Munetaka Nakamura

Epstein-barr virus in gastric carcinoma.

The Epstein-Barr virus (EBV) is detected in about 10% of gastric carcinoma cases throughout the world. In EBV-associated gastric carcinoma, all tumor cells harbor the clonal EBV genome. Gastric carcinoma associated with EBV has distinct clinicopathological features, occurs predominately in men and in younger-aged individuals, and presents a generally diffuse histological type. Most cases of EBV-associated gastric carcinoma exhibit a histology rich in lymphocyte infiltration. The immunological reactiveness in the host may represent a relatively preferable prognosis in EBV-positive cases. This fact highlights the important role of EBV in the development of EBV-associated gastric carcinoma. We have clearly proved direct infection of human gastric epithelialcells by EBV. The infection was achieved by using a recombinant EBV. Promotion of growth by EBV infection was observed in the cells. Considerable data suggest that EBV may directly contribute to the development of EBV-associated GC. This tumor-promoting effect seems to involve multiple mechanisms, because EBV affects several host proteins and pathways that normally promote apoptosis and regulate cell proliferation.

Role of DNA methylation in the development of Epstein–Barr virus-associated gastric carcinoma†

The frequencies of DNA methylation of certain tumor‐related genes are higher in Epstein–Barr virus (EBV)‐associated gastric carcinomas than in EBV‐negative gastric carcinomas. EBV‐associated gastric carcinomas have distinct clinicopathological features; however, there are no case‐control studies comparing methylation frequency between EBV‐associated gastric carcinomas and controls that have been adjusted according to the clinicopathological features of EBV‐associated gastric carcinomas. This study evaluated 25 EBV‐associated gastric carcinomas that were positive for EBV‐encoded small RNA 1 (EBER‐1) by in situ hybridization and 50 EBV‐negative gastric carcinomas that were matched with the EBV‐associated gastric carcinomas by age, sex, histology, depth of tumor invasion, and stage. Methylation status of 16 loci associated with tumor‐related genes was analyzed by methylation‐specific polymerase chain reaction (PCR) to identify genes in which DNA methylation specifically occurred in EBV‐associated gastric carcinomas. Methylation frequencies of 12 of the 16 genes were higher in EBV‐associated gastric carcinomas than in EBV‐negative controls, and the frequency of methylation of 6 specific loci (MINT2, MINT31, p14, p16, p73, and RUNX3) was significantly higher in EBV‐associated gastric carcinomas than in EBV‐negative controls. There were no significant differences in the methylation frequencies of the other genes. The mean methylation index in EBV‐associated gastric carcinomas was significantly higher than that in EBV‐negative controls. DNA methylation of tumor suppressor genes that regulate the cell cycle and apoptosis specifically occurred in EBV‐associated gastric carcinomas. Aberrant DNA methylation might lead to the development and progression of EBV‐associated gastric carcinoma. J. Med. Virol. 85:121–127, 2012.

Identification of genes specifically methylated in Epstein–Barr virus‐associated gastric carcinomas

We studied the comprehensive DNA methylation status in the naturally derived gastric adenocarcinoma cell line SNU‐719, which was infected with the Epstein–Barr virus (EBV) by methylated CpG island recovery on chip assay. To identify genes specifically methylated in EBV‐associated gastric carcinomas (EBVaGC), we focused on seven genes, TP73, BLU, FSD1, BCL7A, MARK1, SCRN1, and NKX3.1, based on the results of methylated CpG island recovery on chip assay. We confirmed DNA methylation of the genes by methylation‐specific PCR and bisulfite sequencing in SNU‐719. The expression of the genes, except for BCL7A, was upregulated by a combination of 5‐Aza‐2′‐deoxycytidine and trichostatin A treatment in SNU‐719. After the treatment, unmethylated DNA became detectable in all seven genes by methylation‐specific PCR. We verified DNA methylation of the genes in 75 primary gastric cancer tissues from 25 patients with EBVaGC and 50 EBV‐negative patients who were controls. The methylation frequencies of TP73, BLU, FSD1, BCL7A, MARK1, SCRN1, and NKX3.1 were significantly higher in EBVaGC than in EBV‐negative gastric carcinoma. We identified seven genes with promoter regions that were specifically methylated in EBVaGC. Inactivation of these genes may suppress their function as tumor suppressor genes or tumor‐associated antigens and help to develop and maintain EBVaGC.

Risk factors for delayed bleeding from endoscopic submucosal dissection of gastric neoplasms

Abstract Objective. Delayed bleeding is a major complication of endoscopic submucosal dissection (ESD) of gastric neoplasms. We aimed to clarify risk factors for delayed bleeding from ESD. Material and methods. This study included 447 patients in whom 544 gastric neoplasms were resected by ESD between April 2006 and March 2011 in Yamaguchi University Hospital. We analyzed risk factors for delayed bleeding from ESD in relation to various clinical and pathological factors. Results. En bloc resection rate was 95.4% (519/544), and curative resection rate was 87.8% (477/544). Delayed bleeding occurred in 7.0% (38/544) and perforation occurred in 1.8% (10/544) of patients. Univariate analysis revealed platelet count (Plt) <15 × 104/μl (p = 0.013), prothrombin time (PT) <70% (p = 0.044), resected size ≥50 mm (p = 0.038), and positive/indeterminate lateral margin (p = 0.012) to be risk factors for delayed bleeding. Multivariate analysis showed that Plt <15 × 104/μl (odds ratio [OR], 2.62; 95% confidence interval [CI]: 1.17–5.53, p = 0.020) and positive/indeterminate lateral margin (OR, 5.45; 95% CI: 1.39–17.95, p = 0.018) were independent risk factors for delayed bleeding. Conclusions. Low Plt, low PT, large resected size, and positive/indeterminate lateral margin were significant risk factors for delayed bleeding from ESD. Patients with these risk factors must be carefully observed for signs of delayed bleeding.

Use of hyperspectral imaging technology to develop a diagnostic support system for gastric cancer

Abstract. Hyperspectral imaging (HSI) is a new technology that obtains spectroscopic information and renders it in image form. This study examined the difference in the spectral reflectance (SR) of gastric tumors and normal mucosa recorded with a hyperspectral camera equipped with HSI technology and attempted to determine the specific wavelength that is useful for the diagnosis of gastric cancer. A total of 104 gastric tumors removed by endoscopic submucosal dissection from 96 patients at Yamaguchi University Hospital were recorded using a hyperspectral camera. We determined the optimal wavelength and the cut-off value for differentiating tumors from normal mucosa to establish a diagnostic algorithm. We also attempted to highlight tumors by image processing using the hyperspectral camera’s analysis software. A wavelength of 770 nm and a cut-off value of 1/4 the corrected SR were selected as the respective optimal wavelength and cut-off values. The rates of sensitivity, specificity, and accuracy of the algorithm’s diagnostic capability were 71%, 98%, and 85%, respectively. It was possible to enhance tumors by image processing at the 770-nm wavelength. HSI can be used to measure the SR in gastric tumors and to differentiate between tumorous and normal mucosa.

Decitabine inhibits tumor cell proliferation and up‐regulates E‐cadherin expression in Epstein‐Barr virus‐associated gastric cancer

The present study investigated the effect of a DNA demethylating agent, decitabine, against Epstein–Barr virus‐associated gastric cancer (EBVaGC). Decitabine inhibited cell growth and induced G2/M arrest and apoptosis in EBVaGC cell lines. The expression of E‐cadherin was up‐regulated and cell motility was significantly inhibited in the cells treated with decitabine. The promoter regions of p73 and RUNX3 were demethylated, and their expression was up‐regulated by decitabine. They enhanced the transcription of p21, which induced G2/M arrest and apoptosis through down‐regulation of c‐Myc. Decitabine also induced the expression of BZLF1 in SNU719. Induction of EBV lytic infection was an alternative way to cause apoptosis of the host cells. This study is the first report to reveal the effectiveness of a demethylating agent in inhibiting tumor cell proliferation and up‐regulation of E‐cadherin in EBVaGC. J. Med. Virol. 89:508–517, 2017.

Preliminary study of photodynamic diagnosis using 5-aminolevulinic acid in gastric and colorectal tumors.

AIM To investigate the utility of photodynamic diagnosis (PDD) using 5-aminolevulinic acid (5-ALA) to detect gastric/colorectal tumors. METHODS This prospective single-center study investigated inter-subject variability in patients with early-stage gastric/colorectal tumor indicated for endoscopic resection. Subjects were patients with gastric or colorectal tumors who had undergone endoscopic resection between November 2012 and November 2013. Selection criteria included age 20-80 years, either sex, and provision of informed consent. Patients were orally administered 20 mg/kg of 5-ALA enteric-coated capsules (SBI ALApromo Co., Tokyo, Japan). Administration of 5-ALA was followed by endoscopic resection of gastric or colorectal tumors, and the resected specimens were examined using a video autofluorescence processor and a fluorescence endoscope (SAFE-3000 and EB-1970AK, respectively; Pentax, Tokyo, Japan). The primary endpoint was the presence of fluorescence in tumors. Endoscopic, macroscopic, and histopathologic findings of tumors were assessed. We also evaluated adverse events of the present procedure as a secondary endpoint and examined each patient for the presence of known adverse effects of 5-ALA, namely, hematocytopenia, liver dysfunction, hypotension, nausea, and photosensitivity. RESULTS We enrolled 10 patients (7 men, 3 women) (n = 13 lesions: 10 gastric/3 colorectal tumors). Fluorescence was detected in 7/13 (53.8%) lesions. No significant differences in sex (male: 55.6% vs female: 50.5%, P = 1.00), age (67.1 ± 1.9 years vs 65.0 ± 2.0 years, P = 0.45), tumor color (reddish: 60.0% vs discolored: 33.3%, P = 0.56), tumor diameter (15.0 ± 2.1 mm vs 14.2 ± 2.3 mm, P = 0.80), macroscopic type (protruded: 70.0% vs depressed 0%, P = 0.07), histologic type (differentiated type: 58.3% vs 0%, P = 0.46), invasion depth (mucosal layer: 55.6% vs submucosal layer: 33.3%, P = 1.00), lymphatic invasion (present: 33.3% vs absent: 50.0%, P = 1.00), venous invasion (present: 0% vs absent: 54.5%, P = 1.00) or procedure time of endoscopic resection (36.3 ± 8.3 min vs 36.7 ± 9.0 min, P = 0.98) were observed between the patients with and without fluorescence. Fluorescence detection rate tended to be high for elevated lesions. Liver dysfunction developed in 4/10 (40.0%) patients. The extent of the liver dysfunction was a slight increase in transaminases and total bilirubin levels, which spontaneously improved in the patients. None of the patients developed photosensitivity. CONCLUSION Results of this preliminary study suggest the utility of PDD using 5-ALA for screening of gastric and colorectal cancers.

Efficacy of i-Scan Imaging for the Detection and Diagnosis of Early Gastric Carcinomas

We determined comparative efficacy of i-Scan for detection and diagnosis of gastric cancer. Ten patients diagnosed with early gastric cancer based on histopathological findings were analyzed. White light and i-Scan moving images recorded from these patients in twin mode were separated into white light and i-Scan. Twelve endoscopists (three different skill levels) blinded to patient information evaluated the images. Correlation between demarcation accuracy and lesion brightness on still images was investigated. No significant differences were found in diagnostic accuracy between white light and i-Scan moving images for tumor detection rate (91.7% versus 90.8%, P = 0.777). Diagnostic accuracy of tumor size was comparable between novice and experienced endoscopists for i-Scan moving images (65.7% versus 71.1%, P = 0.528), whereas it was significantly lower for white light moving images (41.2% versus 79.5%, P = 0.019). Tumor demarcation accuracy was significantly better with white light than i-Scan still images (71.0% versus 65.8%, P = 0.033). Correlations between demarcation accuracy and brightness reached highs of 0.75 for white light and 0.89 for i-Scan imaging. Efficacy of i-Scan over that of white light imaging for detecting and diagnosing gastric cancer was not shown; however, the diagnostic capability of i-Scan can be improved if imaging conditions are optimized.

A case of EMRC for basaloid squamous carcinoma of the cervical esophagus

Basaloid squamous carcinoma (BSC) of the esophagus is a rare esophageal tumor. A 79-year-old man with a history of proximal gastrectomy for gastric adenocarcinoma in 2000 was followed-up by esophagogastroduodenoscopy (EGD) annually. In June 2010, EGD revealed a new protruding lesion in the cervical esophagus. The small lesion was approximately 5 mm in size. A biopsy specimen showed poorly differentiated squamous cell carcinoma. We performed endoscopic mucosal resection using a cap-fitted endoscope (EMRC). The histological diagnosis of the endoscopically resected specimen was BSC and the invasion depth was limited to the muscularis mucosae. Horizontal and vertical margins were negative. We report the case of superficial BSC in the cervical esophagus successfully resected by EMRC.

Evaluation of the Diagnostic Ability of Optical Enhancement System in Early Gastric Cancer Demarcation

This study aimed to evaluate the utility of optical enhancement (OE) in early gastric cancer demarcation. Twenty lesions of early gastric cancer were examined by PENTAX endoscopy system with OE-1 and OE-2 functions. The areas of tumor demarcation identified by 12 evaluators (6 novice and 6 experienced) were compared to the corresponding correct areas determined by postoperative histopathology findings. The misdiagnosed scores that were the sums of false-positive and false-negative areas were compared. Color of one hundred pixels from the inside of the cancerous area and the outside of the cancerous area was expressed as three-dimensional RGB component vectors. The mean vectors and covariance matrixes were calculated and the Mahalanobis distance, indicative of color differences between two areas, was tested. Comparisons of the misdiagnosed score revealed that OE-1 was preferred over WL-1 for gastric cancer demarcation for all 12 evaluators (p = 0.008) and in novice evaluators (p = 0.026). OE-2 was not significantly different from WL-2 in all cases. OE-1 images gave significantly larger Mahalanobis distances, indicative of color differences, than WL-1 images (p = 0.002). It was demonstrated that the OE Mode 1 has a significant advantage over the white light mode in demarcation of early gastric cancer.