RPS6KB1 and melanoma: To further explore this unexpected link between MCL1 level and mTORC1 signaling and assess whether it is a unique feature of MCL1 or a shared effect with other anti-apoptotic members of the Bcl-2 family of proteins, we examined by immunoblotting the phosphorylation of downstream targets of S6K1 and S6 in CHL-1 melanoma cells depleted of either MCL1, Bcl-2 or Bcl-xL.