EIF2AK3 and cancer: We found that phosphorylated ERK (pERK), a downstream effector of MAPK signaling, was not detectable in proliferating premalignant lesions (Fig. 7B, top row, column d), whereas, similar to p19Arf, foci of pERK positivity were evident in malignant tumors (Fig. 7D, upper row, column d).