title: In vitro stemness characterization of radio-resistant clones isolated from a medulloblastoma cell line ONS-76.
abstract: One-third of patients with medulloblastoma die due to recurrence after various treatments including radiotherapy. Although it has been postulated that cancer stem-like cells are radio-resistant and play an important role in tumor recurrence, the "stemness" of medulloblastoma cells surviving irradiation has not yet been elucidated. Using a medulloblastoma cell line ONS-76, cells that survived gamma irradiation were investigated on their "stemness" in vitro. From 10 500 cells, 20 radio-resistant clones were selected after gamma ray irradiation (5 Gy × two fractions) using the replica micro-well technique. These 20 resistant clones were screened for CD133 positivity by flow cytometry followed by side population assay, tumor sphere formation assay and clonogenic survival assay. Results revealed CD133 fractions were significantly elevated in three clones, which also exhibited significantly increased levels of tumor sphere formation ability and side population fraction. Clonogenic survival assay demonstrated that their radio-resistance was significantly higher than the parental ONS-76. This may support the hypothesis that a small number of cancer stem-like cells (CSCs) are the main culprits in local recurrence after radiotherapy, and disruption of the resistance mechanism of these CSCs is a critical future issue in improving the outcome of patients with medulloblastoma.
authors.affiliation: Graduate School of Comprehensive Human Sciences, University of Tsukuba, 1-1-1 Tennodai, Tsukuba, Ibaraki 305-8575, Japan.
authors.forename: Lue
authors.initials: L
authors.lastname: Sun
authors.forename: Takashi
authors.initials: T
authors.lastname: Moritake
authors.forename: Yun-Wen
authors.initials: YW
authors.lastname: Zheng
authors.forename: Kenshi
authors.initials: K
authors.lastname: Suzuki
authors.forename: Ariungerel
authors.initials: A
authors.lastname: Gerelchuluun
authors.forename: Zhengshan
authors.initials: Z
authors.lastname: Hong
authors.forename: Junko
authors.initials: J
authors.lastname: Zenkoh
authors.forename: Hideki
authors.initials: H
authors.lastname: Taniguchi
authors.forename: Koji
authors.initials: K
authors.lastname: Tsuboi
mesh_terms: D017209:Apoptosis / Q000528:radiation effects*; D045744:Cell Line, Tumor; D002469:Cell Separation; D002470:Cell Survival / Q000528:radiation effects*; D002675:Child, Preschool; D019976:Cloning, Organism; D005260:Female; D006801:Humans; D008527:Medulloblastoma / Q000473:pathology* / Q000503:physiopathology* / Q000532:radiotherapy; D014411:Neoplastic Stem Cells / Q000473:pathology* / Q000528:radiation effects*; D011829:Radiation Dosage; D011836:Radiation Tolerance