title: Ascl2 knockdown results in tumor growth arrest by miRNA-302b-related inhibition of colon cancer progenitor cells.
abstract: BACKGROUND
  Achaete scute-like 2 (Ascl2), a basic helix-loop-helix (bHLH) transcription factor, controls the fate of intestinal stem cells. However, the role of Ascl2 in colon cancer progenitor cells remains unknown. The cell line HT-29 (47.5-95% of CD133(+) population) and LS174T (0.45% of CD133(+) population) were chosen for functional evaluation of Ascl2 in colon cancer progenitor cells after gene knockdown by RNA interference.
  
  
  RESULTS
  Immunohistochemistry demonstrated that Ascl2 was significantly increased in colorectal adenocarcinomas. Downregulation of Ascl2 using RNA interference in cultured colonic adenocarcinoma HT-29 and LS174T cells reduced cellular proliferation, colony-forming ability, invasion and migration in vitro, and resulted in the growth arrest of tumor xenografts in vivo. The Ascl2 protein level in CD133(+) HT-29 cells was significantly higher than in CD133(-) HT-29 cells. Ascl2 blockade via shRNA interference in HT-29 cells (shRNA-Ascl2/HT-29 cells) resulted in 26.2% of cells staining CD133(+) compared with 54.7% in control shRNA-Ctr/HT-29 cells. The levels of 'stemness' associated genes, such as CD133, Sox2, Oct4, Lgr5, Bmi1, and C-myc, were significantly decreased in shRNA-Ascl2/HT-29 and shRNA-Ascl2/LS174T cells in vitro as well as in the corresponding tumor xenograft (CD133 was not performed in shRNA-Ascl2/LS174T cells). The shRNA-Ascl2/HT-29 cells had inhibited abilities to form tumorspheres compared with control. The microRNA (miRNAs) microarrays, identified 26 up-regulated miRNAs and 58 down-regulated miRNAs in shRNA-Ascl2/HT-29 cells. Expression levels of let-7b, miRNA-124, miRNA-125b, miRNA-17, miRNA-20a and miRNA-302b, involved in the regulation of 'stemness', were quantified with qPCR, which confirmed their identities. Restoration of miRNA-302b, via its mimic, led to the restoration of shRNA-Ascl2/HT-29 'stemness' characteristics, including tumorsphere formation and 'stemness' associated genes levels, and the recovery of cellular behaviors, including colony-forming ability, invasion and migration in vitro.
  
  
  CONCLUSIONS
  Ascl2 may be a potential target for the inhibition of colon cancer progenitor cells, and functions through a miR-302b-related mechanism.
authors.affiliation: Department of Gastroenterology, Southwest Hospital, Third Military Medical University, Chongqing, People's Republic of China.
authors.forename: Rong
authors.initials: R
authors.lastname: Zhu
authors.forename: Yongtao
authors.initials: Y
authors.lastname: Yang
authors.forename: Yin
authors.initials: Y
authors.lastname: Tian
authors.forename: Jianying
authors.initials: J
authors.lastname: Bai
authors.forename: Xin
authors.initials: X
authors.lastname: Zhang
authors.forename: Xiaohuan
authors.initials: X
authors.lastname: Li
authors.forename: Zhihong
authors.initials: Z
authors.lastname: Peng
authors.forename: Yonghong
authors.initials: Y
authors.lastname: He
authors.forename: Lei
authors.initials: L
authors.lastname: Chen
authors.forename: Qiong
authors.initials: Q
authors.lastname: Pan
authors.forename: Dianchun
authors.initials: D
authors.lastname: Fang
authors.forename: Wensheng
authors.initials: W
authors.lastname: Chen
authors.forename: Chen
authors.initials: C
authors.lastname: Qian
authors.forename: Xiuwu
authors.initials: X
authors.lastname: Bian
authors.forename: Rongquan
authors.initials: R
authors.lastname: Wang
mesh_terms: D000071916:AC133 Antigen; D000818:Animals; D015703:Antigens, CD / Q000096:biosynthesis; D051792:Basic Helix-Loop-Helix Proteins / Q000378:metabolism*; D045744:Cell Line, Tumor; D002465:Cell Movement; D049109:Cell Proliferation; D003110:Colonic Neoplasms / Q000378:metabolism*; D006023:Glycoproteins / Q000096:biosynthesis; D006801:Humans; D007150:Immunohistochemistry; D008297:Male; D051379:Mice; D008807:Mice, Inbred BALB C; D008819:Mice, Nude; D035683:MicroRNAs / Q000378:metabolism*; D009361:Neoplasm Invasiveness; D009368:Neoplasm Transplantation; D010455:Peptides; D034622:RNA Interference; D013234:Stem Cells / Q000166:cytology
chemical_list: D000071916:AC133 Antigen; D015703:Antigens, CD; D051792:Basic Helix-Loop-Helix Proteins; D006023:Glycoproteins; D035683:MicroRNAs; D010455:Peptides; C065501:ASCL2 protein, human; C532169:MIRN302A microRNA, human; C000606023:PROM1 protein, human; C000606024:Prom1 protein, mouse