Ikuko Ogawa

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.

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.

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.

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.

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.

Verruciform xanthoma--biological profile of 282 oral lesions based on a literature survey with nine new cases from Japan.

The biological profile of oral verruciform xanthoma (VX) is presented based on a world-wide literature survey of 282 cases. From 1979 onwards, extraoral cases have also been reported. This rare, harmless lesion with a sessile or pedunculated base is a red/pink, papillary/granular/verrucous mucosal growth, occurring in females (mean age, 54.9 yrs) and males (mean age, 44.2 yrs) in a female:male ratio of 1:1.1. The most common location is by far the gingival margin and other areas of the masticatory oral mucosa. Comparison between 173 non-Japanese and 109 Japanese patients with oral VX showed few discrepancies in epidemiological data, indicating only few significant ethnic differences between the two cohorts. Histomorphologically, the epithelium covering the lesion can be divided into three groups: (A) a verrucous, (B) a papillary and (C) a flat pattern. The hallmark of all VX, irrespective of the lesion being intra- or extraoral is, however, the presence of vacuolated, foam or xanthoma cells which ultimately replace the connective tissue between the epithelial ridges. The xanthoma cells have been shown to be cells of the monocyte/macrophage lineage. The present concept of the etiology and pathogenesis of VX, including the possible viral (HPV) association is revised, based on both intra- and some extraoral cases, and it is concluded that it is still far from being clarified.

Characterization of established cementoblast-like cell lines from human cementum-lining cells in vitro and in vivo.

To study cellular characteristics of human cementoblasts using a cellular model is important for understanding the mechanisms of homeostasis and regeneration of periodontal tissues. However, at present no immortalized human cementoblast cell line has been established due to limitation of the life span. In the present study, therefore, we attempted to establish human cementoblast-like cell lines by transfection with telomerase catalytic subunit hTERT gene. Two stable clones (HCEM-1 and -2) with high telomerase activity were obtained and they grew over 200 population doublings without significant growth retardation. The expression of mRNA for differentiation markers, type I collagen, alkaline phosphatase (ALP), runt-related transcription factor 2, osteocalcin, bone sialoprotein and cementum-derived protein was revealed in these clones by RT-PCR. Moreover, these cells showed high ALP activity and calcified nodule formation in vitro. Interestingly, HCEM-2 showed cementum like formation on the surface of hydroxyapatites granules by subcutaneous transplantation into immunodeficient mice with hydroxyapatite granules. Thus, we established human cementoblast-like cell lines. We suggest that HCEM cell lines can be useful cell models for investigating the characteristics of human cementoblasts.

Reduced expression of p27Kip1 correlates with an early stage of cancer invasion in oral squamous cell carcinoma

Down-regulation of p27Kip1 has been reported to correlate with poor survival of various carcinoma patients including oral squamous cell carcinomas (OSCCs). It is still unclear, however, at what stage of oral carcinogenesis the down-regulation of this protein occurs. In this study, therefore, we evaluated immunoexpression of p27Kip1 protein in 17 cases of oral epithelial dysplasia and succeeding invasive OSCC in the same patient. We reported here that 88% cases showed high p27Kip1 expression in dysplastic lesions, whereas 82% cases of succeeding invasive OSCC exhibited reduced expression. The reduction of p27Kip1 expression was also observed in 16 of 19 (84%) early invasive lesions and well correlated with Ki-67 expression which is good indicator of cell proliferation. We also investigated immunoexpression of p53 protein of which abnormality has been known to occur during the early stage of OSCC development. Overexpression of p53 protein was demonstrated in 29% of dysplastic lesions, 42% of early invasive and 71% of invasive OSCCs. These findings suggest that abnormalities of both p53 and p27Kip1 are involved in the carcinogenesis of OSCC, but they seem to play their role at different stages of oral cancer development, respectively. Reduced expression of p27Kip1 may concern the cancer invasion directly or indirectly as well as abnormal proliferation.

Spindle cell squamous carcinoma of the oral region An immunohistochemical and ultrastructural study on the histogenesis and differential diagnosis with a clinicopathological analysis of six cases

Six cases of spindle cell squamous carcinoma (SCSC) of the oral cavity were studied clinicopathologically, immunohistochemically and ultrastructurally to summarize the clinicopathological features of this rare neoplasm and to discuss the debatable histogenesis of the sarcomatoid component and the differential diagnosis of SCSC. The mean age of the patients was 72 years and the female to male ratio was 1:2. Four of them had a history of irradiation for pre-existing squamous cell carcinoma. One patient died of SCSC. While clinical and histological prognostic factors of SCSC could not be determined, it was shown that radical surgery resulted in good prognosis. The epithelial nature of the sarcomatoid component of SCSC was clearly revealed by a combination of immunohistochemical staining for keratins and electron microscopic demonstration of tonofilament-like filaments and/or desmosome-like structures. Together with electron microscopic evaluation of the tumour cells, immunohistochemical characterization of tumour cells using antibodies to keratin, vimentin, glial fibrillary acidic protein and S-100 protein is very helpful in differentiating SCSC from true spindle cell sarcoma, melanoma and malignant myoepithelioma. In the immunohistochemical differential diagnosis of SCSC, it is important to remember that SCSC should not be ruled out of the differential diagnosis by a positive reaction for vimentin in sarcomatoid tumour cells. Absence of staining for keratin in the sarcomatoid tumour cells does not always exclude SCSC, because some SCSCs show immunoreactivity of keratin in their sarcomatoid components only with some anti-keratin antibodies. Different kinds of anti-keratin antibodies should be applied in the differential diagnosis of SCSC.