title: MicroRNA expression profiling identifies miR-328 regulates cancer stem cell-like SP cells in colorectal cancer.
abstract: BACKGROUND
  Side population (SP) cells and their relationship to stem cell-like properties have been insufficiently studied in colorectal cancer (CRC). MicroRNAs (miRNAs) have attracted much attention but their roles in the maintenance of SP phenotype remain unclear.
  
  
  METHODS
  The SPs from CRC cell lines and primary cell cultures were analysed for stem cell-like properties. MiRNA microarray analysis identified miR-328 as a potential stemness miRNA of SP phenotype. The level of miR-328 expression in clinical samples and its correlation with SP fraction were determined. Gain-of-function and loss-of-function studies were performed to examine its roles in cancer stem-like SP cells. Furthermore, bioinformatics prediction and experimental validation were used to identify miR-328 target genes.
  
  
  RESULTS
  The SP cells sorted from CRC possess cancer stem cell (CSC)-like properties, including self-renewal, differentiation, resistance to chemotherapy, invasive and strong tumour formation ability. MiR-328 expression was significantly reduced in SP cells compared with Non-SP cells (P<0.05). Moreover, miR-328 expression was downregulated in CRC (n=33, P<0.05) and low miR-328 expression tend to correlate with high SP fraction (n=15, r=0.6559, P<0.05, Pearson's correlation). Functional studies indicated that miR-328 expression affects the number of SP cells. In addition, miR-328 overexpression reversed drug resistance and inhibited cell invasion of SP cells. Furthermore, luciferase reporter assay demonstrated that miR-328 directly targets ABCG2 and MMP16 and affects the levels of mRNA and protein expression in SP cells.
  
  
  CONCLUSIONS
  These findings indicate that CRC contain cancer stem-like SP cells. MiR-328 has an important role in maintaining cancer stem-like SP phenotype that may be a potential target for effective CRC therapy.
authors.affiliation: Division of Gastroenterology and Hepatology, Shanghai Jiao-Tong University School of Medicine Renji Hospital, Shanghai Institute of Digestive Disease, Key Laboratory of Gastroenterology and Hepatology, Ministry of Health (Shanghai Jiao-Tong University), 145 Middle Shandong Road, Shanghai 200001, China.
authors.forename: X T
authors.initials: XT
authors.lastname: Xu
authors.forename: Q
authors.initials: Q
authors.lastname: Xu
authors.forename: J L
authors.initials: JL
authors.lastname: Tong
authors.forename: M M
authors.initials: MM
authors.lastname: Zhu
authors.forename: F
authors.initials: F
authors.lastname: Nie
authors.forename: X
authors.initials: X
authors.lastname: Chen
authors.forename: S D
authors.initials: SD
authors.lastname: Xiao
authors.forename: Z H
authors.initials: ZH
authors.lastname: Ran
mesh_terms: D000070997:ATP Binding Cassette Transporter, Subfamily G, Member 2; D018528:ATP-Binding Cassette Transporters / Q000235:genetics; D002454:Cell Differentiation; D045744:Cell Line, Tumor; D002471:Cell Transformation, Neoplastic; D015179:Colorectal Neoplasms / Q000235:genetics* / Q000473:pathology; D015536:Down-Regulation; D019008:Drug Resistance, Neoplasm; D005434:Flow Cytometry; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D053513:Matrix Metalloproteinase 16 / Q000235:genetics; D035683:MicroRNAs / Q000378:metabolism / Q000502:physiology*; D009361:Neoplasm Invasiveness; D009363:Neoplasm Proteins / Q000235:genetics; D014411:Neoplastic Stem Cells / Q000502:physiology*
chemical_list: C116614:ABCG2 protein, human; D000070997:ATP Binding Cassette Transporter, Subfamily G, Member 2; D018528:ATP-Binding Cassette Transporters; C548170:MIRN328 microRNA, human; C507102:MMP16 protein, human; D035683:MicroRNAs; D009363:Neoplasm Proteins; D053513:Matrix Metalloproteinase 16