Why pregnancy and cancer are dangerous duo

During pregnancy a decline in the number of natural killer cells, which are a type of immune system cell, ripens conditions in the body for existing tumors to spread to new locations, a new study shows.


The finding may explain why researchers have long-observed that pregnant women with cancer face an increased risk of their tumors metastasizing, said study researcher Ivan Stamenkovic, director of the Department of Experimental Pathology at the University of Lausanne in Switzerland.

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Further, the findings may help researchers better understand what happens when cancer metastasizes, and could reveal a new approach to keeping metastasis at bay, the researchers said.
"Our work provides evidence that innate immunity plays a major role in protecting tissues against metastatic tumor growth," Stamenkovic said.
How it works
Several years ago, scientists observed that tumors send out signals that change the chemistry of other sites in the body in ways that make it easier for cells that break free of a tumor to begin growing in those other sites, Stamenkovic said.
But normally, such growths are kept in check by immune system cells called natural killer cells. They move through the body and kill cancerous cells that they encounter.
Stamenkovic and his colleagues found pregnant mice had fewer natural killers than other mice, and the natural killer cells they had were less effective at doing their job.

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