Tumours in mice grow faster at night

The ability of an animal’s immune system to fight cancer is dependent on the time of day, according to new research using mice.

Researchers at the University of Geneva (UNIGE), Switzerland, and Ludwig-Maximilians University of Munich, Germany, had previously found that immune activity can fluctuate over a 24-hour period, due in part to the movement of key cells in the immune response, called dendritic cells.

In their latest study, the group injected mice with cancer cells at six different times of day to investigate how changing immune activity may affect tumours.

Chen Wang, of UNIGE, said: ‘‘By varying only the time of injection, we observed very surprising results: tumours implanted in the afternoon grew little, while those implanted at night grew much faster, in accordance with the rhythm of activation of the mice’s immune system.”

The findings may mean that simply changing when a cancer treatment is given can significantly increase its effectiveness.

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