Biphosphonate

Abstract: Bisphosphonates are generally considered to act on bone resorption by binding to bone mineral and subsequently inhibiting the activity of the osteoclasts which ingest them. This has been supported by the fact that bisphosphonates adsorbed on mineralized tissue inhibit the resorbing activity of isolated osteoclasts in vitro. However, the effectiveness of different bisphosphonates determined in this system does not reflect their relative potencies in vivo. Employing the well-described isolated osteoclast resorption pit assay, with ivory as the resorption substrate, we show here that this lack of correlation prevails only when the bisphosphonates are added to the mineral before addition of osteoclasts, but not when the cells are treated for a short time (5 min) before allowing them to adhere onto ivory. By using this approach with five different bisphosphonates, a stringent correlation of relative potencies was obtained with those found, both in the rat and in the human, in vivo. Furthermore, by using an osteoblastic cell line (CRP 10/30) which is a powerful promoter of osteoclastic resorption in vitro, we obtained evidence that the inhibitory effect of bisphosphonates was the result of an action on osteoblasts rather than on osteoclasts. Thus, in experiments in which the osteoblastic cells were pretreated for 5 min with bisphosphonates and then cocultured with osteoclasts, inhibition of osteoclastic resorbing activity was obtained. Moreover, it was found that this treatment resulted in a decrease of the stimulatory effect found in CRP 10/30-conditioned medium. In conclusion the present study shows that part of the osteoclast inhibiting action of the bisphosphonates is mediated through an action on osteoblasts.

Abstract: The presence of skeletal metastases in patients suffering from cancer leads to a variety of clinical complications. Bisphosphonates are a class of drugs with a potent bone resorption inhibition activity that have found increasing utility in treating and managing patients with metastatic bone disease. Several clinical trials have demonstrated that bisphosphonates have clinical value in the treatment and management of skeletal metastases derived from advanced prostate cancer. Currently, the mechanism(s) through which bisphosphonates exert their activity is only beginning to be understood. We have studied the effects of bisphosphonate treatment on the growth of prostate cancer cell lines in vitro . Treatment of PC3, DU145, and LNCaP cells with pamidronate or zoledronate significantly reduced the growth of all three cell lines. Using flow cytometry, pamidronate treatment (100 μm) was shown to induce significant amounts of cell death in all three cell lines studied. In contrast, treatment with zoledronate (100 μm) did not induce cell death, instead exerting dramatic effects on cell proliferation, as evidenced by a major increase in cells present in the G 0 -G 1 and S phase. Although both drugs reduced prostate cancer cell growth in the presence of serum, zoledronate was more potent under these conditions, disrupting growth at doses as low as 25 μm in the presence of 5% fetal bovine serum. These results raise the intriguing possibility that the observed clinical utility of bisphosphonates in managing skeletal metastases may in part derive from direct inhibition of prostate cancer cell growth in the bone microenvironment.

Abstract: Many patients with advanced cancer experience decreased bone strength due to metastatic foci, underlying osteoporosis and/or cancer treatment induced bone loss. The clinical consequences of metastatic disease involving the skeleton are widespread. This review focuses on the efficacy, pharmacology, and safety when using intravenous biphosphonate such a zoledronic acid for cancer bone metastases. Zoledronic acid is the gold standard for the medical management of metastatic bone disease. The indications for treatment include prevention of skeletal relevant events (SRE), osteoporotic complications, and palliation of bone pain, among others. Zoledronic acid is the only bisphosphonate effective in decreasing SREs associated with bone metastases from advanced renal cell carcinoma and prostate cancer. Regarding prostate cancer, zoledronic acid effectively prevents both bone loss in patients with locally advanced disease receiving androgen deprivation therapy and SREs in men with hormone-refractory or hormone-sensitive metastatic disease. Zoledronic acid has an acceptable safety profile and tolerability, and has been effective at significantly decreasing the incidence, delaying the onset, and reducing the overall risk of experiencing an SRE compared to placebo. It is the only bisphosphonate currently approved for the prevention and treatment of skeletal complications in patients with bone metastases due to all solid tumors.