title: miRNA analysis of prostate cancer by quantitative real time PCR: comparison between formalin-fixed paraffin embedded and fresh-frozen tissue.
abstract: OBJECTIVE
  Micro RNA (miRNA) is a class of small noncoding RNA that plays a major role in the regulation of gene expression, which has been related to cancer behavior. The possibility of analyzing miRNA from the archives of pathology laboratories is exciting, as it allows for large retrospective studies. Formalin is the most common fixative used in the surgical pathology routine, and its promotion of nucleic acid degradation is well known. Our aim is to compare miRNA profiles from formalin-fixed paraffin embedded (FFPE) tissues with fresh-frozen prostate cancer tissues.
  
  
  METHODS
  The expression of 14 miRNAs was determined by quantitative real time polymerase chain reaction (qRT-PCR) in 5 paired fresh-frozen and FFPE tissues, which were representative of prostate carcinoma.
  
  
  RESULTS
  There was a very good correlation of the miRNA expression of miR-let7c and miR-32 between the fresh-frozen and FFPE tissues, with Pearson's correlation coefficients of 0.927 (P = 0.023) and 0.960 (P = 0.010), respectively. For the remaining miRNAs, the correlation was good with Spearman correlation coefficient of 0.638 (P < 0.001).
  
  
  CONCLUSIONS
  Analysis of miRNAs from routinely processed and stored FFPE prostate tissue is feasible for some miRNAs using qRT-PCR. Further studies should be conducted to confirm the reliability of using stock tissues for miRNA expression determination.
authors.affiliation: Laboratory of Medical Investigation-LIM55, Urology Department, University of Sao Paulo Medical School, Sao Paulo, Brazil. katiaramos@uol.com.br
authors.forename: Katia R M
authors.initials: KR
authors.lastname: Leite
authors.forename: Juliana M S
authors.initials: JM
authors.lastname: Canavez
authors.forename: Sabrina T
authors.initials: ST
authors.lastname: Reis
authors.forename: Alberto H
authors.initials: AH
authors.lastname: Tomiyama
authors.forename: Camila B
authors.initials: CB
authors.lastname: Piantino
authors.forename: Adriana
authors.initials: A
authors.lastname: Sañudo
authors.forename: Luiz Heraldo
authors.initials: LH
authors.lastname: Camara-Lopes
authors.forename: Miguel
authors.initials: M
authors.lastname: Srougi
mesh_terms: D000368:Aged; D005557:Formaldehyde / Q000737:chemistry; D005629:Frozen Sections; D006801:Humans; D008297:Male; D035683:MicroRNAs / Q000032:analysis* / Q000235:genetics*; D008875:Middle Aged; D016612:Paraffin Embedding; D011471:Prostatic Neoplasms / Q000235:genetics*; D060888:Real-Time Polymerase Chain Reaction; D016707:Tissue Fixation / Q000379:methods*
chemical_list: D035683:MicroRNAs; D005557:Formaldehyde