DNA topoisomerase IIalpha expression in optic pathway gliomas of childhood

The Implication of Topoisomerase II Inhibitors in Synthetic Lethality for Cancer Therapy

DNA topoisomerase II (Top2) is essential for all eukaryotic cells in the regulation of DNA topology through the generation of temporary double-strand breaks. Cancer cells acquire enhanced Top2 functions to cope with the stress generated by transcription and DNA replication during rapid cell division since cancer driver genes such as Myc and EZH2 hijack Top2 in order to realize their oncogenic transcriptomes for cell growth and tumor progression. Inhibitors of Top2 are therefore designed to target Top2 to trap it on DNA, subsequently causing protein-linked DNA breaks, a halt to the cell cycle, and ultimately cell death. Despite the effectiveness of these inhibitors, cancer cells can develop resistance to them, thereby limiting their therapeutic utility. To maximize the therapeutic potential of Top2 inhibitors, combination therapies to co-target Top2 with DNA damage repair (DDR) machinery and oncogenic pathways have been proposed to induce synthetic lethality for more thorough tumor suppression. In this review, we will discuss the mode of action of Top2 inhibitors and their potential applications in cancer treatments.

Potential molecular target screening and bioinformatics analysis of cholangiocarcinoma based on GEO database

BACKGROUND

Cholangiocarcinoma is a highly malignant tumor with a poor prognosis. Targeted therapy is important for the treatment of cholangiocarcinoma, and it is therefore of great clinical importance to identify novel molecular targets for targeted therapy of this malignancy.

AIM

To identify potential molecular targets for the treatment of cholangiocarcinoma and identify the key genes involved in cholangiocarcinoma by bioinformatics analysis.

METHODS

We downloaded two sets of cholangiocarcinoma expression profile data from GEO database. GEO2R online analysis tool was used to screen differentially expressed genes in cholangiocarcinoma tumor tissues and normal tissues, and we performed GO enrichment analysis, KEGG pathway analysis, and protein interaction network for differentially expressed genes. We used Cytoscape software to calculate key genes. The GEPIA database was used to verify the expression of hub genes in cholangiocarcinoma tissues.

RESULTS

A total of 158 differentially expressed genes were identified. GO enrichment analysis showed that these differential genes were mainly involved in the cellular response to zinc ion, negative regulation of growth, cell adhesion, metabolic process, and protein homotetramerization. They were enriched in exosomes, extracellular spaces, elastic fibers, and organelle membranes. The main molecular functions are related to heparin binding, cysteine-type endopeptidase inhibitor activity, protein homodimerization activity, receptor binding, and pyridoxal phosphate binding. KEGG pathway analysis showed that differential genes are mainly involved in processes such as mineral absorption, carbon and propanoate metabolism, PPAR signaling pathway, and fatty acid degradation. A protein interaction network diagram was constructed based on the String database, and the CytoHubba plug-in of the Cytoscape software was used to calculate the key genes. The key genes were all up-regulated ones. GEPIA analysis verified that the expression of key genes in cholangiocarcinoma tissues was significantly higher than that in normal tissues.

CONCLUSION

In this study, eight key genes related to cholangiocarcinoma were identified, including NUSAP1, TOP2A, RAD51AP1, MCM4, KIAA0101, CDCA5, TYMS, and ZWINT. These genes provide new ideas for in-depth study of the targeted therapy of cholangiocarcinoma, and are expected to become new molecular therapeutic targets.

Prognostic value of survivin and DNA topoisomerase IIα in diffuse and anaplastic astrocytomas

Distinguishing WHO grade II astrocytomas from grade III is a difficult task. This study looks into the potential prognostic use of mitotic activity and the proliferation markers Ki67/MiB-1 (Ki67), survivin and DNA topoisomerase IIα (TIIα) in 59 WHO grade II diffuse astrocytomas (DA) and 33 WHO grade III anaplastic astrocytomas (AA), IDH1 R132H-mutated and not otherwise specified (NOS) by means of immunohistochemistry. All proliferation markers showed higher expression in AA compared with DA. Only Ki67 had significantly greater expression in astrocytomas, NOS vs. astrocytomas, IDH1-mutated. Uni-/multivariable COX-regression analyses showed that greater expression of both survivin and TIIα were associated with poorer survival when stratified for IDH1-mutation status and, additionally, achieved hazard rates surpassing clinically established prognostic factors such as age and WHO performance status. Ki67 achieved only statistical significance in univariable analyses, whereas mitoses did not reveal any relation to survival. IDH1-mutated astrocytomas had significantly better survival than astrocytomas, NOS. Among IDH1-mutated astrocytomas no significant difference in survival was shown between DA and AA. Our findings suggest a potential usefulness of proliferation markers in the prognostic setting of astrocytomas independent of IDH1-mutation status, and survivin and TIIα are potential candidates in that regard.

Expression of DNA topoisomerase II-α: Clinical significance in laryngeal carcinoma

DNA topoisomerase II-α (Topo II-α) is essential for numerous cell processes, including DNA replication, transcription, recombination, and chromosome separation and condensation. Altered Topo II-α expression may lead to carcinogenesis and cancer progression. The aim of the present study was to investigate the association between Topo II-α expression levels and clinicopathological data from laryngeal cancer patients. Immunohistochemistry was used to analyze Topo II-α expression in laryngeal squamous cell carcinoma and distant healthy tissues obtained from 70 patients. In addition, fluorescence in situ hybridization was used to detect Topo II-α amplification and chromosome 17 ploidy using a laryngeal cancer tissue microarray. The expression of Topo II-α protein was detected in 71.43% (50/70) of laryngeal carcinoma tissues, in contrast to 9% of healthy tissues (2/22). Furthermore, the expression of Topo II-α protein was found to be associated with tumor de-differentiation and advanced tumor T stage. However, the expression of Topo II-α protein was not identified to be associated with Topo II-α amplification in laryngeal carcinoma, although was found to positively correlate with chromosome 17 aneuploidy (P<0.05). A higher aneuploidy rate contributed to increased expression levels of Topo II-α protein. Aberrant Topo II-α expression and chromosome 17 aneuploidy contributed to the development and progression of laryngeal cancer, indicating that targeting Topo II-α may provide a treatment strategy for patients with laryngeal cancer.

Management of optic-hypothalamic gliomas in children: still a challenging problem

Optic pathway-hypothalamic gliomas (OPHGs) are rare, often unresectable tumors that mostly occur in childhood. Their biological behavior is unpredictable, although they tend to follow an aggressive clinical course in infants and a benign course in children with neurofibromatosis type 1. Optimal management is still controversial. Nonprogressing OPHGs are usually followed by surveillance alone. Surgery is advocated for progressing tumors to decompress the optic pathways, obtain a quick relief from intracranial hypertension and allow histologic examination (when needed). The current trend is in favor of conservative surgical behavior, except for resectable tumors. Chemotherapy is increasingly used in the management of OPHGs, especially in infants, to delay radiotherapy. Carboplatin and vincristine are the most frequently used drugs, although several chemotherapeutic agents in different combinations are currently employed with good results. Radiotherapy is utilized in children over 5 years of age as an adjuvant or as an alternative to surgery. The prognosis of OPHGs is quite good, with regard to the overall survival rate (70-100% at 5 years), but less favorable in terms of late morbidity.

Optic glioma warranting treatment in children

PURPOSE

To describe cases of optic pathway glioma (OPG) warranting treatment in children.

METHODS

This is a retrospective review of pediatric patients treated for OPG. The clinical data and imaging studies were obtained from the medical records and radiology files of patients seen at the Pediatric Neuro-Ophthalmology Clinic at the University of Illinois, Chicago and the private office of the author (LMK).

RESULTS

A total of seven cases with an age range of 3-48 months at presentation were reviewed. Three of the patients were also ultimately diagnosed with neurofibromatosis type 1. Presenting symptoms included proptosis, decreased vision, gaze deficit, and nystagmus. Four patients underwent biopsies that confirmed OPG. Six of the patients were treated with intravenous chemotherapy, with three patients requiring a second chemotherapy cycle. One patient was successfully treated with an en-bloc optic nerve excision. Two patients underwent unilateral enucleation owing to globe complications.

CONCLUSION

Although benign tumours, OPG can behave very aggressively in young children. Both chemotherapy and en-bloc excision can be employed for treatment.

Expression of Ki-67, Topoisomerase II? and c-MYC in astrocytic tumors: Correlation with the histopathological grade and proliferative status

Astrocytomas represent the most frequent primary tumors of the central nervous system. Recently, the determination of the proliferative index of astrocytic tumors by different methods has been proposed as a valuable tool for tumor grading and also as a prognostic marker. The aim of the present study was to evaluate the expression of cell proliferation-related proteins in human astrocytic tumors of different histopathological grades (WHO). An immunohistochemical study of the Ki-67, Topoisomerase IIalpha (Topo IIalpha) and c-MYC proteins using the avidin-biotin-peroxidase method was performed in 55 astrocytomas (13 grade I, 14 grade II, 7 grade III and 21 grade IV) and five samples of non-tumor brain tissue (control group). Ki-67, Topo IIalpha and c-MYC positive indices tended to increase according to malignant progression, were absent in non-tumor brain tissue and showed maximum values in high-grade astrocytomas (III and IV). A gradual increase in Ki-67 antigen expression was observed in agreement with mitotic index and histopathological classification. The same was not observed for Topo IIalpha and c-MYC. Ki-67 antigen detection in more than 8.0% of the tumor cells distinguished astrocytoma grade IV, while a labeling index between 1.5 and 8.0% characterized astrocytomas grade III and values below 1.5% discriminated low-grade tumors (I and II). These results indicate that Topo IIalpha and c-MYC expression is associated with cell proliferation in astrocytomas, although not in an exclusive way. Moreover, Ki-67 antigen was found to be the best marker of cellular proliferation, and its expression predicts the grade of astrocytic tumors.

Prognosis-related histomorphological and immunohistochemical markers in central nervous system tumors of childhood and adolescence

Brain tumors account for approximately 20% of all childhood cancers, and are the leading cause of cancer morbidity and mortality among children. Although numerous demographic, clinical and therapeutic parameters have been identified over the past few years that have significant prognostic bearing for some pediatric brain tumors, predicting the clinical course and outcome among children with central nervous system tumors is still difficult. A survey of publications on prognosis-related histopathological and immunohistochemical features among pediatric brain tumors revealed 172 series, of which 91 presented statistically significant outcome-associated parameters as defined by a P value of less than 0.05. Most investigations revealing significant prognosis-related markers were performed on medulloblastomas (30 publications), ependymomas (25) and astrocytic tumors (18). In total, 16 cohorts consisted of more than 100 cases (5 on ependymomas, 3 each on medulloblastomas and astrocytic tumors). On the other hand, there were also 13 series with fewer than 20 cases (5 on medulloblastomas). Potentially prognostic histopathological markers vary among different entities and consist of assessment of necroses, mitoses, differentiation, vascular proliferation, and growth pattern, whereas immunohistochemical features include proliferation markers (Ki-67, MIB-1), expression of oncogenes/tumor suppressor genes and their proteins (TP53, c-erbB2), growth factor and hormonal receptors (VEGF, EGFR, HER2, HER4, ErbB-2), cell cycle genes (p27, p14ARF) and cell adhesion molecules, as well as factors potentially related to therapeutic resistance (DNA topoisomerase IIalpha, metallothionein, P-glycoprotein, tenascin). This review discusses the prognostic potential of histopathological and immunohistochemical markers that can be investigated by the practicing neuropathologist as part of the routine diagnostic workload, and scrutinizes their benefit for predicting therapy response and patient outcome among children with brain tumors.

Brain-tumour drug resistance: the bare essentials

Chemotherapy lacks efficacy in most histological types of primary human brain tumours and has, for most types, failed to improve outcome for patients. The unsatisfactory results with chemotherapeutic intervention in these cancers have been chiefly attributed to tumour-cell resistance. This review summarises some of the major molecular markers that, although neither exclusive for nor specific to brain tumours, have been associated with the formation of a chemoresistant phenotype. Elucidation of the cellular mechanisms involved in resistance regulation is needed for future progress in efficient approaches to selective modulation of drug resistance in these lesions.