For analysis of whether breast cancer bone metastasis was associated with osteoblastic ERK1/2 activation, three samples from human breast cancer metastasis to bone and uncompromised bone samples were surgically resected during tumor debulking/resection and total knee arthroplasty (TKA), respectively, and stained for pERK1/2 and osteocalcin (Fig. 3a). The gene discussed is MAPK3; the disease is breast cancer.