- Mdm2, but not Mdm4, protects terminally differentiated smooth muscle cells from p53-mediated caspase-3-independent cell death. Boesten, L.S., Zadelaar, S.M., De Clercq, S., Francoz, S., van Nieuwkoop, A., Biessen, E.A., Hofmann, F., Feil, S., Feil, R., Jochemsen, A.G., Zurcher, C., Havekes, L.M., van Vlijmen, B.J., Marine, J.C. Cell Death Differ. (2006)