title: Identification of chemoradiation-resistant osteosarcoma stem cells using an imaging system for proteasome activity.
abstract: Osteosarcoma is the most common primary bone malignancy in pediatric and adolescent populations. Recurrence and metastatic potential can be due to a subpopulation of cells with stem cell-like characteristics, such as tumor-initiating cells (TICs), which maintain the capacity to regenerate entire tumors. Targeting the TICs in osteosarcoma is a promising avenue for the development of new therapies for this devastating disease. TICs are usually quiescent with a low protein turnover, decreased metabolism, and downregulation of proteasome activity. Recently, cancer cells with low proteasome activity have been identified as TICs in several types of cancer. We stably infected two osteosarcoma cell lines, MG-63 and U2-OS, with an expression vector for a fusion protein between the green fluorescent protein, ZsGreen, and the C-terminal degron of the murine ornithine decarboxylase to monitor the 26S proteasome activity in living cells. We separated the osteosarcoma cells with low proteasome activity using fluorescence-activated cell sorting (FACS) and verified whether these ZsGreen+ cells had TIC-like properties. The ZsGreen+ cells showed enhanced sphere formation capacity and underwent asymmetric divisions into ZsGreen+ and ZsGreen- cells, whereas ZsGreen- cells underwent only symmetric divisions into ZsGreen- cells. Moreover, the ZsGreen+ cells were more chemo- and radioresistant. Thus, the present study demonstrated that chemoradiation-resistant TICs can be visualized by this system and suggested the rationale for further study of osteosarcoma stem cells.
authors.affiliation: Department of Radiation Oncology, Osaka University, Graduate School of Medicine, Suita, Osaka 565-0871, Japan.
authors.forename: Keisuke
authors.initials: K
authors.lastname: Tamari
authors.affiliation: Department of Radiation Oncology, Osaka University, Graduate School of Medicine, Suita, Osaka 565-0871, Japan.
authors.forename: Kazuhiko
authors.initials: K
authors.lastname: Hayashi
authors.affiliation: Department of Frontier Science for Cancer and Chemotherapy, Osaka University, Graduate School of Medicine, Suita, Osaka 565-0871, Japan.
authors.forename: Hideshi
authors.initials: H
authors.lastname: Ishii
authors.affiliation: Department of Frontier Science for Cancer and Chemotherapy, Osaka University, Graduate School of Medicine, Suita, Osaka 565-0871, Japan.
authors.forename: Yoshihiro
authors.initials: Y
authors.lastname: Kano
authors.affiliation: Department of Frontier Science for Cancer and Chemotherapy, Osaka University, Graduate School of Medicine, Suita, Osaka 565-0871, Japan.
authors.forename: Masamitsu
authors.initials: M
authors.lastname: Konno
authors.affiliation: Department of Frontier Science for Cancer and Chemotherapy, Osaka University, Graduate School of Medicine, Suita, Osaka 565-0871, Japan.
authors.forename: Koichi
authors.initials: K
authors.lastname: Kawamoto
authors.affiliation: Department of Frontier Science for Cancer and Chemotherapy, Osaka University, Graduate School of Medicine, Suita, Osaka 565-0871, Japan.
authors.forename: Naohiro
authors.initials: N
authors.lastname: Nishida
authors.affiliation: Department of Cancer Profiling Discovery, Osaka University, Graduate School of Medicine, Suita, Osaka 565-0871, Japan.
authors.forename: Jun
authors.initials: J
authors.lastname: Koseki
authors.affiliation: Department of Frontier Science for Cancer and Chemotherapy, Osaka University, Graduate School of Medicine, Suita, Osaka 565-0871, Japan.
authors.forename: Takahito
authors.initials: T
authors.lastname: Fukusumi
authors.affiliation: Department of Frontier Science for Cancer and Chemotherapy, Osaka University, Graduate School of Medicine, Suita, Osaka 565-0871, Japan.
authors.forename: Shinichiro
authors.initials: S
authors.lastname: Hasegawa
authors.affiliation: Department of Frontier Science for Cancer and Chemotherapy, Osaka University, Graduate School of Medicine, Suita, Osaka 565-0871, Japan.
authors.forename: Hisataka
authors.initials: H
authors.lastname: Ogawa
authors.affiliation: Department of Frontier Science for Cancer and Chemotherapy, Osaka University, Graduate School of Medicine, Suita, Osaka 565-0871, Japan.
authors.forename: Atsushi
authors.initials: A
authors.lastname: Hamabe
authors.affiliation: Department of Frontier Science for Cancer and Chemotherapy, Osaka University, Graduate School of Medicine, Suita, Osaka 565-0871, Japan.
authors.forename: Masaaki
authors.initials: M
authors.lastname: Miyo
authors.affiliation: Department of Frontier Science for Cancer and Chemotherapy, Osaka University, Graduate School of Medicine, Suita, Osaka 565-0871, Japan.
authors.forename: Kozo
authors.initials: K
authors.lastname: Noguchi
authors.affiliation: Department of Radiation Oncology, Osaka University, Graduate School of Medicine, Suita, Osaka 565-0871, Japan.
authors.forename: Yuji
authors.initials: Y
authors.lastname: Seo
authors.affiliation: Department of Gastroenterological Surgery, Osaka University, Graduate School of Medicine, Suita, Osaka 565-0871, Japan.
authors.forename: Yuichiro
authors.initials: Y
authors.lastname: Doki
authors.affiliation: Department of Gastroenterological Surgery, Osaka University, Graduate School of Medicine, Suita, Osaka 565-0871, Japan.
authors.forename: Masaki
authors.initials: M
authors.lastname: Mori
authors.affiliation: Department of Radiation Oncology, Osaka University, Graduate School of Medicine, Suita, Osaka 565-0871, Japan.
authors.forename: Kazuhiko
authors.initials: K
authors.lastname: Ogawa
mesh_terms: D000818:Animals; D045744:Cell Line, Tumor; D059248:Chemoradiotherapy; D005434:Flow Cytometry; D049452:Green Fluorescent Proteins; D006801:Humans; D051379:Mice; D014411:Neoplastic Stem Cells / Q000378:metabolism / Q000473:pathology*; D009955:Ornithine Decarboxylase / Q000235:genetics; D012516:Osteosarcoma / Q000188:drug therapy / Q000235:genetics* / Q000473:pathology / Q000532:radiotherapy; D046988:Proteasome Endopeptidase Complex / Q000235:genetics*; D011836:Radiation Tolerance / Q000235:genetics*
chemical_list: D049452:Green Fluorescent Proteins; D046988:Proteasome Endopeptidase Complex; C061553:ATP dependent 26S protease; D009955:Ornithine Decarboxylase