Elevated topoisomerase I activity in cervical cancer as a target for chemoradiation therapy

The Antibacterial Activity and Mechanism of Action of Luteolin Against Trueperella pyogenes

Purpose

This research aimed to investigate the antibacterial activity and potential mechanism of luteolin against T. pyogenes.

Materials and Methods

The broth microdilution method was used to determine the minimum inhibitory concentrations (MICs) of luteolin against various T. pyogenes strains. The potential mechanism of action of luteolin was elucidated through testing and analysing the luteolin-induced alterations of T. pyogenes in several aspects, including cell wall, cell membrane, protein expression, nucleic acid content, topoisomerase activity and energy metabolism.

Results

The MIC values of luteolin against various T. pyogenes isolates and ATCC19411 were 78 µg/mL. The increased cell membrane permeability, destruction of cell wall integrity and TEM images after exposure to luteolin showed that the cell wall and membrane were damaged. The content of total protein and nucleic acid in T. pyogenes decreased significantly after treatment with luteolin (1/2 MIC) for 12, 24, and 36 h. Moreover, a hypochromic effect was observed in the absorption spectrum of luteolin when deoxyribonucleic acid (DNA) was added. In addition, after treatment with luteolin, a decrease in nicked or relaxed DNA content, which was catalysed by T. pyogenes-isolated DNA topoisomerase, was observed. In addition, the adenosine triphosphate (ATP) content in cells and the activity of succinate dehydrogenase (SDH) both decreased when T. pyogenes was exposed to different concentrations (1/4 MIC, 1/2 MIC, 1 MIC, 2 MIC) of luteolin for 1 h.

Conclusion

Luteolin showed distinct antibacterial activity against T. pyogenes by multiple actions, which mainly include destroying the integrity of the cell wall and cell membrane, influencing the expression of proteins, inhibiting nucleic acid synthesis, and interfering with energy metabolism.

Formulation of injectable glycyrrhizic acid-hydroxycamptothecin micelles as new generation of DNA topoisomerase I inhibitor for enhanced antitumor activity

To develop a new drug delivery system is one of the useful approaches to break through the limitation of hydroxycamptothecin (HCPT), a typical DNA topoisomerase I (Topo I) inhibitor in clinical appliance. Injectable glycyrrhizic acid-hydroxycamptothecin (GL-HCPT) micelles that were able to dramatically improve the solubility and stability of HCPT were prepared through self-assembly process and evaluated both in vitro and in vivo. With a mean particle size (PS) of 105.7 ± 9.7 nm and a drug loading (DL) of 9.0 ± 1.5%, GL-HCPT micelles were rapidly internalized by HepG2 cells after 1 h, significantly increasing the intracellular accumulation of HCPT. Compared with the current used HCPT injection and HCPT/GL physical mixture, GL-HCPT micelles showed enhanced antitumor activity against liver cancer cells (HepG2 and Huh7) as well as a superior suppression on the tumor growth of HepG2 tumor bearing mice. Interestingly, GL-HCPT micelles gathered in liver and simultaneously reduced the drug accumulation in normal tissues, thereby exhibiting minimal cytotoxicity to human normal liver cells (LO2). Therefore, we offered a convenient and cost-effective strategy to construct an intravenous drug delivery system (GL-HCPT micelles) as new generation of DNA Topo I inhibitor for enhanced cancer chemotherapy.

Allosteric inhibition of topoisomerase I by pinostrobin: Molecular docking, spectroscopic and topoisomerase I activity studies

Cancer, the second major cause of mortality trailing the cardiovascular diseases, is a multifactorial heterogeneous disease and growing public health problem worldwide. Owing to severe adverse effects of currently available therapies, there is a growing interest in natural compounds present in our daily diet. Among various natural products, flavonoids-polyphenolic compounds have attracted much attention and have been well-documented for their biological activities. Some flavonoids may inhibit cancer cell proliferation by modulating the action of different enzymes and signal transduction pathways. In the present study, we have evaluated the effect of pinostrobin, a natural flavonoid, on the catalytic activity of topoisomerase I, an essential enzyme for normal DNA replication. Catalytic inhibition of topoisomerase I activity would impair DNA replication of rapidly dividing cancer cells and hence inhibits tumor progression. Pinostrobin interaction with the topoisomerase I and DNA assessed in silico indicated it to form a ternary complex with both. In silico data also suggested pinostrobin to be an effective allosteric inhibitor for topoisomerase I. Further, in vitro investigations such as ethidium bromide displacement assay and spectroscopic studies supported in silico results on the binding of pinostrobin at the interface of topoisomerase I and DNA. Pinostrobin effectively inhibited topoisomerase I activity in vitro further confirming our in silico and in vitro findings. Since topoisomerase I is essential for DNA replication, inhibition of its activity by pinostrobin highlights the therapeutic potential of pinostrobin as an anti-proliferative agent.

Phenotypic screening reveals topoisomerase I as a breast cancer stem cell therapeutic target

Cancer stem cells (CSCs) are a subpopulation generally thought to be responsible for cancer initiation and progression. Because CSCs are often rare in the total tumor cell population and differentiate rapidly when grown in culture, it has been challenging to uncover compounds that selectively target CSCs. We previously described CSC-emulating cells derived from breast cancer cell lines that maintained a stable undifferentiated state. We optimized a phenotypic assay with these cells and screened 1,280-bioactive compounds, identifying five that preferentially inhibited CSC-like cell proliferation. Using a compound-guided target identification approach, we found high topoisomerase I (Topo I) expression levels in breast CSC-like cells and primary breast CSCs. Structurally unrelated small molecules targeting Topo I preferentially inhibited CSC-like cells. These results illustrate the substantial power of this CSC phenotypic screening platform and promote Topo I as a potential molecular therapeutic target for therapies aimed at expunging CSCs.

Pharmacotherapy options for locally advanced and advanced cervical cancer

Cervical cancer continues to be a significant health burden worldwide. Globally, the majority of cancers are locally advanced at diagnosis; hence, radiation remains the most frequently used therapeutic modality. Currently, the value of adding cisplatin or cisplatin-based chemotherapy to radiation for the treatment of locally advanced cervical cancer is strongly supported by randomized studies and meta-analyses. Nevertheless, despite these significant achievements, therapeutic results are far from optimal; thus, novel therapies need to be investigated. A recent, randomized, phase III trial has shown for the first time that combination chemotherapy with cisplatin and gemcitabine concurrently with radiation improves parameters of survival over cisplatin alone and establishes a new standard for the management of locally advanced cervical cancer. On the other hand, advanced disease, presenting either as an International Federation of Gynecology and Obstetrics (FIGO) stage IVB or as persistent or recurrent to primary therapy without local curative options, remains a devastating group of diseases with no options other than palliative chemotherapy. Recent results from the GOG (Gynecologic and Oncologic Group)-204 study demonstrate that cisplatin-doublets with paclitaxel, vinorelbine, gemcitabine or topotecan only produce small improvements in survival, although with different toxicity patterns; hence, patient-related factors are important when choosing any one of these regimens. The role of targeted therapies both in locally advanced and advanced disease is promising, but still at an investigational stage.

Topoisomerase I amplification in melanoma is associated with more advanced tumours and poor prognosis

In this study, we used array-comparative genomic hybridization (aCGH) and fluorescent in situ hybridization (FISH) to examine genetic aberrations in melanoma cell lines and tissues. Array-comparative genomic hybridization revealed that the most frequent genetic changes found in melanoma cell lines were amplifications on chromosomes 7p and 20q, along with disruptions on Chr 9, 10, 11, 12, 22 and Y. Validation of the results using FISH on tissue microarrays (TMAs) identified TOP1 as being amplified in melanoma tissues. TOP1 amplification was detected in a high percentage (33%) of tumours and was associated with thicker, aggressive tumours. These results show that TOP1 amplification is associated with advanced tumours and poor prognosis in melanoma. These observations open the possibility that TOP1-targeted therapeutics may be of benefit in a particular subgroup of advanced stage melanoma patients.

Phase I pharmacokinetic and pharmacodynamic study of Carboplatin and topotecan administered intravenously every 28 days to patients with malignant solid tumors

PURPOSE

Preclinical studies have shown that the combination of topotecan and carboplatin is synergistic. To evaluate the schedule dependency of this interaction, the following phase I trial was designed to determine the safety and maximum tolerated dose (MTD), pharmacokinetics, and pharmacodynamics of carboplatin and topotecan in patients with malignant solid tumors.

EXPERIMENTAL DESIGN

In part 1, patients received carboplatin on day 1 and topotecan on days 1, 2, and 3 (C-->T schedule). In part 2, topotecan was administered on days 1, 2, and 3, followed by carboplatin on day 3 (T-->C schedule). Pharmacokinetics were determined in plasma and DNA topoisomerase I catalytic activity and Pt-DNA adducts in WBC and tumor tissue.

RESULTS

Forty-one patients were included. Dose-limiting toxicities during the C-->T schedule were grade 4 thrombocytopenia and febrile neutropenia (MTD: carboplatin target area under the free carboplatin plasma concentration versus time curve, 4 min mg/mL; topotecan, 0.5 mg/m(2)/d). Dose-limiting toxicities during the T-->C schedule included grade 4 neutropenia, thrombocytopenia, neutropenic fever, and grade 4 nausea and vomiting (MTD: carboplatin target area under the free carboplatin plasma concentration versus time curve, 6 min mg/mL; topotecan, 0.9 mg/m(2)/d). One complete response and five partial responses were observed. The clearance of and exposure to carboplatin and topotecan did not depend on the sequence of drug administration. No schedule-dependent effects were seen in Pt-DNA levels and DNA topoisomerase I catalytic activity in WBC and tumor tissue. However, myelotoxicity was clearly more evident in the C-->T schedule.

CONCLUSION

The T-->C schedule was better tolerated because both hematologic and nonhematologic toxicities were milder. Other pharmacodynamic factors than the ones investigated must explain the schedule-dependent differences in toxicities.

Membrane-localized activation of glucuronide prodrugs by β-glucuronidase enzymes

Gene-mediated enzyme prodrug therapy (GDEPT) seeks to increase the therapeutic index of anti-neoplastic agents by promoting selective activation of relatively nontoxic drug derivatives at sites of specific enzyme expression. Glucuronide prodrugs are attractive for GDEPT due to their low toxicity, bystander effect in the interstitial tumor space and the large range of possible glucuronide drug targets. In this study, we expressed human, murine and Esherichia coli beta-glucuronidase on tumor cells and examined their in vitro and in vivo efficacy for the activation of glucuronide prodrugs of 9-aminocamptothecin and p-hydroxy aniline mustard. We show that (1) fusion of beta-glucuronidase to the Ig-like C(2)-type and Ig-hinge-like domains of the B7-1 antigen followed by the B7-1 transmembrane domain anchored high levels of active murine and human beta-glucuronidase on cells, (2) strong bystander killing of tumor cells was achieved in vitro by murine beta-glucuronidase activation of prodrug, (3) potent in vivo anti-tumor activity was achieved by prodrug treatment of tumors that expressed murine beta-glucuronidase and (4) the p-hydroxy aniline prodrug was more effective in vivo than the 9-aminocamptothecin prodrug. Our results demonstrate that surface expression of murine beta-glucuronidase for activation of a glucuronide prodrug of p-hydroxy aniline mustard may be useful for more selective therapy of cancer.

Radiosensitizers in cervical cancer. Cisplatin and beyond

Cervical cancer continues to be a significant health burden worldwide. Globally, the majority of cancers are locally advanced at diagnosis; hence, radiation remains the most frequently used therapeutical modality. Currently, the value of adding cisplatin or cisplatin-based chemotherapy to radiation for treatment of locally advanced cervical cancer is strongly supported by randomized studies and meta-analyses. Nevertheless, despite these significant achievements, therapeutic results are far from optimal; thus, novel therapies need to be assayed. A strategy currently being investigated is the use of newer radiosensitizers alone or in combination with platinum compounds. In the present work, we present preclinical information on known and newer cytotoxic agents as radiosensitizers on cervical cancer models, as well as the clinical information emanating from early phase trials that incorporate them to the cervical cancer management. In addition, we present the perspectives on the combined approach of radiation therapy and molecular target-based drugs with proven radiosensitizing capacity.

A quantitative RT-PCR method to determine topoisomerase I mRNA levels in human tissue samples

DNA topoisomerase I (Topo I) is involved in DNA replication, transcription, recombination and repair. Clinical interest has focused on Topo I as it is the molecular target of camptothecin (CPT), used in first and second lines of treatment for different cancer types. Furthermore, it is well demonstrated that the patients who best responded to CPT-based chemotherapy were generally those with the greatest tumoral Topo I expression and/or activity. We developed a sensitive, simple and reproducible method to measure Topo I mRNA expression in human cancer samples. Experiments were performed in two steps. First, we checked the accuracy of the reverse transcription-polymerase chain reaction (RT-PCR) method by testing intra- and interassay reproducibility of Topo I and G6PDH gene amplification in different cell types. We observed that crossing-points (Cps) were different, depending on the cell type, dilution or cDNA concentration, but that the intra- and interassay Cp standard deviation (SD) never exceeded 0.77% and 1.39% for Topo I amplification, or 1.63% and 2.9% for G6PDH amplification, respectively. Secondly, we used our method to measure Topo I mRNA levels in primary tumor samples obtained from 27 patients with advanced colorectal cancer and 10 patients with pharyngeal/laryngeal cancer. The accuracy of G6PDH as a housekeeping gene was tested by analyzing its correlation with the mRNA level of a second housekeeping gene, porphobilinogen deaminase (PBG-D) in the tumoral samples. We found that the normalized Topo I/G6PDH mRNA ratios were significantly correlated with that of Topo I/PBGD in colorectal tumors (r(2)=0.47, p=0.02) but not in pharyngeal/laryngeal tumors (r(2)=0.35, p=0.3). Neither ratio showed any significant association with clinicopathological parameters, such as gender, age, tumor size, or grade and lymph node status. We believe that RT-PCR is a reliable and highly reproducible technique. However, the choice of the reference gene is an important point and must be defined based on the samples studied.

Microarray analysis of genes controlled by progesterone in human endometrial stromal cells in vitro

The steroid hormone progesterone is a key factor in establishment and maintenance of pregnancy in the human endometrium. To obtain a global view and identify new target genes for progesterone in human endometrial stromal cells in short-term (3 days) culture, we used a screening strategy to analyze the expression of nearly 1000 human genes by DNA microarray analysis. The results showed that six genes were up-regulated (at least a two-fold increase), and 27 genes were down-regulated (at least a two-fold decrease) after progesterone treatment compared with control. Progesterone stimulated the expression of the interleukin (IL)-1 receptor type 1, fibulin-1, fibulin-2, microsomal glutathione S-transferase 1, fumarylacetoacetate hydrolase and orphan G protein-coupled receptor (RDC1). Progesterone inhibited the expression of insulin-like growth factor binding protein-5, heparin-binding epidermal growth factor-like growth factor, and IL-13 receptor alpha2. In addition, progesterone inhibited the expression of genes involved in immune modulators, DNA/chromatin-related proteins, signal transduction, transcription factors, transport proteins, enzyme, receptor and structural proteins. Our results demonstrate that microarray analysis can be used to identify progesterone-regulated genes in endometrial stromal cells, thus contributing to a more detailed understanding of the molecular mechanisms in response to progesterone in the endometrium during the preparatory period for implantation.

Homocamptothecins: potent topoisomerase I inhibitors and promising anticancer drugs

Homocamptothecins (hCPTs) represent a new generation of antitumor agents targeting DNA topoisomerase I. The expanded seven-membered lactone E-ring that characterizes hCPTs enhances the plasma stability of the drug and reinforces the inhibition of topoisomerase I compared with conventional six-membered CPTs. hCPTs are more efficient than the CPTs at promoting cleavage at T/G sites and induce additional cleavage at C/G sites. Compound BN80765 and its difluoro analogue diflomotecan (DN80915) are potent cytotoxic agents and efficiently induce apoptosis in tumor cells. They display strong antiproliferative activities against specific tumor types. Diflomotecan is remarkably efficient at inhibiting the growth of human colon cancer cells in vivo and, administered orally, it also shows superior activities against human prostate cancers compared with the benchmark products topotecan (TPT) and irinotecan (IRT). Diflomotecan has entered phase I clinical testing and antitumor activity has been observed in patients. This 9,10-difluoro-hCPTs derivative is one of the most promising new members of the 'tecan' family. This review summarizes the recent discoveries in the topoisomerase I field and presents the different camptothecin (CPT) analogues currently evaluated as anticancer agents. The specific properties of hCPTs are highlighted.

Phase I study of topotecan and radiation therapy in advanced cervical cancer

OBJECTIVE

The goal of this study was to determine the maximal tolerated dose (MTD) of topotecan given with external-beam radiotherapy in advanced cervical cancer.

METHODS

A prospective Phase I trial of topotecan given with standard external-beam radiotherapy was performed in patients with advanced squamous cell carcinoma of the cervix. Patients were treated with a starting dose of 0.5 mg/m(2) and escalated by 0.25 mg/m(2). Nine patients were treated. Hematologic and nonhematologic toxicity were measured.

RESULTS

Patients were treated with 1.0 mg/m(2) daily for 5 days on Days 1-5 and 22-26 concomitantly with radiotherapy without significant toxicity. Grade III anemia in one case and Grade II leukopenia in two cases were seen in the three patients at this dose level. Dose-limiting toxicity was not reached.

CONCLUSION

Topotecan can be safely administered at a dose of 1.0 mg/m(2) during external-beam radiotherapy for advanced cervical cancer.