EIF4EBP1 and Merkel cell skin cancer: Consistent with published reports on other solid tumors, MLN0128 markedly inhibited phosphorylation of both mTOR and its downstream effectors, including 4E-BP1 (Thr37/46) and S6 kinase (Ser235/236) in all three MCV negative MCC cell lines (Figure 4A) [21].