title: 5-Fluorouracil upregulates the activity of Wnt signaling pathway in CD133-positive colon cancer stem-like cells.
abstract: OBJECTIVE
  CD133-positive colon cancer stem like cells (CSLCs) are resistant to the conventional cytotoxic drug 5-fluorouracil (5-FU). Wnt signaling pathway plays important roles in colon cancer carcinogenesis and metastasis, and regulates the self-renewal capacity of CSLCs. In the present study, we explored the impact of 5-FU on Wnt signaling pathway of CD133-positive colon CSLCs, and the relation between Wnt signaling pathway and drug resistance of CD133-positive colon CSLCs.
  
  
  METHODS
  Magnetic activation cell separation was used to collect CD133-positive cells from colon cancer cell line DLD1, which was transfected with luciferase reporter for Wnt signaling activity. The activity of Wnt signaling pathway was compared between CD133-positive and CD133-negative cells. After the treatment with 1 μg/mL of 5-FU, the cell proliferation rates of DLD1 cells, CD133-positive cells, and CD133-negative cells were compared. After the treatment with 1 μg/mL and 10 μg/mL of 5-FU for 48 h, Wnt activity was compared between CD133-positive and CD133-negative cells. The expression of CD133 and cell apoptosis of CD133-positive cells was detected after exposure to 50 ng/mL of dickkopf (DKK)-1, a Wnt pathway inhibitor.
  
  
  RESULTS
  After the treatment with 5-FU, the cell proliferation rate of CD133-positive cells was higher than that of CD133-negative cells and the sensitivity of CD133-positive cells to 5-FU decreased. Wnt activity was higher in CD133-positive cells than in CD133-negative cells [(46.3 ± 0.3)% vs. (33.9 ± 2.7)%, P = 0.009]. After the treatment with 1 μg/mL and 10 μg/mL of 5-FU, Wnt activity of CD133-positive cells was (90.1 ± 10.0)% (P = 0.012) and (52.9 ± 2.5)% (P = 0.047), respectively, whereas that of CD133-negative cells was (35.5 ± 3.3)% (P = 0.434) and (26.5 ± 0.4)% (P = 0.046), respectively. CD133 expression in CD133-positive cells decreased from (87.2 ± 5.3)% to (60.6 ± 3.1)% (P = 0.022) after treatment with DKK-1, whereas the cell apoptosis rate increased from (11.8 ± 0.2)% to (28.3 ± 0.6)% (P = 0.013).
  
  
  CONCLUSIONS
  Wnt activity is higher in CD133-positive DLD1 cells than in CD133-negative DLD1 cells. 5-FU can upregulate Wnt activity of CD133-positive colon CSLCs. Blocking Wnt activity may reverse drug sensitivity of CD133-positive cells to 5-FU.
authors.affiliation: Department of Medical Oncology, the Sixth Affiliated Hospital, Sun Yat-sen University, Guangzhou, Guangdong 510655, PR China. littleqicat@163.com
authors.forename: Yan-Hong
authors.initials: YH
authors.lastname: Deng
authors.forename: Xing-Xiang
authors.initials: XX
authors.lastname: Pu
authors.forename: Mei-Jin
authors.initials: MJ
authors.lastname: Huang
authors.forename: Jian
authors.initials: J
authors.lastname: Xiao
authors.forename: Jia-Ming
authors.initials: JM
authors.lastname: Zhou
authors.forename: Tong-Yu
authors.initials: TY
authors.lastname: Lin
authors.forename: Edward H
authors.initials: EH
authors.lastname: Lin
mesh_terms: D000071916:AC133 Antigen; D015703:Antigens, CD / Q000378:metabolism*; D000964:Antimetabolites, Antineoplastic / Q000494:pharmacology; D017209:Apoptosis / Q000187:drug effects; D045744:Cell Line, Tumor; D049109:Cell Proliferation / Q000187:drug effects*; D003110:Colonic Neoplasms / Q000378:metabolism / Q000473:pathology*; D019008:Drug Resistance, Neoplasm; D005472:Fluorouracil / Q000494:pharmacology*; D006023:Glycoproteins / Q000378:metabolism*; D006801:Humans; D036341:Intercellular Signaling Peptides and Proteins / Q000494:pharmacology; D014411:Neoplastic Stem Cells / Q000378:metabolism / Q000473:pathology*; D010455:Peptides / Q000378:metabolism*; D060449:Wnt Signaling Pathway / Q000187:drug effects*
chemical_list: D000071916:AC133 Antigen; D015703:Antigens, CD; D000964:Antimetabolites, Antineoplastic; C501126:DKK1 protein, human; D006023:Glycoproteins; D036341:Intercellular Signaling Peptides and Proteins; C000606023:PROM1 protein, human; D010455:Peptides; D005472:Fluorouracil