Differential expression of DNA topoisomerase II alpha and II beta genes between small cell and non-small cell lung cancer

Targeting TOP2B as a vulnerability in aging and aging-related diseases

The ongoing trend of rapid aging of the global population has unavoidably resulted in an increase in aging-related diseases. There is an immense amount of interest in the scientific community for the identification of molecular targets that may effectively mitigate the process of aging and aging-related diseases. The enzyme Topoisomerase IIβ (TOP2B) plays a crucial role in resolving the topological challenges that occur during DNA-related processes. It is believed that the disruption of TOP2B function contributes to the aging of cells and tissues, as well as the development of age-related diseases. Consequently, targeting TOP2B appears to be a promising approach for interventions aimed at mitigating the effects of aging. This review focuses on recent advancements in the understanding of the role of TOP2B in the processing of aging and aging-related disorders, thus providing a novel avenue for the development of anti-aging strategies.

Identification of crucial genes associated with lung adenocarcinoma by bioinformatic analysis

Lung cancer is the world's most common malignancies and ranks first among all cancer-related deaths. Lung adenocarcinoma (LUAD) is the most frequent histological type in lung cancer. Its pathogenesis has not yet been fully elucidated, so it is of great significance to explore related genes for elucidating the molecular mechanism involved in occurrence and development of LUAD.To explore the crucial genes associated with LUAD development and progression, microarray datasets GSE7670, GSE10072, and GSE31547 were acquired from the Gene Expression Omnibus (GEO) database. R language Limma package was adopted to screen the differentially expressed genes (DEGs). The clusterProfiler package was used for enrichment analysis and annotation of the Gene ontology (GO) and Kyoto Encyclopedia of Genes and Genome (KEGG) pathways for DEGs. The Search Tool for the Retrieval of Interacting Genes database (STRING) was used to construct the protein interaction network for DEGs, while Cytoscape was adopted to visualize it. The functional module was screened with Cytoscape's MCODE (The Molecular Complex Detection) plugin. The crucial genes associated with LUAD were identified by cytoHubba plugin. Kaplan-Meier plotter online tool was used to perform survival analysis of the hub gene.Three hundred twenty-one DEGs in total were screened, of which 105 were upregulated and 216 were downregulated. It was found that some GO terms and pathways (e.g., collagen trimer, extracellular structure organization, heparin binding, complement and coagulation cascades, malaria, protein digestion and absorption, and PPAR signaling pathway) were considerably enriched in DEGs. UBE2C, TOP2A, RRM2, CDC20, CCNB2, KIAA0101, BUB1B, TPX2, PRC1, and CDK1 were identified as crucial genes. Survival analysis showed that the overexpression of UBE2C, TOP2A, RRM2, CDC20, CCNB2, KIAA0101, BUB1B, TPX2, and PRC1 significantly reduced the overall survival of LUAD patients. One of the crucial genes: UBE2C was validated by immunohistochemistry to be upregulated in LUAD tissues.This study screened out potential biomarkers of LUAD, providing a theoretical basis for elucidating the pathogenesis and evaluating the prognosis of LUAD.

Mining expression and prognosis of topoisomerase isoforms in non-small-cell lung cancer by using Oncomine and Kaplan-Meier plotter

DNA topoisomerases are essential to modulate DNA topology during various cellular genetic processes. The expression and distinct prognostic value of topoisomerase isoforms in non-small-cell lung cancer (NSCLC) is not well established. In the current study, we have examined the mRNA expression of topoisomerase isoforms by using Oncomine analysis and investigated their prognostic value via the Kaplan–Meier plotter database in NSCLC patients. Our analysis indicated that the expression level of topoisomerases in lung cancer was higher compared with normal tissues. Especially, high expression of two topoisomerase isoforms, TOP2A and TOP3A, was found to be correlated to worse overall survival (OS) in all NSCLC and lung adenocarcinoma (Ade) patients, but not in lung squamous cell carcinoma (SCC) patients. In a contrast, high expression of isoforms TOP1 and TOP2B indicated better OS in all NSCLC and Ade, but not in SCC patients. Meanwhile, high expression of TOP1MT and TOP3B was not correlated with OS in NSCLC patients. Furthermore, we also demonstrated a relationship between topoisomerase isoforms and the clinicopathological features for the NSCLC patients, such as grades, clinical stages, lymph node status, smoking status, gender, chemotherapy and radiotherapy. These results support that TOP2A and TOP3A are associated with worse prognosis in NSCLC patients. In addition, our study also shows that TOP1 and TOP2B contribute to favorable prognosis in NSCLC patients. The exact prognostic significance of TOP1MT and TOP3B need to be further elucidated. Comprehensive evaluation of expression and prognosis of topoisomerase isoforms will be a benefit for the better understanding of heterogeneity and complexity in the molecular biology of NSCLC, paving a way for more accurate prediction of prognosis and discovery of potential drug targets for NSCLC patients.

Identification of genes whose expression is upregulated in lung adenocarcinoma cells in comparison with type II alveolar cells and bronchiolar epithelial cells in vivo

To identify genes whose expression is upregulated in lung adenocarcinoma (AdC) cells in comparison with noncancerous peripheral lung epithelial cells, type II alveolar cells and bronchiolar epithelial cells, as well as AdC cells, were isolated by laser capture microdissection, and subjected to cDNA microarray analysis of 637 human cancer-related genes. Each of the component cells was obtained from several different individuals and analysed independently. As a comparison, two lung AdC cell lines and two primarily cultured normal lung epithelial cell lines were also subjected to cDNA microarray analysis. Four genes, TOP2A, MMP15, MX2 and KOC1, were commonly upregulated in microdissected AdC cells in comparison with microdissected epithelial cells. Hierarchical clustering analysis revealed that differences in gene-expression profiles were more evident between cultured and uncultured cells than between cancerous and noncancerous cells. To further identify the common molecular targets of AdC cells in vivo, quantitative real-time RT-PCR was performed against the four genes upregulated by cDNA microarray analysis. The TOP2A, MMP15, MX2 and KOC1 genes were overexpressed in 10/10 (100%), 8/10 (80%), 5/10 (50%) and 3/10 (30%) microdissected AdC cell samples, respectively, in comparison with any of nine independently microdissected noncancerous epithelial cell samples. The TOP2A gene was commonly overexpressed in lung AdC cells, as previously reported. In addition, the MMP15 and MX2 genes were identified, for the first time, as being commonly overexpressed in lung AdC cells. These results strongly indicate that the MMP15 and MX2 genes could be novel markers for molecular diagnosis and therapy of lung AdC.

Topoisomerase IIalpha gene expression is regulated by the p53 tumor suppressor gene in nonsmall cell lung carcinoma patients

BACKGROUND

Topoisomerase IIalpha (Topo IIalpha) is an essential nuclear enzyme for chromosome segregation during mitosis. Previous experimental studies using cell lines reported that Topo IIalpha expression was negatively regulated by wild-type p53 through the gene's promoter region.

METHODS

Surgically resected tumor specimens from 98 nonsmall cell lung carcinoma (NSCLC) patients who were not treated with preoperative chemotherapy were studied. Quantitative reverse-transcription polymerase chain reaction analysis was done to evaluate Topo IIalpha gene expression. Polymerase chain reaction single strand conformation polymorphism following sequencing was performed to investigate mutations of p53.

RESULTS

Topo IIalpha gene expression in squamous cell carcinomas was significantly higher than in adenocarcinomas (P = 0.0007). Topo IIalpha gene expression in moderately differentiated tumors and poorly differentiated tumors was significantly higher than in well differentiated tumors (P = 0.0032 and P = 0.0005, respectively). Thirty nine tumors (40%) had mutations of p53. Topo IIalpha gene expression in tumors with mutant p53 was significantly higher than in those with wild-type p53 (P = 0.0224).

CONCLUSIONS

The current study suggests that Topo IIalpha gene expression is regulated by p53 gene status in NSCLC patients and that the overexpression of Topo IIalpha induced by mutant p53 might cause more aggressive carcinogenesis.

Simultaneous quantitation of topoisomerase II alpha and beta isoform mRNAs in lung tumor cells and normal and malignant lung tissue

Certain drugs used in the treatment of lung cancer and other human malignancies are cytotoxic because of their ability to interact with the two isoforms of topoisomerase II (topo II), topo IIalpha and topo IIbeta. As part of an effort to evaluate the contribution of topo II alterations to drug sensitivity and resistance in lung cancer, we have developed a semi-quantitative reverse transcriptase-polymerase chain reaction (RT-PCR) assay to measure levels of topo II alpha and beta mRNAs simultaneously using a single pair of primers with sequences common to both isoforms. The PCR products derived from the topo II alpha and beta mRNAs are both 446 bp but have different electrophoretic mobilities in a nondenaturing polyacrylamide gel, allowing sensitive, rapid quantitation when the products are radiolabeled with [35S]-dATP. Using this RT-PCR method, poly(A+) RNA from 13 non-small cell lung cancer (NSCLC) cell lines was analyzed. The results obtained indicated that the cell lines express a wide range of topo II alpha mRNA levels (12-fold) and topo IIbeta mRNA levels (5.5-fold). Tumor and normal lung tissues from 25 patients with NSCLC were also examined. In the tumor samples, the levels of the topo II alpha and beta mRNAs were similar. However, mean topo IIalpha mRNA levels in the tumors were approximately 7-fold higher than those of the paired normal lung tissues. In contrast, topo IIbeta mRNA levels were similar in both tumor and normal lung. Topo II alpha and beta mRNA levels were both significantly lower in the squamous cell tumors than in the adenocarcinoma samples. Topo IIbeta mRNA levels in the squamous cell tumors were also significantly lower than those in paired normal lung tissue. The RT-PCR method described is reliable and convenient, and for the first time, makes the rapid simultaneous direct comparison of topo IIalpha and topo IIbeta mRNA levels feasible in large numbers of clinical samples.

Expression of drug resistance-related genes in head and neck squamous cell carcinomas and normal mucosa

We examined the expression levels of mRNA for multidrug resistance 1 (MDR1), multidrug resistance-associated protein (MRP), human canalicular multispecific organic anion transporter (cMOAT), lung resistance-related protein (LRP), topoisomerase IIalpha, beta (Topo IIalpha, beta) and topoisomerase I (Topo I) genes in human head and neck squamous cell carcinoma (HNSCC) specimens and mucosa (HNM) specimens, to elucidate their roles in relation to the biological characteristics and drug resistance in vivo. Fifty-eight samples (45 head and neck carcinomas and 13 head and neck mucosa) obtained during surgical resection or biopsy from 38 patients were analyzed using the quantitative reverse transcription-polymerase chain reaction (RT-PCR) method. MDR1, MRP, LRP, Topo IIalpha, Topo IIbeta, and Topo I gene transcripts were detected in all the samples tested, but cMOAT mRNA was not detected in them. Comparisons of the expression levels in HNSCC with those in HNM showed that the Topo IIalpha gene expression level was higher in HNSCC than in HNM (P=0.0298). Moreover, the Topo IIalpha mRNA level was significantly higher in metastatic lymph node samples of HNSCC than in HNM samples (P=0.0205). There were no significant differences in the six genes' expression levels between samples exposed to platinum drugs and those not exposed to platinum drugs. These results suggest that it may be effective in anticancer therapy to use topoisomerase-targetting drugs against HNSCC, especially metastatic neck tumors, and that the expression of these genes in HNSCC is not associated with platinum drug exposure.