPV-DNA(+) infection (83/110) and 29.1 % showed cellular abnormalities (32/110). Two atypical cells of undetermined significance, one low-grade squamous intraepithelial lesion, and one high-grade squamous intraepithelial lesion samples showed no HPV-DNA. TOP2A was positive in 71.9 % of samples, while Ki-67 was positive in 81.2 %. Immunocytochemistry results were positive in 4 of 5 atypical cells of undetermined significance samples. In HPV-DNA(+) samples with cytological abnormalities, immunocytochemistry results were positive 96.4 % of samples (p < 0.0001; odds ratio = 28.0). Among the samples infected with HR-HPV, TOP2A(+) was effective in 71 % samples, while and Ki-67(+) was 77.4 %. Ki-67 and TOP2A were positive for all samples infected with HPV6, HPV11, and HPV18. Ki-67 was also positive for all HPV16 samples, except for one negative sample in cytopathology analysis. CONCLUSIONS: TOP2A and Ki-67 antibodies may be used in combination for cervical cancer screening in immunocytochemistry assays.

Influence of nucleotide excision repair on mitoxantrone cytotoxicity.

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.

TOP2A copy number and TOP2A expression in uterine benign smooth muscle tumours and leiomyosarcoma.

AIMS: To examine TOP2A copy number, TOP2A expression, and its prognostic value in uterine leiomyosarcoma (LMS) and other benign smooth muscle tumours. METHODS: We analysed 37 patients treated for uterine LMS with immunohistochemistry for protein expression and fluorescence in situ hybridisation (FISH) for copy number. Twelve cases of leiomyoma variants (LMVs), 4 smooth muscle tumours of uncertain malignant potential (STUMP) and 23 leiomyomas (LMs) were also included. RESULTS: Eighteen patients with LMS (48.6%) were International Federation of Gynecology and Obstetrics (FIGO) stage I, six (16.2%) were stage II, four (10.8%) were stage III, and nine (24.3%) were stage IV. Twenty-one (56.8%) patients with LMS showed high expression of TOP2A. Greater TOP2A levels were found in patients with stage ≥II disease compared with stage I and also in high mitotic index tumours (>20/10 HPF (high power field)). Eleven (36.7%) cases had abnormal TOP2A copy numbers. There was no link between TOP2A copy number and TOP2A expression. All patients with benign smooth muscle tumours had low TOP2A immunohistochemical expression and one (7.7%) patient had TOP2A amplification. TOP2A expression and TOP2A copy number had no impact on disease outcomes. Only the presence of disease outside of the uterus negatively impacted survival compared with early disease (53.4 vs 15.8 months; p<0.001). CONCLUSIONS: TOP2A is highly expressed in advanced LMS but not in non-malignant diseases. TOP2A expression does not correlate with FISH results and does not predict outcome. TOP2A levels are higher in high-mitotic index tumours and in more advanced stages of disease.