Yasusei Kudo

Control of Meiotic and Mitotic Progression by the F Box Protein β-Trcp1 In Vivo

SCF ubiquitin ligases, composed of three major subunits, Skp1, Cul1, and one of many F box proteins (Fbps), control the proteolysis of important cellular regulators. We have inactivated the gene encoding the Fbp beta-Trcp1 in mice. beta-Trcp1(-/-) males show reduced fertility correlating with an accumulation of methaphase I spermatocytes. beta-Trcp1(-/-) MEFs display a lengthened mitosis, centrosome overduplication, multipolar metaphase spindles, and misaligned chromosomes. Furthermore, cyclin A, cyclin B, and Emi1, an inhibitor of the anaphase promoting complex, are stabilized in mitotic beta-Trcp1(-/-) MEFs. Indeed, we demonstrate that Emi1 is a bona fide substrate of beta-Trcp1. In contrast, stabilization of beta-catenin and IkappaBalpha, two previously reported beta-Trcp1 substrates, does not occur in the absence of beta-Trcp1 and instead requires the additional silencing of beta-Trcp2 by siRNA. Thus, beta-Trcp1 regulates the timely order of meiotic and mitotic events.

miR-22 represses cancer progression by inducing cellular senescence

The microRNA miR-22 targets CDK6, SIRT1, and Sp1—genes involved in regulation of the senescence program—to suppress cell growth and proliferation.

Invasion and Metastasis of Oral Cancer Cells Require Methylation of E-Cadherin and/or Degradation of Membranous β-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 β-catenin in these cells. The isolated, highly invasive clones showed significant invasive capacity and reduction of E-cadherin and membranous β-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 β-catenin was due to its protein degradation. Reduced expression of membranous β-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 β-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.

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.

The role of periostin in tissue remodeling across health and disease

Periostin, also termed osteoblast-specific factor 2, is a matricellular protein with known functions in osteology, tissue repair, oncology, cardiovascular and respiratory systems, and in various inflammatory settings. However, most of the research to date has been conducted in divergent and circumscribed areas meaning that the overall understanding of this intriguing molecule remains fragmented. Here, we integrate the available evidence on periostin expression, its normal role in development, and whether it plays a similar function during pathologic repair, regeneration, and disease in order to bring together the different research fields in which periostin investigations are ongoing. In spite of the seemingly disparate roles of periostin in health and disease, tissue remodeling as a response to insult/injury is emerging as a common functional denominator of this matricellular molecule. Periostin is transiently upregulated during cell fate changes, either physiologic or pathologic. Combining observations from various conditions, a common pattern of events can be suggested, including periostin localization during development, insult and injury, epithelial–mesenchymal transition, extracellular matrix restructuring, and remodeling. We propose mesenchymal remodeling as an overarching role for the matricellular protein periostin, across physiology and disease. Periostin may be seen as an important structural mediator, balancing appropriate versus inappropriate tissue adaption in response to insult/injury.

Reduced expression of cyclin-dependent kinase inhibitor p27Kip1 is associated with advanced stage and invasiveness of gastric carcinomas

Reduced expression of a cyclin–dependent kinase inhibitor p27Kipl has recently been shown to predict poor survival of patients with breast and colorectal cancers. We studied the expression of p27Kipl in gastric carcinomas by northern blotting, western blotting and immunohistochemistry to determine whether lack of p27 has implications for aggressiveness of gastric cancer. Reduced expression of p27 was detected in 40% of the gastric carcinomas at the mRNA level, while it was detected in 57% at the protein level. No gross alterations of the p27 gene were observed in any of the cases examined by Southern blot analysis. Inimunohistochemical studies revealed that the expression of p27 was well preserved in most of the gastric adenomas, whereas it was so in only 26% of the gastric carcinomas. Fifty–six percent of the carcinomas showed almost no p27–positive cells. Decrease of p27–positive cells significantly correlated with advanced stage, depth of tumor invasion and lymph node metastasis. The expression of p27 showed an inverse correlation with the expression of cyclin E. These findings suggest that reduction of p27Klpl protein may reflect the progression of gastric carcinomas and may be an indicator of high–grade malignancy.

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.

Peripheral ameloblastoma: biological profile based on 160 cases from the literature

The present profile of the peripheral ameloblastoma (PA) is based on a literature survey of 160 published tumour cases. The PA is an exophytic growth localized to the soft tissues overlying the tooth-bearing areas of the jaws, the initial diagnosis often being fibrous epulis. In most cases there is no radiological evidence of bone involvement, but a superficial bone erosion--known as cupping or saucerization--may be detected at operation. The PA accounts for 2-10% of all ameloblastomas. The overall average age is 52.1 years, slightly higher for males (52.9 years) than for females (50.6 years). Thus, the PA occurs at a significantly higher age than the intraosseous ameloblastoma (IA; 37.4 years). The male/female ratio amounts to 1.9:1, as opposed to 1.2:1 for the IA. The male/female ratio for the Japanese cases included in this survey is 2.5:1 as opposed to that of non-Japanese cases 1.4:1. As to the location of PA, the maxilla/mandible ratio is 1:2.6. The mandibular premolar region accounts for 32.6% of all sites. Five extra-gingival lesions have been reported under the term PA. As these cases most likely represent salivary gland tumours, they are not accepted under the diagnosis of PA. The odontogenic gingival epithelial hamartoma shows clinical, histological and behavioural features almost identical to the PA, and it is discussed whether this lesion and the PA should be considered one and the same entity. Pathogenetically, two major sources are discussed: remnants of the dental lamina and the oral surface epithelium. Histologically, the PA consists of proliferating odontogenic epithelium exhibiting the same histomorphological cell types and patterns as seen in the IA. The stroma is that of a mature, fibrous connective tissue. The indolent biological behaviour dictates a conservative therapeutical approach. It is discussed whether PA is a true neoplastic counterpart of the IA or rather an odontogenic hamartomatous lesion. Six cases of malignant PA have been reported.

Aurora-B expression and its correlation with cell proliferation and metastasis in oral cancer

Aurora-B kinase is a chromosomal passenger protein and is essential for chromosome segregation and cytokinesis. Aurora-B overexpression in various cancer cells induces chromosomal number instability to produce multinuclearity and relates to metastasis. Here, we examined the expression of Aurora-B in oral squamous cell carcinoma (OSCC) to elucidate the relationship between Aurora-B expression and clinico-pathological findings by immunohistochemistry. Aurora-B expression was observed in normal oral squamous epithelia and OSCC cases, but the number of positive cells was significantly higher in OSCC than in normal squamous epithelium (p < 0.01). The labeling index of Aurora-B was significantly correlated with lymph node metastasis (p < 0.01) and histological grades of differentiation (p < 0.01). We also compared Aurora-B expression with Ki-67 expression and a positive correlation was found (p < 0.0001). Moreover, Aurora-B expression is significantly more frequent in multinuclear tumor cells than in total tumor cells. In summary, we found that Aurora-B expression was well correlated with cell proliferation, induction of multinuclear cells, histological differentiation, and metastasis in OSCC. These findings suggest that Aurora-B may be involved in tumor progression and that Aurora-B can be a new diagnostic and therapeutic target for OSCC.

Survivin, a Potential Early Predictor of Tumor Progression in the Oral Mucosa

Survivin is a recently described apoptosis inhibitor selectively over-expressed in most tumors. Immunohistochemistry was used to investigate a potential role of survivin as an early predictor of malignant transformation in precancerous and cancerous lesions of the oral cavity. Survivin was present in 10/30 cases (33%) of oral precancerous lesions without malignant progression, and in 15/16 cases (94%) of oral precancerous lesions evolved into full-blown squamous cell carcinoma. Tumors that progressed from these precancerous lesions retained widespread survivin positivity (100%). Variations among group means were highly statistically significant (p < 0.001). No significant correlation was found between survivin expression and the degree of dysplasia. High expression of cytoplasmic/nuclear survivin is an early event during oral carcinogenesis and may provide a useful tool for the identification of precancerous lesions at higher risk of progression into invasive carcinoma.