MAPKAPK5 and papilloma: In previous experiments the one step DMBA treatment of mice resulted in superficial papillomas in 8% of wild type animals (1of 12) after about 300 days, whereas 54% (7 of 13) of Δex8/Δex8 mice and 40% (12 of 30) of Δex8/+ mice developed papillomas, indicating an important role of MK5/PRAK in tumor suppression [6,13].