Bisphosphonates: biological response modifiers in breast cancer

Bisphosphonates-much more than only drugs for bone diseases

α,α-Bisphosphonates (BPs) are well established in the treatment of bone diseases such as osteoporosis and Paget's disease. Their successful application originates from their high affinity to hydroxyapatite. While the initially appreciated features of BPs are already beneficial to many patients, recent developments have further expanded their pleiotropic applications. This review describes the background of the interactions of BPs with bone cells that form the basis of the classical treatment. A better understanding of the mechanism behind their interactions allows for the parallel application of BPs against bone cancer and metastases followed by palliative pain relief. Targeted therapy with bone-seeking BPs coupled with a diagnostic agent in one particle resulted in theranostics which is also described here. For example, in such a system, BP moieties are bound to contrast agents used in magnetic resonance imaging or radionuclides used in positron emission tomography. In addition, another example of the pleiotropic function of BPs which involves targeting the imaging agents to bone tissues accompanied by pain reduction is presented in this work.

Optimal management of metastatic bone disease

OBJECTIVES

Skeletal-related events (SREs) from bone metastases are a major cause of morbidity and significantly decrease patients' quality of life. Strategies for the optimal management of SREs with bisphosphonates are explored.

METHODS

Existing and novel therapies were identified and published guidelines were reviewed through PubMed key word searches.

RESULTS

Nitrogen-containing bisphosphonates effectively reduce the risk of SREs in patients with bone metastases from a variety of solid tumors and bone lesions from multiple myeloma. Review of placebo-controlled trials in breast cancer patients with bone metastases indicated that zoledronic acid produced the greatest SRE risk reduction of all bisphosphonates evaluated. Zoledronic acid has demonstrated significant long-term benefits for prevention of SREs and palliative effects for bone pain. Zoledronic acid also improves quality of life. Analysis of recent trials indicates that early zoledronic acid intervention provides greater benefit in asymptomatic patients.

CONCLUSIONS

Patients with malignant bone disease are at a continuous risk for SREs, and bisphosphonates reduce the incidence and delay the onset of SREs. Zoledronic acid has demonstrated the greatest SRE risk reduction of all bisphosphonates and significantly improves pain scores in patients with breast cancer. Zoledronic acid is the only bisphosphonate to show efficacy in prostate cancer, lung cancer, and other solid tumors.

Synthesis, characterization, and in vitro antitumor activity of osteotropic diam(m)ineplatinum(II) complexes bearing a N,N-bis(phosphonomethyl)glycine ligand

A series of osteotropic (bone-seeking) [(bis(phosphonomethyl)amino-kappaN)acetato-kappaO(2-)]platinum(II) complexes attached to diammine, ethane-1,2-diamine, cis-R,S-cyclohexane-1,2-diamine, trans-S,S-cyclohexane-1,2-diamine, or trans-R,R-cyclohexane-1,2-diamine has been synthesized in accord with the concept of drug targeting and characterized by elemental analysis, (1)H, (13)C, and (31)P NMR spectroscopy. The in vitro antitumor activity in ovarian cancer cells (CH1) has been determined by means of the MTT assay. In this cisplatin-sensitive cell line the complexes containing cyclohexane-1,2-diamine (chxn) displayed a high activity in comparison to the diammine and ethane-1,2-diamine counterparts. In agreement with structure-activity relationships of other chxn-containing platinum(II) complexes both [(bis(phosphonomethyl)amino-kappaN)acetato-kappaO(2-)](trans-cyclohexane-1,2-diamine)platinum(II) complexes show superior potency than the corresponding cis-congener whereas the trans-R,R isomer displays the highest activity. Within the series of complexes under investigation, potency decreases depending on the coordinated amine ligand in the following order: trans-R,R-chxn > trans-S,S-chxn > NH(3) > or = cis-R,S-chxn > en.