RHO and osteoporosis: Zoledronic acid (ZA), a drug commonly used for the treatment of osteoporosis and to prevent skeletal complications of bone metastasis, is a amino-bisphosphonate that blocks the activity of farnesyl pyrophosphate synthase (FPPS), a key component in the HMG-CoA reductase pathway, which is necessary for prenylation and lipid modification of a variety of proteins including Ras, Rho and Rac [35], [36].