MesP1 drives vertebrate cardiovascular differentiation through Dkk-1-mediated blockade of Wnt-signalling

ES-cell-based cardiovascular repair requires an in-depth understanding of the molecular mechanisms underlying the differentiation of cardiovascular ES cells. A candidate cardiovascular-fate inducer is the bHLH transcription factor MesP1. As one of the earliest markers, it is expressed specifically in almost all cardiovascular precursors and is required for cardiac morphogenesis. Here we show that MesP1 is a key factor sufficient to induce the formation of ectopic heart tissue in vertebrates and increase cardiovasculogenesis by ES cells. Electrophysiological analysis showed all subtypes of cardiac ES-cell differentiation. MesP1 overexpression and knockdown experiments revealed a prominent function of MesP1 in a gene regulatory cascade, causing Dkk-1-mediated blockade of canonical Wnt-signalling. Independent evidence from ChIP and in vitro DNA-binding studies, expression analysis in wild-type and MesP knockout mice, and reporter assays confirm that Dkk-1 is a direct target of MesP1. Further analysis of the regulatory networks involving MesP1 will be required to preprogramme ES cells towards a cardiovascular fate for cell therapy and cardiovascular tissue engineering. This may also provide a tool to elicit cardiac transdifferentiation in native human adult stem cells.

Diagnostics of a He(+) beam extracted from a compact magnetic bucket-type ion source

Performance of a compact He(+) ion source was investigated before installing it to the experiment system developed for studying the efficiency of autodetachment neutralization from He(-) to He(0). Dependence of the extracted ion current upon the plasma parameters and that upon the extraction voltage indicated that the source performance was limited by space charge effect. The beam emittance was measured with a multislit system for various operation conditions. The experimentally determined emittance agreed well with the emittance obtained from ion trajectories calculated with input plasma parameters measured by a Langmuir probe. The beam current density of 60 mA/cm(2) and the emittance of less than 25pi mm mrad are expected to deliver enough current to the downstream of the He(-) neutralizer system to clarify factors affecting the final He(0) intensity.

Energy straggling of low-energy ion beam in a charge exchange cell for negative ion production

Energy straggling in a charge exchange cell, which is frequently used for negative ion production, was studied experimentally and compared with the results of theoretical evaluation. The change of the energy spectrum of a He(+) beam due to charge exchange processes in argon gas was measured in the energy range of 2-6 keV. Energy straggling by multiple collisions is expressed by the energy loss formula due to inelastic and elastic processes. The impact parameter is related to the elastic scattering angle, and the geometry of the charge exchange cell and other components of the beam transportation system determines the maximum acceptable scattering angle. The energy spread was evaluated taking the integral limit over the impact parameter into consideration. The theoretical results showed good agreement with those of actual measurement.

Development of a strongly focusing high-intensity He(+) ion source for a confined alpha particle measurement at ITER

A strongly focusing high-intensity He(+) ion source has been designed and constructed as a beam source for a high-energy He(0) beam probe system for diagnosis of fusion produced alpha particles in the thermonuclear fusion plasmas. The He(+) beam was extracted from the ion source at an acceleration voltage of 18-35 kV. Temperature distributions of the beam target were observed with an IR camera. The 1/e-holding beam profile half-width was about 15 mm at optimum perveance (Perv) of 0.03 (I(beam)=2.4 A). A beam current about 3 A was achieved at an acceleration voltage of 26.7 kV with an arc power of 10 kW (Perv=0.023).

A beam transport system for an intense He(-) beam source

We have been developing a test stand for fast He(0) beam production. One of the major issues is how to transport effectively the He(+) and He(-) beams from which the He(0) beam is produced. The beam should be focused in two transverse focal points, the center of the charge exchange cell and the electrostatic accelerator. We studied the beam transport system and effect of space charge neutralization in the test stand by experiments and calculation.

Constitutive phosphorylation of aurora-a on ser51 induces its stabilization and consequent overexpression in cancer

BACKGROUND

The serine/threonine kinase Aurora-A (Aur-A) is a proto-oncoprotein overexpressed in a wide range of human cancers. Overexpression of Aur-A is thought to be caused by gene amplification or mRNA overexpression. However, recent evidence revealed that the discrepancies between amplification of Aur-A and overexpression rates of Aur-A mRNA were observed in breast cancer, gastric cancer, hepatocellular carcinoma, and ovarian cancer. We found that aggressive head and neck cancers exhibited overexpression and stabilization of Aur-A protein without gene amplification or mRNA overexpression. Here we tested the hypothesis that aberration of the protein destruction system induces accumulation and consequently overexpression of Aur-A in cancer.

PRINCIPAL FINDINGS

Aur-A protein was ubiquitinylated by APC(Cdh1) and consequently degraded when cells exited mitosis, and phosphorylation of Aur-A on Ser51 was observed during mitosis. Phosphorylation of Aur-A on Ser51 inhibited its APC(Cdh1)-mediated ubiquitylation and consequent degradation. Interestingly, constitutive phosphorylation on Ser51 was observed in head and neck cancer cells with protein overexpression and stabilization. Indeed, phosphorylation on Ser51 was observed in head and neck cancer tissues with Aur-A protein overexpression. Moreover, an Aur-A Ser51 phospho-mimetic mutant displayed stabilization of protein during cell cycle progression and enhanced ability to cell transformation.

CONCLUSIONS/SIGNIFICANCE

Broadly, this study identifies a new mode of Aur-A overexpression in cancer through phosphorylation-dependent inhibition of its proteolysis in addition to gene amplification and mRNA overexpression. We suggest that the inhibition of Aur-A phosphorylation can represent a novel way to decrease Aur-A levels in cancer therapy.

Induction of apoptosis and cellular senescence in mice lacking transcription elongation factor, Elongin A

Elongin A is a transcription elongation factor that increases the overall rate of mRNA chain elongation by RNA polymerase II. To gain more insight into the physiological functions of Elongin A, we generated Elongin A-deficient mice. Elongin A homozygous mutant (Elongin A(-/-)) embryos demonstrated a severely retarded development and died at between days 10.5 and 12.5 of gestation, most likely due to extensive apoptosis. Moreover, mouse embryonic fibroblasts (MEFs) derived from Elongin A(-/-) embryos exhibited not only increased apoptosis but also senescence-like growth defects accompanied by the activation of p38 MAPK and p53. Knockdown of Elongin A in MEFs by RNA interference also dramatically induced the senescent phenotype. A study using inhibitors of p38 MAPK and p53 and the generation of Elongin A-deficient mice with p53-null background suggests that both the p38 MAPK and p53 pathways are responsible for the induction of senescence-like phenotypes, whereas additional signaling pathways appear to be involved in the mediation of apoptosis in Elongin A(-/-) cells. Taken together, our results suggest that Elongin A is required for the transcription of genes essential for early embryonic development and downregulation of its activity is tightly associated with cellular senescence.

Establishment and characterization of a spindle cell squamous carcinoma cell line

BACKGROUND

Spindle cell squamous carcinoma (SCSC) is a rare and peculiar biphasic malignant neoplasm that occurs mainly in the upper aerodigestive tract. It consists of sarcomatoid proliferation of pleomorphic spindle-shaped cells and squamous cell carcinoma.

METHODS

Here, we established a SCSC cell line from a tumour arisen in gingiva. We characterized the feature of a SCSC cell line by immunohistochemistry. To know the biological feature, we examined the cell growth, invasiveness and epithelial-mesenchymal transition markers of a SCSC cell line in comparison with oral squamous cell carcinoma (OSCC) cell lines.

RESULTS

By immunohistochemical analyses, the primary tumour expressed cytokeratin and vimentin, indicating carcinosarcoma-like characters. This tumour also showed overexpression of p53 protein. Cultured SCSC cells resulted in bypass of crisis and maintenance over passage 100. The established SCSC cell line was spindle-shaped and showed identical immunohistochemical characters to those of primary tumour cells. Similar to the primary tumour, the cell line showed p53 overexpression and had p53 mutation at codon 132: AAG (lys)-->AAT (asp). The SCSC cell line grew slower than two other OSCC cell lines (MSCC-1 and HSC-2), whereas SCSC cells had remarkable invasiveness in comparison with these cell lines. Moreover, SCSC cells expressed wnt-5a and vimentin mRNA at high levels, but did not express E-cadherin mRNA. This expression pattern of the markers was similar to that of mesenchymal cells, not of epithelial cells.

CONCLUSION

In the present study, we newly established a SCSC cell line with strong invasiveness. This is the first report on the establishment of SCSC cell line. The SCSC cell line can be a useful cell model for the study to know the cytodifferentiation and nature of SCSC.

Periostin is frequently overexpressed and enhances invasion and angiogenesis in oral cancer

Oral squamous-cell carcinoma (OSCC) is one of the most common types of human cancer. Typically OSCC cells show persistent invasion that frequently leads to local recurrence and distant lymphatic metastasis. We previously identified Periostin as the gene demonstrating the highest fold change expression in the invasive clone by comparing the transcriptional profile of parent OSCC cell line and a highly invasive clone. Here, we demonstrated that Periostin overexpression enhanced invasiveness in oral cancer cell lines. To know the role of Periostin in invasion, angiogenesis and metastasis in OSCC cases, we first examined the expression of Periostin mRNA in 31 OSCC cases by RT-PCR and Periostin protein in 74 OSCC cases by immunohistochemistry. Then, we compared the Periostin expression with invasion pattern, metastasis and blood vessel density. Periostin mRNA and protein overexpression were frequently found in OSCC cases and Periostin expression was well correlated with the invasion pattern and metastasis. Moreover, blood vessel density of Periostin-positive cases was higher than those of Periostin-negative cases. Interestingly, recombinant Periostin enhanced capillary formation in vitro in a concentration-dependant manner. In summary, these findings suggest that Periostin may promote invasion and angiogenesis in OSCC, and that Periostin can be a strong marker for prediction of metastasis in oral cancer patients.

Periostin promotes invasion and anchorage-independent growth in the metastatic process of head and neck cancer

Head and neck squamous cell carcinoma (HNSCC) is one of the most common types of human cancer. Typically, HNSCC cells show persistent invasion that frequently leads to local recurrence and distant lymphatic metastasis. However, molecular mechanisms associated with the invasion and metastasis of HNSCC remain poorly understood. Here, we identified periostin as an invasion-promoting factor in HNSCC by comparing the gene expression profiles between parent HNSCC cells and a highly invasive clone. Indeed, periostin overexpression promoted invasion and anchorage-independent growth both in vitro and in vivo in HNSCC cells. Moreover, periostin-overexpressing cells spontaneously metastasized to cervical lymph nodes and to the lung through their aggressive invasiveness in an orthotopic mouse model of HNSCC. Interestingly, periostin was highly expressed in HNSCCs in comparison with normal tissues, and the level of periostin expression was well correlated with the invasiveness of HNSCC cases. In summary, these findings suggest that periostin plays an important role in the invasion and anchorage-independent growth of HNSCC.

Aurora-B/AIM-1 kinase activity is involved in Ras-mediated cell transformation

Aurora-B, previously known as AIM-1, is a conserved eukaryotic mitotic protein kinase. In mammals, this kinase plays an essential role in chromosomal segregation processes, including chromosome condensation, alignment, control of spindle checkpoints, chromosome segregation, and cytokinesis. Aurora-B is overexpressed in various cancer cells, suggesting that the kinase activity perturbs chromosomal segregation processes. Its forced overexpression induces chromosomal number instability and progressive tumorigenicity in rodent cells in vitro and in vivo. Nevertheless, based on focus formation in BALB/c 3T3 A31-1-1 cells, Aurora-B is not oncogenic. Here, we show that Aurora-B kinase activity augments Ras-mediated cell transformation. RNA interference with short hairpin RNA inhibits transformation by Ras and its upstream oncogene Src, but not by the downstream oncogene Raf. In addition, the inner centromere protein, which is a passenger protein associated with Aurora-B, has a similar ability to potentiate the activity of oncogenic Ras. These data indicate that elevated Aurora-B activity promotes transformation by oncogenic Ras by enhancing oncogenic signaling and by converting chromosome number-stable cells to aneuploid cells.

Down-regulation of Cdk inhibitor p27 in oral squamous cell carcinoma

Oral squamous cell carcinoma (OSCC) is the most frequent malignant neoplasm of the head and neck region. Conversion of normal cells to cancer cells is achieved through a multi-step process that is closely associated with the accumulation of multiple gene changes including both oncogenes and tumour suppressor genes. The proliferation and progression of cancer may be caused by abnormalities of various positive and negative cell cycle regulators. Cell cycle progression is positively regulated by multiple cyclins and cyclin-dependent kinases (Cdks) and cyclin/Cdk complexes are negatively regulated by a number of Cdk inhibitors including p27. p27 is a Cdk inhibitor and plays an important role in negative regulation of the cell cycle during G0 and G1 phases. Degradation of p27 is a critical event for the G1/S transition and occurs through ubiquitination by SCF(Skp2) and subsequent degradation by the 26S proteasome. It has been revealed that down-regulation of p27 is frequently found in various cancers, including OSCC, and is due to an enhancement of its degradation. Importantly, down-regulation of p27 is well associated with its malignancy including poor prognosis in various cancers. Moreover, aggressive human cancers express low levels of p27 because of its decreased stability. More recent evidence suggests that Skp2 and Cks1, the specific recognition factors for p27 ubiquitination, have oncogenic properties. This review will focus on down-regulation of p27 and mechanism of its down-regulation in OSCC.

Small interfering RNA targeting of S phase kinase–interacting protein 2 inhibits cell growth of oral cancer cells by inhibiting p27 degradation

S phase kinase-interacting protein 2 (Skp2), an F box protein, is required for the ubiquitination and consequent degradation of p27. It is well known that reduced expression of p27 is frequently observed in various cancers including oral squamous cell carcinoma and is due to an enhancement of its protein degradation. Our previous study showed that overexpression of Skp2 was frequently found in oral squamous cell carcinoma and inversely correlated with p27 expression. Recently, a technique known as RNA interference has been successfully adapted to mammalian cells. In the present study, we investigated if small interfering RNA (siRNA)-mediated gene silencing of Skp2 can be employed in order to inhibit p27 down-regulation in oral squamous cell carcinoma. We used a siRNA plasmid vector, which has an advantage over synthetic siRNAs in determining the effects of decreasing the high constitutive levels of Skp2 protein in oral squamous cell carcinoma. We showed that Skp2 siRNA transfection decreased Skp2 protein and induced the accumulation of p27 protein in oral squamous cell carcinoma cells. Moreover, p27 protein in Skp2 siRNA-transfected cells is more stabilized than that in control siRNA-transfected cells. Interestingly, Skp2 siRNA inhibited the cell proliferation of oral squamous cell carcinoma cells both in vitro and in vivo. Our findings suggest that siRNA-mediated gene silencing of Skp2 can be a novel modality of cancer gene therapy for suppression of p27 down-regulation.

Elevated macrophage migration inhibitory factor (MIF) levels in the urine of patients with focal glomerular sclerosis

The pathogenesis of focal glomerular sclerosis (FGS) is poorly understood. Macrophage migration inhibitory factor (MIF) is a potent pro-inflammatory cytokine released from T cells and macrophages, and is a key molecule in inflammation. To examine further the possible role of MIF in FGS, we measured MIF levels in the urine. The purpose of the present study was to evaluate the involvement of MIF in FGS. Urine samples were obtained from 20 FGS patients. The disease controls included 40 patients with minimal-change nephrotic syndrome (MCNS) and membranous nephropathy (MN). A group of healthy subjects also served as controls. Biopsies were performed in all patients prior to entry to the study. The samples were assayed for MIF protein by a sandwich enzyme-linked immunosorbent assay (ELISA). The levels of MIF in the urine of FGS patients were significantly higher than those of the normal controls and patients with MCNS and MN. In contrast, the levels of urinary MIF (uMIF) in patients with MCNS and MN did not differ significantly from normal values. In the present study, attention also focused on the relationship between uMIF levels and pathological features. Among the patients with FGS, uMIF levels were significantly correlated with the grade of mesangial matrix increase and that of interstitial fibrosis. There was also a significant correlation between uMIF levels and the number of both intraglomerular and interstitial macrophages. Although the underlying mechanisms remain to be determined, our study presents evidence that urinary excretion of MIF is increased in FGS patients with active renal lesions.

Overexpression of Aurora-A potentiates HRAS-mediated oncogenic transformation and is implicated in oral carcinogenesis

Aurora kinases are known to play a key role in maintaining mitotic fidelity, and overexpression of aurora kinases has been noted in various tumors. Overexpression of aurora kinase activity is thought to promote cancer development through a loss of centrosome or chromosome number integrity. Here we observed augmentation of G12V-mutated HRAS-induced neoplastic transformation in BALB/c 3T3 A31-1-1 cells transfected with Aurora-A. Aurora-A-short hairpin RNA (shRNA) experiments showed that the expression level of Aurora-A determines susceptibility to transformation. Aurora-A gene amplification was noted in human patients with tongue or gingival squamous carcinoma (4/11). Amplification was observed even in pathologically normal epithelial tissue taken at sites distant from the tumors in two patients with tongue cancer. However, overexpression of Aurora-A mRNA was observed only within the tumors of all patients examined (11/11). Our data indicate that Aurora-A gene amplification and overexpression play a role in human carcinogenesis, largely due to the effect of Aurora-A on oncogenic cell growth, rather than a loss of maintenance of centrosomal or chromosomal integrity.

Invasion and metastasis of oral cancer cells require methylation of E-cadherin and/or degradation of membranous beta-catenin

The extent of lymph node metastasis is a major determinant in the prognosis of oral squamous cell carcinoma (OSCC). Abnormalities of cell adhesion molecules are known to play an important role in invasion and metastasis of cancer cells through the loss of cell-to-cell adhesion. In this study, we isolated highly invasive clones from an OSCC cell line established from a lymph node metastasis by using an in vitro invasion assay method and compared the abnormalities of cell adhesion molecule E-cadherin and beta-catenin in these cells. The isolated, highly invasive clones showed significant invasive capacity and reduction of E-cadherin and membranous beta-catenin protein in comparison with parent cells. We found that reduced expression of E-cadherin was due to methylation of its promoter region. In fact, most invasive and metastatic area of OSCCs showed reduced expression and methylation of E-cadherin. Moreover, we found that reduced expression of membranous beta-catenin was due to its protein degradation. Reduced expression of membranous beta-catenin was also found frequently in invasive and metastatic areas of OSCCs. In summary, invasion and metastasis of OSCC cells require methylation of E-cadherin and/or degradation of membranous beta-catenin. In addition, we suggest that the method of isolation of highly invasive clones may be useful for studies aimed at discovering novel genes involved in invasion and metastasis.

Role of Cks1 overexpression in oral squamous cell carcinomas: cooperation with Skp2 in promoting p27 degradation

Down-regulation of p27 is frequently observed in various cancers due to an enhancement of its degradation. Skp2 is required for the ubiquitination and consequent degradation of p27 protein. Another protein called Cks1 is also required for p27 ubiquitination in the SCF(Skp2) ubiquitinating machinery. In the present study, we examined Cks1 expression and its correlation with p27 in oral squamous cell carcinoma (OSCC) derived from tongue and gingiva. By immunohistochemical analysis, high expression of Cks1 was present in 62% of OSCCs in comparison with 0% of normal mucosae. In addition, 65% of samples with low p27 expression displayed high Cks1 levels. Finally, Cks1 expression was well correlated with Skp2 expression and poor prognosis. To study the role of Cks1 overexpression in p27 down-regulation, we transfected Cks1 with or without Skp2 into OSCC cells. Cks1 transfection could not induce a p27 down-regulation by itself, but both Cks1 and Skp2 transfection strongly induced. Moreover, we inhibited Cks1 expression by small interference RNA (siRNA) in OSCC. Cks1 siRNA transfection induced p27 accumulation and inhibited the growth of OSCC cells. These findings suggest that Cks1 overexpression may play an important role for OSCC development through Skp2-mediated p27 degradation, and that Cks1 siRNA can be a novel modality of gene therapy.

Ruptured aneurysm at a duplicated middle cerebral artery with accessory middle cerebral artery

Although many cerebral vascular anomalies are widely recognized, others are less well known or unclassified. Accessory middle cerebral artery (MCA) and duplicated MCA are among uncommon anomalies. We present a very rare case of subarachnoid haemorrhage due to rupture of a saccular aneurysm arising from a duplicated middle cerebral artery which was associated with an accessory middle cerebral artery.