Our data are in agreement with the observation that PC-3 prostate cancer cells, which induce osteolytic lesions in animals, secrete Dkk-1 and that osteoblastic lesions caused by C4-2B prostate cancer cells revert to an osteolytic phenotype upon transfection of C4-2B cells with a plasmid encoding for Dkk-1 (Hall et al, 2005). The gene discussed is DKK1; the disease is prostate cancer.