Overexpression of B-type cyclins alters chromosomal segregation

Bidirectional Mendelian randomization and potential mechanistic insights into the causal relationship between gut microbiota and malignant mesothelioma

Malignant mesothelioma (MM) is a rare but aggressive cancer originating from mesothelial cells, which presents significant challenges to patients' physical and psychological well-being. The gut-lung axis underscores the connection between gut microbiota and respiratory diseases, with emerging evidence suggesting a strong association between gut microbiota and the development of MM. In this study, we conducted a two-sample Mendelian randomization (MR) analysis to investigate the potential causal relationship between gut microbiota and MM, while also exploring the underlying mechanisms through bioinformatics approaches. Gut microbiota summary data were obtained from the MiBioGen consortium, while MM data were sourced from the FinnGen R11 dataset. Causality was examined using the inverse variance weighted method as the primary analysis. Additional methods, including the weighted median, simple mode, MR-Egger, and weighted mode, were also employed. The robustness of the findings was validated through sensitivity analyses, and reverse causality was considered to further strengthen the MR results. Moreover, bioinformatics analyses were conducted on genetic loci associated with both gut microbiota and MM to explore potential underlying mechanisms. Our study suggests that genetically predicted increases in class.Bacilli, family.Rikenellaceae, genus.Clostridium innocuum group, and order.Lactobacillales were suggestively associated with a higher risk of MM, whereas increases in genus.Ruminococcaceae UCG004, genus.Flavonifractor, phylum.Firmicutes, genus.Anaerofilum, genus.Clostridium sensu stricto 1, and genus.Lactobacillus appeared to confer protective effects. Bioinformatics analysis indicated that differentially expressed genes near loci associated with gut microbiota might affect MM by modulating pathways and the tumor microenvironment. The results of this study point to a potential genetic predisposition linking gut microbiota to MM. Further experimental validation is crucial to confirm these candidate microbes, establish causality, and elucidate the underlying mechanisms.

Cell cycle dysregulation in cancer

Cancer is a systemic manifestation of aberrant cell cycle activity and dysregulated cell growth. Genetic mutations can determine tumor onset by either augmenting cell division rates or restraining normal controls such as cell cycle arrest or apoptosis. As a result, tumor cells not only undergo uncontrolled cell division but also become compromised in their ability to exit the cell cycle accurately. Regulation of cell cycle progression is enabled by specific surveillance mechanisms known as cell cycle checkpoints, and aberrations in these signaling pathways often culminate in cancer. For instance, DNA damage checkpoints, which preclude the generation and augmentation of DNA damage in the G1, S, and G2 cell cycle phases, are often defective in cancer cells, allowing cell division in spite of the accumulation of genetic errors. Notably, tumors have evolved to become dependent on checkpoints for their survival. For example, checkpoint pathways such as the DNA replication stress checkpoint and the mitotic checkpoint rarely undergo mutations and remain intact because any aberrant activity could result in irreparable damage or catastrophic chromosomal missegregation leading to cell death. In this review, we initially focus on cell cycle control pathways and specific functions of checkpoint signaling involved in normal and cancer cells and then proceed to examine how cell cycle control and checkpoint mechanisms can provide new therapeutic windows that can be exploited for cancer therapy. SIGNIFICANCE STATEMENT: DNA damage checkpoints are often defective in cancer cells, allowing cell division in spite of the accumulation of genetic errors. Conversely, DNA replication stress and mitotic checkpoints rarely undergo mutations because any aberrant activity could result in irreparable damage or catastrophic chromosomal missegregation, leading to cancer cell death. This review focuses on the checkpoint signaling mechanisms involved in cancer cells and how an emerging understanding of these pathways can provide new therapeutic opportunities for cancer therapy.

Identification of a transcription factor‑cyclin family genes network in lung adenocarcinoma through bioinformatics analysis and validation through RT‑qPCR

Lung adenocarcinoma (LUAD) is the predominant pathological subtype of lung cancer, which is the most prevalent and lethal malignancy worldwide. Cyclins have been reported to regulate the physiology of various types of tumors by controlling cell cycle progression. However, the key roles and regulatory networks associated with the majority of the cyclin family members in LUAD remain unclear. In total, 556 differentially expressed genes were screened from the GSE33532, GSE40791 and GSE19188 mRNA microarray datasets by R software. Subsequently, protein-protein interaction network containing 499 nodes and 4,311 edges, in addition to a significant module containing 76 nodes and 2,631 edges, were extracted through the MCODE plug-in of Cytoscape. A total of four cyclin family genes [cyclin (CCNA2, CCNB1, CCNB2 and CCNE2] were then found in this module. Further co-expression analysis and associated gene prediction revealed forkhead box M1 (FOXM1), the common transcription factor of CCNB2, CCNB1 and CCNA2. In addition, using GEPIA database, it was found that the high expression of these four genes were simultaneously associated with poorer prognosis in patients with LUAD. Experimentally, it was proved that these four hub genes were highly expressed in LUAD cell lines (Beas-2B and H1299) and LUAD tissues through qPCR, western blot analysis and immunohistochemical studies. The diagnostic value of these 4 hub genes in LUAD was analyzed by logistic regression, CCNA2 was deleted, following which a nomogram diagnostic model was constructed accordingly. The area under the curve values of CCNB1, CCNB2 and FOXM1 diagnostic models were calculated to be 0.92, 0.91 and 0.96 in the training set (Combined dataset of GSE33532, GSE40791 and GSE19188) and two validation sets (GSE10072 and GSE75037), respectively. To conclude, data from the present study suggested that the FOXM1/cyclin (CCNA2, CCNB1 and/or CCNB2) axis may serve a regulatory role in the development and prognosis of LUAD. Specifically, CCNB1, CCNB2 and FOXM1 have potential as diagnostic markers and/or therapeutic targets for LUAD treatment.

Establishment and validation of a predictive model of preeclampsia based on transcriptional signatures of 43 genes in decidua basalis and peripheral blood

Preeclampsia (PE) has an increasing incidence worldwide, and there is no gold standard for prediction. Recent progress has shown that abnormal decidualization and impaired vascular remodeling are essential to PE pathogenesis. Therefore, it is of great significance to analyze the decidua basalis and blood changes of PE to explore new methods. Here, we performed weighted gene co-expression network analysis based on 9553 differentially expressed genes of decidua basalis data (GSE60438 includes 25 cases of PE and 23 non-cases) from Gene Expression Omnibus to screen relevant module-eigengenes (MEs). Among them, MEblue and MEgrey are the most correlated with PE, which contains 371 core genes. Subsequently, we applied the logistic least absolute shrinkage and selection operator regression, screened 43 genes most relevant to prediction from the intersections of the 371 genes and training set (GSE48424 includes 18 cases of PE and 18 non-cases) genes, and built a predictive model. The specificity and sensitivity are illustrated by receiver operating characteristic curves, and the stability was verified by two validation sets (GSE86200 includes 12 cases of PE and 48 non-cases, and GSE85307 includes 47 cases of PE and 110 non-cases). The results demonstrated that our predictive model shows good predictions, with an area under the curve of 0.991 for the training set, 0.874 and 0.986 for the validation sets. Finally, we found the 43 key marker genes in the model are closely associated with the clinically accepted predictive molecules, including FLT1, PIGF, ENG and VEGF. Therefore, this predictive model provides a potential approach for PE diagnosis and treatment.

Cuproptosis regulator-mediated patterns associated with immune infiltration features and construction of cuproptosis-related signatures to guide immunotherapy

Background

Liver hepatocellular carcinoma (HCC) is a prevalent cancer that lacks a sufficiently efficient approach to guide immunotherapy. Additionally, cuproptosis is a recently identified regulated cell death program that is triggered by copper ionophores. However, its possible significance in tumor immune cell infiltration is still unclear.

Methods

Cuproptosis subtypes in HCC were identified using unsupervised consensus cluster analysis based on 10 cuproptosis regulators expressions, and a cuproptosis-related risk signature was generated using univariate and LASSO Cox regression and validated using the ICGC data. Moreover, the relationship between signature and tumor immune microenvironment (TME) was studied through tumor immunotherapy responsiveness, immune cell infiltration, and tumor stem cell analysis. Finally, clinical specimens were analyzed using immunohistochemistry to verify the expression of the three genes in the signature.

Results

Two subtypes of cuproptosis regulation were observed in HCC, with different immune cell infiltration features. Genes expressed differentially between the two cuproptosis clusters in the TCGA were determined and used to construct a risk signature that was validated using the ICGC cohort. Greater immune and stromal cell infiltration were observed in the high-risk group and were associated with unfavorable prognosis. Elevated risk scores were linked with higher RNA stemness scores (RNAss) and tumor mutational burden (TMB), together with a greater likelihood of benefitting from immunotherapy.

Conclusion

It was found that cuproptosis regulatory patterns may play important roles in the heterogeneity of immune cell infiltration. The risk signature associated with cuproptosis can assess each patient's risk score, leading to more individualized and effective immunotherapy.

Cyclin-dependent kinases as potential targets for colorectal cancer: past, present and future

Colorectal cancer (CRC) is a common cancer in the world and its prevalence is increasing in developing countries. Deregulated cell cycle traverse is a hallmark of malignant transformation and is often observed in CRC as a result of imprecise activity of cell cycle regulatory components, viz. cyclins and cyclin-dependent kinases (CDKs). Apart from cell cycle regulation, some CDKs also regulate processes such as transcription and have also been shown to be involved in colorectal carcinogenesis. This article aims to review cyclin-dependent kinases as potential targets for CRC. Furthermore, therapeutic candidates to target CDKs are also discussed.

Survivin' Acute Myeloid Leukaemia-A Personalised Target for inv(16) Patients

Despite recent advances in therapies including immunotherapy, patients with acute myeloid leukaemia (AML) still experience relatively poor survival rates. The Inhibition of Apoptosis (IAP) family member, survivin, also known by its gene and protein name, Baculoviral IAP Repeat Containing 5 (BIRC5), remains one of the most frequently expressed antigens across AML subtypes. To better understand its potential to act as a target for immunotherapy and a biomarker for AML survival, we examined the protein and pathways that BIRC5 interacts with using the Kyoto Encyclopedia of Genes and Genomes (KEGG), search tool for recurring instances of neighbouring genes (STRING), WEB-based Gene Set Analysis Toolkit, Bloodspot and performed a comprehensive literature review. We then analysed data from gene expression studies. These included 312 AML samples in the Microarray Innovations In Leukemia (MILE) dataset. We found a trend between above median levels of BIRC5 being associated with improved overall survival (OS) but this did not reach statistical significance (p = 0.077, Log-Rank). There was some evidence of a beneficial effect in adjusted analyses where above median levels of BIRC5 were shown to be associated with improved OS (p = 0.001) including in Core Binding Factor (CBF) patients (p = 0.03). Above median levels of BIRC5 transcript were associated with improved relapse free survival (p < 0.0001). Utilisation of a second large cDNA microarray dataset including 306 AML cases, again showed no correlation between BIRC5 levels and OS, but high expression levels of BIRC5 correlated with worse survival in inv(16) patients (p = 0.077) which was highly significant when datasets A and B were combined (p = 0.001). In addition, decreased BIRC5 expression was associated with better clinical outcome (p = 0.004) in AML patients exhibiting CBF mainly due to patients with inv(16) (p = 0.007). This study has shown that BIRC5 expression plays a role in the survival of AML patients, this association is not apparent when we examine CBF patients as a cohort, but when those with inv(16) independently indicating that those patients with inv(16) would provide interesting candidates for immunotherapies that target BIRC5.

Therapeutic Potency of Nanoformulations of siRNAs and shRNAs in Animal Models of Cancers

RNA Interference (RNAi) has brought revolutionary transformations in cancer management in the past two decades. RNAi-based therapeutics including siRNA and shRNA have immense scope to silence the expression of mutant cancer genes specifically in a therapeutic context. Although tremendous progress has been made to establish catalytic RNA as a new class of biologics for cancer management, a lot of extracellular and intracellular barriers still pose a long-lasting challenge on the way to clinical approval. A series of chemically suitable, safe and effective viral and non-viral carriers have emerged to overcome physiological barriers and ensure targeted delivery of RNAi. The newly invented carriers, delivery techniques and gene editing technology made current treatment protocols stronger to fight cancer. This review has provided a platform about the chronicle of siRNA development and challenges of RNAi therapeutics for laboratory to bedside translation focusing on recent advancement in siRNA delivery vehicles with their limitations. Furthermore, an overview of several animal model studies of siRNA- or shRNA-based cancer gene therapy over the past 15 years has been presented, highlighting the roles of genes in multiple cancers, pharmacokinetic parameters and critical evaluation. The review concludes with a future direction for the development of catalytic RNA vehicles and design strategies to make RNAi-based cancer gene therapy more promising to surmount cancer gene delivery challenges.

Exosomes from asbestos-exposed cells modulate gene expression in mesothelial cells

Asbestos exposure is a determinate cause of many diseases, such as mesothelioma, fibrosis, and lung cancer, and poses a major human health hazard. At this time, there are no identified biomarkers to demarcate asbestos exposure before the presentation of disease and symptoms, and there is only limited understanding of the underlying biology that governs asbestos-induced disease. In our study, we used exosomes, 30-140 nm extracellular vesicles, to gain insight into these knowledge gaps. As inhaled asbestos is first encountered by lung epithelial cells and macrophages, we hypothesize that asbestos-exposed cells secrete exosomes with signature proteomic cargo that can alter the gene expression of mesothelial cells, contributing to disease outcomes like mesothelioma. In the present study using lung epithelial cells (BEAS2B) and macrophages (THP-1), we first show that asbestos exposure causes changes in abundance of some proteins in the exosomes secreted from these cells. Furthermore, exposure of human mesothelial cells (HPM3) to these exosomes resulted in gene expression changes related to epithelial-to-mesenchymal transition and other cancer-related genes. This is the first report to indicate that asbestos-exposed cells secrete exosomes with differentially abundant proteins and that those exosomes have a gene-altering effect on mesothelial cells.-Munson, P., Lam, Y.-W., Dragon, J. MacPherson, M., Shukla, A. Exosomes from asbestos-exposed cells modulate gene expression in mesothelial cells.

Use of Serum Circulating Ccnb2 in Cancer Surveillance

Cyclin B2 (CCNB2), a member of the cyclin protein family, has been found to be up-regulated in human cancers. To evaluate the potential use of circulating CCNB2 in serum in cancer surveillance, we examined relative expression levels of serum circulating CCNB2 mRNA in 103 cancer patients, 19 normal controls, and 40 benign disease patients using real-time quantitative reverse transcriptase polymerase chain reaction. We found that the relative expression level of circulating CCNB2 mRNA in cancer patients was significantly higher (p<0.0001) than that in normal controls and benign diseases group. Circulating CCNB2 mRNA level was significantly (p<0.001) correlated with cancer stage and metastasis status. Receiver operating characteristic (ROC) analysis showed an area under the curve (AUC) of 0.87 and 0.83 (p<0.05) in identifying cancer patients' metastasis status in lung and digestive tract cancer, respectively. Moreover, we observed that expression levels of circulating CCNB2 mRNA in cancer patients significantly decreased (p=0.0084) after their therapeutic treatments. These data suggest that detection of serum circulating CCNB2 mRNA may have potential clinical applications in screening and monitoring of metastasis and therapeutic treatments.

The interplay between chromosome stability and cell cycle control explored through gene-gene interaction and computational simulation

Chromosome stability models are usually qualitative models derived from molecular-genetic mechanisms for DNA repair, DNA synthesis, and cell division. While qualitative models are informative, they are also challenging to reformulate as precise quantitative models. In this report we explore how (A) laboratory experiments, (B) quantitative simulation, and (C) seriation algorithms can inform models of chromosome stability. Laboratory experiments were used to identify 19 genes that when over-expressed cause chromosome instability in the yeast Saccharomyces cerevisiae To better understand the molecular mechanisms by which these genes act, we explored their genetic interactions with 18 deletion mutations known to cause chromosome instability. Quantitative simulations based on a mathematical model of the cell cycle were used to predict the consequences of several genetic interactions. These simulations lead us to suspect that the chromosome instability genes cause cell-cycle perturbations. Cell-cycle involvement was confirmed using a seriation algorithm, which was used to analyze the genetic interaction matrix to reveal an underlying cyclical pattern. The seriation algorithm searched over 10(14) possible arrangements of rows and columns to find one optimal arrangement, which correctly reflects events during cell cycle phases. To conclude, we illustrate how the molecular mechanisms behind these cell cycle events are consistent with established molecular interaction maps.

Overexpression screens identify conserved dosage chromosome instability genes in yeast and human cancer

Somatic copy number amplification and gene overexpression are common features of many cancers. To determine the role of gene overexpression on chromosome instability (CIN), we performed genome-wide screens in the budding yeast for yeast genes that cause CIN when overexpressed, a phenotype we refer to as dosage CIN (dCIN), and identified 245 dCIN genes. This catalog of genes reveals human orthologs known to be recurrently overexpressed and/or amplified in tumors. We show that two genes, TDP1, a tyrosyl-DNA-phosphdiesterase, and TAF12, an RNA polymerase II TATA-box binding factor, cause CIN when overexpressed in human cells. Rhabdomyosarcoma lines with elevated human Tdp1 levels also exhibit CIN that can be partially rescued by siRNA-mediated knockdown of TDP1 Overexpression of dCIN genes represents a genetic vulnerability that could be leveraged for selective killing of cancer cells through targeting of an unlinked synthetic dosage lethal (SDL) partner. Using SDL screens in yeast, we identified a set of genes that when deleted specifically kill cells with high levels of Tdp1. One gene was the histone deacetylase RPD3, for which there are known inhibitors. Both HT1080 cells overexpressing hTDP1 and rhabdomyosarcoma cells with elevated levels of hTdp1 were more sensitive to histone deacetylase inhibitors valproic acid (VPA) and trichostatin A (TSA), recapitulating the SDL interaction in human cells and suggesting VPA and TSA as potential therapeutic agents for tumors with elevated levels of hTdp1. The catalog of dCIN genes presented here provides a candidate list to identify genes that cause CIN when overexpressed in cancer, which can then be leveraged through SDL to selectively target tumors.

Identification of biomarkers for diagnosis of gastric cancer by bioinformatics

BACKGROUND

We aimed to discover potential gene biomarkers for gastric cancer (GC) diagnosis.

MATERIALS AND METHODS

Genechips of 10 GC tissues and 10 gastric mucosa (GM, para-carcinoma tissue, normal control) tissues were generated using an exon array of Affymetrix containing 30,000 genes. The differentially expressed genes (DEGs) between GC tissues and normal control were identified by the Limma package and analyzed by hierarchical clustering analysis. Gene ontology (GO) and pathway enrichment analyses were performed for investigating the functions of DEGs. Receiver operating characteristics (ROC) analysis was performed to measure the effects of biomarker candidates for diagnosis of GC.

RESULTS

Totals of 896 up-regulated and 60 down-regulated DEGs were identified to be differentially expressed between GC samples and normal control. Hierarchical clustering analysis showed that DEGs were highly differentially expressed and most DEGs were up-regulated. The most significantly enriched GO-BP term was revealed to be mitotic cell cycle and the most significantly enriched pathway was cell cycle. The intersection analysis showed that most significant DEGs were cyclin B1 (CCNB1) and cyclin B2 (CCNB2). The sensitivities and specificities of CCNB1 and CCNB2 were both high (p<0.0001). Areas under the ROC curve for CCNB1 and CCNB2 were both greater than 0.9 (p<0.0001).

CONCLUSIONS

CCNB1 and CCNB2, which were involved in cell cycle, played significant roles in the progression and development of GC and these genes may be potential biomarkers for diagnosis and prognosis of GC.

Ubiquitin-specific protease 22 is a deubiquitinase of CCNB1

The elevated level of CCNB1 indicates more aggressive cancer and poor prognosis. However, the factors that cause CCNB1 upregulation remain enigmatic. Herein, we identify USP22 as a CCNB1 interactor and discover that both USP22 and CCNB1 are dramatically elevated with a strong positive correlation in colon cancer tissues. USP22 stabilizes CCNB1 by antagonizing proteasome-mediated degradation in a cell cycle-specific manner. Phosphorylation of USP22 by CDK1 enhances its activity in deubiquitinating CCNB1. The ubiquitin ligase anaphase-promoting complex (APC/C) targets USP22 for degradation by using the substrate adapter CDC20 during cell exit from M phase, presumably allowing CCNB1 degradation. Finally, we discover that USP22 knockdown leads to slower cell growth and reduced tumor size. Our study demonstrates that USP22 is a CCNB1 deubiquitinase, suggesting that targeting USP22 might be an effective approach to treat cancers with elevated CCNB1 expression.

Effects of KRC-108 on the Aurora A activity and growth of colorectal cancer cells

Aurora A is involved in regulating multiple steps of mitosis. Over-expression of Aurora A is related to tumorigenesis and poor prognosis. KRC-108 is a novel multi-kinase inhibitor which has anti-tumor activity in vivo. In this study, we identified the inhibitory effects of KRC-108 on Aurora A kinase and growth-inhibitory characteristics of KRC-108. The in vitro kinase activity assay, immunoblot, and immunofluorescence analyses demonstrated that KRC-108 inhibited Aurora A activity. KRC-108 exhibited cytotoxicity against human colorectal cancer cell line HT-29. Colony formation assays showed that KRC-108 reduced the colony growth of HT-29 cells. KRC-108 also inhibited migration of HT-29 cells. The expression levels of cyclin B1 and CDC2 were decreased by KRC-108 in HT-29 cells. Cell cycle analysis and flow cytometry indicated that the inhibitory effects of KRC-108 on cell growth are due to induction of G2/M arrest and apoptosis by inhibition of Aurora A. KRC-108 induces cell-cycle arrest and apoptosis in colorectal cancer cell line by Aurora A inhibition. The reported in vivo anti-tumor effects of KRC-108 might partly be due to anti-Aurora A effects. This study suggests that KRC-108 has potential for development as an anti-tumor agent, although further studies are needed.

Transcriptional control of mitosis: deregulation and cancer

Research over the past few decades has well established the molecular functioning of mitosis. Deregulation of these functions has also been attributed to the generation of aneuploidy in different tumor types. Numerous studies have given insight into the regulation of mitosis by cell cycle specific proteins. Optimum abundance of these proteins is pivotal to timely execution of mitosis. Aberrant expressions of these mitotic proteins have been reported in different cancer types. Several post-transcriptional mechanisms and their interplay have subsequently been identified that control the level of mitotic proteins. However, to date, infrequent incidences of cancer-associated mutations have been reported for the genes expressing these proteins. Therefore, altered expression of these mitotic regulators in tumor samples can largely be attributed to transcriptional deregulation. This review discusses the biology of transcriptional control for mitosis and evaluates its role in the generation of aneuploidy and tumorigenesis.

Whole genome sequence analysis suggests intratumoral heterogeneity in dissemination of breast cancer to lymph nodes

BACKGROUND

Intratumoral heterogeneity may help drive resistance to targeted therapies in cancer. In breast cancer, the presence of nodal metastases is a key indicator of poorer overall survival. The aim of this study was to identify somatic genetic alterations in early dissemination of breast cancer by whole genome next generation sequencing (NGS) of a primary breast tumor, a matched locally-involved axillary lymph node and healthy normal DNA from blood.

METHODS

Whole genome NGS was performed on 12 µg (range 11.1-13.3 µg) of DNA isolated from fresh-frozen primary breast tumor, axillary lymph node and peripheral blood following the DNA nanoball sequencing protocol. Single nucleotide variants, insertions, deletions, and substitutions were identified through a bioinformatic pipeline and compared to CIN25, a key set of genes associated with tumor metastasis.

RESULTS

Whole genome sequencing revealed overlapping variants between the tumor and node, but also variants that were unique to each. Novel mutations unique to the node included those found in two CIN25 targets, TGIF2 and CCNB2, which are related to transcription cyclin activity and chromosomal stability, respectively, and a unique frameshift in PDS5B, which is required for accurate sister chromatid segregation during cell division. We also identified dominant clonal variants that progressed from tumor to node, including SNVs in TP53 and ARAP3, which mediates rearrangements to the cytoskeleton and cell shape, and an insertion in TOP2A, the expression of which is significantly associated with tumor proliferation and can segregate breast cancers by outcome.

CONCLUSION

This case study provides preliminary evidence that primary tumor and early nodal metastasis have largely overlapping somatic genetic alterations. There were very few mutations unique to the involved node. However, significant conclusions regarding early dissemination needs analysis of a larger number of patient samples.

Cyclin B2 and p53 control proper timing of centrosome separation

Cyclins B1 and B2 are frequently elevated in human cancers and are associated with tumour aggressiveness and poor clinical outcome; however, whether and how B-type cyclins drive tumorigenesis is unknown. Here we show that cyclin B1 and B2 transgenic mice are highly prone to tumours, including tumour types where B-type cyclins serve as prognosticators. Cyclins B1 and B2 both induce aneuploidy when overexpressed but through distinct mechanisms, with cyclin B1 inhibiting separase activation, leading to anaphase bridges, and cyclin B2 triggering aurora-A-mediated Plk1 hyperactivation, resulting in accelerated centrosome separation and lagging chromosomes. Complementary experiments revealed that cyclin B2 and p53 act antagonistically to control aurora-A-mediated centrosome splitting and accurate chromosome segregation in normal cells. These data demonstrate a causative link between B-type cyclin overexpression and tumour pathophysiology, and uncover previously unknown functions of cyclin B2 and p53 in centrosome separation that may be perturbed in many human cancers.

Systemic delivery of sticky siRNAs targeting the cell cycle for lung tumor metastasis inhibition

RNA interference allows the design of new inhibitors that target deregulated pathways in cancer. However systemic delivery of siRNA for the treatment of solid tumors still remains an issue. In our study, in order to suppress the progression of lung cancer metastasis in mice, we developed sticky siRNA (ssiRNA) to inhibit survivin and cyclin B1, two candidates involved in cell survival and proliferation. We exploited the linear polyethylenimine (PEI) as potent non-viral carrier to efficiently deliver our inhibitors. As a proof of concept, we have chosen a very aggressive mammary adenocarcinoma model (TSA-Luc cells), which forms lung metastases upon systemic cell injection. We confirmed in vitro, that the ssiRNAs delivered with PEI are not only able to inhibit our target genes at the mRNA and protein levels, but are also able to block the cell cycle and cell proliferation through a mechanism of RNA interference. More importantly, we showed in vivo by luciferase dosage, bioimaging and tissue section, an inhibition of lung tumor metastases after systemic delivery of cyclin B1 and survivin ssiRNA complexed with PEI. Alternating treatment with cisplatin and ssiRNA/PEI showed an additive effect between the two anticancer drugs on lung tumor inhibition leading to a significant increase in animal survival. Moreover a promising window between activity (IC₅₀) and toxicity (LD₅₀), essential for therapeutic application, was observed. Our data show that systemic delivery of ssiRNA/PEI complexes targeting the cell cycle is a valuable strategy for the treatment of lung tumor metastasis and that it can be combined with chemotherapy.

Cyclins and cell cycle control in cancer and disease

Cyclin D1 overexpression is found in more than 50% of human breast cancers and causes mammary cancer in transgenic mice. Dysregulation of cyclin D1 gene expression or function contributes to the loss of normal cell cycle control during tumorigenesis. Recent studies have demonstrated that cyclin D1 conducts additional specific functions to regulate gene expression in the context of local chromatin, promote cellular migration, and promote chromosomal instability. It is anticipated that these additional functions contribute to the pathology associated with dysregulated cyclin D1 abundance. This article discusses evidence that examines the functional roles that cyclin D1 may play in cancer with an emphasis on other cyclin family members that also may contribute to cancer and disease in a similar fashion.

Alterations in the ribosomal machinery in cancer and hematologic disorders

Ribosomes are essential components of the protein translation machinery and are composed of more than 80 unique large and small ribosomal proteins. Recent studies show that in addition to their roles in protein translation, ribosomal proteins are also involved in extra-ribosomal functions of DNA repair, apoptosis and cellular homeostasis. Consequently, alterations in the synthesis or functioning of ribosomal proteins can lead to various hematologic disorders. These include congenital anemias such as Diamond Blackfan anemia and Shwachman Diamond syndrome; both of which are associated with mutations in various ribosomal genes. Acquired uniallelic deletion of RPS14 gene has also been shown to lead to the 5q syndrome, a distinct subset of MDS associated with macrocytic anemia. Recent evidence shows that specific ribosomal proteins are overexpressed in liver, colon, prostate and other tumors. Ribosomal protein overexpression can promote tumorigenesis by interactions with the p53 tumor suppressor pathway and also by direct effects on various oncogenes. These data point to a broad role of ribosome protein alterations in hematologic and oncologic diseases.

SPARC expression induces cell cycle arrest via STAT3 signaling pathway in medulloblastoma cells

Dynamic cell interaction with ECM components has profound influence in cancer progression. SPARC is a component of the ECM, impairs the proliferation of different cell types and modulates tumor cell aggressive features. We previously reported that SPARC expression significantly impairs medulloblastoma tumor growth in vivo. In this study, we demonstrate that expression of SPARC inhibits medulloblastoma cell proliferation. MTT assay indicated a dose-dependent reduction in tumor cell proliferation in adenoviral mediated expression of SPARC full length cDNA (Ad-DsRed-SP) in D425 and UW228 cells. Flow cytometric analysis showed that Ad-DsRed-SP-infected cells accumulate in the G2/M phase of cell cycle. Further, immunoblot and immunoprecipitation analyses revealed that SPARC induced G2/M cell cycle arrest was mediated through inhibition of the Cyclin-B-regulated signaling pathway involving p21 and Cdc2 expression. Additionally, expression of SPARC decreased STAT3 phosphorylation at Tyr-705; constitutively active STAT3 expression reversed SPARC induced G2/M arrest. Ad-DsRed-SP significantly inhibited the pre-established orthotopic tumor growth and tumor volume in nude-mice. Immunohistochemical analysis of tumor sections from mice treated with Ad-DsRed-SP showed decreased immunoreactivity for pSTAT3 and increased immunoreactivity for p21 compared to tumor section from mice treated with mock and Ad-DsRed. Taken together our studies further reveal that STAT3 plays a key role in SPARC induced G2/M arrest in medulloblastoma cells. These new findings provide a molecular basis for the mechanistic understanding of the effects of SPARC on medulloblastoma tumor cell proliferation.

Upregulation of Cyclin B1 by miRNA and its implications in cancer

It is largely recognized that microRNAs (miRNAs) function to silence gene expression by targeting 3′UTR regions. However, miRNAs have also been implicated to positively-regulate gene expression by targeting promoter elements, a phenomenon known as RNA activation (RNAa). In the present study, we show that expression of mouse Cyclin B1 (Ccnb1) is dependent on key factors involved in miRNA biogenesis and function (i.e. Dicer, Drosha, Ago1 and Ago2). In silico analysis identifies highly-complementary sites for 21 miRNAs in the Ccnb1 promoter. Experimental validation identified three miRNAs (miR-744, miR-1186 and miR-466d-3p) that induce Ccnb1 expression in mouse cell lines. Conversely, knockdown of endogenous miR-744 led to decreased Ccnb1 levels. Chromatin immunoprecipitation (ChIP) analysis revealed that Ago1 was selectively associated with the Ccnb1 promoter and miR-744 increased enrichment of RNA polymerase II (RNAP II) and trimethylation of histone 3 at lysine 4 (H3K4me3) at the Ccnb1 transcription start site. Functionally, short-term overexpression of miR-744 and miR-1186 resulted in enhanced cell proliferation, while prolonged expression caused chromosomal instability and in vivo tumor suppression. Such phenotypes were recapitulated by overexpression of Ccnb1. Our findings reveal an endogenous system by which miRNA functions to activate Ccnb1 expression in mouse cells and manipulate in vivo tumor development/growth.

Oncogenic functions of secreted Frizzled-related protein 2 in human renal cancer

The secreted Frizzled-related proteins (sFRP) are modulators of the Wnt signaling pathway, which is involved in embryonic development and tumor progression. The functions of sFRP2 have not been studied in renal cancer. Transient transfection of sFRP2 promoted cell growth in renal carcinoma cells, whereby the largest effect was observed in A498 cells. To further study the functions of sFRP2 gene in renal carcinoma cells, we established A498 renal cancer cell lines, which stably expressed sFRP2. Stably expressed sFRP2 significantly promoted cell proliferation in vitro and in vivo tumor growth. The stably expressed sFRP2 cells were also found to have reduced UV-induced apoptosis and increased G(2) phase of the cell cycle. The phosphorylation level at Ser(33/37)/Thr(41) of beta-catenin was lower in the stable sFRP2 cell lines compared with the control cell line. sFRP2 significantly activated T-cell factor/lymphoid enhancer factor transcriptional activity. In the stable sFRP2 cell line, expression of c-Fos, Bcl2, Bcl-w, cyclin B2, and cyclin E2 genes was significantly increased and p53 expression was decreased. This is the first report documenting that sFRP2 activates the canonical Wnt pathway and promotes cell growth by evoking diverse signaling cascades in renal cancer cells. This study may provide better strategies for the management of renal cancer through regulation of sFRP2 pathways.

Ribosomopathies: human disorders of ribosome dysfunction

Ribosomopathies compose a collection of disorders in which genetic abnormalities cause impaired ribosome biogenesis and function, resulting in specific clinical phenotypes. Congenital mutations in RPS19 and other genes encoding ribosomal proteins cause Diamond-Blackfan anemia, a disorder characterized by hypoplastic, macrocytic anemia. Mutations in other genes required for normal ribosome biogenesis have been implicated in other rare congenital syndromes, Schwachman-Diamond syndrome, dyskeratosis congenita, cartilage hair hypoplasia, and Treacher Collins syndrome. In addition, the 5q- syndrome, a subtype of myelodysplastic syndrome, is caused by a somatically acquired deletion of chromosome 5q, which leads to haploinsufficiency of the ribosomal protein RPS14 and an erythroid phenotype highly similar to Diamond-Blackfan anemia. Acquired abnormalities in ribosome function have been implicated more broadly in human malignancies. The p53 pathway provides a surveillance mechanism for protein translation as well as genome integrity and is activated by defects in ribosome biogenesis; this pathway appears to be a critical mediator of many of the clinical features of ribosomopathies. Elucidation of the mechanisms whereby selective abnormalities in ribosome biogenesis cause specific clinical syndromes will hopefully lead to novel therapeutic strategies for these diseases.

Global gene expression profiling of human pleural mesotheliomas: identification of matrix metalloproteinase 14 (MMP-14) as potential tumour target

BACKGROUND

The goal of our study was to molecularly dissect mesothelioma tumour pathways by mean of microarray technologies in order to identify new tumour biomarkers that could be used as early diagnostic markers and possibly as specific molecular therapeutic targets.

METHODOLOGY

We performed Affymetrix HGU133A plus 2.0 microarray analysis, containing probes for about 39,000 human transcripts, comparing 9 human pleural mesotheliomas with 4 normal pleural specimens. Stringent statistical feature selection detected a set of differentially expressed genes that have been further evaluated to identify potential biomarkers to be used in early diagnostics. Selected genes were confirmed by RT-PCR. As reported by other mesothelioma profiling studies, most of genes are involved in G2/M transition. Our list contains several genes previously described as prognostic classifier. Furthermore, we found novel genes, never associated before to mesotheliom that could be involved in tumour progression. Notable is the identification of MMP-14, a member of matrix metalloproteinase family. In a cohort of 70 mesothelioma patients, we found by a multivariate Cox regression analysis, that the only parameter influencing overall survival was expression of MMP14. The calculated relative risk of death in MM patients with low MMP14 expression was significantly lower than patients with high MMp14 expression (P = 0.002).

CONCLUSIONS

Based on the results provided, this molecule could be viewed as a new and effective therapeutic target to test for the cure of mesothelioma.

Cartilage-hair hypoplasia: molecular basis and heterogeneity of the immunological phenotype

PURPOSE OF REVIEW

To report on the expanding clinical and immunological spectrum associated with ribonuclease mitochondrial RNA-processing mutations and to review the cellular and molecular mechanisms involved in the pathophysiology of cartilage-hair hypoplasia (CHH) and related disorders in humans.

RECENT FINDINGS

Different types of mutations are associated with skeletal or extraskeletal manifestations of CHH, respectively. In particular, severe immunodeficiency is mostly associated with mutations that alter cyclin B2 mRNA cleavage and thus are likely to reflect disturbances in cell cycle control. The first cases of ribonuclease mitochondrial RNA-processing mutations with severe immunodeficiency, but no skeletal abnormalities, have been identified.

SUMMARY

Abnormalities of ribosome biogenesis have been shown to cause distinct bone marrow failure syndromes, including CHH. However, the specific role of ribosomal and extraribosomal defects in the pathophysiology of the various phenotypic features of CHH remains undefined. Development of suitable animal models is needed to address this important issue.

HMGA proteins up-regulate CCNB2 gene in mouse and human pituitary adenomas

The high mobility group As (HMGAs) belong to a family of nonhistone nuclear proteins that orchestrate the assembly of nucleoprotein complexes. Through a complex network of protein-DNA and protein-protein interaction, they play important roles in gene transcription, recombination, and chromatin structure. This protein family is involved, through different mechanisms, in both benign and malignant neoplasias. We have recently reported that transgenic mice carrying the Hmga1 or Hmga2 genes under transcriptional control of the cytomegalovirus promoter develop pituitary adenomas secreting prolactin and growth hormone. We have shown that the mechanism of the HMGA2-induced pituitary adenoma is based on the increased E2F1 activity. The expression profile of mouse normal pituitary glands and adenomas induced in HMGA transgenic mice revealed an increased expression of the ccnb2 gene, coding for the cyclin B2 protein, in the neoplastic tissues compared with the normal pituitary gland. Here, we show, by electrophoretic mobility shift assay and chromatin immunoprecipitation, a direct binding of HMGA proteins to the promoter of ccnb2 gene, whereas luciferase assays showed that HMGAs are able to up-regulate ccnb2 promoter activity. Finally, we report an increased CCNB2 expression in human pituitary adenomas of different histotypes that is directly correlated with HMGA1 and HMGA2 expression. Because cyclin B2 is involved in the regulation of the cell cycle, these results taken together indicate that HMGA-induced cyclin B2 overexpression gives an important contribution to experimental and human pituitary tumorigenesis.

Type and level of RMRP functional impairment predicts phenotype in the cartilage hair hypoplasia-anauxetic dysplasia spectrum

Mutations in the RMRP gene lead to a wide spectrum of autosomal recessive skeletal dysplasias, ranging from the milder phenotypes metaphyseal dysplasia without hypotrichosis and cartilage hair hypoplasia (CHH) to the severe anauxetic dysplasia (AD). This clinical spectrum includes different degrees of short stature, hair hypoplasia, defective erythrogenesis, and immunodeficiency. The RMRP gene encodes the untranslated RNA component of the mitochondrial RNA-processing ribonuclease, RNase MRP. We recently demonstrated that mutations may affect both messenger RNA (mRNA) and ribosomal RNA (rRNA) cleavage and thus cell-cycle regulation and protein synthesis. To investigate the genotype-phenotype correlation, we analyzed the position and the functional effect of 13 mutations in patients with variable features of the CHH-AD spectrum. Those at the end of the spectrum include a novel patient with anauxetic dysplasia who was compound heterozygous for the null mutation g.254_263delCTCAGCGCGG and the mutation g.195C-->T, which was previously described in patients with milder phenotypes. Mapping of nucleotide conservation to the two-dimensional structure of the RMRP gene revealed that disease-causing mutations either affect evolutionarily conserved nucleotides or are likely to alter secondary structure through mispairing in stem regions. In vitro testing of RNase MRP multiprotein-specific mRNA and rRNA cleavage of different mutations revealed a strong correlation between the decrease in rRNA cleavage in ribosomal assembly and the degree of bone dysplasia, whereas reduced mRNA cleavage, and thus cell-cycle impairment, predicts the presence of hair hypoplasia, immunodeficiency, and hematological abnormalities and thus increased cancer risk.

Gene expression profiling in familial adenomatous polyposis adenomas and desmoid disease

Gene expression profiling is a powerful method by which alterations in gene expression can be interrogated in a single experiment. The disease familial adenomatous polyposis (FAP) is associated with germline mutations in the APC gene, which result in aberrant β-catenin control. The molecular mechanisms underlying colorectal cancer development in FAP are being characterised but limited information is available about other symptoms that occur in this disorder. Although extremely rare in the general population, desmoid tumours in approximately 10% of FAP patients. The aim of this study was to determine the similarities and differences in gene expression profiles in adenomas and compare them to those observed in desmoid tumours. Illumina whole genome gene expression BeadChips were used to measure gene expression in FAP adenomas and desmoid tumours. Similarities between gene expression profiles and mechanisms important in regulating formation of FAP adenomas and desmoid tumours were identified. This study furthers our understanding of the mechanisms underlying FAP and desmoid tumour formation.

NF-Y-dependent cyclin B2 expression in colorectal adenocarcinoma

PURPOSE

Cyclin B2, a G(2)-M cyclin, is overexpressed in colorectal adenocarcinomas compared with the normal mucosa. This study examined the level of cyclin B2 overexpression according to the histologic findings and investigated the mechanism(s) and clinical implications of cyclin B2 overexpression in colorectal adenocarcinomas.

EXPERIMENTAL DESIGN

The immunoreactivity of the polyclonal antibodies to cyclin B2 was determined in colorectal cancer cells. The transcriptional regulation of cyclin B2 by NF-Y was analyzed using an in vitro transfection assay and an in vivo chromatin immunoprecipitation assay. The proliferative activity of the colorectal cancer cells in relation to cyclin B2 overexpression was further examined.

RESULTS

The cytoplasmic distribution of cyclin B2 immunoreactivity was positive in 42 of 65 (64.6%) cases of colorectal adenocarcinoma, and the level was similar regardless of the histologic type. A dominant-negative form of NF-YA effectively inhibited the cyclin B2 promoter activity, and NF-Y was found to bind three conserved CCAAT boxes in the cyclin B2 promoter in colorectal adenocarcinoma cells. Tumor cells with a higher functional cyclin B2 activity grew faster than those with a lower activity. Furthermore, there was a correlation between the cells showing immunoreactivity to cyclin B2 and those containing the proliferating cell nuclear antigen, a G1-S cyclin, which is also downstream of NF-Y in colorectal adenocarcinoma cells.

CONCLUSIONS

Cyclin B2 seems to be a molecular marker of a colorectal adenocarcinoma and that its up-regulation and coordinate expression of the other cell cycle-related genes by NF-Y might contribute to tumor cell proliferation by accelerating cell cycle progression.

Molecular signatures of soy-derived phytochemicals in androgen-responsive prostate cancer cells: a comparison study using DNA microarray

The present study utilized microarray technology as a tool to elucidate the molecular signatures of soy-derived phytochemicals in the human androgen-responsive prostate cancer cell line LNCaP. Global gene expression pattern analysis of LNCaP cells exposed to 0, 1, 5, or 25 microM of the soy-derived phytochemicals equol and daidzein were conducted and compared. The data were further compared with previously generated data from exposure of LNCaP cells to the same doses of genistein, a soy isoflavone. Multidimensional scaling (MDS) analyses of the expression patterns suggest that these compounds exerted differential effects on gene expression in LNCaP cells. Further examination of specific gene changes revealed that these compounds differentially modulated genes in multiple cellular pathways, including the cell-cycle pathway genes. However, the three compounds also exerted similar effect on genes belonging to several other important cellular pathways. A universal effect of the three compounds on androgen-responsive genes, IGF-1 pathway gene, and MAP kinase-related pathway gene was observed. These results provide the foundation for establishing molecular signatures for equol, daidzein, and genistein. Moreover, these results also allow for the identification of candidate mechanism(s) by which soy phytochemicals and soy may act in prostate cancer cells.

Contribution of the BOP1 gene, located on 8q24, to colorectal tumorigenesis

The most common form of genomic instability observed in colorectal cancer is chromosomal instability (CIN), whose molecular bases remain to be determined. We have previously demonstrated that inactivation in human cells of several components of the Pes1-Bop1 complex (BOP1, GRWD1, PES1, ORC6L, and RPL3), involved in ribosome biogenesis, altered chromosome segregation. To determine the contribution to colorectal tumorigenesis of somatic alterations of genes involved in ribosome biogenesis, we screened 56 primary colorectal cancers, using quantitative multiplex PCR of short fluorescent fragments, a sensitive method for the detection of gene dosage alterations. We found that dosage increase of the BOP1 gene was a frequent event, being detected in 39% of the tumors, and we show that it is associated with an increase of BOP1 mRNA. Scanning of 8q24, on which BOP1 is located, revealed that in colorectal cancers, gene dosage increase of BOP1 can be independent from that of MYC and was more frequent than that affecting MYC. Finally, transient overexpression of BOP1 in human cells increased the percentage of multipolar spindles. Together with our previous results, the present study strongly suggests that deregulation of the BOP1 pathway contributes to colorectal tumorigenesis.

Induction of cell apoptosis in non-small cell lung cancer cells by cyclin A1 small interfering RNA

Cyclin A1 and cyclin B1 are overexpressed in various tumors but are present at low levels in normal tissues. Cyclin A1 is restricted to germ cells undergoing meiosis. In order to explore the possibility of using cyclin A1 and cyclin B1 as anticancer targets, we knocked them down in two lung cancer cell lines, H157 and H596, using siRNA. As with cyclin A1 siRNA in lung cancer cell lines, cyclin B1, Cdc2 and CDK2 were all significantly downregulated. The S phase fraction increased significantly, and they eventually underwent apoptosis by way of downregulated intrinsic apoptotic pathways and modulators with upregulated extrinsic apoptotic pathways. Our study suggests that cyclin A1 might be a promising anticancer target specific to lung cancer.

Pathocycles: Ustilago maydis as a model to study the relationships between cell cycle and virulence in pathogenic fungi

Activation of virulence in pathogenic fungi often involves differentiation processes that need the reset of the cell cycle and induction of a new morphogenetic program. Therefore, the fungal capability to modify its cell cycle constitutes an important determinant in carrying out a successful infection. The dimorphic fungus Ustilago maydis is the causative agent of corn smut disease and has lately become a highly attractive model in addressing fundamental questions about development in pathogenic fungi. The different morphological and genetic changes of U. maydis cells during the pathogenic process advocate an accurate control of the cell cycle in these transitions. This is why this model pathogen deserves attention as a powerful tool in analyzing the relationships between cell cycle, morphogenesis, and pathogenicity. The aim of this review is to summarize recent advances in the unveiling of cell cycle regulation in U. maydis. We also discuss the connection between cell cycle and virulence and how cell cycle control is an important downstream target in the fungus-plant interaction.

Knockdown of MBP-1 in human prostate cancer cells delays cell cycle progression

We have previously shown that MBP-1 acts as a general transcriptional repressor, and forced expression of MBP-1 exerts an anti-proliferative effect on a number of human cancer cells. In this report, we have investigated the role of endogenous MBP-1 in cell growth regulation. For this, we generated human prostate cancer cells (PC3) stably transfected with short hairpin RNA targeting MBP-1. We have observed retarded growth and longer doubling time of MBP-1 knockdown PC3 cells as compared with control mock-transfected PC3 cells. Fluorescence-activated cell sorter analysis suggested that PC3 cells expressing MBP-1-specific small interfering RNA accumulated during G2/M phase of the cell cycle. Further analysis suggested that depletion of MBP-1 was associated with reduction of cyclin A and cyclin B1 expression when compared with that of the control cells. A delayed induction of cyclin A and B1 expression was observed in MBP-1-depleted PC3 cells (PC3-4.2) upon serum stimulation, although the level of expression was much lower than that of control PC3 cells. Supplementation of MBP-1 in PC3-4.2 cells restored cyclin A and cyclin B1 expression. Together, these results suggest that knockdown of MBP-1 in prostate cancer cells perturbs cell proliferation by inhibiting cyclin A and cyclin B1 expression.

Ubiquitin ligases: cell-cycle control and cancer

A driving force of the cell cycle is the activation of cyclin-dependent kinases (CDKs), the activities of which are controlled by the ubiquitin-mediated proteolysis of key regulators such as cyclins and CDK inhibitors. Two ubiquitin ligases, the SKP1-CUL1-F-box-protein (SCF) complex and the anaphase-promoting complex/cyclosome (APC/C), are responsible for the specific ubiquitylation of many of these regulators. Deregulation of the proteolytic system might result in uncontrolled proliferation, genomic instability and cancer. Cumulative clinical evidence shows alterations in the ubiquitylation of cell-cycle regulators in the aetiology of many human malignancies. A better understanding of the ubiquitylation machinery will provide new insights into the regulatory biology of cell-cycle transitions and the development of anti-cancer drugs.

Stable gene silencing of cyclin B1 in tumor cells increases susceptibility to taxol and leads to growth arrest in vivo

Cyclin B1 is the regulatory subunit of cyclin-dependent kinase 1 (Cdk1) and is critical for the initiation of mitosis. Accumulating data indicate that the deregulation of cyclin B1 is tightly linked to neoplastic transformation. To study the phenotype and the potential preclinical relevance, we generated HeLa cell lines stably transfected with the plasmids encompassing short hairpin RNA (shRNA) targeting cyclin B1. We demonstrate that the reduction of cyclin B1 caused inhibition of proliferation by arresting cells in G2 phase and by inducing apoptosis. Cells, entering mitosis, were impaired in chromosome condensation and alignment. Importantly, HeLa cells with reduced cyclin B1 were more susceptible to the treatment of small interfering RNA targeting Polo-like kinase 1 (Plk1) and to the administration of the chemotherapeutic agent taxol. Finally, HeLa cells with reduced cyclin B1 showed inhibited tumor growth in nude mice compared to that of control cells. In summary, our data indicate that cyclin B1 is an essential molecule for tumor cell survival and aggressive proliferation, suggesting that the downregulation of cyclin B1, especially in combination with other molecular targets, might become an interesting strategy for antitumor intervention.

Alteration of subcellular and cellular expression patterns of cyclin B1 in renal cell carcinoma is significantly related to clinical progression and survival of patients

Cyclin B1, identified as a regulator of late cell cycle, is involved in the development and progression of a variety of human malignancies. To clarify the role of cyclin B1 in the pathogenesis and prognosis of renal cell carcinoma (RCC), protein expression was compared with clinicopathological characteristics of patients as well as the long-term survival after surgical therapy. Expression analysis was carried out by immunohistochemistry and tissue microarray analysis. The microarrays that represented the primary tumors, their invasion front and normal peritumoral renal parenchyma contained 753 tissue cores obtained from 251 randomly selected nephrectomy specimens. Immunopositivity within the primary tumors was significantly associated with tumor stage (pT) (p < 0.01), lymph node status (pN) (p < 0.01) as well as the presence of systemic metastatic disease (p = 0.01). Subcellular expression in the cytoplasm of tumor cells significantly correlated with pT (p = 0.02) and pN (p = 0.03). When peritumoral tissue samples exhibited a relative amount of <10% of positively reacting epithelial cells, cyclin B positivity was identified to predict long-term survival of patients in univariate analysis (p < 0.01) whereas borderline significance was observed in multivariate statistical analysis (p = 0.05). Increased intratumoral cyclin B1 positivity and aberrant localization of signals within the cytoplasm of tumor cells is positively correlated with the tendency towards tumor progression, indicating the significant role of cyclin B1 in the development and pathogenesis of RCC. The result of uni- and multivariate statistical analysis suggests the prognostic value of cyclin B1 for RCC patients.

Severely incapacitating mutations in patients with extreme short stature identify RNA-processing endoribonuclease RMRP as an essential cell growth regulator

The growth of an individual is deeply influenced by the regulation of cell growth and division, both of which also contribute to a wide variety of pathological conditions, including cancer, diabetes, and inflammation. To identify a major regulator of human growth, we performed positional cloning in an autosomal recessive type of profound short stature, anauxetic dysplasia. Homozygosity mapping led to the identification of novel mutations in the RMRP gene, which was previously known to cause two milder types of short stature with susceptibility to cancer, cartilage hair hypoplasia, and metaphyseal dysplasia without hypotrichosis. We show that different RMRP gene mutations lead to decreased cell growth by impairing ribosomal assembly and by altering cyclin-dependent cell cycle regulation. Clinical heterogeneity is explained by a correlation between the level and type of functional impairment in vitro and the severity of short stature or predisposition to cancer. Whereas the cartilage hair hypoplasia founder mutation affects both pathways intermediately, anauxetic dysplasia mutations do not affect B-cyclin messenger RNA (mRNA) levels but do severely incapacitate ribosomal assembly via defective endonucleolytic cleavage. Anauxetic dysplasia mutations thus lead to poor processing of ribosomal RNA while allowing normal mRNA processing and, therefore, genetically separate the different functions of RNase MRP.

Chromosomal instability induced by Pim-1 is passage-dependent and associated with dysregulation of cyclin B1

Overexpression of the oncogenic serine/threonine kinase Pim-1 has been shown to induce chromosomal missegregation and polyploidy in prostate epithelial cell lines (1). Here we demonstrated that Pim-1-induced polyploidy develops in a passage-dependent manner in culture consistent with a stochastic mode of progression. Induction of chromosomal instability by Pim-1 was not restricted to prostate cells as it was also observed in telomerase-immortalized normal human mammary epithelial cells. Elevated levels of cyclin B1 protein, but not its messenger RNA, were evident in early passage Pim-1 overexpressing cells, suggesting that increased cyclin B1 levels contribute to the development of polyploidy. Furthermore, regulation of cyclin B1 protein and cyclin B1/CDK1 activity after treatment with anti-microtubule agents was impaired. Small interfering RNA targeting cyclin B1 reversed the cytokinesis delay but not the mitotic checkpoint defect in Pim-1 overexpressing cells. These results indicated that chronic Pim-1 overexpression dysregulates cyclin B1 protein expression, which contributes to the development of polyploidy by delaying cytokinesis.

Over-expression of Aurora-A targets cytoplasmic polyadenylation element binding protein and promotes mRNA polyadenylation of Cdk1 and cyclin B1

Aurora-A is a centrosomal serine-threonine kinase that regulates mitosis. Over-expression of Aurora-A has been found in a wide range of tumors and has been implicated in oncogenic transformation. However, how Aurora-A over-expression contributes to promotion of carcinogenesis remains elusive. Immunohistochemical analysis of breast tumors revealed that over-expressed Aurora-A is not restricted to the centrosomes but is also found in the cytoplasm. This over-expressed Aurora-A appeared to be phosphorylated on Thr288, which is known to be required for its enzymatic activation. In analogy to Aurora-A's role in oocyte maturation and the early embryonic cell cycle, here we investigated whether ectopically over-expressed Aurora-A can similarly stimulate polyadenylation of mRNA in human somatic cultured cells by interacting with a human ortholog of cytoplasmic polyadenylation element binding protein, h-CPEB. In vitro experiments revealed that Aurora-A binds directly to, and phosphorylates, h-CPEB. We found that polyadenylation of mRNA tails of cyclin B1 and Cdk1 was synergistically stimulated when Aurora-A and h-CPEB were over-expressed, and they were further promoted in the presence of an Aurora-A activator Ajuba. Our results suggest a function of ectopically over-expressed Aurora-A that might be relevant for carcinogenesis.

Loss of Cyclin B1 followed by downregulation of Cyclin A/Cdk2, apoptosis and antiproliferation in Hela cell line

Recent studies have shown that Cyclin B1 is overexpressed in various tumor types but present at low levels in normal tissues. To explore the possibility of employing Cyclin B1 as an anticancer target, we knocked down Cyclin B1 in an HeLa cell line using RNA interference (RNAi). Subsequently, we monitored cell cycle-related molecules by Western blot together with immunofluorescence and determined cell cycle distribution by flow cytometry. XTT and soft agar colony growth experiments were performed to detect cell viability and proliferation. Furthermore, we analyzed cell apoptosis by measuring Bcl-2 and Bax protein level and DNA-ladder assay. After performing Cyclin B1 RNAi, Cyclin B1, Cyclin A and Cdk2 protein levels were found to be markedly downregulated, whereas Cdc2 was almost unaffected; S-phase fraction increased significantly; HeLa cell viability and cell colony forming ability were markedly diminished after the RNAi; Bcl-2 was noticeably attenuated but Bax was hardly changed; and HeLa cells displayed typical DNA ladder. The loss of Cyclin B1 resulted in the downregulation of Cyclin A and Cdk2, S-phase delay and eventually led to cell apoptosis and the decrease of cell viability and proliferation. Our studies suggest that Cyclin B1 may be a promising anticancer target.

Gene expression analysis in human gastric cancer cell line treated with trichostatin A and S-adenosyl-L-homocysteine using cDNA microarray

Trichostatin A (TSA) and S-adenosyl-L-homocysteine (AdoHcy) have been reported to affect histone modifications. To investigate the effects of two drugs that can reportedly affect chromatin remodeling, we analyzed the gene expression profiles of TSA and AdoHcy in a gastric cancer cell line using 14 K cDNA microarray. The significant analysis of microarray (SAM) identified 98 and 43 differentially expressed genes in TSA and AdoHcy treated sets, respectively, and selected genes were functionally classified. In the gastric cancer cell line, genes related to cell communication, cell growth/maintenance, and morphogenesis were highly expressed with TSA, and genes with cell growth/maintenance, metabolism, oxidoreductase activity were upregulated with AdoHcy. Genes downregulated with TSA included those controlling the cell cycle, cell growth/proliferation, DNA binding, and metabolism, whereas genes involved in calcium signaling, cell growth/proliferation, and metabolism were downregulated with AdoHcy. Furthermore, we identified the genes commonly expressed in both drug treatments. Compared to TSA, AdoHcy did not induce apoptosis in the SNU-16 gastric cancer cell line, and RT-PCR was performed for selective genes to confirm the microarray data. This gene expression profile analysis with TSA and AdoHcy should contribute to a greater understanding of the molecular mechanism of chromatin remodeling and cancer, and provide candidate genes for further studies involving the roles of histone modifications in gastric cancer.

Gene expression profiling of microdissected pancreatic ductal carcinomas using high-density DNA microarrays

Pancreatic ductal adenocarcinoma (PDAC) remains an important cause of malignancy-related death and is the eighth most common cancer with the lowest overall 5-year relative survival rate. To identify new molecular markers and candidates for new therapeutic regimens, we investigated the gene expression profile of microdissected cells from 11 normal pancreatic ducts, 14 samples of PDAC, and 4 well-characterized pancreatic cancer cell lines using the Affymetrix U133 GeneChip set. RNA was extracted from microdissected samples and cell lines, amplified, and labeled using a repetitive in vitro transcription protocol. Differentially expressed genes were identified using the significance analysis of microarrays program. We found 616 differentially expressed genes. Within these, 140 were also identified in PDAC by others, such as Galectin-1, Galectin-3, and MT-SP2. We validated the differential expression of several genes (e.g., CENPF, MCM2, MCM7, RAMP, IRAK1, and PTTG1) in PDAC by immunohistochemistry and reverse transcription polymerase chain reaction. We present a whole genome expression study of microdissected tissues from PDAC, from microdissected normal ductal pancreatic cells and pancreatic cancer cell lines using high-density microarrays. Within the panel of genes, we identified novel differentially expressed genes, which have not been associated with the pathogenesis of PDAC before.

Genetic interactions between Cdk1-CyclinB and the Separase complex in Drosophila

Cdk1-CycB plays a key role in regulating many aspects of cell-cycle events, such as cytoskeletal dynamics and chromosome behavior during mitosis. To investigate how Cdk1-CycB controls the coordination of these events, we performed a dosage-sensitive genetic screen, which is based on the observations that increased maternal CycB (four extra gene copies) leads to higher Cdk1-CycB activity in early Drosophila embryos, delays anaphase onset, and generates a sensitized non-lethal phenotype at the blastoderm stage (defined as six cycB phenotype). Here, we report that mutations in the gene three rows (thr) enhance, while mutations in pimples (pim, encoding Drosophila Securin) or separase (Sse) suppress, the sensitized phenotype. In Drosophila, both Pim and Thr are known to regulate Sse activity, and activated Sse cleaves a Cohesin subunit to initiate anaphase. Compared with the six cycB embryos, reducing Thr in embryos with more CycB further delays the initiation of anaphase, whereas reducing either Pim or Sse has the opposite effect. Furthermore, nuclei move slower during cortical migration in embryos with higher Cdk1-CycB activity, whereas reducing either Pim or Sse suppresses this phenotype by causing a novel nuclear migration pattern. Therefore, our genetic screen has identified all three components of the complex that regulates sister chromatid separation, and our observations indicate that interactions between Cdk1-CycB and the Pim-Thr-Sse complex are dosage sensitive.

Silencing of human Int-6 impairs mitosis progression and inhibits cyclin B-Cdk1 activation

The Int-6 protein has been originally identified as the product of a mouse gene being a frequent integration site of the mouse mammary tumour virus. Here, we show that reducing Int-6 expression by RNA interference in HeLa cells markedly alters mitosis progression. Defects in spindle formation, chromosome segregation and cytokinesis were observed. These abnormalities of mitosis completion are correlated with an inhibition of cyclin B-Cdk1 kinase activity, due to a prolonged inhibitory phosphorylated state of Cdk1. In line with this observation, the Wee1 tyrosine kinase that negatively controls Cdk1 was less efficiently inactivated during G2 in Int-6-depleted cells. These findings support the notion that the oncogenic properties associated with alteration of Int-6 originate from chromosomal instability.