title: Clinical relevance of microRNA miR-21, miR-31, miR-92a, miR-101, miR-106a and miR-145 in colorectal cancer.
abstract: BACKGROUND
  MicroRNAs (miRNAs) regulate gene expression by binding to mRNA, and can function as oncogenes or tumor suppressors depending on the target. In this study, using qRT-PCR, we examined the expression of six miRNAs (miR-21, miR-31, miR-92a, miR-101, miR-106a and miR-145) in tumors from 193 prospectively recruited patients with colorectal cancer, and associations with clinicopathological parameters and patient outcome were analyzed. The miRNAs were chosen based on previous studies for their biomarker potential and suggested biological relevance in colorectal cancer.
  
  
  METHODS
  The miRNA expression was examined by qRT-PCR. Associations between miRNA expression and clinicopathological variables were explored using Mann-Whitney U and Kruskal-Wallis test while survival was estimated using the Kaplan-Meier method and compared using the log-rank test.
  
  
  RESULTS
  MiR-101 was hardly expressed in the tumor samples, while for the other miRNAs, variable expression levels and expression ranges were observed, with miR-21 being most abundantly expressed relative to the reference (RNU44). In our study cohort, major clinical significance was demonstrated only for miR-31, as high expression was associated with advanced tumor stage and poor differentiation. No significant associations were found between expression of the investigated miRNAs and metastasis-free or overall survival.
  
  
  CONCLUSIONS
  Investigating the expression of six miRNAs previously identified as candidate biomarkers in colorectal cancer, few clinically relevant associations were detected in our patient cohort. Our results emphasize the importance of validating potential tumor markers in independent patient cohorts, and indicate that the role of miRNAs as colorectal cancer biomarkers is still undetermined.
authors.affiliation: Departments of Tumor Biology, The Norwegian Radium Hospital, Oslo University Hospital, N-0310, Oslo, Norway. kristina.schee@rr-research.no
authors.forename: Kristina
authors.initials: K
authors.lastname: Schee
authors.forename: Kjetil
authors.initials: K
authors.lastname: Boye
authors.forename: Torveig Weum
authors.initials: TW
authors.lastname: Abrahamsen
authors.forename: Øystein
authors.initials: Ø
authors.lastname: Fodstad
authors.forename: Kjersti
authors.initials: K
authors.lastname: Flatmark
mesh_terms: D000368:Aged; D015331:Cohort Studies; D015179:Colorectal Neoplasms / Q000235:genetics* / Q000473:pathology; D005260:Female; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D008297:Male; D035683:MicroRNAs / Q000096:biosynthesis / Q000235:genetics*; D011446:Prospective Studies
chemical_list: D035683:MicroRNAs