title: Telomere length varies by DNA extraction method: implications for epidemiologic research.
abstract: BACKGROUND
  Both shorter and longer telomeres in peripheral blood leukocyte (PBL) DNA have been associated with cancer risk. However, associations remain inconsistent across studies of the same cancer type. This study compares DNA preparation methods to determine telomere length from patients with colorectal cancer.
  
  
  METHODS
  We examined PBL relative telomere length (RTL) measured by quantitative PCR (qPCR) in 1,033 patients with colorectal cancer and 2,952 healthy controls. DNA was extracted with phenol/chloroform, PureGene, or QIAamp.
  
  
  RESULTS
  We observed differences in RTL depending on DNA extraction method (P < 0.001). Phenol/chloroform-extracted DNA had a mean RTL (T/S ratio) of 0.78 (range 0.01-6.54) compared with PureGene-extracted DNA (mean RTL of 0.75; range 0.00-12.33). DNA extracted by QIAamp yielded a mean RTL of 0.38 (range 0.02-3.69). We subsequently compared RTL measured by qPCR from an independent set of 20 colorectal cancer cases and 24 normal controls in PBL DNA extracted by each of the three extraction methods. The range of RTL measured by qPCR from QIAamp-extracted DNA (0.17-0.58) was less than from either PureGene or phenol/chloroform (ranges, 0.04-2.67 and 0.32-2.81, respectively).
  
  
  CONCLUSIONS
  RTL measured by qPCR from QIAamp-extracted DNA was less than from either PureGene or phenol/chloroform (P < 0.001).
  
  
  CONCLUSIONS
  Differences in DNA extraction method may contribute to the discrepancies between studies seeking to find an association between the risk of cancer or other diseases and RTL.
authors.affiliation: Authors' Affiliations: Departments of Laboratory Medicine and Pathology, Health Sciences Research, and Gastroenterology, Mayo Clinic College of Medicine; Mayo Clinic Cancer Center, Biomedical Statistics and Informatics, Mayo Clinic College of Medicine, Rochester, Minnesota; Departments of Population Health Sciences, and Biostatistics and Medical Informatics, School of Medicine and Public Health, University of Wisconsin, Madison, Wisconsin; University of Michigan, Ann Arbor, Michigan; Division of Gastroenterology, Mayo Clinic, Jacksonville, Florida; Biostatistics & Epidemiology, Geisel School of Medicine, Dartmouth University, Hanover, New Hampshire; Public Health Sciences Division, Cancer Prevention Program, Fred Hutchinson Cancer Research Center, Seattle, Washington; The Stanford Cancer Institute and Stanford School of Medicine, Department of Medicine, Stanford, California; Queensland Institute of Medical Research, Clive Berghofer Cancer Research Centre, Brisbane, Queensland; and Melbourne School of Population Health, The University of Melbourne, Parkville, Victoria, Australia.
authors.forename: Julie M
authors.initials: JM
authors.lastname: Cunningham
authors.forename: Ruth A
authors.initials: RA
authors.lastname: Johnson
authors.forename: Kristin
authors.initials: K
authors.lastname: Litzelman
authors.forename: Halcyon G
authors.initials: HG
authors.lastname: Skinner
authors.forename: Songwon
authors.initials: S
authors.lastname: Seo
authors.forename: Corinne D
authors.initials: CD
authors.lastname: Engelman
authors.forename: Russell J
authors.initials: RJ
authors.lastname: Vanderboom
authors.forename: Grace W
authors.initials: GW
authors.lastname: Kimmel
authors.forename: Ronald E
authors.initials: RE
authors.lastname: Gangnon
authors.forename: Douglas L
authors.initials: DL
authors.lastname: Riegert-Johnson
authors.forename: John A
authors.initials: JA
authors.lastname: Baron
authors.forename: John D
authors.initials: JD
authors.lastname: Potter
authors.forename: Robert
authors.initials: R
authors.lastname: Haile
authors.forename: Daniel D
authors.initials: DD
authors.lastname: Buchanan
authors.forename: Mark A
authors.initials: MA
authors.lastname: Jenkins
authors.forename: David N
authors.initials: DN
authors.lastname: Rider
authors.forename: Stephen N
authors.initials: SN
authors.lastname: Thibodeau
authors.forename: Gloria M
authors.initials: GM
authors.lastname: Petersen
authors.forename: Lisa A
authors.initials: LA
authors.lastname: Boardman
mesh_terms: D016022:Case-Control Studies; D015179:Colorectal Neoplasms / Q000097:blood / Q000235:genetics; D004247:DNA / Q000097:blood / Q000235:genetics / Q000302:isolation & purification*; D004273:DNA, Neoplasm / Q000097:blood / Q000235:genetics / Q000302:isolation & purification; D016021:Epidemiologic Studies; D005260:Female; D006801:Humans; D007962:Leukocytes / Q000737:chemistry* / Q000648:ultrastructure; D008297:Male; D008875:Middle Aged; D016615:Telomere / Q000737:chemistry* / Q000235:genetics
chemical_list: D004273:DNA, Neoplasm; D004247:DNA
references.citation: Nucleic Acids Res. 2002 May 15;30(10):e47
references.pmid: 12000852
references.citation: Cancer Epidemiol Biomarkers Prev. 2010 Feb;19(2):605-13
references.pmid: 20142254
references.citation: Lung Cancer. 2009 Nov;66(2):157-61
references.pmid: 19285750
references.citation: Cancer Epidemiol Biomarkers Prev. 2011 Jun;20(6):1238-50
references.pmid: 21467229
references.citation: Int J Mol Epidemiol Genet. 2011 Jan 1;2(1):19-29
references.pmid: 21537398
references.citation: Recent Pat Anticancer Drug Discov. 2012 Jan;7(1):102-17
references.pmid: 21854360
references.citation: Cancer Causes Control. 2010 Jan;21(1):77-82
references.pmid: 19784860
references.citation: Cancer Epidemiol Biomarkers Prev. 2007 Dec;16(12):2649-55
references.pmid: 18086770
references.citation: J Invest Dermatol. 2009 Feb;129(2):415-21
references.pmid: 18668136
references.citation: J Med Genet. 2012 May;49(5):341-4
references.pmid: 22493152
references.citation: Exp Hematol. 2007 Jun;35(6):939-46
references.pmid: 17533048
references.citation: Cancer Epidemiol Biomarkers Prev. 2012 Nov;21(11):2095-100
references.pmid: 23093543
references.citation: Cancer Epidemiol Biomarkers Prev. 2009 Nov;18(11):3103-9
references.pmid: 19861514
references.citation: Aging Cell. 2009 Aug;8(4):405-13
references.pmid: 19493248
references.citation: BMC Genet. 2012 Sep 06;13:77
references.pmid: 22954451
references.citation: Carcinogenesis. 2005 Jul;26(7):1263-71
references.pmid: 15746160
references.citation: Nat Rev Cancer. 2011 Mar;11(3):161-76
references.pmid: 21346783
references.citation: Gut. 2012 Feb;61(2):248-54
references.pmid: 21708826
references.citation: Cancer. 2010 Sep 15;116(18):4275-82
references.pmid: 20549820
references.citation: Cancer Epidemiol Biomarkers Prev. 2007 Apr;16(4):815-9
references.pmid: 17416776
references.citation: Cancer. 1994 Jun 15;73(12):2978-84
references.pmid: 7911069
references.citation: JAMA. 2010 Jul 7;304(1):69-75
references.pmid: 20606151
references.citation: Anticancer Res. 1998 May-Jun;18(3A):1345-9
references.pmid: 9673338
references.citation: Cancer Epidemiol Biomarkers Prev. 2009 Apr;18(4):1152-6
references.pmid: 19293310
references.citation: Hum Mutat. 2010 Sep;31(9):1050-8
references.pmid: 20597107
references.citation: Hum Genet. 2011 Mar;129(3):247-53
references.pmid: 21116649
references.citation: Br J Cancer. 2011 Nov 22;105(11):1772-5
references.pmid: 22033273
references.citation: Trends Ecol Evol. 2012 Jan;27(1):27-39
references.pmid: 21978464
references.citation: Cancer Epidemiol Biomarkers Prev. 2011 May;20(5):1043-5
references.pmid: 21357377
references.citation: Cancer Prev Res (Phila). 2009 May;2(5):459-65
references.pmid: 19401529
references.citation: Cancer Sci. 2009 Jul;100(7):1300-5
references.pmid: 19432888
references.citation: Nucleic Acids Res. 2011 Nov 1;39(20):e134
references.pmid: 21824912
references.citation: Haematologica. 2012 Mar;97(3):353-9
references.pmid: 22058220
references.citation: Cancer Epidemiol Biomarkers Prev. 2012 Oct;21(10):1807-13
references.pmid: 22911335
references.citation: Cancer Res. 2008 May 15;68(10):3618-23
references.pmid: 18483243
references.citation: J Mol Med (Berl). 2002 Nov;80(11):689-95
references.pmid: 12436345
references.citation: Cancer Res. 2010 Apr 15;70(8):3170-6
references.pmid: 20395204
references.citation: Cancer Epidemiol Biomarkers Prev. 2009 Aug;18(8):2280-2
references.pmid: 19661087
references.citation: PLoS Genet. 2011 Jul;7(7):e1002182
references.pmid: 21829373
references.citation: Cancer Res. 2007 Jun 1;67(11):5538-44
references.pmid: 17545637
references.citation: Nat Biotechnol. 1998 Aug;16(8):743-7
references.pmid: 9702772
references.citation: Cancer Epidemiol Biomarkers Prev. 2007 Nov;16(11):2331-43
references.pmid: 17982118
references.citation: Cancer Sci. 2008 Jul;99(7):1385-9
references.pmid: 18452563
references.citation: Anticancer Drugs. 2002 Jul;13(6):595-8
references.pmid: 12172504
references.citation: PLoS One. 2011;6(6):e20466
references.pmid: 21695195
references.citation: Br J Haematol. 2012 Mar;156(5):573-87
references.pmid: 22233151
references.citation: J Urol. 2007 Oct;178(4 Pt 1):1492-6
references.pmid: 17707063
references.citation: Cancer Res. 2003 May 15;63(10):2589-95
references.pmid: 12750284