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Imiquimod immune effect explained


Imiquimod, a drug used to treat skin cancer, has been shown to have a previously unknown immune effect on nerve cells. 


The drug transforms cells known as dendritic cells into “tumour killers” that attack the tumour directly and destroy its cells. 


The dendritic cells adopt a novel prophylactic repsonse – they produce special substances with a cell-damaging effect and fight the tumour without the help of T and B cells and natural killer (NK) cells. 


This complex interaction was discovered by scientists participating in a doctoral programme of the Austrian Science Fund FWF.


It was also recently published and commented on in the Journal of Clinical Investigation.


For 15 years now the drug Imiquimod has been authorised for the treatment of certain skin diseases, including some types of skin cancer. 


During that period, the drug, which is administered as a skin cream, has proven to be an effective treatment. Despite this therapeutic success, the drug´s exact mechanism of action was not known. 


A research group working with Prof. Maria Sibilia, Head of the Institute for Cancer Research at the Medical University of Vienna, has now succeeded in determining some unknown and surprising effects of Imiquimod (Imi) on special immune cells.


In a mouse model for malignant melanoma, Prof. Sibilia and her team demonstrated that Imiquimod triggers the “recruitment” of special immune cells and “arms” them to attack tumour cells.


“We were able to show that Imi has an immediate and direct effect on mast cells in the skin,” explains Dr. Barbara Drobits, key scientist in the FWF-funded doctoral programme responsible for the discovery.


“Mast cells are immune system cells that can release messenger substances for the control of an immune response. 


“In reaction to Imi, which activates special receptors known as toll-like receptors, mast cells release CCL2 messenger substances – a starting signal that triggers a response with fatal consequences for tumour cells.”


Journal of Clinical Investigation

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