title: Opposite effects of microchimerism on breast and colon cancer.
abstract: BACKGROUND
  Detection of Y chromosome, thought to originate from previous pregnancies with a male fetus, is common in women. Lower concentrations have been reported in women with breast cancer than cancer-free women. Data in women with other types of cancer are sparse. The purpose of the study was to determine whether the lower concentrations predate cancer diagnosis, and whether a possible beneficial effect was specific to breast cancer.
  
  
  METHODS
  We conducted a prospective case-cohort study of 50-64-year-old Danish women enrolled in the diet, cancer and health cohort. Blood samples and questionnaire data were obtained during 1993-1997 when all women were cancer-free. In 2006 all women were followed up for incident breast and colon cancer in national registers. In blinded analyses, we analysed buffy coat DNA for Y chromosome (DYS14) as a marker of male microchimerism.
  
  
  RESULTS
  We detected male microchimerism in 70% of 272 cancer-free women, 40% of 89 women who later developed breast cancer, and 90% of 67 women who later developed colon cancer. The corresponding odds ratios were 0.30 (95% confidence interval (CI) 0.17-0.52) for breast, and 3.9 (95%CI 1.6-9.5) for colon cancer.
  
  
  CONCLUSIONS
  Detection of male microchimerism was strongly associated with reduced risk of developing breast cancer and also the increased risk of developing colon cancer. Confirmatory findings based on an improved study design, failure to identify important confounders and the strength of the associations lead us to believe that microchimerism may be highly relevant to later cancer development. However, the present study does not allow us to identify the underlying biological mechanisms.
authors.affiliation: University of Copenhagen, Institute of Public Health, Section of Social Medicine, Øster Farimagsgade 5, Post Box 2099, DK-1014 Copenhagen K, Denmark. maka@sund.ku.dk
authors.forename: Mads
authors.initials: M
authors.lastname: Kamper-Jørgensen
authors.forename: Robert J
authors.initials: RJ
authors.lastname: Biggar
authors.forename: Anne
authors.initials: A
authors.lastname: Tjønneland
authors.forename: Henrik
authors.initials: H
authors.lastname: Hjalgrim
authors.forename: Niels
authors.initials: N
authors.lastname: Kroman
authors.forename: Klaus
authors.initials: K
authors.lastname: Rostgaard
authors.forename: Casey L
authors.initials: CL
authors.lastname: Stamper
authors.forename: Anja
authors.initials: A
authors.lastname: Olsen
authors.forename: Anne-Marie N
authors.initials: AM
authors.lastname: Andersen
authors.forename: Vijayakrishna K
authors.initials: VK
authors.lastname: Gadi
mesh_terms: D001943:Breast Neoplasms / Q000453:epidemiology / Q000235:genetics* / Q000517:prevention & control; D016022:Case-Control Studies; D046528:Chimerism; D041322:Chromosomes, Human, Y; D003110:Colonic Neoplasms / Q000453:epidemiology / Q000235:genetics*; D003718:Denmark / Q000453:epidemiology; D005260:Female; D020022:Genetic Predisposition to Disease; D006801:Humans; D015994:Incidence; D016015:Logistic Models; D008297:Male; D008875:Middle Aged; D016017:Odds Ratio; D011247:Pregnancy; D016016:Proportional Hazards Models; D011446:Prospective Studies; D012042:Registries; D018570:Risk Assessment; D012307:Risk Factors; D013997:Time Factors