Hiraga et al (2001) describe a substantial increase in apoptotic MDA-MB-231 cells in the bones of mice treated with ibandronate, especially at the bone–tumour interface. Several other mechanisms of action have also been suggested for both drugs. In vitro, zoledronate has also been reported to stimulate osteoprotegerin production in primary human osteoblasts (Viereck et al, 2002), inhibit prostate cancer cell proliferation (Corey et al, 2003), MMP activity (Boissier et al, 2000) and adhesion to bone extracellular matrix (Boissier et al, 1997). The gene discussed is TNFRSF11B; the disease is prostate cancer.