MAPK1 and breast neoplasm: The ERK/MSK1/Elk-1/Snail signaling pathway has been associated with breast cancer progression in vitro and in vivo; exogenous chemokine (C-X-C motif) ligand 5 (CXCL5) mimicked the effect of breast tumor-associated osteoblast (TAOBs) activities to induce Raf/MEK/ERK mediated up-regulation of Snail in MCF-7 and MDA-MB-231, which resulted in decreased E-cadherin expression [18].