MAPK3 and neoplasm: Moreover, at the protein level, restoration of miR-3151 in completely methylated cells resulted in 66% downregulation of MADD protein, in association with 77% repression of the downstream phospho-ERK1/2 protein, indicating that miR-3151 may function as a tumor suppressor by inhibiting MADD/MEK/ERK signaling (Figure 6B).