Miki Hashimura

Requirement of the Akt/β-Catenin Pathway for Uterine Carcinosarcoma Genesis, Modulating E-Cadherin Expression Through the Transactivation of Slug

Uterine carcinosarcomas (UCSs) are considered to represent true examples of the epithelial-mesenchymal transition. Akt plays a key role in the induction of epithelial-mesenchymal transition, but little is known about its involvement in tumorigenesis. Here we examined the functional roles of the Akt/beta-catenin pathway in UCSs. In clinical samples, phospho-Akt (pAkt) expression was found to be significantly increased in mesenchymal compared with epithelial components, exhibiting both positive and negative correlations with nuclear beta-catenin and E-cadherin, respectively. Expression levels of the transcription factor Slug were also significantly up-regulated in the mesenchymal components and strongly correlated with both pAkt and nuclear beta-catenin. In endometrial cancer cell lines, active Akt induced the stabilization of nuclear beta-catenin through the phosphorylation of GSK-3beta, and this, in turn, led to the transactivation of Slug, which was mediated by nuclear beta-catenin. Moreover, Slug overexpression itself caused repression of E-cadherin, with subtle changes in cell morphology. In addition, knockdown of the retinoblastoma gene product (Rb) up-regulated pAkt and repressed E-cadherin, consistent with the in vivo finding of significantly decreased Rb expression in mesenchymal components. These findings suggest that changes in the Akt/beta-catenin pathway, as well as alterations in Rb expression, may be essential for both the establishment and maintenance of phenotypic characteristics of UCSs, playing key roles in the regulation of E-cadherin through the transactivation of the Slug gene.

The possible role of bcl-2 expression in the progression of tumors of the uterine cervix.

Background. A close link between human papillomavirus (HPV) and the development of uterine cervical neoplasias has been proposed. However, other cofactors also are required for malignant transformation.

β-Catenin Simultaneously Induces Activation of the p53-p21WAF1 Pathway and Overexpression of Cyclin D1 during Squamous Differentiation of Endometrial Carcinoma Cells

The functional consequences of up-regulation of β-catenin as a transcription factor are complex in different tumors. To clarify roles during squamous differentiation (SqD) of endometrial carcinoma (Em Ca) cells, we investigated expression of β-catenin, as well as cyclin D1, p53, p21WAF1, and PML (promyelocytic leukemia) in 80 cases of Em Ca with SqD areas, in comparison with cell proliferation determined with reference to Ki-67 antigen positivity. The impact of β-catenin-T-cell factor (TCF)-mediated transcription was also examined using Em Ca cells. In clinical cases, nuclear β-catenin accumulation was more frequent in SqD areas, being positively linked with expression of cyclin D1, p53, and p21WAF1, and inversely with Ki-67 and PML immunoreactivity. Significant correlations of nuclear β-catenin, cyclin D1, p53, and p21WAF1 were noted between SqD and the surrounding carcinoma lesions. The Ishikawa cell line, with stable or tetracycline-regulated expression of mutant β-catenin, showed an increase in expression levels of cyclin D1, p14ARF, p53, and p21WAF1 but not PML, and activation of β-catenin-TCF4-mediated transcription determined with TOP/FOP constructs. The cell morphology was senescence-like rather than squamoid in appearance. Moreover, overexpressed β-catenin could activate transcription from p14ARF and cyclin D1 promoters, in a TCF4-dependent manner. These findings indicate that in Em Cas, nuclear β-catenin can simultaneously induce activation of the p53-p21WAF1 pathway and overexpression of cyclin D1, leading to suppression of cell proliferation or induction of cell senescence. However, overexpression of β-catenin alone is not sufficient for development of a squamoid phenotype in Em Ca cells, suggesting that nuclear accumulation is an initial signal for trans-differentiation.

HPV type 16 in conjunctival and junctional papilloma, dysplasia, and squamous cell carcinoma.

AIMS--To clarify the role of human papillomavirus (HPV) infection in the development of papilloma, dysplasia, squamous cell carcinoma, and basal cell epithelioma arising from the eyelids, including the tunica conjunctiva palpebrum (conjunctiva), its junction to epidemis of eyelid skin (junction), and eyelid skin. METHODS--Sixteen cases of papilloma, four of dysplasia, four of squamous cell carcinoma, and 12 of basal cell epithelioma were examined using formalin fixed and paraffin embedded samples. Detection of HPV-DNA was performed by PCR-RFLP and in situ hybridisation (ISH) methods. RESULTS--HPV-16 was detected in 12/16 papillomas (75%), 2/4 dysplasias (50%), and 1/4 squamous cell carcinomas (25%) but in none of the basal cell epitheliomas. No other HPV subtypes were found. ISH assay showed positive signals in only two cases of dysplasia and squamous cell carcinoma. The mean age of HPV-16 positive dysplasia and squamous cell carcinoma cases (81.7 years) was significantly higher than that of HPV-16 positive papilloma cases (p < 0.01). CONCLUSIONS--Based on the presence of HPV-16 in both benign and malignant lesions and the age distribution, it seems likely that HPV-16 alone may be incapable of causing development of conjunctival and junctional dysplasia and squamous cell carcinoma, and that any correlation between the papilloma-squamous cell carcinoma sequence and HPV infection may be due to rare events.

CD44 expression in normal, hyperplastic, and malignant endometrium

A total of 140 endometrial carcinomas (endometrioid type), as well as 72 hyperplasias (41 of simple or complex and 31 of atypical type) and 141 normal endometria (35 in the proliferative and 106 in the secretory phase), were immunohistochemically investigated for expression of the standard and variant‐3 and ‐6 isoforms of CD44, and the results compared with several known prognostic factors. A combination of the reverse transcription‐polymerase chain reaction (RT‐PCR) and Southern blot hybridization (SBH) for CD44 mRNA levels was also carried out on 27 endometrial carcinomas. In normal endometrium, the expression of standard and variant CD44 forms was remarkably higher in the secretory than in the proliferative phase, with immunoreactivity scores being inversely correlated with numbers of oestrogen and progesterone receptors. Significantly elevated levels of CD44 expression in endometrial carcinomas compared with the proliferative phase and hyperplasia were also revealed by both the immunohistochemical and the RT‐PCR/SBH assays, while no association was noted with any prognostic factors. The results indicate that CD44 expression in the normal menstrual cycle is closely related to the secretory differentiation of the glandular epithelium. Moreover, detection of aberrant expression may be useful for the early diagnosis of endometrial carcinoma, but not as an indicator of tumour progression.

Upregulation of TCF4 expression as a transcriptional target of β -catenin/p300 complexes during trans -differentiation of endometrial carcinoma cells

Nuclear stabilization of β-catenin and its interaction with TCF/LEF factors are key events in transduction of the Wnt/β-catenin signal pathway. Our previous study indicated that nuclear β-catenin accumulation provides an initial signal for trans-differentiation toward the squamoid phenotype of endometrial carcinoma (Em Ca) cells in a TCF4-dependent manner, which makes this a possible factor for a positive prognosis. However, little is known about regulation of TCF4 expression in Em Cas. We show here that β-catenin can directly induce transcription from the TCF4 promoter, the effect being enhanced by the p300 coactivator. In clinical cases, nuclear β-catenin accumulation was found to frequently overlap with TCF4 immunoreactivity in morules and surrounding glandular carcinoma lesions, showing a significant positive correlation (r=0.82, P<0.0001), in contrast to areas of squamous metaplasia (SqM) within Em Cas. In cases with coexistence of two squamoid features in trans-differentiated areas, loss of nuclear β-catenin and TCF4 immunoreactivity was closely related to change in the morphology from the morular to the SqM phenotype. The TCF4 promoter contains a single consensus TCF-binding site that is critical for activation by β-catenin. The p300 coactivator, in particular N-terminal residues 1 to 670, appears sufficient to enhance β-catenin-dependent transcription, again with TCF4-dependence. These findings indicate that a positive feedback loop of TCF4 expression mediated by β-catenin/p300 may be important for initial steps during trans-differentiation of Em Ca cells. In addition, its downregulation is associated with induction of a more-differentiated squamoid phenotype.

Crosstalk between NF‐κB/p65 and β‐catenin/TCF4/p300 signalling pathways through alterations in GSK‐3β expression during trans‐differentiation of endometrial carcinoma cells

β‐Catenin/TCF4/p300 signalling loops play an important role in trans‐differentiation towards the morular phenotype of endometrial carcinomas. Crosstalk between NF‐κB and β‐catenin pathways has been proposed and we focused here on associations between these two pathways during trans‐differentiation. In normal endometrium, nuclear phosphorylated p65 (pp65), the active form NF‐κB subunit, was found to be significantly increased in the secretory phase, correlating positively with vimentin and E‐cadherin and inversely with Snail mRNA expression. On transfection of p65, vimentin, E‐cadherin, and Snail were transcriptionally altered, indicating possible roles in establishment and maintenance of the secretory phenotype. In endometrial carcinomas with morules, levels of nuclear pp65, Snail mRNA, vimentin, and cytoplasmic TNF‐α were reduced during trans‐differentiation, correlating inversely with nuclear β‐catenin. Nuclear accumulation of GSK‐3β, along with β‐catenin, was observed in morules. In cell lines, overexpression of p65 inhibited β‐catenin/TCF4‐mediated transcription, while transfection of GSK‐3β resulted in repression of TNF‐α‐induced NF‐κB activity. Moreover, nuclear GSK‐3β was increased by overexpression of β‐catenin, as well as induction of G1‐cell cycle arrest. These findings provide evidence that a shift from NF‐κB to β‐catenin signalling pathways through alterations in GSK‐3β expression may be essential for the induction of trans‐differentiation of endometrial carcinoma cells, leading to a shut‐down of mesenchymal markers. Copyright

Down-regulation of CD44 standard and variant isoforms during the development and progression of uterine cervical tumours.

To clarify the possible role of CD44 in the development or progression of uterine cervical tumours, an immunohistochemical investigation was carried out on 125 cases of cervical intraepithelial neoplasia (CIN), 78 invasive squamous cell carcinomas (ISCC), 61 cervical adenocarcinomas (AC), nine adenosquamous carcinomas (ASq), and 15 carcinomas with co‐existent SCC and AC components, as well as 87 samples of normal cervix. A combination of reverse transcription‐polymerase chain reaction (RT‐PCR) and Southern blot hybridization (SBH) was also applied to 16 cervical carcinomas and 24 normal cervical specimens. Immunoreactivity for CD44s, CD44v3, and CD44v6 did not alter during the progression of CIN, while significantly decreased expression was observed in ISCC, associated with invasive features in some tumours. Reduced levels of CD44 expression in AC were also found, compared with normal cervical glandular epithelia. The average immunoreactivity scores for CD44s, CD44v3, and CD44v6 were significantly higher in ISCC than in AC, in line with the RT‐PCR/SBH assay results. However, CD44 scores did not correlate with any clinicopathological factors or with survival in ISCC or AC. The ASq and AC CD44 scores were similar, while staining patterns in mixed tumours were dependent on the morphological phenotype, suggesting a close association between CD44 expression and the cell types. The results suggest that whereas CD44 is down‐regulated during cervical tumourigenesis, positivity may not be useful as a consistent prognostic indicator. Copyright

CD44 expression in benign, premalignant, and malignant ovarian neoplasms: relation to tumour development and progression

To clarify the possible role of CD44 expression in ovarian tumour development and progression, an immunohistochemical investigation was undertaken of a series of 115 carcinomas, 32 tumours with low malignant potential (LMP), and 53 cystadenomas. A combination of the reverse transcription‐polymerase chain reaction (RT‐PCR) and Southern blot hybridization (SBH) assays was also performed for 17 malignant, four LMP, six cystadenoma, and seven normal ovarian samples. Immunoreactivity scores for CD44s, CD44v3, and CD44v6 were significantly higher in LMP and malignant tumours than in the benign or normal cases, in line with the results of gross mRNA‐based assays. Exon‐specific RT‐PCR/SBH assays revealed that the expression of large CD44 transcripts containing v6 to v8 exons and small isoforms containing v2 and v3 was common among normal and neoplastic tissues, while a simultaneous increase of large isoforms containing v2 to v5 was also revealed in LMP and malignant tumours. In ovarian carcinomas, the scores for CD44s, CD44v3, and CD44v6 were inversely related to the FIGO stage, but there was no association with lymph node status or expression of hormone receptors. Multivariate analysis revealed loss of CD44v3 expression to be an independent factor for poor survival. The findings indicate that CD44 is up‐regulated during the development of ovarian carcinomas but is subsequently down‐regulated during their progression, resulting in aggressive behaviour and an unfavourable prognosis. Copyright

Sox4 functions as a positive regulator of β -catenin signaling through upregulation of TCF4 during morular differentiation of endometrial carcinomas

Sox factors function as either activators or repressors of β-catenin/TCF transcription depending on the cellular context and associated interacting proteins. Our previous study provided evidence that alteration in β-catenin signaling is an essential event during transdifferentiation toward the morular phenotype of endometrial carcinomas (Em Cas). Here, we focused on related functional roles of Sox factors. Of eight Sox factors investigated, Sox4 could enhance β-catenin/TCF4 transcription, through upregulation of TCF4 at the transcription level, without any direct β-catenin association. Cells stably overexpressing Sox4 showed significant decreases in proliferation rate, along with increases in expression of p21WAF1, as well as TCF4, in contrast to increased cell growth observed with knockdown. Of these factors, only Sox7 could transcriptionally upregulate Sox4 expression, but it also resulted in not only inhibition of Sox4-meditated activation of β-catenin/TCF4-driven transcription, but also repression of its own promoter activity, indicating the existence of very complex feedback loop for Sox-mediated signal cascades. Finally, Sox4 immunoreactivity was frequently pronounced in morular lesions of Em Cas, the expression being positively correlated with status of β-catenin, TCF4, and Sox7, and inversely with cell proliferation. These data therefore suggest that Sox4 may serve as a positive regulator of β-catenin signaling through alteration in TCF4 expression during morular differentiation of Em Ca cells, leading to inhibition of cell proliferation. In addition, Sox7 may also participate in the process, having complex roles in modulation of signaling.