MAPK3 and neoplasm: This last observation suggests that mechanisms for restoring p53 will stress tumor cells to delete p53. This was observed in the Jacks study above (Ventura et al., 2007) where loss of Cre-ERT2 occurred in one tumor and in theMartins et al. (2006) study where one mechanism of resistance to Eμ-myc;p53ERTAM/+-induced B-cell lymphomas was loss of p53ERTAM.