title: Holoclone forming cells from pancreatic cancer cells enrich tumor initiating cells and represent a novel model for study of cancer stem cells.
abstract: BACKGROUND
  Pancreatic cancer is one of the direct causes of cancer-related death. High level of chemoresistance is one of the major obstacles of clinical treatment. In recent years, cancer stem cells have been widely identified and indicated as the origin of chemoresistance in multi-types of solid tumors. Increasing evidences suggest that cancer stem cells reside in the cells capable of forming holoclones continuously. However, in pancreatic cancer, holoclone-forming cells have not been characterized yet. Therefore, the goal of our present study was to indentify the holoclone-forming pancreatic cancer stem cells and develop an in vitro continuous colony formation system, which will greatly facilitate the study of pancreatic cancer stem cells.
  
  
  RESULTS
  Pancreatic cancer cell line BxPC3 was submitted to monoclonal cultivation to generate colonies. Based on the morphologies, colonies were classified and analyzed for their capacities of secondary colony formation, long-term survival in vitro, tumor formation in vivo, and drug resistance. Flowcytometry and quantitative RT-PCR were performed to detect the expression level of cancer stem cells associated cell surface markers, regulatory genes and microRNAs in distinct types of colonies. Three types of colonies with distinct morphologies were identified and termed as holo-, mero-, and paraclones, in which only holoclones generated descendant colonies of all three types in further passages. Compared to mero- and paraclones, holoclones possessed higher capacities of long-term survival, tumor initiation, and chemoresistance. The preferential expression of cancer stem cells related marker (CXCR4), regulatory genes (BMI1, GLI1, and GLI2) and microRNAs (miR-214, miR-21, miR-221, miR-222 and miR-155) in holoclones were also highlighted.
  
  
  CONCLUSIONS
  Our results indicate that the pancreatic tumor-initiating cells with high level of chemoresistance were enriched in holoclones derived from BxPC3 cell line. Generation of holoclones can serve as a novel model for studying cancer stem cells, and attribute to developing new anti-cancer drugs.
authors.affiliation: College of Life Sciences, Peking University, Beijing, China.
authors.forename: Lei
authors.initials: L
authors.lastname: Tan
authors.forename: Xin
authors.initials: X
authors.lastname: Sui
authors.forename: Hongkui
authors.initials: H
authors.lastname: Deng
authors.forename: Mingxiao
authors.initials: M
authors.lastname: Ding
mesh_terms: D000818:Animals; D014408:Biomarkers, Tumor / Q000378:metabolism; D045744:Cell Line, Tumor; D005434:Flow Cytometry; D006801:Humans; D051741:Kruppel-Like Transcription Factors / Q000378:metabolism; D051379:Mice; D016688:Mice, Inbred NOD; D016513:Mice, SCID; D035683:MicroRNAs / Q000378:metabolism; D014411:Neoplastic Stem Cells / Q000378:metabolism*; D009687:Nuclear Proteins / Q000378:metabolism; D010190:Pancreatic Neoplasms / Q000378:metabolism*; D063150:Polycomb Repressive Complex 1; D011518:Proto-Oncogene Proteins / Q000378:metabolism; D019718:Receptors, CXCR4 / Q000378:metabolism; D012097:Repressor Proteins / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D014157:Transcription Factors / Q000378:metabolism; D000071676:Zinc Finger Protein GLI1; D000075746:Zinc Finger Protein Gli2
chemical_list: C069077:BMI1 protein, human; D014408:Biomarkers, Tumor; C527276:CXCR4 protein, human; C400551:GLI1 protein, human; C082593:GLI2 protein, human; D051741:Kruppel-Like Transcription Factors; D035683:MicroRNAs; D009687:Nuclear Proteins; D011518:Proto-Oncogene Proteins; D019718:Receptors, CXCR4; D012097:Repressor Proteins; D014157:Transcription Factors; D000071676:Zinc Finger Protein GLI1; D000075746:Zinc Finger Protein Gli2; D063150:Polycomb Repressive Complex 1