Yamasaki, Juntaro



School of Medicine, Institute for Advanced Medical Research (Division of Gene Regulation) (Shinanomachi)


Project Assistant Professor (Non-tenured)/Project Research Associate (Non-tenured)/Project Instructor (Non-tenured)

Career 【 Display / hide

  • 2022.04

    慶應義塾大学, 特任助教

Academic Background 【 Display / hide

  • 2012.04

    慶應義塾大学, 薬学部, 薬科学科

    University, Graduated

  • 2016.04

    慶應義塾大学大学院, 医学研究科, 医科学専攻

    Graduate School, Completed, Master's course

  • 2018.04

    慶應義塾大学大学院, 医学研究科, 医学研究系専攻

    Graduate School, Completed, Doctoral course

Academic Degrees 【 Display / hide

  • 博士(医学), Keio University, Coursework, 2022.03


Papers 【 Display / hide

  • Presence of spontaneous epithelial-mesenchymal plasticity in esophageal cancer

    Tsuchihashi K., Hirata Y., Yamasaki J., Suina K., Tanoue K., Yae T., Masuda K., Baba E., Akashi K., Kitagawa Y., Saya H., Nagano O.

    Biochemistry and Biophysics Reports (Biochemistry and Biophysics Reports)  30   101246 2022.07

     View Summary

    Epithelial-mesenchymal plasticity (EMP) refers to the reversible cellular transition between epithelial and mesenchymal status. Spontaneous EMP is also reported in breast and prostate cancer, leading to the acquisition of stem-cell properties and chemoresistance. However, the presence of spontaneous EMP is still not reported in esophageal cancer. We screened 11 esophageal squamous cancer cell (ESCC) cell lines by CD44 isoform expression. KYSE520 was found to comprise heterogenous populations consisting of CD44v+ and CD44v– subpopulations. CD44v+ and CD44v– cells showed the expression of epithelial and mesenchymal markers, respectively. Single-cell sorting of CD44v+ and CD44v– cells revealed both cells gave rise to cell populations consisting of CD44v+ and CD44v– cells, indicating CD44v+ epithelial-like and CD44v− mesenchymal-like cells can generate counterparts, respectively. The ablation of Epithelial splicing regulatory protein 1 (ESRP1), a major regulator of CD44 mRNA splicing, resulted in the shift from CD44v+ to CD44v– cells in KYSE520. However, the expression of epithelial-mesenchymal transition (EMT)-related markers or transcriptional factors were almost not affected, suggesting ESRP1 functions downstream of EMP. Our results revealed the presence of spontaneous EMP in esophageal cancer and KYSE520 is useful model to understand spontaneous EMP.

  • Angiopoietin-like 4 promotes glucose metabolism by regulating glucose transporter expression in colorectal cancer

    Mizuno S., Seishima R., Yamasaki J., Hattori K., Ogiri M., Matsui S., Shigeta K., Okabayashi K., Nagano O., Li L., Kitagawa Y.

    Journal of Cancer Research and Clinical Oncology (Journal of Cancer Research and Clinical Oncology)  148 ( 6 ) 1351 - 1361 2022.06

    ISSN  01715216

     View Summary

    Purpose: Angiopoietin-like 4 (ANGPTL4) was recently shown to be associated with cancer progression but little is known about its contribution to cancer metabolism. The purpose of this study was to elucidate the role of ANGPTL4 in glucose metabolism in colorectal cancer (CRC). Methods: Immunohistochemical staining of CRC specimens classified 84 patients into two groups according to ANGPTL4 expression. Clinicopathological characteristics, gene mutation status obtained by next-generation sequencing, and fluorodeoxyglucose (FDG) uptake measured by positron emission tomography/computed tomography (PET/CT) were compared between the two groups. Furthermore, the impact of ANGPTL4 expression on cancer metabolism was investigated by a subcutaneous xenograft mouse model using the ANGPTL4 knockout CRC cell line, and glucose transporter (GLUT) expression was evaluated. Results: There were significantly more cases of T3/4 tumours (94.3% vs. 57.1%, P < 0.001) and perineural invasion (42.9% vs. 22.4%, P = 0.046) in the ANGPTL4-high group than in the low group. Genetic exploration revealed a higher frequency of KRAS mutation (54.3% vs. 22.4%, P = 0.003) in the ANGPTL4-high tumours. All the FDG uptake parameters were significantly higher in ANGPTL4-high tumours. In vivo analysis showed a significant reduction in tumour size due to ANGPTL4 knockout with lower expression of GLUT1 and GLUT3, and suppression of AKT phosphorylation. Conclusion: ANGPTL4 regulates the expression of GLUTs by activating the PI3K–AKT pathway and thereby promoting glucose metabolism in CRC. These findings establish a new functional role of ANGPTL4 in cancer progression and lay the foundation for developing a novel therapeutic target.

  • MEK inhibition suppresses metastatic progression of KRAS-mutated gastric cancer

    Yamasaki J., Hirata Y., Otsuki Y., Suina K., Saito Y., Masuda K., Okazaki S., Ishimoto T., Saya H., Nagano O.

    Cancer Science (Cancer Science)  113 ( 3 ) 916 - 925 2022.03

    ISSN  13479032

     View Summary

    Metastatic progression of tumors is driven by genetic alterations and tumor-stroma interaction. To elucidate the mechanism underlying the oncogene-induced gastric tumor progression, we have developed an organoid-based model of gastric cancer from GAstric Neoplasia (GAN) mice, which express Wnt1 and the enzymes COX2 and microsomal prostaglandin E synthase 1 in the stomach. Both p53 knockout (GAN-p53KO) organoids and KRASG12V-expressing GAN-p53KO (GAN-KP) organoids were generated by genetic manipulation of GAN mouse-derived tumor (GAN wild-type [WT]) organoids. In contrast with GAN-WT and GAN-p53KO organoids, which manifested Wnt addiction, GAN-KP organoids showed a Wnt-independent phenotype and the ability to proliferate without formation of a Wnt-regulated three-dimensional epithelial architecture. After transplantation in syngeneic mouse stomach, GAN-p53KO cells formed only small tumors, whereas GAN-KP cells gave rise to invasive tumors associated with the development of hypoxia as well as to liver metastasis. Spatial transcriptomics analysis suggested that hypoxia signaling contributes to the metastatic progression of GAN-KP tumors. In particular, such analysis identified a cluster of stromal cells located at the tumor invasive front that expressed genes related to hypoxia signaling, angiogenesis, and cell migration. These cells were also positive for phosphorylated extracellular signal-regulated kinase (ERK), suggesting that mitogen-activated protein kinase (MAPK) signaling promotes development of both tumor and microenvironment. The MEK (MAPK kinase) inhibitor trametinib suppressed the development of GAN-KP gastric tumors, formation of a hypoxic microenvironment, tumor angiogenesis, and liver metastasis. Our findings therefore establish a rationale for application of trametinib to suppress metastatic progression of KRAS-mutated gastric cancer.

  • Vasodilator oxyfedrine inhibits aldehyde metabolism and thereby sensitizes cancer cells to xCT-targeted therapy

    Otsuki Y., Yamasaki J., Suina K., Okazaki S., Koike N., Saya H., Nagano O.

    Cancer Science (Cancer Science)  111 ( 1 ) 127 - 136 2020.01

    ISSN  13479032

     View Summary

    The major cellular antioxidant glutathione (GSH) protects cancer cells from oxidative damage that can lead to the induction of ferroptosis, an iron-dependent form of cell death triggered by the aberrant accumulation of lipid peroxides. Inhibitors of the cystine-glutamate antiporter subunit xCT, which mediates the uptake of extracellular cystine and thereby promotes GSH synthesis, are thus potential anticancer agents. However, the efficacy of xCT-targeted therapy has been found to be diminished by metabolic reprogramming that affects redox status in cancer cells. Identification of drugs for combination with xCT inhibitors that are able to overcome resistance to xCT-targeted therapy might thus provide the basis for effective cancer treatment. We have now identified the vasodilator oxyfedrine (OXY) as a sensitizer of cancer cells to GSH-depleting agents including the xCT inhibitor sulfasalazine (SSZ). Oxyfedrine contains a structural motif required for covalent inhibition of aldehyde dehydrogenase (ALDH) enzymes, and combined treatment with OXY and SSZ was found to induce accumulation of the cytotoxic aldehyde 4-hydroxynonenal and cell death in SSZ-resistant cancer cells both in vitro and in vivo. Microarray analysis of tumor xenograft tissue showed cyclooxygenase-2 expression as a potential biomarker for the efficacy of such combination therapy. Furthermore, OXY-mediated ALDH inhibition was found to sensitize cancer cells to GSH depletion induced by radiation therapy in vitro. Our findings thus establish a rationale for repurposing of OXY as a sensitizing drug for cancer treatment with agents that induce GSH depletion.

  • Glutaminolysis-related genes determine sensitivity to xCT-targeted therapy in head and neck squamous cell carcinoma

    Okazaki S., Umene K., Yamasaki J., Suina K., Otsuki Y., Yoshikawa M., Minami Y., Masuko T., Kawaguchi S., Nakayama H., Banno K., Aoki D., Saya H., Nagano O.

    Cancer Science (Cancer Science)  110 ( 11 ) 3453 - 3463 2019.11

    ISSN  13479032

     View Summary

    Targeting the function of membrane transporters in cancer stemlike cells is a potential new therapeutic approach. Cystine-glutamate antiporter xCT expressed in CD44 variant (CD44v)-expressing cancer cells contributes to the resistance to oxidative stress as well as cancer therapy through promoting glutathione (GSH)-mediated antioxidant defense. Amino acid transport by xCT might, thus, be a promising target for cancer treatment, whereas the determination factors for cancer cell sensitivity to xCT-targeted therapy remain unclear. Here, we demonstrate that high expression of xCT and glutamine transporter ASCT2 is correlated with undifferentiated status and diminished along with cell differentiation in head and neck squamous cell carcinoma (HNSCC). The cytotoxicity of the xCT inhibitor sulfasalazine relies on ASCT2-dependent glutamine uptake and glutamate dehydrogenase (GLUD)-mediated α-ketoglutarate (α-KG) production. Metabolome analysis revealed that sulfasalazine treatment triggers the increase of glutamate-derived tricarboxylic acid cycle intermediate α-KG, in addition to the decrease of cysteine and GSH content. Furthermore, ablation of GLUD markedly reduced the sulfasalazine cytotoxicity in CD44v-expressing stemlike HNSCC cells. Thus, xCT inhibition by sulfasalazine leads to the impairment of GSH synthesis and enhancement of mitochondrial metabolism, leading to reactive oxygen species (ROS) generation and, thereby, triggers oxidative damage. Our findings establish a rationale for the use of glutamine metabolism (glutaminolysis)-related genes, including ASCT2 and GLUD, as biomarkers to predict the efficacy of xCT-targeted therapy for heterogeneous HNSCC tumors.

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Presentations 【 Display / hide

  • 遺伝子操作とオルガノイド技術を用いた新しい胃癌モデルの作成

    平田 雄紀, 永野 修, 山崎 淳太郎, 新谷 昴, 推名 健太郎, 齋藤 慶幸, 川久保 博文, 佐谷 秀行, 北川 雄光




  • 小細胞肺癌において、xCTはがん幹細胞性に寄与する(xCT confers cancer stem-like properties in small cell lung cancer cells)

    推名 健太郎, 山崎 淳太郎, 大槻 雄士, 平田 雄紀, 岡崎 章悟, 土橋 賢司, サンペトラ・オルテア , 光石 陽一郎, 高橋 史行, 高橋 和久, 佐谷 秀行, 永野 修




  • Clinicopathological findings and molecular profile of gastric cancer with a gastric mucin phenotype 胃型腫瘍の臨床病理と分子異常 オルガノイド技術と遺伝子操作を用いた新たな胃癌モデルの作成(Clinicopathological findings and molecular profile of gastric cancer with a gastric mucin phenotype A novel gastric cancer mouse model by using organoid technique and genetic manipulation)

    平田 雄紀, 永野 修, 齋藤 慶幸, 山崎 淳太郎, 新谷 昴, 推名 健太郎, 岡崎 章悟, 佐谷 秀行, 川久保 博文, 北川 雄光




  • オルガノイド技術を用いた、遺伝子操作による新しい型胃癌モデルの作成(A novel gastric cancer mouse model by using organoid technique and genetic manipulation)

    平田 雄紀, 永野 修, 齋藤 慶幸, 山崎 淳太郎, 新谷 昴, 推名 健太郎, 岡崎 章悟, 川久保 博文, 佐谷 秀行, 北川 雄光




Research Projects of Competitive Funds, etc. 【 Display / hide

  • 新規胃がんマウスモデルの作成及び腸型-びまん型移行を誘導する分子メカニズムの解明


    MEXT,JSPS, Grant-in-Aid for Scientific Research, 研究活動スタート支援, Principal investigator