Case-control study of fetal microchimerism and breast cancer

Abstract

Bacground: Prior pregnancy is known to protect against development of breast cancer. Recent studies have demonstrated that pregnancy has the capacity to establish small numbers of immunologically active fetal-derived cells in the mother, a phenomenon known as fetal microchimerism (FMc). We asked whether presence of FMc, routinely acquired during pregnancy, is a protective factor for breast cancer. Methodology/Principal Findings: DNA extracts from peripheral blood specimens were obtained from a population-based PCR for presence and concentrations of male DNA presumed to derive from prior pregnancies with a male fetus. Odds ratios (OR) and 95% confidence intervals (CI) were estimated with considerations of multiple established reproductive and environmental risk factors for breast cancer. FMc prevalence was 56% (25/45) and (14/54) in controls and cases, respectively. Women harboring FMc were less likely to have breast cancer (OR=0.29, 95% Cl 0.11==0.83; p=0.02, adjusting for age, number of children, birth of a son, history of miscarriage, and total DNA tested), in addition, FMc concentrations were higher in controls versus cases (p=0.01). Median concentrations were 2 (0=78) and 0 (0=374) fetal genomes/106 maternal genomes in controls ans cases, respectively. Conclusions: Results suggests that the enigma of why some parous women are not afforded protection from breast cancer by pregnancy might in part be explained by differences in FMc. Mechanistic studies of FMc-derived protection against breast cancer are warranted. © 2008 Gadi et al.