Fetal Microchimerism in Cancer Protection and Promotion: Current Understanding in Dogs and the Implications for Human Health

Abstract

Abstract. Fetal microchimerism is the co-existence of small numbers of cells from genetically distinct individuals living within a mother's body following pregnancy. During pregnancy, bi-directional exchange of cells occurs resulting in maternal microchimerism and even sibling microchimerism in offspring. The presence of fetal microchimerism has been identified with lower frequency in patients with cancers such as breast and lymphoma and with higher frequency in patients with colon cancer and autoimmune diseases. Microchimeric cells have been identified in healing and healed tissues as well as normal and tumor tissues. This has led to the hypothesis that fetal microchimerism may play a protective role in some cancers and may provoke other cancers or autoimmune disease. The long periods of risk for these diseases make it a challenge to prospectively study this phenomenon in human populations. Dogs get similar cancers as humans, share our homes and environmental exposures, and live compressed lifespans, allowing easier prospective study of disease development. This review describes the current state of understanding of fetal microchimerism in humans and dogs and highlights the similarities of the common cancers mammary carcinoma, lymphoma, and colon cancer between the two species. Study of fetal microchimerism in dogs might hold the key to characterization of the type and function of microchimeric cells and their role in health and disease. Such an understanding could then be applied to preventing and treating disease in humans.

A Survey on the Role of Fetal Microchimerism in the Maternal Body

“…An overview of the results and data obtained from related studies over recent 10-15 years demonstrates different roles for fetal microchimeric cell in the maternal body, including natural microchimerism (no biological role), utility (damaged tissue repair) and pathogenesis (causing autoimmune disease and cancer) (91)(92)(93)(94)(95)(96)(97).…”

The ‘communicatome’ of pregnancy: spotlight on cellular and extravesicular chimerism

“…Nevertheless, the presence of microchimeric cells in different eutherian placental mammals underpins that pregnancy-induced microchimerism is a highly conserved phenomenon which has not been eliminated during evolution (Boddy et al, 2015 ). Intriguingly, placental diversity between species (hemochorial, epithelial, endothelial) plays a minor role, as microchimerism has also been found in primates, dogs, cows and mice (Bryan, 2015 ; Lindtke et al, 2023 ). Since human studies have known limitations, especially when it comes to obtaining biological samples in a pregnancy cohort, mice represent an excellent model organism for studying pregnancy-related microchimerism.…”