Expression of a Novel Human Gene,Human Wings Apart-Like (hWAPL), Is Associated with Cervical Carcinogenesis and Tumor Progression

Suppression of antitumor cytokine IL‑24 by PRG4 and PAI‑1 may promote myxoid liposarcoma cell survival

Suppression of the antitumor cytokine interleukin-24 (IL-24) is critical for the survival of myxoid liposarcoma (MLS) cells. It has been previously demonstrated by the authors that an MLS-specific chimeric oncoprotein, translocated in liposarcoma-CCAAT/enhancer-binding protein homologous protein (TLS-CHOP), supresses IL24 mRNA expression via induction of proteoglycan 4 (PRG4) to sustain MLS cell proliferation. However, IL-24 has also been revealed to be suppressed by the ubiquitin-proteasome system in human ovarian and lung cancer cells. Therefore, the aim of the present study was to elucidate the mechanism of IL-24 suppression in MLS cells. The results revealed that the proteasome inhibitor, MG-132, induced cell death in MLS cells in vitro; this effect was reduced following IL-24 knockdown. This indicated that proteasomal degradation of IL-24 may be an important process for MLS cell survival. In addition, it was also previously revealed by the authors that knockdown of plasminogen activator inhibitor-1 (PAI-1), a TLS-CHOP downstream molecule, suppressed the growth of MLS cells, thus instigating the investigation of the effect of PAI-1 on IL-24 expression in MLS cells. Double knockdown of PAI-1 and IL-24 negated the growth-suppressive effect of PAI-1 single knockdown in MLS cells. Interestingly, PAI-1 single knockdown did not increase the mRNA expression of IL24, but it did increase the protein abundance of IL-24, indicating that PAI-1 suppressed IL-24 expression by promoting its proteasomal degradation. Moreover, treatment of MLS cells with a PAI-1 inhibitor, TM5275, induced IL-24 protein expression and apoptosis. Collectively, the results of the present as well as previous studies indicated that IL-24 expression may be suppressed at the transcriptional level by PRG4 and at the protein level by PAI-1 in MLS cells. Accordingly, PAI-1 may represent an effective therapeutic target for MLS treatment.

Regulation of loop extrusion on the interphase genome

In the human cell nucleus, dynamically organized chromatin is the substrate for gene regulation, DNA replication, and repair. A central mechanism of DNA loop formation is an ATPase motor cohesin-mediated loop extrusion. The cohesin complexes load and unload onto the chromosome under the control of other regulators that physically interact and affect motor activity. Regulation of the dynamic loading cycle of cohesin influences not only the chromatin structure but also genome-associated human disorders and aging. This review focuses on the recently spotlighted genome organizing factors and the mechanism by which their dynamic interactions shape the genome architecture in interphase.

Cohesin in DNA damage response and double-strand break repair

Cohesin, a four-subunit ring comprising SMC1, SMC3, RAD21 and SA1/2, tethers sister chromatids by DNA replication-coupled cohesion (RC-cohesion) to guarantee correct chromosome segregation during cell proliferation. Postreplicative cohesion, also called damage-induced cohesion (DI-cohesion), is an emerging critical player in DNA damage response (DDR). In this review, we sum up recent progress on how cohesin regulates the DNA damage checkpoint activation and repair pathway choice, emphasizing postreplicative cohesin loading and DI-cohesion establishment in yeasts and mammals. DI-cohesion and RC-cohesion show distinct features in many aspects. DI-cohesion near or far from the break sites might undergo different regulations and execute different tasks in DDR and DSB repair. Furthermore, some open questions in this field and the significance of this new scenario to our understanding of genome stability maintenance and cohesinopathies are discussed.

Genetically induced redox stress occurs in a yeast model for Roberts syndrome

Roberts syndrome (RBS) is a multispectrum developmental disorder characterized by severe limb, craniofacial, and organ abnormalities and often intellectual disabilities. The genetic basis of RBS is rooted in loss-of-function mutations in the essential N-acetyltransferase ESCO2 which is conserved from yeast (Eco1/Ctf7) to humans. ESCO2/Eco1 regulate many cellular processes that impact chromatin structure, chromosome transmission, gene expression, and repair of the genome. The etiology of RBS remains contentious with current models that include transcriptional dysregulation or mitotic failure. Here, we report evidence that supports an emerging model rooted in defective DNA damage responses. First, the results reveal that redox stress is elevated in both eco1 and cohesion factor Saccharomyces cerevisiae mutant cells. Second, we provide evidence that Eco1 and cohesion factors are required for the repair of oxidative DNA damage such that ECO1 and cohesin gene mutations result in reduced cell viability and hyperactivation of DNA damage checkpoints that occur in response to oxidative stress. Moreover, we show that mutation of ECO1 is solely sufficient to induce endogenous redox stress and sensitizes mutant cells to exogenous genotoxic challenges. Remarkably, antioxidant treatment desensitizes eco1 mutant cells to a range of DNA damaging agents, raising the possibility that modulating the cellular redox state may represent an important avenue of treatment for RBS and tumors that bear ESCO2 mutations.

Lysosomal degradation ensures accurate chromosomal segregation to prevent chromosomal instability

Lysosomes, as primary degradative organelles, are the endpoint of different converging pathways, including macroautophagy. To date, lysosome degradative function has been mainly studied in interphase cells, while their role during mitosis remains controversial. Mitosis dictates the faithful transmission of genetic material among generations, and perturbations of mitotic division lead to chromosomal instability, a hallmark of cancer. Heretofore, correct mitotic progression relies on the orchestrated degradation of mitotic factors, which was mainly attributed to ubiquitin-triggered proteasome-dependent degradation. Here, we show that mitotic transition also relies on lysosome-dependent degradation, as impairment of lysosomes increases mitotic timing and leads to mitotic errors, thus promoting chromosomal instability. Furthermore, we identified several putative lysosomal targets in mitotic cells. Among them, WAPL, a cohesin regulatory protein, emerged as a novel SQSTM1-interacting protein for targeted lysosomal degradation. Finally, we characterized an atypical nuclear phenotype, the toroidal nucleus, as a novel biomarker for genotoxic screenings. Our results establish lysosome-dependent degradation as an essential event to prevent chromosomal instability.Abbreviations: 3D: three-dimensional; APC/C: anaphase-promoting complex; ARL8B: ADP ribosylation factor like GTPase 8B; ATG: autophagy-related; BORC: BLOC-one-related complex; CDK: cyclin-dependent kinase; CENPE: centromere protein E; CIN: chromosomal instability; ConcA: concanamycin A; CQ: chloroquine; DAPI: 4,6-diamidino-2-penylinole; FTI: farnesyltransferase inhibitors; GFP: green fluorescent protein; H2B: histone 2B; KIF: kinesin family member; LAMP2: lysosomal associated membrane protein 2; MAP1LC3/LC3: microtubule associated protein 1 light chain 3; MEF: mouse embryonic fibroblast; MTOR: mechanistic target of rapamycin kinase; PDS5B: PDS5 cohesin associated factor B; SAC: spindle assembly checkpoint; PLEKHM2: pleckstrin homology and RUN domain containing M2; SQSTM1: sequestosome 1; TEM: transmission electron microscopy; ULK1: unc-51 like autophagy activating kinase 1; UPS: ubiquitin-proteasome system; v-ATPase: vacuolar-type H+-translocating ATPase; WAPL: WAPL cohesion release factor.

WAPL induces cervical intraepithelial neoplasia modulated with estrogen signaling without HPV E6/E7

Since cervical cancer still afflicts women around the world, it is necessary to understand the underlying mechanism of cervical cancer development. Infection with HPV is essential for the development of cervical intraepithelial neoplasia (CIN). In addition, estrogen receptor signaling is implicated in the development of cervical cancer. Previously, we have isolated human wings apart-like (WAPL), which is expected to cause chromosomal instability in the process of HPV-infected precancerous lesions to cervical cancer. However, the role of WAPL in the development of CIN is still unknown. In this study, in order to elucidate the role of WAPL in the early lesion, we established WAPL overexpressing mice (WAPL Tg mice) and HPV E6/E7 knock-in (KI) mice. WAPL Tg mice developed CIN lesion without HPV E6/E7. Interestingly, in WAPL Tg mice estrogen receptor 1 (ESR1) showed reduction as compared with the wild type, but cell growth factors MYC and Cyclin D1 controlled by ESR1 expressed at high levels. These results suggested that WAPL facilitates sensitivity of ESR1 mediated by some kind of molecule, and as a result, affects the expression of MYC and Cyclin D1 in cervical cancer cells. To detect such molecules, we performed microarray analysis of the uterine cervix in WAPL Tg mice, and focused MACROD1, a co-activator of ESR1. MACROD1 expression was increased in WAPL Tg mice compared with the wild type. In addition, knockdown of WAPL induced the downregulation of MACROD1, MYC, and Cyclin D1 but not ESR1 expression. Furthermore, ESR1 sensitivity assay showed lower activity in WAPL or MACROD1 downregulated cells than control cells. These data suggested that WAPL increases ESR1 sensitivity by activating MACROD1, and induces the expression of MYC and Cyclin D1. Therefore, we concluded that WAPL not only induces chromosomal instability in cervical cancer tumorigenesis, but also plays a key role in activating estrogen receptor signaling in early tumorigenesis.

Suppression of MKL1 promotes adipocytic differentiation and reduces the proliferation of myxoid liposarcoma cells

Myxoid liposarcoma (MLS) is thought to occur due to defective adipocytic differentiation in mesenchymal stem cells. A promising strategy for MLS treatment is the prevention of sarcomagenesis by promoting the terminal differentiation of MLS cells into adipocytes. Previous studies have reported that the suppression of megakaryoblastic leukemia 1 (MKL1) expression induces adipocytic differentiation in preadipocyte cell lines. The present study aimed to investigate the effects of MKL1 suppression on MLS cells. In the present study, MKL1 knockdown was demonstrated to promote the adipocytic differentiation of an MLS-derived cell line, designated 1955/91, under adipogenic conditions. This suggests that therapeutic targeting of the MKL1-associated molecular pathway has potential as a promising method of MLS treatment. However, the induction of adipogenesis by MKL knockdown was incomplete, and Oil Red O staining indicated that intracellular lipid droplets were only sporadically generated. Conversely, MKL1 knockdown reduced the growth of the MLS cells. As adipocytic differentiation in vitro requires cellular confluence, the decreased growth rate of the MLS cells following MKL1 knockdown could be attributed to the incomplete induction of adipogenesis. Translocated in liposarcoma-CCAAT/enhancer-binding protein homologous protein (TLS-CHOP) is an MLS-specific oncoprotein that is thought to play key roles in sarcomagenesis and the suppression of adipocytic differentiation. However, the results of western blotting analyses suggest that TLS-CHOP has limited effects on MKL1 expression in MLS cells and that MKL1 knockdown hardly affects TLS-CHOP expression. Thus, it is postulated that the inhibitory effect of TLS-CHOP on adipogenesis is not associated with MKL1 expression. However, MKL1 and the molecular pathway involving MKL1 appear to be attractive targets for the differentiation therapy of MLS.

Clinical significance of hWAPL polymorphisms in the risk of cervical carcinogenesis

To investigate the clinical significance of human wings apart-like (hWAPL) genetic polymorphisms in cervical carcinogenesis. hWAPL polymorphisms and human papillomavirus (HPV) types were examined in 175 cervical smears of exfoliated cervical cell samples using a real-time polymerase chain reaction system. A significant difference was detected in the frequency of the CC genotype between the HPV(+) low-grade squamous intraepithelial lesion (LSIL) and high-grade squamous intraepithelial lesion (HSIL) groups [Odds ratio 0.21, 95% confidence interval (CI) 0.0723-0.61; P = 0.0029]. A significant difference was noted in the frequency of the CC genotype between the high-risk HPV-positive LSIL and HSIL groups (odds ratio 0.2955, 95% CI 0.0893-0.9771; P = 0.0414). The CC genotype of hWAPL gene promoter polymorphism may be associated with cervical carcinogenesis.

TAT-mediated si-hWAPL inhibits the invasion and metastasis of cervical cancer stem cells

Human wings apart-like (hWAPL) is reported to have an association with cervical cancer. In the present study, the role of hWAPL in cervical cancer stem cells (CCSCs) was evaluated. Cervical tumorspheres were generated from cervical cancer tissues cultured in stem cell medium, and the expression of hWAPL by the tumorspheres was detected using immunohistochemistry. hWAPL expression levels in the tumorspheres were then upregulated using hWAPL adenoviral vectors or downregulated via the TAT-mediated knockdown of hWAPL and the effects on the tumorspheres were evaluated using colony formation, cell invasion and western blotting assays. The results demonstrated that the expression of hWAPL and human papillomavirus (HPV) was associated with the pluripotency of CCSCs, with hWAPL expression decreasing following the differentiation of cervical tumorspheres. Knockdown of hWAPL expression decreased HPV E6 expression and inhibited tumor invasion and colony formation. TAT-mediated knockdown of hWAPL with short interfering RNA significantly reduced tumor growth in nude mice. These results suggest that hWAPL is a marker of CCSC proliferation and is potentially a therapeutic target for cervical carcinoma through the downregulation of HPV E6.

Cohesin Mutations in Myeloid Malignancies

Acute Myeloid Leukemia (AML) is a hematologic malignancy with a poor prognosis. Recent genome-wide sequencing studies have identified frequent mutations in genes encoding members of the cohesin complex. Mutations in cohesin contribute to myeloid malignancies by conferring enhanced self-renewal of hematopoietic stem and progenitor cells but the mechanisms behind this phenotype have not been fully elucidated. Of note, cohesin mutations are highly prevalent in acute megakaryocytic leukemia associated with Down syndrome (DS-AMKL), where they occur in over half of patients. Evidence suggests that cohesin mutations alter gene expression through changes in chromatin accessibility and/or aberrant targeting of epigenetic complexes. In this review we discuss the pathogenic mechanisms by which cohesin mutations contribute to myeloid malignancies.

Phage Immunoprecipitation Sequencing of Autoantigens in Autoimmune Retinopathy

PURPOSE

To identify autoantigens in autoimmune retinopathy patients by phage immunoprecipitation sequencing (PhIP-Seq), a new technique for autoantigen discovery.

METHODS

PhIP-Seq was used to sequence putative autoantibodies in plasma from 11 patients with autoimmune retinopathy and eight controls. We compared the autoantibodies' molecular weights with those of proteins detected by Western blot.

RESULTS

Several autoantigens were found in cases and not detected in the controls. Autoantigens RTN3, PRPF6, TRPC6, and B3GNT8, four proteins expressed in the retina, were detected in plasma as autoantibodies from one patient each and no controls. Only one patient had an autoantibody, B3GNT8 (43.4 kDa), within a similar weight range as that detected by antiretinal antibody Western blot (42 kDa). Autoantibody POLR3A, which has a well-characterized role in scleroderma, was detected in two cases and no controls.

CONCLUSION

PhIP-Seq detected autoantigens that are expressed in the retina as well as scleroderma-related autoantigens in autoimmune retinopathy patients.

SMC1A promotes growth and migration of prostate cancer in vitro and in vivo

Structural maintenance of chromosome 1 alpha (SMC1A) gene has been reported to be related to tumor development in some types of human cancers. However, the misregulation of SMC1A and its functions in castration-resistant prostate cancer (CRPC) have not been well understood. In the present study, we found that SMC1A was elevated in androgen-independent PCa cell lines PC-3 and DU-145 compared to androgen sensitive LNCap and 22RV1 cells by qPCR and western blot assay. Knockdown of SMC1A inhibited cell growth, colony formation and cell migration abilities of PC-3 and DU145 cells by MTT, colony formation and transwell assays, and affected cell cycle progression in PC-3 and DU145 cells by flow cytometry. Moreover, SMC1A knockdown significantly reduced tumor growth in vivo in a nude mouse model. Additionally, we also found that the expression of SMC1A gene was higher in prostate cancer tissues than in the adjacent normal tissues by immunohistochemical staining, and was positively correlated to tumor metastasis and recurrence by Oncomine database mining. Taken together, the present study indicates that SMC1A may play an important role in malignant transformation of PCa under conditions of androgen deprivation and act as a new target for PCa diagnosis and treatment.

Human wings apart-like gene is specifically overexpressed in cervical cancer

Cervical cancer is the third most commonly diagnosed cancer in women. The human wings apart-like (hWAPL) gene, which is 30,793 bp long and located on 10q23.2., is a human homologue of the WAPL gene in Drosophila melanogaster. hWAPL has the characteristics of an oncogene in uterine cervical cancer. The present study investigated the expression of the hWAPL gene in tissues, including 9 common cancers, consisting of cervical, gastric and lung cancers, liver, bladder, esophageal, endometrial, renal and rectal carcinomas, cervical intraepithelial neoplasia (CIN) and benign squamous epithelia. The immunohistochemical analysis was conducted using paraffin-embedded tissues obtained from 413 patients, consisting of 27 benign squamous epithelial tissue samples, and 47 cervical cancer, 30 cervical intraepithelial neoplasia (CIN)I, 33 CINII, 38 CINIII, 29 gastric cancer, 28 liver carcinoma, 26 bladder carcinoma, 35 esophageal carcinoma, 25 endometrial, 26 renal carcinoma, 36 rectal carcinoma and 33 lung cancer tissues. The expression of hWAPL mRNA was evaluated by reverse transcription-quantitative polymerase chain reaction in 8 benign squamous epithelia and 11 cervical cancer tissues. Compared to benign squamous epithelia and the 8 other cancers, hWAPL protein was significantly increased in cervical cancer (P<0.001). The expression of the hWAPL protein in cervical cancer and CINIII tissues was markedly increased compared to the expression in CINI and CINII tissues (P<0.001). Despite the significant difference in the staining scores (P<0.001), no significant difference was observed in the percentage of tissues expressing hWAPL (P=0.102) between cervical cancer and CINIII. The hWAPL gene may therefore be specifically overexpressed in cervical cancer. The overexpression of hWAPL may play an important role in occurrence and development of cervical cancer.

The sister chromatid cohesion pathway suppresses multiple chromosome gain and chromosome amplification

Gain or loss of chromosomes resulting in aneuploidy can be important factors in cancer and adaptive evolution. Although chromosome gain is a frequent event in eukaryotes, there is limited information on its genetic control. Here we measured the rates of chromosome gain in wild-type yeast and sister chromatid cohesion (SCC) compromised strains. SCC tethers the newly replicated chromatids until anaphase via the cohesin complex. Chromosome gain was measured by selecting and characterizing copper-resistant colonies that emerged due to increased copies of the metallothionein gene CUP1. Although all defective SCC diploid strains exhibited increased rates of chromosome gain, there were 15-fold differences between them. Of all mutants examined, a hypomorphic mutation at the cohesin complex caused the highest rate of chromosome gain while disruption of WPL1, an important regulator of SCC and chromosome condensation, resulted in the smallest increase in chromosome gain. In addition to defects in SCC, yeast cell type contributed significantly to chromosome gain, with the greatest rates observed for homozygous mating-type diploids, followed by heterozygous mating type, and smallest in haploids. In fact, wpl1-deficient haploids did not show any difference in chromosome gain rates compared to wild-type haploids. Genomic analysis of copper-resistant colonies revealed that the "driver" chromosome for which selection was applied could be amplified to over five copies per diploid cell. In addition, an increase in the expected driver chromosome was often accompanied by a gain of a small number of other chromosomes. We suggest that while chromosome gain due to SCC malfunction can have negative effects through gene imbalance, it could also facilitate opportunities for adaptive changes. In multicellular organisms, both factors could lead to somatic diseases including cancer.

Cohesin: functions beyond sister chromatid cohesion

Faithful segregation of chromosomes during mitosis and meiosis is the cornerstone process of life. Cohesin, a multi-protein complex conserved from yeast to human, plays a crucial role in this process by keeping the sister chromatids together from S-phase to anaphase onset during mitosis and meiosis. Technological advancements have discovered myriad functions of cohesin beyond its role in sister chromatid cohesion (SCC), such as transcription regulation, DNA repair, chromosome condensation, homolog pairing, monoorientation of sister kinetochore, etc. Here, we have focused on such functions of cohesin that are either independent of or dependent on its canonical role of sister chromatid cohesion. At the end, human diseases associated with malfunctioning of cohesin, albeit with mostly unperturbed sister chromatid cohesion, have been discussed.

Genomic instability and colon carcinogenesis: from the perspective of genes

Colon cancer is the second most lethal cancer; approximately 600,000 people die of it annually in the world. Colon carcinogenesis generally follows a slow and stepwise process of accumulation of mutations under the influence of environmental and epigenetic factors. To adopt a personalized (tailored) cancer therapy approach and to improve current strategies for prevention, diagnosis, prognosis, and therapy overall, advanced understanding of molecular events associated with colon carcinogenesis is necessary. A contemporary approach that combines genetics, epigenomics, and signaling pathways has revealed many genetic/genomic alterations associated with colon cancer progression and their relationships to a genomic instability phenotype prevalent in colon cancer. In this review, we describe the relationship between gene mutations associated with colon carcinogenesis and a genomic instability phenotype, and we discuss possible clinical applications of genomic instability studies. Colon carcinogenesis is associated with frequent mutations in several pathways that include phosphatidylinositol 3-kinase, adenomatous polyposis coli, p53 (TP53), F-box and WD repeat domain containing 7, transforming growth factor-β, chromosome cohesion, and K-RAS. These genes frequently mutated in pathways affecting colon cancer were designated colon cancer (CAN) genes. Aberrations in major colon CAN genes have a causal relationship to genomic instability. Conversely, genomic instability itself plays a role in colon carcinogenesis in experimental settings, as demonstrated in transgenic mouse models with high genomic instability. Thus, there is a feedback-type relationship between CAN gene mutations and genomic instability. These genetic/genomic studies have led to emerging efforts to apply the knowledge to colon cancer prognosis and to targeted therapy.

SIRT3 functions in the nucleus in the control of stress-related gene expression

SIRT3 is a member of the Sir2 family of NAD(+)-dependent protein deacetylases that promotes longevity in many organisms. The processed short form of SIRT3 is a well-established mitochondrial protein whose deacetylase activity regulates various metabolic processes. However, the presence of full-length (FL) SIRT3 in the nucleus and its functional importance remain controversial. Our previous studies demonstrated that nuclear FL SIRT3 functions as a histone deacetylase and is transcriptionally repressive when artificially recruited to a reporter gene. Here, we report that nuclear FL SIRT3 is subjected to rapid degradation under conditions of cellular stress, including oxidative stress and UV irradiation, whereas the mitochondrial processed form is unaffected. FL SIRT3 degradation is mediated by the ubiquitin-proteasome pathway, at least partially through the ubiquitin protein ligase (E3) activity of SKP2. Finally, we show by chromatin immunoprecipitation that some target genes of nuclear SIRT3 are derepressed upon degradation of SIRT3 caused by stress stimuli. Thus, SIRT3 exhibits a previously unappreciated role in the nucleus, modulating the expression of some stress-related and nuclear-encoded mitochondrial genes.

Systemically injected exosomes targeted to EGFR deliver antitumor microRNA to breast cancer cells

Despite the therapeutic potential of nucleic acid drugs, their clinical application has been limited in part by a lack of appropriate delivery systems. Exosomes or microvesicles are small endosomally derived vesicles that are secreted by a variety of cell types and tissues. Here, we show that exosomes can efficiently deliver microRNA (miRNA) to epidermal growth factor receptor (EGFR)-expressing breast cancer cells. Targeting was achieved by engineering the donor cells to express the transmembrane domain of platelet-derived growth factor receptor fused to the GE11 peptide. Intravenously injected exosomes delivered let-7a miRNA to EGFR-expressing xenograft breast cancer tissue in RAG2(-/-) mice. Our results suggest that exosomes can be used therapeutically to target EGFR-expressing cancerous tissues with nucleic acid drugs.

Deregulation of RAD21 and RUNX1 expression in endometrial cancer

Cohesins and cohesin-regulated genes are deregulated in numerous types of human cancer. However, data concerning their status and role in endometrial cancer are scarce. This study aimed to determine the clinical significance of double-strand-break repair protein rad21 homolog (RAD21) and runt-related transcription factor 1 (RUNX1) gene dosage and mRNA expression in endometrial cancer. RAD21 is a component of the cohesin complex, crucial for chromosome segregation and DNA repair. RUNX1 is the transcription factor implicated in RAD21 regulation. The study group included 144 endometrial cancer patients. RAD21 and RUNX1 expression profiles were measured by reverse-transcription quantitative PCR. RAD21 gene dosage was determined by quantitative PCR. RAD21 gene dosage was associated with RAD21 mRNA expression (ϱ=0.22; p=0.009). Furthermore, RAD21 expression strongly correlated with RUNX1 expression (ϱ=0.43; p<0.0000001). Increased RAD21 gene dosage correlated with more advanced tumor stage (p=0.021), higher grade (p=0.021), cervical involvement (p=0.01) and the absence of obesity (p=0.025), while RAD21 mRNA expression correlatd with cervical involvement (p=0.027). The mRNA expression of RAD21 and RUNX1 was found to be deregulated and co-dependent in endometrial cancer. RAD21 gene dosage is associated with unfavorable tumor characteristics. However, elucidating the role of these molecular markers in endometrial oncogenesis requires further investigation, including functional studies and survival analysis.

A novel oncogenic pathway by TLS-CHOP involving repression of MDA-7/IL-24 expression

Background:

Translocated in liposarcoma-CCAAT/enhancer binding protein homologous protein (TLS–CHOP) (also known as FUS-DDIT3) chimeric oncoprotein is found in the majority of human myxoid liposarcoma (MLS), but its molecular function remains unclear.

Methods:

We knockdowned TLS–CHOP expression in MLS-derived cell lines by a specific small interfering RNA, and analysed the gene expression profiles with microarray.

Results:

TLS-CHOP knockdown inhibited growth of MLS cells, and induced an anticancer cytokine, melanoma differentiation-associated gene 7 (MDA-7)/interleukin-24 (IL-24) expression. However, double knockdown of TLS–CHOP and MDA-7/IL-24 did not inhibit MLS cell growth.

Conclusion:

Repression of MDA-7/IL-24 expression by TLS–CHOP is required for MLS tumour growth, and TLS–CHOP may become a promising therapeutic target for MLS treatment.

Synthetic lethality of cohesins with PARPs and replication fork mediators

Synthetic lethality has been proposed as a way to leverage the genetic differences found in tumor cells to affect their selective killing. Cohesins, which tether sister chromatids together until anaphase onset, are mutated in a variety of tumor types. The elucidation of synthetic lethal interactions with cohesin mutants therefore identifies potential therapeutic targets. We used a cross-species approach to identify robust negative genetic interactions with cohesin mutants. Utilizing essential and non-essential mutant synthetic genetic arrays in Saccharomyces cerevisiae, we screened genome-wide for genetic interactions with hypomorphic mutations in cohesin genes. A somatic cell proliferation assay in Caenorhabditis elegans demonstrated that the majority of interactions were conserved. Analysis of the interactions found that cohesin mutants require the function of genes that mediate replication fork progression. Conservation of these interactions between replication fork mediators and cohesin in both yeast and C. elegans prompted us to test whether other replication fork mediators not found in the yeast were required for viability in cohesin mutants. PARP1 has roles in the DNA damage response but also in the restart of stalled replication forks. We found that a hypomorphic allele of the C. elegans SMC1 orthologue, him-1(e879), genetically interacted with mutations in the orthologues of PAR metabolism genes resulting in a reduced brood size and somatic cell defects. We then demonstrated that this interaction is conserved in human cells by showing that PARP inhibitors reduce the viability of cultured human cells depleted for cohesin components. This work demonstrates that large-scale genetic interaction screening in yeast can identify clinically relevant genetic interactions and suggests that PARP inhibitors, which are currently undergoing clinical trials as a treatment of homologous recombination-deficient cancers, may be effective in treating cancers that harbor cohesin mutations.

Mutability and mutational spectrum of chromosome transmission fidelity genes

It has been more than two decades since the original chromosome transmission fidelity (Ctf) screen of Saccharomyces cerevisiae was published. Since that time the spectrum of mutations known to cause Ctf and, more generally, chromosome instability (CIN) has expanded dramatically as a result of systematic screens across yeast mutant arrays. Here we describe a comprehensive summary of the original Ctf genetic screen and the cloning of the remaining complementation groups as efforts to expand our knowledge of the CIN gene repertoire and its mutability in a model eukaryote. At the time of the original screen, it was impossible to predict either the genes and processes that would be overrepresented in a pool of random mutants displaying a Ctf phenotype or what the entire set of genes potentially mutable to Ctf would be. We show that in a collection of 136 randomly selected Ctf mutants, >65% of mutants map to 13 genes, 12 of which are involved in sister chromatid cohesion and/or kinetochore function. Extensive screening of systematic mutant collections has shown that ~350 genes with functions as diverse as RNA processing and proteasomal activity mutate to cause a Ctf phenotype and at least 692 genes are required for faithful chromosome segregation. The enrichment of random Ctf alleles in only 13 of ~350 possible Ctf genes suggests that these genes are more easily mutable to cause genome instability than the others. These observations inform our understanding of recurring CIN mutations in human cancers where presumably random mutations are responsible for initiating the frequently observed CIN phenotype of tumors.

The dark side of cohesin: the carcinogenic point of view

Genome instability is a hallmark of cancer cells and how it arises is still not completely understood. Correct chromosome segregation is a pre-requisite for preserving genome integrity. Cohesin helps to ensure faithful chromosome segregation during cell cycle, however, much evidence regarding its functions have come to light over the last few years and suggest that cohesin plays multiple roles in the maintenance of genome stability. Here we review our rapidly increasing knowledge on the involvement of cohesin pathway in genome stability and cancer.

miR-92 is a key oncogenic component of the miR-17-92 cluster in colon cancer

MicroRNAs (miRNAs) belong to a class of endogenously expressed non-coding small RNAs that function primarily as gene regulators. Growing evidence suggests that miRNAs play a significant role in tumor development, making them potential biomarkers for cancer diagnosis and prognosis. The miR-17-92 cluster has emerged as an important locus, being highly overexpressed in several cancers in association with cancer development and progression. The miR-17-92 miRNA cluster generates a single polycistronic primary transcript that yields six mature miRNAs: miR-17, miR-18a, miR-19a, miR-20a, miR-19b, and miR-92a. In colon cancer development, the pathophysiologic roles of these transcripts and their targets are largely unknown. In the present study, we performed copy number analyses of the six miRNAs transcribed from the miR-17-92 cluster in colon tumor tissues. We determined that miR-92a was transcribed at higher levels than the other five miRNAs in both adenomas and carcinoma. In addition, miR-92a directly targeted the anti-apoptotic molecule BCL-2-interacting mediator of cell death (BIM) in colon cancer tissues. An anti-miR-92a antagomir induced apoptosis of colon cancer-derived cell lines. These data indicate that miR-92a plays a pivotal role in the development of colorectal carcinoma.

Can corruption of chromosome cohesion create a conduit to cancer?

Cohesin is a conserved multisubunit protein complex with diverse cellular roles, making key contributions to the coordination of chromosome segregation, the DNA damage response and chromatin regulation by epigenetic mechanisms. Much has been learned in recent years about the roles of cohesin in a physiological context, whereas its potential and emerging role in tumour initiation and/or progression has received relatively little attention. In this Opinion article we examine how cohesin deregulation could contribute to cancer development on the basis of its physiological roles.

The expanding universe of cohesin functions: a new genome stability caretaker involved in human disease and cancer

Cohesin is responsible for sister chromatid cohesion, ensuring the correct chromosome segregation. Beyond this role, cohesin and regulatory cohesin genes seem to play a role in preserving genome stability and gene transcription regulation. DNA damage is thought to be a major culprit for many human diseases, including cancer. Our present knowledge of the molecular basis underlying genome instability is extremely limited. Mutations in cohesin genes cause human diseases such as Cornelia de Lange syndrome and Roberts syndrome/SC phocomelia, and all the cell lines derived from affected patients show genome instability. Cohesin mutations have also been identified in colorectal cancer. Here, we will discuss the human disorders caused by alterations of cohesin function, with emphasis on the emerging role of cohesin as a genome stability caretaker.

Cornelia de Lange syndrome, cohesin, and beyond

Cornelia de Lange syndrome (CdLS) (OMIM #122470, #300590 and #610759) is a dominant genetic disorder with multiple organ system abnormalities which is classically characterized by typical facial features, growth and mental retardation, upper limb defects, hirsutism, gastrointestinal and other visceral system involvement. Mutations in three cohesin proteins, a key regulator of cohesin, NIPBL, and two structural components of the cohesin ring SMC1A and SMC3, etiologically account for about 65% of individuals with CdLS. Cohesin controls faithful chromosome segregation during the mitotic and meiotic cell cycles. Multiple proteins in the cohesin pathway are also involved in additional fundamental biological events such as double-strand DNA break repair and long-range regulation of transcription. Moreover, chromosome instability was recently associated with defective sister chromatid cohesion in several cancer studies, and an increasing number of human developmental disorders is being reported to result from disruption of this pathway. Here, we will discuss the human disorders caused by alterations of cohesin function (termed 'cohesinopathies'), with an emphasis on the clinical manifestations of CdLS and mechanistic studies of the CdLS-related proteins.

Expression of G protein-coupled receptor kinase 4 is associated with breast cancer tumourigenesis

G-protein-coupled receptor kinases (GRKs) comprise a family of seven mammalian serine/threonine protein kinases that phosphorylate and regulate agonist-bound, activated, G-protein-coupled receptors (GPCRs). GRKs and beta-arrestins are key participants in the canonical pathways leading to phosphorylation-dependent GPCR desensitization, endocytosis, intracellular trafficking and resensitization. Here we show that GRK4 isoforms are expressed in human breast cancer but not in normal epithelia. In addition, GRK4-over-expressing cells activated the mitogen-activated protein kinase (MAPK) mediated by ERK 1/2 and JNK phosphorylation in breast cancer-derived cell lines. Furthermore, suppression of beta-arrestins decreased GRK4-stimulated ERK 1/2 or JNK phosphorylations. These data indicate that high-level expression of GRK4 may activate MAPK signalling pathways mediated by beta-arrestins in breast cancer cells, suggesting that GRK4 may be implicated in breast cancer carcinogenesis.

Expression of various types of alternatively spliced WAPL transcripts in human cervical epithelia

We have previously identified a novel gene WAPL that is inducible by human papillomavirus (HPV) E6 and E7 oncoproteins, and is associated with uterine cervical carcinogenesis. A WAPL splice variant named Friend of EBNA2 (FOE) has also been characterized as a binding partner of the Epstein-Barr virus transformation-related protein EBNA2. On the other hand, recent studies have revealed that WAPL is a cohesin-binding protein and promotes sister-chromatid resolution in mitotic prophase. These data demonstrate that WAPL plays an important role in tumorigenesis and cell cycle progression. In this study, we have isolated a large number of additional alternatively spliced WAPL variants from various cervical epithelia. Each variant consists of a variable 5'-terminal region and the conserved remainder. In addition, we have confirmed the genomic organization of the 5'-region of the WAPL gene, and have investigated the characteristic features of the WAPL variants and their products. Furthermore, we have determined the HPV types of the expressed E6/E7 transcripts in the cervical epithelia with a novel PCR protocol. These results should shed light on a novel aspect of WAPL function.

Mechanisms of sister chromatid pairing

The continuance of life through cell division requires high fidelity DNA replication and chromosome segregation. During DNA replication, each parental chromosome is duplicated exactly and one time only. At the same time, the resulting chromosomes (called sister chromatids) become tightly paired along their length. This S-phase pairing, or cohesion, identifies chromatids as sisters over time. During mitosis in most eukaryotes, sister chromatids bi-orient to the mitotic spindle. After each chromosome pair is properly oriented, the cohesion established during S phase is inactivated in a tightly regulated fashion, allowing sister chromatids to segregate away from each other. Recent findings of cohesin structure and enzymology provide new insights into cohesion, while many critical facets of cohesion (how cohesins tether together sister chromatids and how those tethers are established) remain actively debated.

Immunization of mice with plasmids coexpressing HPV16 E5 and the novel oncogene hWAPL

The novel human oncogene hWAPL is associated with uterine cervical cancer. The HPV16 E5 oncoprotein could induce genomic instability in normal human cells. However, the mechanism of E5 interaction with hWAPL still awaits definition. In our present studies, the eukaryotic expression plasmids, pcDNA3-hWAPL and pcDNA3-hWAPL-E5 were constructed and carried out to vaccinate mice directly. The result that indicated the polyclonal antibody titer in immunized mice sera was increased by enzyme-linked immunosorbent assay. In addition, the proliferative responses of immunized mice spleen cells showed the optical densities values in vaccinated group remarkably higher than that in the control group. In conclusion, the recombinant plasmids could induce strong humoral and cellular immune response and exhibited great potential as therapeutic targets in the treatment of cervical cancer. However, the result didn't show significant difference in group with coexpression of HPV16 E5-hWAPL and group with only hWAPL expression. Consistent with these observations, we demonstrated that HPV16 E5 was not the optimal factor to cooperate with hWAPL in gene therapy.

Correlation between liver metastasis of the colocalization of actin-related protein 2 and 3 complex and WAVE2 in colorectal carcinoma

Directed movement of normal cells occurs when actin-related protein 2 and 3 complex (Arp2/3 complex) triggers the actin polymerization that forms lamellipodia immediately after binding to WAVE2. In order to determine whether the same mechanism correlates with liver metastasis from colorectal cancer, paired mirror sections of 154 cancer specimens (29 cases with liver metastasis and 125 cases without liver metastasis in which T factor, gender, primary tumor site, and age at operation were matched) were examined immunohistochemically for the localization of Arp2 and WAVE2. Expression of both Arp2 and WAVE2 was detected in the same cancer cells in 55 (35.7%) of the 154 cases, but not detected in the normal colonic epithelial cells. Univariate analysis showed that the colocalization was significantly predictive of liver metastasis (risk ratio [RR] 8.760. Likewise, histological grade (RR 2.46), lymphatic invasion (RR 9.95), and tumor budding (RR 4.00) were significant predictors. Among these, colocalization and lymphatic invasion were shown to be independent risk factors by multivariate analysis. Another 59 colorectal specimens were examined for mRNA expression of Arp2 by real time polymerase chain reaction. High mRNA levels of Arp2, that in situ hybridization revealed to be expressed by the cancer cells, were significantly associated with liver metastasis. However, its effect was absorbed by the influence of risk of the colocalization that is closely related to high expression of Arp2. These results indicate that the colocalization of Arp2 and WAVE2 is an independent risk factor for liver metastasis of colorectal carcinoma.

Unscheduled overexpression of human WAPL promotes chromosomal instability

Previously, we have isolated and characterized a novel human gene termed human WAPL that has the characteristics of an oncogene in uterine cervical cancer. WAPL is inducible by human papillomavirus (HPV) E6 and E7 oncoproteins. On the other hand, recent studies have revealed that WAPL regulates sister chromatid resolution by controlling the association of cohesin and chromatin. However, the effects of WAPL overexpression on cervical carcinogenesis are still unclear. Here, we show that WAPL overexpression induces generation of multinucleated cells. In addition, WAPL-overexpressing cells demonstrated increases in chromatid breaks in comparison with control cells. These results were obtained even in HPV-negative cell lines. High frequent premature sister separation by disregulation of cohesin may lead to these results. Thus, our study suggests that unscheduled overexpression of WAPL disturbs mitosis and cytokinesis, and contributes to tumor progression by induction of chromosomal instability (CIN).

Human Wapl is a cohesin-binding protein that promotes sister-chromatid resolution in mitotic prophase

BACKGROUND

The linkage between duplicated chromosomes (sister chromatids) is established during S phase by the action of cohesin, a multisubunit complex conserved from yeast to humans. Most cohesin dissociates from chromosome arms when the cell enters mitotic prophase, leading to the formation of metaphase chromosomes with two cytologically discernible chromatids. This process is known as sister-chromatid resolution. Although two mitotic kinases have been implicated in this process, it remains unknown exactly how the cohesin-mediated linkage is destabilized at a mechanistic level.

RESULTS

The wings apart-like (Wapl) protein was originally identified as a gene product that potentially regulates heterochromatin organization in Drosophila melanogaster. We show that the human ortholog of Wapl is a cohesin-binding protein that facilitates cohesin's timely release from chromosome arms during prophase. Depletion of Wapl from HeLa cells causes transient accumulation of prometaphase-like cells with chromosomes that display poorly resolved sister chromatids with a high level of cohesin. Reduction of cohesin relieves the Wapl-depletion phenotype, and depletion of Wapl rescues premature sister separation observed in Sgo1-depleted or Esco2-depleted cells. Conversely, overexpression of Wapl causes premature separation of sister chromatids. Wapl physically associates with cohesin in HeLa-cell nuclear extracts. Remarkably, in vitro reconstitution experiments demonstrate that Wapl forms a stoichiometric, ternary complex with two regulatory subunits of cohesin, implicating its noncatalytic function in inactivating cohesin's ability to interact with chromatin.

CONCLUSIONS

Wapl is a new regulator of sister chromatid resolution and promotes release of cohesin from chromosomes by directly interacting with its regulatory subunits.

Wapl controls the dynamic association of cohesin with chromatin

Cohesin establishes sister-chromatid cohesion from S phase until mitosis or meiosis. To allow chromosome segregation, cohesion has to be dissolved. In vertebrate cells, this process is mediated in part by the protease separase, which destroys a small amount of cohesin, but most cohesin is removed from chromosomes without proteolysis. How this is achieved is poorly understood. Here, we show that the interaction between cohesin and chromatin is controlled by Wapl, a protein implicated in heterochromatin formation and tumorigenesis. Wapl is associated with cohesin throughout the cell cycle, and its depletion blocks cohesin dissociation from chromosomes during the early stages of mitosis and prevents the resolution of sister chromatids until anaphase, which occurs after a delay. Wapl depletion also increases the residence time of cohesin on chromatin in interphase. Our data indicate that Wapl is required to unlock cohesin from a particular state in which it is stably bound to chromatin.

A wapl a day keeps the sisters apart: wapl and cohesin dynamics

Sister chromatids are held together by the cohesin complex from the time they are made until cell division. In recent articles published in Cell and Current Biology, the characterization of Wapl, a newly identified cohesin-interacting protein, suggests that a dynamic interaction between the cohesin complex and chromatin is important for normal regulation of sister chromatid cohesion.

Effects of 3-methylcholanthrene on the transcriptional activity and mRNA accumulation of the oncogene hWAPL

hWAPL is a human oncogene associated with uterine cervical cancer. Here, we demonstrate that hWAPL transcription is induced by 3-methylcholanthrene (3-MC) in the cervical carcinoma-derived cell line SiHa. hWAPL transcription was analyzed with evaluation of the mRNA and heterogeneous nuclear RNA (hnRNA) levels by quantitative real time PCR analysis. Flow cytometric analysis suggested that the alteration of hWAPL mRNA levels is independent of cell cycle profile. We also found that DMSO and some components of FBS affect hWAPL transcription. Interestingly, when the aryl hydrocarbon receptor (AhR) function was inhibited by alpha-naphthoflavone (ANF), the induction of hWAPL transcription by 3-MC was greater than that in AhR-functioning normal cells. These observations suggest that there are complex mechanisms regulating the transcription of hWAPL. Furthermore, mRNA level of a mouse homolog of hWAPL in mouse uterus was induced by 3-MC injection into the abdominal cavity. Thus, some effects from 3-MC exposure on uterus may be mediated by the unscheduled overexpression of hWAPL.

The human papillomavirus E6 and E7 inducible oncogene, hWAPL, exhibits potential as a therapeutic target

Here we show that human papillomavirus (HPV) E6 and E7 oncoproteins induce hWAPL expression. In addition, small interfering RNA (siRNA) of hWAPL suppressed the growth of tumours derived from SiHa cells in nude mice. Thus, hWAPL may be one of the effective targets of uterine cervical cancer therapy.

A dioxin sensitive gene, mammalian WAPL, is implicated in spermatogenesis

2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) is an endocrine disruptor that produces a variety of toxic effects. We have isolated a mouse homolog of the hWAPL gene, termed mouse WAPL (mWAPL), as a target of TCDD by cDNA representational difference analysis from mouse embryonic stem cells. A statistically significant increase in mWAPL expression was observed at 0.1 microM TCDD in AhR-/- mouse embryonic fibroblast cells. Interestingly, at 1 microM TCDD, mWAPL mRNA levels decreased in AhR+/+ cells, but further increased in AhR-/- cells. hWAPL and mWAPL were highly expressed only in testes among normal tissue samples, and we observed mWAPL localization in the synaptonemal complex of testicular chromosomes. In addition, mouse testes decreased the expression of mWAPL mRNA after a single intraperitoneal injection of TCDD. Thus, mammalian WAPL such as hWAPL and mWAPL may be involved in spermatogenesis and be target genes mediating the reproductive toxicity induced by TCDD.