Sunburns hurt twice

UV radiation not only promotes skin cancer, but also its life-threatening metastases

Green fluorescent cancer cells spread on orange-fluorescent blood vessel surfaces. © Tobias Bald / UKB
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Sunburns not only cause skin cancer. They also favor the formation of life-threatening metastases, as an experiment by German researchers shows. The cancer cells get through the inflammatory reactions of the skin easier in the blood vessels, migrate faster through them and get more efficient in other organs, as the researchers report in the journal "Nature".

The black skin cancer is considered particularly dangerous. Because it can very quickly form metastases in vital organs such as lungs, liver or brain. The Robert Koch Institute predicts that this year alone about 20, 000 people will develop malignant melanoma and around 2, 500 patients will die as a result of the resulting metastases.

It has long been known that UV light can trigger black skin cancer. But the extent to which sunburns affect the life-threatening, the formation of metastases, that was so far unclear. A team of researchers from the University Hospital and the LIMES Institute of the University of Bonn has therefore closely examined this relationship.

Immune cells pave the way for cancer cells

The researchers irradiated specific laboratory mice, which are suffering from skin cancer, with UV light. "Again and again, we have seen more and more melanoma metastases in the lungs of UV-irradiated mice, " says dermatologist Evelyn Gaffal from Bonn University Hospital. But the researchers were particularly interested in the way the degenerate cells from the skin into the body took.

If the UV radiation was so strong that the mice had formed inflammations on the skin, then the melanoma cells deposited themselves particularly frequently on the surface of the blood vessels, as the scientists observed. A strikingly close relationship between the cancer cells and certain cells of the immune system, the neutrophilic granulocytes, was particularly noticeable to the scientists. display

Experiments with transgenic mice that lack innate immune response explained this observation: the UV-damaged skin cells send out an alarm signal to the immune system. This then sends the neutrophil granulocytes to the site of inflammation. Unfortunately not for the benefit of those affected, because there they favor the migration of melanoma cells into the body.

Messengers make the cancer cells faster

But even the speed at which the cancer cells set off is not unaffected by inflammation. The researchers tracked the cells as they traveled along the endothelial cells inside the blood vessel. It showed that the mobility of cancer cells in an inflammatory environment increases.

Inflammatory messengers also stimulate the migration of degenerate cells in human cancer cells, as the researchers also observed. VorThe precursors of pigment cells during embryonic development travel long distances along blood vessels in the body to get their proper place in the skin. It is precisely these disconnected programs that are falsely activated by inflammation, "explains Michael H lzel from the University Hospital Bonn.

Can deadly metastases be prevented soon?

"Now we may also know why patients with superficially dysfunctional melanoma interspersed with neutrophilic granulocytes develop organ metastases most often, " said Thomas T ting of the University Klintsklinikum Bonn.

In the future, new forms of therapy could intervene in the inflammatory reactions and thus slow down or even prevent the migration of cancer cells within the blood vessels. The researchers hope to be able to slow down or even suppress the development of life-threatening metastases in the future. (Nature, 2014; doi: 10.1038 / nature13111)

(Rheinische Friedrich-Wilhelms-University Bonn, 27.02.2014 - KEL)