SPARC and cancer: Unlike osteocalcin promoter that has been proposed for prostate cancer/bone stroma co-targeting gene therapy based on the conventional osteoblastic reactions demonstrated in experimental models and clinical manifestations of prostate cancer skeletal metastasis [23, 36], elevated osteonectin expression was also observed in prostate cancer epithelium and cancer-associated stroma in primary prostate tumors through RT-PCR and IHC analyses.