They showed that in a Jnk-knockout breast cancer mouse model, Wap-Cre+/−:Trp53LoxP/LoxP:Jnk1LoxP/LoxP:Jnk2LoxP/LoxP (JNKKO) mice exhibited more rapid breast tumor formation than control Wap-Cre+/−:Trp53LoxP/LoxP (JNKWT) mice, implicating the role of JNK signaling as a tumor suppressor. This evidence concerns the gene MAPK8 and breast cancer.