Researchers from Amsterdam institute for Infection and Immunity and Cancer Center Amsterdam have identified a new mechanism that tumor cells may use to evade immune cells. “The tumor cells hijack biological mechanisms that originally support embryonic development in the mother's womb,” says immunologist Professor Arjan Griffioen, principal investigator of the study. The findings were published last week in Science Immunology.

In people with cancer, the immune cells in the blood want to attack the tumor cells. But the tumor makes the blood vessel wall impermeable and thus escapes the immune system. As a result, the immune cells cannot get to the tumor tissue and the tumor can grow undisturbed. The article in Science Immunology answers the question of how the tumor manages to do that.

Protected growth process
The same mechanism is at play in the development of an embryo. "When the embryo develops complex organs, it is an advantage that this happens out of sight of immune cells," Griffioen explains. "In the embryo, therefore, the blood vessel wall is an impregnable barrier for these cells. An embryo has to grow very quickly in a short period of time to make, for example, a liver, a kidney or an eye. For this growth spurt, it creates new blood vessels. At the same time, the embryo switches off the immune system, because it only suffers from immune cells. And exactly this protected growth mechanism mimics the tumor."

Fending off immune cells
Millions of years of evolution have ensured that blood vessels in the embryo prevent immune cells from entering the embryo tissue. Co-researcher Else Huijbers: "By knowing how a tumor escapes immune cells, researchers can make better drugs to treat cancer." 

Picture: Marieke de Lorijn

Read the article in Science Immunology.