Fetal microchimerism might ward off breast cancer

Abstract

Fetal microchimerism is signifi cantly more common in women who have not developed breast cancer than in women with the disease say research ers (Cancer Research 2007; 67: 9035–38). So, can fetal immune cells that cross into a mother’s blood stream re duce her risk of developing breast cancer? “Fetal cells routinely enter the maternal blood stream where they can survive for years”, explains fi rst author V K Gadi (Fred Hutchinson Cancer Research Center, Seattle, WA, USA). “Since breast cancer is less common in women who have had a child, we hypothesised that fetal allogeneic immune cells might be aff ording them protection.” As an initial test of their hypothesis, the team analysed the blood of 82 women: 35 with breast cancer and 47 healthy controls. 74% and 72% of these women, respectively, had been pregnant at least once. 63% and 62%, respectively, had given birth to at least one son. Using real-time PCR the team tested the blood of these women for a malespecifi c gene, DYS14, that could not be of maternal origin and was presumed to indicate foetal microchimerism. “Fetal cells were found in 43% of the healthy women but in just 14% of those with breast cancer”, explains Gadi. “That translates into an odds ratio of 4·4 (95%CI 1·34–16·99), and of 5·9 (1·26–6·69) when restricting the analysis to women who actually gave birth to a son.” Protection might lie in the priming of fetal immune cells against maternal cancer antigens, thus providing a backup allogeneic immune surveillance system. However, the cells could be a double-edged sword. “Fetal microchimerism may be associated with certain autoimmune diseases, which are more common in women”, explains David Abraham (University College London, London, UK). “However, the development of these diseases and possible breast cancer protection may be diff erent things; more studies are needed to understand the underlying mechanisms.”