BCL2L1 and breast cancer: ERK phosphorylates cytoplasmic targets including ribosomal protein S6 kinase (RSK) and Bcl-2 family proteins such as Bcl-2, Bcl-xL and Mcl-1 [63]: RSK converts non-transformed epithelial cells to motile, mesenchymal carcinoma cells [64], and the application of an RSK inhibitor or siRNA blocks breast cancer cell initiation and proliferation [65,66].