Seiya Yokoyama

Dr. Seiya Yokoyama

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Research Focus & Metrics

Academic Career Length

34Years (1993-Present)

(Calculated once Scilit publication data is synced: current year − year of first publication + 1)

Representative Publications

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29 September 2009 in Journal of Hepato-Biliary-Pancreatic Sciences
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Journal Article
Closed access
SYSuguru Yonezawa
Suguru Yonezawa
MHMichiyo Higashi
Michiyo Higashi
NYNorishige Yamada
Norishige Yamada
Seiya YokoyamaSeiya Yokoyama
Seiya Yokoyama
MGMasamichi Goto
Masamichi Goto

25 October 2011 in Pathology International
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Journal Article
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SYSuguru Yonezawa
Suguru Yonezawa
MHMichiyo Higashi
Michiyo Higashi
NYNorishige Yamada
Norishige Yamada
Seiya YokoyamaSeiya Yokoyama
Seiya Yokoyama
SKSho Kitamoto
Sho Kitamoto
MGMasamichi Goto
Masamichi Goto

20 October 2014 in Pathology International
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Journal Article
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THTsubasa Hiraki
Tsubasa Hiraki
MYMakoto Yoshimitsu
Makoto Yoshimitsu
TSTadaki Suzuki
Tadaki Suzuki
YGYuko Goto
Yuko Goto
MHMichiyo Higashi
Michiyo Higashi
SYSuguru Yonezawa
Suguru Yonezawa
We report two autopsy cases of severe fever with thrombocytopenia syndrome (SFTS) with a high fatality rate in aged Japanese patients. Both cases were caused by a tick‐bite. The pathognomonic histological feature was necrotizing lymphadenitis of systemic lymphoid tissue with SFTS viruses and SFTSV‐RNA copies. Marked fungal infections were also observed in the lungs of both patients. Since cellular immune function may be suppressed in SFTS patients, physicians should be aware of possible fungal infections.

15 May 2020 in Clinical Cancer Research
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Journal Article
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Seiya YokoyamaSeiya Yokoyama
Seiya Yokoyama
THTaiji Hamada
Taiji Hamada
MHMichiyo Higashi
Michiyo Higashi
KMKei Matsuo
Kei Matsuo
KMKousei Maemura
Kousei Maemura
ATAkihide Tanimoto
Akihide Tanimoto
Purpose: Pancreatic cancer remains a disease of high mortality despite advanced diagnostic techniques. Mucins (MUC) play crucial roles in carcinogenesis and tumor invasion in pancreatic cancers. MUC1 and MUC4 expression are related to the aggressive behavior of human neoplasms and a poor patient outcome. In contrast, MUC2 is a tumor suppressor, and we have previously reported that MUC2 is a favorable prognostic factor in pancreatic neoplasia. This study investigates whether the methylation status of three mucin genes from postoperative tissue specimens from patients with pancreatic neoplasms could serve as a predictive biomarker for outcome after surgery. Experimental Design: We evaluated the methylation status of MUC1, MUC2, and MUC4 promoter regions in pancreatic tissue samples from 191 patients with various pancreatic lesions using methylation-specific electrophoresis. Then, integrating these results and clinicopathological features, we used support vector machine-, neural network-, and multinomial-based methods to develop a prognostic classifier. Results: Significant differences were identified between the positive- and negative-prediction classifiers of patients in 5-year overall survival (OS) in the cross-validation test. Multivariate analysis revealed that these prognostic classifiers were independent prognostic factors analyzed by not only neoplastic tissues but also non-neoplastic tissues. These classifiers had higher predictive accuracy for OS than tumor size, lymph node metastasis, distant metastasis, and age and can complement the prognostic value of the TNM staging system. Conclusions: Analysis of epigenetic changes in mucin genes may be of diagnostic utility and one of the prognostic predictors for patients with pancreatic ductal adenocarcinoma.

17 January 2012 in Cancer
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Journal Article
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SNSatoshi Nagata
Satoshi Nagata
THTomofumi Hamada
Tomofumi Hamada
NYNorishige Yamada
Norishige Yamada
Seiya YokoyamaSeiya Yokoyama
Seiya Yokoyama
SKSho Kitamoto
Sho Kitamoto
KSKazumasa Sugihara
Kazumasa Sugihara
BACKGROUND: The early detection of oral squamous cell carcinoma (OSCC) is important, and a screening test with high sensitivity and specificity is urgently needed. Therefore, in this study, the authors investigated the methylation status of tumor‐related genes with the objective of establishing a noninvasive method for the detection of OSCC.METHODS: Oral rinse samples were obtained from 34 patients with OSCC and from 24 healthy individuals (controls). The methylation status of 13 genes was determined by using methylation‐specific polymerase chain reaction analysis and was quantified using a microchip electrophoresis system. Promoter methylation in each participant was screened by receiver operating characteristic analysis, and the utility of each gene's methylation status, alone and in combination with other genes, was evaluated as a tool for oral cancer detection.RESULTS: Eight of the 13 genes had significantly higher levels of DNA methylation in samples from patients with OSCC than in controls. The genes E‐cadherin (ECAD), transmembrane protein with epidermal growth factor‐like and 2 follistatin‐like domains 2 (TMEFF2), retinoic acid receptor beta (RARβ), and O‐6 methylguanine DNA methyltransferase (MGMT) had high sensitivity (>75%) and specificity for the detection of oral cancer. OSCC was detected with 100% sensitivity and 87.5% specificity using a combination of ECAD, TMEFF2, RARβ, and MGMT and with 97.1% sensitivity and 91.7% specificity using a combination of ECAD, TMEFF2, and MGMT.CONCLUSIONS: The aberrant methylation of a combination of marker genes present in oral rinse samples was used to detect OSCC with >90% sensitivity and specificity. The detection of methylated marker genes from oral rinse samples has great potential for the noninvasive detection of OSCC. Cancer 2012. © 2012 American Cancer Society.

29 October 2012 in Oncogene
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Journal Article
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SKS Kitamoto
S Kitamoto
Seiya YokoyamaSeiya Yokoyama
Seiya Yokoyama
MHM Higashi
M Higashi
NYN Yamada
N Yamada
STS Takao
S Takao
SYS Yonezawa
S Yonezawa
Pancreatic cancer is one of the most lethal malignancies due to its aggressive growth and rapid development of distant metastases. In this context, mucin 1 (MUC1) overexpression and hypoxia are frequently observed events. However, their functional relationship remains largely unknown. This study provides evidence that MUC1 is overexpressed by hypoxia and contributes to hypoxia-driven angiogenesis. Using the conditioned medium obtained from hypoxia-stressed AsPC1 cells treated with MUC1 siRNAs, we demonstrated that MUC1 enhanced the endothelial tube formation, proliferation and migration ability, which induced by hypoxia-conditioned medium (HCM). In addition, MUC1 was significantly induced by hypoxia, especially in the pancreatic cancer cells derived from metastatic tumors (AsPC1, HPAF2 or Capan1), and MUC1-cytoplasmic tail (MUC1-CT) accumulated in the nucleus under hypoxia. As noted in a previous report, MUC1-CT was recruited to genomic regions upstream of the connective tissue growth factor (CTGF) accompanied with β-catenin and p53, resulting in the hypoxic induction of CTGF. Moreover, hypoxia-induced MUC1 partially regulated two other hypoxia-inducible proangiogenic factors including vascular endothelial growth factor-A and platelet-derived growth factor-B. The neutralization assay revealed that endothelial tube formation induced by HCM was clearly suppressed by antibodies against these three factors, suggesting the importance of these factors in hypoxia-driven angiogenesis. In summary, this is the first report demonstrating a pivotal role of MUC1 in controlling the hypoxia-driven angiogenesis through the regulation of multiple proangiogenic factors in pancreatic cancer. Our findings provide the novel insights into the understanding of complex interactions between pancreatic cancer cells and tumor microenvironments.