title: Therapeutic implications of an enriched cancer stem-like cell population in a human osteosarcoma cell line.
abstract: BACKGROUND
  Osteosarcoma is a bone-forming tumor of mesenchymal origin that presents a clinical pattern that is consistent with the cancer stem cell model. Cells with stem-like properties (CSCs) have been identified in several tumors and hypothesized as the responsible for the relative resistance to therapy and tumor relapses. In this study, we aimed to identify and characterize CSCs populations in a human osteosarcoma cell line and to explore their role in the responsiveness to conventional therapies.
  
  
  METHODS
  CSCs were isolated from the human MNNG/HOS cell line using the sphere formation assay and characterized in terms of self-renewal, mesenchymal stem cell properties, expression of pluripotency markers and ABC transporters, metabolic activity and tumorigenicity. Cell's sensitivity to conventional chemotherapeutic agents and to irradiation was analyzed and related with cell cycle-induced alterations and apoptosis.
  
  
  RESULTS
  The isolated CSCs were found to possess self-renewal and multipotential differentiation capabilities, express markers of pluripotent embryonic stem cells Oct4 and Nanog and the ABC transporters P-glycoprotein and BCRP, exhibit low metabolic activity and induce tumors in athymic mice. Compared with parental MNNG/HOS cells, CSCs were relatively more resistant to both chemotherapy and irradiation. None of the treatments have induced significant cell-cycle alterations and apoptosis in CSCs.
  
  
  CONCLUSIONS
  MNNG/HOS osteosarcoma cells contain a stem-like cell population relatively resistant to conventional chemotherapeutic agents and irradiation. This resistant phenotype appears to be related with some stem features, namely the high expression of the drug efflux transporters P-glycoprotein and BCRP and their quiescent nature, which may provide a biological basis for resistance to therapy and recurrence commonly observed in osteosarcoma.
authors.affiliation: Pharmacology and Experimental Therapeutics - Institute of Biomedical Research in Light and Image (IBILI), Faculty of Medicine, University of Coimbra, Az, de Sta. Comba, Celas, Coimbra 3000-354, Portugal.
authors.forename: Sara R
authors.initials: SR
authors.lastname: Martins-Neves
authors.forename: Áurio O
authors.initials: ÁO
authors.lastname: Lopes
authors.forename: Anália
authors.initials: A
authors.lastname: do Carmo
authors.forename: Artur A
authors.initials: AA
authors.lastname: Paiva
authors.forename: Paulo C
authors.initials: PC
authors.lastname: Simões
authors.forename: Antero J
authors.initials: AJ
authors.lastname: Abrunhosa
authors.forename: Célia M F
authors.initials: CM
authors.lastname: Gomes
mesh_terms: D000818:Animals; D000970:Antineoplastic Agents / Q000494:pharmacology; D017209:Apoptosis / Q000187:drug effects / Q000528:radiation effects; D014408:Biomarkers, Tumor / Q000378:metabolism; D015153:Blotting, Western; D001859:Bone Neoplasms / Q000378:metabolism / Q000473:pathology / Q000628:therapy*; D002453:Cell Cycle / Q000187:drug effects / Q000528:radiation effects; D045744:Cell Line, Tumor; D005434:Flow Cytometry; D006801:Humans; D008297:Male; D051379:Mice; D008807:Mice, Inbred BALB C; D008819:Mice, Nude; D014411:Neoplastic Stem Cells / Q000187:drug effects* / Q000378:metabolism / Q000473:pathology / Q000528:radiation effects*; D012516:Osteosarcoma / Q000378:metabolism / Q000473:pathology / Q000628:therapy*; D017382:Reactive Oxygen Species / Q000378:metabolism; D018874:Spheroids, Cellular / Q000187:drug effects / Q000378:metabolism / Q000473:pathology / Q000528:radiation effects; D014407:Tumor Cells, Cultured
chemical_list: D000970:Antineoplastic Agents; D014408:Biomarkers, Tumor; D017382:Reactive Oxygen Species