Lab mice kept in cool cages grow tumors faster than those living in balmier conditions.

Mice living in cages with temperatures of about 30° Celsius had better control of tumor growth than rodents kept at about 22°, the mandated temperature for lab mice. When kept in warmer cages, the lab mice had more killer T cells active in the diseased tissue and fewer cells that suppressed the immune system, scientists report November 18 in the Proceedings of the National Academy of Sciences.

Cooler cage temperatures may cause the mice to experience cold stress, which would divert energy from an anticancer immune response toward producing body heat. This may influence the animals' responses to experimental cancer therapies that target the immune system, the authors suggest.