title: Abundant nucleostemin expression supports the undifferentiated properties of germ cell tumors.
abstract: Nucleostemin (NS) is a nucleolar GTP-binding protein that is involved in ribosomal biogenesis and protection of telomeres. We investigated the expression of NS in human germ cell tumors and its function in a mouse germ cell tumor model. NS was abundantly expressed in undifferentiated, but not differentiated, types of human testicular germ cell tumors. NS was expressed concomitantly with OCT3/4, a critical regulator of the undifferentiated status of pluripotent stem cells in primordial germ cells and embryonal carcinomas. To investigate the roles of NS in tumor growth in vivo, we used a mouse teratoma model. Analysis of teratomas derived from embryonic stem cells in which the NS promoter drives GFP expression showed that cells highly expressing NS were actively proliferating and exhibited the characteristics of tumor-initiating cells, including the ability to initiate and propagate tumor cells in vivo. NS-expressing cells exhibited higher levels of GTP than non-NS-expressing cells. Because NS protein is stabilized by intracellular GTP, metabolic changes may contribute to abundant NS expression in the undifferentiated cells. OCT3/4 deficiency in teratomas led to loss of NS expression, resulting in growth retardation. Finally, we found that teratomas deficient in NS lost their undifferentiated characteristics, resulting in defective tumor proliferation. These data indicate that abundant expression of NS supports the undifferentiated properties of germ cell tumors.
authors.affiliation: Division of Molecular Genetics, Cancer and Stem Cell Program, Cancer Research Institute, Kanazawa University, Kanazawa, Japan.
authors.forename: Noriyuki
authors.initials: N
authors.lastname: Uema
authors.forename: Takako
authors.initials: T
authors.lastname: Ooshio
authors.forename: Kenichi
authors.initials: K
authors.lastname: Harada
authors.forename: Masako
authors.initials: M
authors.lastname: Naito
authors.forename: Kazuhito
authors.initials: K
authors.lastname: Naka
authors.forename: Takayuki
authors.initials: T
authors.lastname: Hoshii
authors.forename: Yuko
authors.initials: Y
authors.lastname: Tadokoro
authors.forename: Kumiko
authors.initials: K
authors.lastname: Ohta
authors.forename: Mohamed A E
authors.initials: MA
authors.lastname: Ali
authors.forename: Miyuki
authors.initials: M
authors.lastname: Katano
authors.forename: Tomoyoshi
authors.initials: T
authors.lastname: Soga
authors.forename: Yasuni
authors.initials: Y
authors.lastname: Nakanuma
authors.forename: Akihiko
authors.initials: A
authors.lastname: Okuda
authors.forename: Atsushi
authors.initials: A
authors.lastname: Hirao
mesh_terms: D000818:Animals; D002352:Carrier Proteins / Q000378:metabolism*; D049109:Cell Proliferation; D004195:Disease Models, Animal; D019204:GTP-Binding Proteins; D005854:Germ Cells / Q000473:pathology; D006801:Humans; D008297:Male; D051379:Mice; D008822:Mice, Transgenic; D009687:Nuclear Proteins / Q000378:metabolism*; D016601:RNA-Binding Proteins; D013724:Teratoma / Q000378:metabolism* / Q000473:pathology; D013736:Testicular Neoplasms / Q000378:metabolism* / Q000473:pathology; D014407:Tumor Cells, Cultured
chemical_list: D002352:Carrier Proteins; D009687:Nuclear Proteins; D016601:RNA-Binding Proteins; C470311:nucleostemin protein, mouse; D019204:GTP-Binding Proteins