Michinari Hirata

Publications (3)21.83 Total impact

• Article: Heparin-binding EGF-like growth factor is a promising target for ovarian cancer therapy.

  Shingo Miyamoto, Michinari Hirata, Ayano Yamazaki, Takuya Kageyama, Hidetoshi Hasuwa, Hiroto Mizushima, Yoshihiro Tanaka, Hiroshi Yagi, Kenzo Sonoda, Masahiro Kai, Hideo Kanoh, Hitoo Nakano, Eisuke Mekada
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  ABSTRACT: Ovarian cancer is the most frequent cause of cancer death among all gynecologic cancers. We demonstrate here that lysophosphatidic acid (LPA)-induced ectodomain shedding of heparin-binding EGF-like growth factor (HB-EGF) is a critical to tumor formation in ovarian cancer. We found that among the epidermal growth factor receptor (EGFR) family of growth factors, HB-EGF gene expression in cancerous tissues and HB-EGF protein levels in patients' ascites fluid were significantly elevated. The human ovarian cancer cell lines SKOV3 and RMG-1 form tumors in nude mice. Tumor formation of these cells was enhanced by exogenous expression of pro-HB-EGF and completely blocked by pro-HB-EGF gene RNA interference or by CRM197, a specific HB-EGF inhibitor. Transfection with mutant forms of HB-EGF indicated that the release of soluble HB-EGF is essential for tumor formation. LPA, which is constitutively produced by ovarian cancer cells, induced HB-EGF ectodomain shedding in SKOV3 and RMG-1 cells, resulting in the transactivation of EGFR and the downstream kinase extracellular signal-regulated kinase/mitogen-activated protein kinase. LPA-induced transactivation was abrogated by HB-EGF gene RNA interference or by CRM197. Introduction of lipid phosphate phosphohydrolase, which hydrolyzes LPA, decreased the constitutive shedding of HB-EGF, EGFR transactivation, and the tumorigenic potential of SKOV3 and RMG-1 cells. These results indicate that HB-EGF is the primary member of the EGFR family of growth factors expressed in ovarian cancer and that LPA-induced ectodomain shedding of this growth factor is a critical step in tumor formation, making HB-EGF a novel therapeutic target for ovarian cancer.
  Cancer Research 09/2004; 64(16):5720-7. · 7.86 Impact Factor
• Article: The stress- and inflammatory cytokine-induced ectodomain shedding of heparin-binding epidermal growth factor-like growth factor is mediated by p38 MAPK, distinct from the 12-O-tetradecanoylphorbol-13-acetate- and lysophosphatidic acid-induced signaling cascades.

  Hisanori Takenobu, Ayano Yamazaki, Michinari Hirata, Toshiyuki Umata, Eisuke Mekada
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  ABSTRACT: Heparin-binding epidermal growth factor-like growth factor (HB-EGF) is a critical growth factor for a number of physiological and pathological processes. HB-EGF is synthesized as a membrane-anchored form (pro-HB-EGF), and pro-HB-EGF is cleaved at the cell surface to yield soluble HB-EGF by a mechanism called "ectodomain shedding." We show here that the ectodomain shedding of pro-HB-EGF in Vero cells is induced by various stress-inducing stimuli, including UV light, osmotic pressure, hyperoxidation, and translation inhibitors. The pro-inflammatory cytokine interleukin-1beta also stimulated the ectodomain shedding of pro-HB-EGF. An inhibitor of p38 MAPK (SB203580) or the expression of a dominant-negative (dn) form of p38 MAPK inhibited the stress-induced ectodomain shedding of pro-HB-EGF, whereas an inhibitor of JNK (SP600125) or the expression of dnJNK1 did not. 12-O-Tetradecanoylphorbol-13-acetate (TPA) and lysophosphatidic acid (LPA) are also potent inducers of pro-HB-EGF shedding in Vero cells. Stress-induced pro-HB-EGF shedding was not inhibited by the inhibitors of TPA- or LPA-induced pro-HB-EGF shedding or by dn forms of molecules involved in the TPA- or LPA-induced pro-HB-EGF shedding pathway. Reciprocally, SB203580 or dnp38 MAPK did not inhibit TPA- or LPA-induced pro-HB-EGF shedding. These results indicate that stress-induced pro-HB-EGF shedding is mediated by p38 MAPK and that the signaling pathway induced by stress is distinct from the TPA- or LPA-induced pro-HB-EGF shedding pathway.
  Journal of Biological Chemistry 06/2003; 278(19):17255-62. · 4.77 Impact Factor
• Article: A metalloprotease|[ndash]|disintegrin, MDC9/meltrin-|[gamma]|/ADAM9 and PKC|[delta]| are involved in TPA-induced ectodomain shedding of membrane-anchored heparin-binding EGF-like growth factor

  Yasushi Izumi, Michinari Hirata, Hidetoshi Hasuwa, Ryo Iwamoto, Toshiyuki Umata, Kenji Miyado, Yoko Tamai, Tomohiro Kurisaki, Atsuko Sehara-Fujisawa, Shigeo Ohno, Eisuke Mekada
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  ABSTRACT: The ectodomains of many proteins located at the cell surface are shed upon cell stimulation. One such protein is the heparin-binding EGF-like growth factor (HB-EGF) that exists in a membrane-anchored form which is converted to a soluble form upon cell stimulation with TPA, an activator of protein kinase C (PKC). We show that PKC binds in vivo and in vitro to the cytoplasmic domain of MDC9/meltrin-/ADAM9, a member of the metalloprotease–disintegrin family. Furthermore, the presence of constitutively active PKC or MDC9 results in the shedding of the ectodomain of proHB-EGF, whereas MDC9 mutants lacking the metalloprotease domain, as well as kinase-negative PKC, suppress the TPA-induced shedding of the ectodomain. These results suggest that MDC9 and PKC are involved in the stimulus-coupled shedding of the proHB-EGF ectodomain.
  The EMBO Journal 12/1998; 17(24):7260-7272. · 9.20 Impact Factor