MAPK3 and breast cancer: In addition to supporting the use of targeted ERK1/2 therapy to hinder cancer cell proliferation, we suggest several therapeutic benefits of ERK1/2 inhibition in aggressive osteolytic BCCs compared to bisphosphonate and RANKL-antibody treatment: [1] suppression of osteolytic breast cancer proliferation by inhibiting the production of protumor molecules from host bone and osteoblasts and [2] amelioration of osteolysis by reducing rates of bone resorption and promoting new bone formation.