title: Intra-tumor heterogeneity of microRNA-92a, microRNA-375 and microRNA-424 in colorectal cancer.
abstract: Various microRNAs (miRNAs) have been investigated in order to improve diagnostics and risk assessment in colorectal cancer (CRC). To clarify the potential of miRNA profiling in CRC, knowledge of intra-tumor heterogeneity in expression levels is crucial. The study aim was to estimate the intra-tumor variance of three selected miRNAs: miR-92a, miR-375 and miR-424 in CRC tissue.
  
  
  METHODS
  A retrospective study on archived formalin-fixed paraffin embedded tissue from 9 patients with CRC. miRNA tissue expression levels were analyzed by qRT-PCR on tissue representing luminal, central and invasive border zones. Variance components were estimated based on ∆∆Cp values using mixed modeling and presented as coefficients of variation (CV).
  
  
  RESULTS
  Intra-tumor variance was approximately half of the variance observed between patients with a mean intra-tumor CV of 56.4% (range 33.1-77.1%) and a mean inter-patient CV of 101.7% (range 48.8-152.7%). Furthermore we found a significant systematic difference in expression levels between tumor zones for miR-92a and miR-375 with a luminal-invasive difference equal to 0.60 Cp (95% CI: 0.30-0.89, p=0.0003) for miR-92a and a luminal-invasive difference equal to 0.78 Cp (95% CI: 0.10-1.46, p=0.027) for miR-375. Conclusion While the intra-tumor variance of miR-92a, miR-375 and miR-424 is substantial, it only constitutes approximately 30% of the total variation. Functional deregulation between tumor zones might contribute to variations in measured expression levels, and thus knowledge of specific intra-tumor expression patterns is crucial in tissue sampling for research as well as in future diagnostics.
authors.affiliation: Department of Pathology and Molecular Unit, Herlev Hospital, University of Copenhagen, Herlev Ringvej 75, DK-2730 Herlev, Denmark. Electronic address: rikke.karlin.jepsen.01@regionh.dk.
authors.forename: Rikke Karlin
authors.initials: RK
authors.lastname: Jepsen
authors.affiliation: Department of Pathology and Molecular Unit, Herlev Hospital, University of Copenhagen, Herlev Ringvej 75, DK-2730 Herlev, Denmark.
authors.forename: Guy Wayne
authors.initials: GW
authors.lastname: Novotny
authors.affiliation: Department of Pathology and Molecular Unit, Herlev Hospital, University of Copenhagen, Herlev Ringvej 75, DK-2730 Herlev, Denmark.
authors.forename: Louise Laurberg
authors.initials: LL
authors.lastname: Klarskov
authors.affiliation: Department of Pathology and Molecular Unit, Herlev Hospital, University of Copenhagen, Herlev Ringvej 75, DK-2730 Herlev, Denmark.
authors.forename: Ib Jarle
authors.initials: IJ
authors.lastname: Christensen
authors.affiliation: Department of Pathology and Molecular Unit, Herlev Hospital, University of Copenhagen, Herlev Ringvej 75, DK-2730 Herlev, Denmark.
authors.forename: Lene Buhl
authors.initials: LB
authors.lastname: Riis
authors.affiliation: Department of Pathology and Molecular Unit, Herlev Hospital, University of Copenhagen, Herlev Ringvej 75, DK-2730 Herlev, Denmark.
authors.forename: Estrid
authors.initials: E
authors.lastname: Høgdall
mesh_terms: D015179:Colorectal Neoplasms / Q000235:genetics*; D020869:Gene Expression Profiling / Q000379:methods; D005819:Genetic Markers; D006801:Humans; D035683:MicroRNAs / Q000235:genetics*; D060888:Real-Time Polymerase Chain Reaction / Q000379:methods; D012189:Retrospective Studies
chemical_list: D005819:Genetic Markers; C540933:MIRN375 microRNA, human; C554214:MIRN424 microrna, human; C541874:MIRN92 microRNA, human; D035683:MicroRNAs
keywords: Colorectal cancer; Intra-tumor heterogeneity; Intra-tumor variance; MicroRNA