title: Maintenance of Clonogenic KIT(+) Human Colon Tumor Cells Requires Secretion of Stem Cell Factor by Differentiated Tumor Cells.
abstract: OBJECTIVE
  Colon tumors contain a fraction of undifferentiated stem cell-like cancer cells with high tumorigenic potential. Little is known about the signals that maintain these stem-like cells. We investigated whether differentiated tumor cells provide support.
  
  
  METHODS
  We established undifferentiated colonosphere cultures from human colon tumors and used them to generate stably differentiated cell lines. Antibody arrays were used to identify secreted factors. Expression of genes involved in stemness, differentiation, and the epithelial to mesenchymal transition was measured using reverse transcription quantitative polymerase chain reaction. Expression of KIT in human tumors was analyzed with gene expression arrays and by immunohistochemistry. Colonospheres were injected into the livers of CBy.Cg-Foxn1nu/J mice. After liver tumors had formed, hypoxia was induced by vascular clamping.
  
  
  RESULTS
  Differentiated cells from various tumors, or medium conditioned by them, increased the clonogenic capacity of colonospheres. Stem cell factor (SCF) was secreted by differentiated tumor cells and supported the clonogenic capacity of KIT(+) colonosphere cells. Differentiated tumor cells induced the epithelial to mesenchymal transition in colonosperes; this was prevented by inhibition of KIT or SCF. SCF prevented loss of clonogenic potential under differentiation-inducing conditions. Suppression of SCF or KIT signaling greatly reduced the expression of genes that regulate stemness and the epithelial to mesenchymal transition and inhibited clonogenicity and tumor initiation. Bioinformatic and immunohistochemical analyses revealed a correlation between expression of KIT- and hypoxia-related genes in colon tumors, which was highest in relapse-prone mesenchymal-type tumors. Hypoxia induced expression of KIT in cultured cells and in human colon tumor xenografts and this contributed to the clonogenic capacity of the tumor cells.
  
  
  CONCLUSIONS
  Paracrine signaling from SCF to KIT, between differentiated tumor cells and undifferentiated stem-like tumor cells, helps maintain the stem-like features of tumor cells, predominantly under conditions of hypoxia.
authors.affiliation: Department of Surgery, University Medical Center Utrecht, Utrecht, The Netherlands.
authors.forename: Szabolcs
authors.initials: S
authors.lastname: Fatrai
authors.affiliation: Department of Surgery, University Medical Center Utrecht, Utrecht, The Netherlands.
authors.forename: Susanne J
authors.initials: SJ
authors.lastname: van Schelven
authors.affiliation: Department of Surgery, University Medical Center Utrecht, Utrecht, The Netherlands.
authors.forename: Inge
authors.initials: I
authors.lastname: Ubink
authors.affiliation: Department of Surgery, University Medical Center Utrecht, Utrecht, The Netherlands.
authors.forename: Klaas M
authors.initials: KM
authors.lastname: Govaert
authors.affiliation: Department of Surgery, University Medical Center Utrecht, Utrecht, The Netherlands.
authors.forename: Danielle
authors.initials: D
authors.lastname: Raats
authors.affiliation: Department of Oncogenomics, Academic Medical Centre, University of Amsterdam, Amsterdam, The Netherlands.
authors.forename: Jan
authors.initials: J
authors.lastname: Koster
authors.affiliation: Department of Surgery, University Medical Center Utrecht, Utrecht, The Netherlands.
authors.forename: Andre
authors.initials: A
authors.lastname: Verheem
authors.affiliation: Department of Surgery, University Medical Center Utrecht, Utrecht, The Netherlands.
authors.forename: Inne H M
authors.initials: IH
authors.lastname: Borel Rinkes
authors.affiliation: Department of Surgery, University Medical Center Utrecht, Utrecht, The Netherlands. Electronic address: o.kranenburg@umcutrecht.nl.
authors.forename: Onno
authors.initials: O
authors.lastname: Kranenburg
mesh_terms: D000818:Animals; D014408:Biomarkers, Tumor / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D002454:Cell Differentiation; D015687:Cell Hypoxia; D049109:Cell Proliferation; D018920:Coculture Techniques; D003110:Colonic Neoplasms / Q000201:enzymology* / Q000235:genetics / Q000378:metabolism / Q000473:pathology; D058750:Epithelial-Mesenchymal Transition; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D008819:Mice, Nude; D014411:Neoplastic Stem Cells / Q000201:enzymology* / Q000473:pathology; D019899:Paracrine Communication / Q000187:drug effects; D047428:Protein Kinase Inhibitors / Q000494:pharmacology; D019009:Proto-Oncogene Proteins c-kit / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D015398:Signal Transduction; D018874:Spheroids, Cellular; D019089:Stem Cell Factor / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D013997:Time Factors; D047368:Tumor Burden; D014407:Tumor Cells, Cultured
chemical_list: D014408:Biomarkers, Tumor; D047428:Protein Kinase Inhibitors; D019089:Stem Cell Factor; D019009:Proto-Oncogene Proteins c-kit
keywords: Colon Cancer Model; Colorectal; Niche; Tumor Progression