title: The in-vitro spheroid culture induces a more highly differentiated but tumorigenic population from melanoma cell lines.
abstract: Cancer stem cells (CSCs) have been identified in various malignancies, and different properties have been examined to characterize CSCs: tumorigenicity in immunocompromised mice, stem cell surface markers, label-retaining properties, and proliferation as nonadherent spheres. This study explored the consistency and efficiency among these methods. Among the melanoma cell lines examined (A375, A875, MUM-2b, and MUM-2c), only A375 and MUM-2c grew as nonadherent spheres and continuously propagated in a defined serum-free medium in vitro. Flow cytometry and immunofluorescence analysis indicated that sphere-derived cells contained a smaller proportion of cells expressing the candidate surface markers of melanoma stem cells such as ABCB5, CD133, CD20 and CD271, and a larger proportion of cells expressing melanocytic differentiation markers such as HMB45 and S100 protein, compared with adherent cells. Surprisingly, the more highly differentiated sphere-derived melanoma cells exhibited increased tumorigenic potential in vivo, as indicated by shorter tumor incubation (A375) and smaller number of cells required to initiate tumor formation (A375 and MUM-2c) compared with those of parental cells. Despite the similarity in histopathological characteristics, the expression profile indicated that xenografts derived from sphere-derived melanoma cells exhibited a more tumorigenic phenotype with respect to the stem or the differentiation markers detected by immunohistochemical analysis. Therefore, sphere formation in nonadherent cultures may not be a preferred surrogate in-vitro method for enriching melanoma stem cells according to candidate markers but may be a favorable condition for activating potential CSCs.
authors.affiliation: Department of Pathology, Tianjin General Hospital, Tianjin Medical University, Tianjin, China.
authors.forename: Jing
authors.initials: J
authors.lastname: Mo
authors.forename: Baocun
authors.initials: B
authors.lastname: Sun
authors.forename: Xiulan
authors.initials: X
authors.lastname: Zhao
authors.forename: Qiang
authors.initials: Q
authors.lastname: Gu
authors.forename: Xueyi
authors.initials: X
authors.lastname: Dong
authors.forename: Zhiyong
authors.initials: Z
authors.lastname: Liu
authors.forename: Yuemei
authors.initials: Y
authors.lastname: Ma
authors.forename: Nan
authors.initials: N
authors.lastname: Zhao
authors.forename: Yanrong
authors.initials: Y
authors.lastname: Liu
authors.forename: Jiadong
authors.initials: J
authors.lastname: Chi
authors.forename: Ran
authors.initials: R
authors.lastname: Sun
mesh_terms: D000818:Animals; D017209:Apoptosis; D014408:Biomarkers, Tumor / Q000235:genetics / Q000378:metabolism; D015153:Blotting, Western; D002454:Cell Differentiation; D049109:Cell Proliferation; D005260:Female; D005434:Flow Cytometry; D005455:Fluorescent Antibody Technique; D064593:Heterografts; D006801:Humans; D007124:Immunoenzyme Techniques; D066298:In Vitro Techniques; D008545:Melanoma / Q000235:genetics / Q000378:metabolism / Q000473:pathology*; D051379:Mice; D008807:Mice, Inbred BALB C; D008819:Mice, Nude; D014411:Neoplastic Stem Cells / Q000378:metabolism / Q000473:pathology*; D012333:RNA, Messenger / Q000235:genetics; D060888:Real-Time Polymerase Chain Reaction; D020133:Reverse Transcriptase Polymerase Chain Reaction; D018874:Spheroids, Cellular / Q000378:metabolism / Q000473:pathology*; D014407:Tumor Cells, Cultured
chemical_list: D014408:Biomarkers, Tumor; D012333:RNA, Messenger