title: Mouse DNA contamination in human tissue tested for XMRV.
abstract: BACKGROUND
  We used a PCR-based approach to study the prevalence of genetic sequences related to a gammaretrovirus, xenotropic murine leukemia virus-related virus, XMRV, in human prostate cancer. This virus has been identified in the US in prostate cancer patients and in those with chronic fatigue syndrome. However, with the exception of two patients in Germany, XMRV has not been identified in prostate cancer tissue in Europe. Most putative associations of new or old human retroviruses with diseases have turned out to be due to contamination. We have looked for XMRV sequences in DNA extracted from formalin-fixed paraffin- embedded prostate tissues. To control for contamination, PCR assays to detect either mouse mitochondrial DNA (mtDNA) or intracisternal A particle (IAP) long terminal repeat DNA were run on all samples, owing to their very high copy number in mouse cells.
  
  
  RESULTS
  In general agreement with the US prevalence, XMRV-like sequences were found in 4.8% of prostate cancers. However, these were also positive, as were 21.5% of XMRV-negative cases, for IAP sequences, and many, but not all were positive for mtDNA sequences.
  
  
  CONCLUSIONS
  These results show that contamination with mouse DNA is widespread and detectable by the highly sensitive IAP assay, but not always with less sensitive assays, such as murine mtDNA PCR. This study highlights the ubiquitous presence of mouse DNA in laboratory specimens and offers a means of rigorous validation for future studies of murine retroviruses in human disease.
authors.affiliation: Section of Infectious Diseases, Jefferiss Research Trust Laboratories, Imperial College London, St Mary's Campus, London, W2 1PG, UK.
authors.forename: Mark J
authors.initials: MJ
authors.lastname: Robinson
authors.forename: Otto W
authors.initials: OW
authors.lastname: Erlwein
authors.forename: Steve
authors.initials: S
authors.lastname: Kaye
authors.forename: Jonathan
authors.initials: J
authors.lastname: Weber
authors.forename: Oya
authors.initials: O
authors.lastname: Cingoz
authors.forename: Anup
authors.initials: A
authors.lastname: Patel
authors.forename: Marjorie M
authors.initials: MM
authors.lastname: Walker
authors.forename: Wun-Jae
authors.initials: WJ
authors.lastname: Kim
authors.forename: Mongkol
authors.initials: M
authors.lastname: Uiprasertkul
authors.forename: John M
authors.initials: JM
authors.lastname: Coffin
authors.forename: Myra O
authors.initials: MO
authors.lastname: McClure
mesh_terms: D000818:Animals; D001483:Base Sequence; D059018:DNA Contamination; D004272:DNA, Mitochondrial / Q000235:genetics; D007426:Genes, Intracisternal A-Particle; D006801:Humans; D008297:Male; D051379:Mice / Q000235:genetics*; D008969:Molecular Sequence Data; D016133:Polymerase Chain Reaction; D011467:Prostate / Q000821:virology; D011471:Prostatic Neoplasms / Q000235:genetics / Q000821:virology*; D058008:Xenotropic murine leukemia virus-related virus / Q000235:genetics / Q000302:isolation & purification*
chemical_list: D004272:DNA, Mitochondrial