To this end, nude mice were randomized into two groups and orthotopic breast tumor xenografts were created by co-injecting MDA-MB-231 breast cancer cells (2 × 106) with 1.5 × 106 TCF64-OPG-ORF (TCF64-ORF-T) or TCF64-Ctl cells (TCF64-Ctl-T) under the nipple of each mouse (n = 6). The gene discussed is TNFRSF11B; the disease is breast neoplasm.