Women who get breast cancer within five years of giving birth are at much higher risk than those who have never had children of seeing the tumors spread, or metastasize, to the liver. This could be due to changes in the liver as it readjusts after pregnancy.
In rodents, the liver expands during pregnancy. Researchers found that after weaning, the liver shrank and was infiltrated with immune-suppressing white blood cells. They saw hepatocyte apoptosis, ECM remodeling including deposition of collagen and tenascin-C, and myeloid cell influx, data consistent with weaning-induced liver involution and establishment of a pro-metastatic microenvironment.
When the authors injected cancer cells into mice, more liver metastases developed in animals that had just weaned their pups than in those that had never had offspring.
Human relevance is suggested by a ~3-fold increase in liver metastasis in postpartum breast cancer patients (n=564) and by liver-specific tropism (n=117). In sum, the data reveal a previously unknown biology of the rodent liver, weaning-induced liver involution, which may provide insight into the increased liver metastasis and poor prognosis of women diagnosed with postpartum breast cancer.
How pregnancy can boost risk of cancer spread
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