title: Sphere-forming cell subpopulations with cancer stem cell properties in human hepatoma cell lines.
abstract: BACKGROUND
  Cancer stem cells (CSCs) are regarded as the cause of tumor formation and recurrence. The isolation and identification of CSCs could help to develop novel therapeutic strategies specifically targeting CSCs.
  
  
  METHODS
  Human hepatoma cell lines were plated in stem cell conditioned culture system allowed for sphere forming. To evaluate the stemness characteristics of spheres, the self-renewal, proliferation, chemoresistance, tumorigenicity of the PLC/PRF/5 sphere-forming cells, and the expression levels of stem cell related proteins in the PLC/PRF/5 sphere-forming cells were assessed, comparing with the parental cells. The stem cell RT-PCR array was performed to further explore the biological properties of liver CSCs.
  
  
  RESULTS
  The PLC/PRF/5, MHCC97H and HepG2 cells could form clonal nonadherent 3-D spheres and be serially passaged. The PLC/PRF/5 sphere-forming cells possessed a key criteria that define CSCs: persistent self-renewal, extensive proliferation, drug resistance, overexpression of liver CSCs related proteins (Oct3/4, OV6, EpCAM, CD133 and CD44). Even 500 sphere-forming cells were able to form tumors in NOD/SCID mice, and the tumor initiating capability was not decreased when spheres were passaged. Besides, downstream proteins DTX1 and Ep300 of the CSL (CBF1 in humans, Suppressor of hairless in Drosophila and LAG1 in C. elegans) -independent Notch signaling pathway were highly expressed in the spheres, and a gamma-secretase inhibitor MRK003 could significantly inhibit the sphere formation ability.
  
  
  CONCLUSIONS
  Nonadherent tumor spheres from hepatoma cell lines cultured in stem cell conditioned medium possess liver CSC properties, and the CSL-independent Notch signaling pathway may play a role in liver CSCs.
authors.affiliation: Department of Molecular Oncology, Second Military Medical University, Shanghai, China.
authors.forename: Lu
authors.initials: L
authors.lastname: Cao
authors.forename: Yanming
authors.initials: Y
authors.lastname: Zhou
authors.forename: Beibei
authors.initials: B
authors.lastname: Zhai
authors.forename: Jian
authors.initials: J
authors.lastname: Liao
authors.forename: Wen
authors.initials: W
authors.lastname: Xu
authors.forename: Ruixiu
authors.initials: R
authors.lastname: Zhang
authors.forename: Jing
authors.initials: J
authors.lastname: Li
authors.forename: Yu
authors.initials: Y
authors.lastname: Zhang
authors.forename: Lei
authors.initials: L
authors.lastname: Chen
authors.forename: Haihua
authors.initials: H
authors.lastname: Qian
authors.forename: Mengchao
authors.initials: M
authors.lastname: Wu
authors.forename: Zhengfeng
authors.initials: Z
authors.lastname: Yin
mesh_terms: D000818:Animals; D000970:Antineoplastic Agents / Q000494:pharmacology; D014408:Biomarkers, Tumor / Q000378:metabolism; D015153:Blotting, Western; D015197:Carcinogenicity Tests; D006528:Carcinoma, Hepatocellular / Q000378:metabolism / Q000473:pathology*; D045744:Cell Line, Tumor; D005455:Fluorescent Antibody Technique; D006801:Humans; D008113:Liver Neoplasms / Q000378:metabolism / Q000473:pathology*; D008297:Male; D051379:Mice; D016688:Mice, Inbred NOD; D016513:Mice, SCID; D014411:Neoplastic Stem Cells / Q000187:drug effects / Q000378:metabolism / Q000473:pathology*; D016133:Polymerase Chain Reaction; D018874:Spheroids, Cellular / Q000187:drug effects / Q000378:metabolism / Q000473:pathology*; D014407:Tumor Cells, Cultured
chemical_list: D000970:Antineoplastic Agents; D014408:Biomarkers, Tumor