Yusuke Nakajima

Distinct recruitment of E2F family members to specific E2F-binding sites mediates activation and repression of the E2F1 promoter

The activity of E2F transcription factors plays a crucial role in mammalian cell-cycle progression and is controlled by physical association with the pocket proteins (pRb and its related p107 and p130). The E2F1 promoter, which contains two overlapping E2F-binding sites, is activated at the G1/S transition in an E2F-dependent manner. Mutational experiments have shown that the distal E2F-binding site on the E2F1 promoter is required for transcriptional repression in the G0 phase, whereas the proximal E2F-binding site contributes to transcriptional activation at the G1/S boundary. Consistent with these results, chromatin immunoprecipitation assays have revealed that the E2F4/p130 repressor complex specifically binds to the distal E2F-binding site, whereas E2F1 and E2F3 activators preferentially bind to the proximal E2F-binding site. The assays also showed that the specific binding of E2F4/p130 complex to the distal site was dramatically impaired by a mutation introduced into the contiguous repression site (cell Cycle gene Homology Region; CHR). Taken together, these findings indicate that the two E2F-binding sites play distinct roles in the regulation of E2F1 transcription by interacting with different sets of E2F members and cooperating with the contiguous repressor element.

DNA amplification and expression of FADD in oral squamous cell carcinoma

BACKGROUND The Fas-associated death domain-containing protein, FADD, is an adaptor for relaying apoptotic signals. However, recent studies have shown that FADD also plays an important role in the growth and regulation of the cell cycle. The purpose of this study was to elucidate the role of FADD in oral squamous cell carcinoma (SCC). METHODS The DNA amplification of FADD from 30 samples of tongue SCC was analyzed using real-time PCR and the protein expression of FADD from 60 samples of tongue SCC was analyzed using immunohistochemistry. RESULTS The DNA amplifications of FADD were observed in 13 cases (44.3%) and were significantly correlated with the histopathological differentiation grade of SCCs (P = 0.009). FADD expression levels compared with the matched adjacent epithelium increased significantly (P = 0.000). Additionally, the positive expressions of FADD were significantly correlated with lymph node metastasis of SCCs (P = 0.029) and the 5-year disease-specific survival rates (P = 0.049). A positive association between FADD expression level and the histopathological differentiation grade was found to be limited to T1 SCCs (P = 0.019). DNA amplification was moderately correlated (correlation coefficient = 0.406, P = 0.026) with expression of FADD in 30 samples of tongue SCC. CONCLUSION In tongue SCCs, the expression of FADD was higher when compared with that of adjacent areas, which might be determined via genomic amplification in 11q13.3. Thus, SCC cells with the expression of FADD are possibly more likely to become metastatic and to worsen survival rates.

Uptake and kinetics of 5-aminolevulinic acid in oral squamous cell carcinoma

Photodynamic diagnosis (PDD) is a form of cancer detection based on the administration of an exogenous photo-activated compound that accumulates in malignant cells, followed by appropriate photo irradiation. The authors describe a spectroscopic study of 5-aminolevulinic acid (5-ALA)-generated photosensitizer protoporphyrin IX (PpIX) fluorescence in human oral squamous cell carcinoma (OSCC) cell lines to validate its clinical use. 5-ALA-induced PpIX fluorescence intensity was measured in the presence and absence of deferoxamine mesylate (DFO). Two, one and two cell lines produced poorly, moderately and well differentiated carcinomas, respectively, on transplantation in scid mice. The fluorescence intensity was high in the poorly differentiated cell lines, followed by the moderately differentiated cell line; the intensity of the well differentiated cell lines was low and not significantly different from that of normal keratinocytes in the absence of DFO. It was elevated to the level of poorly differentiated cell lines following DFO treatment. This elevation was not observed in normal keratinocytes. The results indicate that DFO enhances the photodynamic sensitivity of 5-ALA in non-responsive carcinoma cells as a result of increased cellular accumulation by inhibiting haeme biosynthesis. This PDD system can be applied clinically to the detection of OSCC irrespective of the degree of differentiation.

Galectin-7 as a potential predictive marker of chemo-and/or radio-therapy resistance in oral squamous cell carcinoma

Treatment of advanced oral squamous cell carcinoma (OSCC) requires the integration of multimodal approaches. The aim of this study was to identify predictors of tumor sensitivity to preoperative radiotherapy/chemotherapy for OSCC in order to allow oncologists to determine optimum therapeutic strategies without the associated adverse effects. Here, the protein expression profiles of formalin‐fixed paraffin‐embedded (FFPE) tissue samples from 18 OSCC patients, termed learning cases, who received preoperative chemotherapy and/or radiotherapy followed by surgery were analyzed by quantitative proteomics and validated by immunohistochemistry in 68 test cases as well as in the 18 learning cases. We identified galectin‐7 as a potential predictive marker of chemotherapy and/or radiotherapy resistance, and the sensitivity and specificity of the galectin‐7 prediction score (G7PS) in predicting this resistance was of 96.0% and 39.5%, respectively, in the 68 test cases. The cumulative 5‐year disease‐specific survival rate was 75.2% in patients with resistant prediction using G7PS and 100% in patients with sensitive prediction. In vitro overexpression of galectin‐7 significantly decreased cell viability in OSCC cell line. Therefore, our findings suggest that galectin‐7 is a potential predictive marker of chemotherapy and/or radiotherapy resistance in patients with OSCC.

The Abnormal Expression of p53 Protein is a Predictive Prognostic Marker in Oral Leukoplakia

Abstract Objectives: The p53 tumour suppresser gene has been studied as a prognostic marker of oral squamous cell carcinoma. This study was conducted to search for a p53 predictive prognostic marker in oral premalignant leukoplakia using p53 immunostaining. Patients and Methods: Oral leukoplakia with epithelial dysplasia (60 patients) and healthy oral mucosa (15 patients) were immunohistochemically stained for the p53 protein. The healthy oral mucosa were obtained from a separate group of patients. Results: Fifty percent of the leukoplakia lesions were positive for p53 protein. Among the 60 lesions, 13 developed into squamous cell carcinoma, of which 10 showed p53 positive staining even before malignant transformation. Conclusion: Overexpression of p53 protein may be a useful diagnostic procedure for oral leukoplakias that have a high probability of developing into oral squamous cell carcinoma.