Bisphosphonates in the treatment of metastatic breast cancer

Using scaffolds as drug delivery systems to treat bone tumor

Surgery is the principal strategy to treat osteosarcoma and other types of bone tumors, but it causes bone defects that cannot be healed spontaneously. After surgery, patients still need to receive radiotherapy and/or chemotherapy to prevent tumor recurrence and metastasis, which leads to systemic side effects. Bone scaffolds exhibit the potentials to load cargos (drugs or growth factors) and act as drug delivery systems (DDSs) in the osteosarcoma postoperative treatment. This review introduces current types of bone scaffolds and highlights representative works using scaffolds as DDSs to treat osteosarcomas. Challenges and perspectives in the scaffold-based DDSs are also discussed. This review may provide references to develop effective and safe strategies for osteosarcoma postoperative treatment.

Targeted nanomedicines for the treatment of bone disease and regeneration

Targeted delivery by either passive or active targeting of therapeutics to the bone is an attractive treatment for various bone related diseases such as osteoporosis, osteosarcoma, multiple myeloma, and metastatic bone tumors. Engineering novel drug delivery carriers can increase therapeutic efficacy and minimize the risk of side effects. Developmnet of nanocarrier delivery systems is an interesting field of ongoing studies with opportunities to provide more effective therapies. In addition, preclinical nanomedicine research can open new opportunities for preclinical bone-targeted drug delivery; nevertheless, further research is needed to progress these therapies towards clinical applications. In the present review, the latest advancements in targeting moieties and nanocarrier drug delivery systems for the treatment of bone diseases are summarized. We also review the regeneration capability and effective delivery of nanomedicines for orthopedic applications.

Osteoclastic miR-214 targets TRAF3 to contribute to osteolytic bone metastasis of breast cancer

The role of osteoclastic miRNAs in regulating osteolytic bone metastasis (OBM) of breast cancer is still underexplored. Here, we examined the expression profiles of osteoclastogenic miRNAs in human bone specimens and identified that miR-214-3p was significantly upregulated in breast cancer patients with OBM. Consistently, we found increased miR-214-3p within osteoclasts, which was associated with the elevated bone resorption, during the development of OBM in human breast cancer xenografted nude mice (BCX). Furthermore, genetic ablation of osteoclastic miR-214-3p in nude mice prevent the development of OBM. Conditioned medium from MDA-MB-231 cells dramatically stimulated miR-214-3p expression to promote osteoclast differentiation. Mechanistically, a series of in vitro study showed that miR-214-3p directly targeted Traf3 to promote osteoclast activity and bone-resorbing activity. In addition, osteoclast-specific miR-214-3p knock-in mice showed remarkably increased bone resorption when compared to the littermate controls, which was attenuated after osteoclast-targeted treatment with Traf3 3'UTR-containing plasmid. In BCX nude mice, osteoclast-targeted antagomir-214-3p delivery could recover the TRAF3 protein expression and attenuate the development of OBM, respectively. Collectively, inhibition of osteoclastic miR-214-3p may be a potential therapeutic strategy for breast cancer patients with OBM. Meanwhile, the intraosseous TRAF3 could be a promising biomarker for evaluation of the treatment response of antagomir-214-3p.

The role of the bone microenvironment in skeletal metastasis

The bone microenvironment provides a fertile soil for cancer cells. It is therefore not surprising that the skeleton is a frequent site of cancer metastasis. It is believed that reciprocal interactions between tumour and bone cells, known as the “vicious cycle of bone metastasis” support the establishment and orchestrate the expansion of malignant cancers in bone. While the full range of molecular mechanisms of cancer metastasis to bone remain to be elucidated, recent research has deepened our understanding of the cell-mediated processes that may be involved in cancer cell survival and growth in bone. This review aims to address the importance of the bone microenvironment in skeletal cancer metastasis and discusses potential therapeutic implications of novel insights.

Treatment Options for Breast Cancer and Bone Metastases

The most common destination for breast cancer metastases is bone. If bone metastases are detected, treatment algorithms should include the continuation of cytoreductive therapy with the addition of treatment to counter skeletal-related events, including bone pain. The range of current treatment options includes bisphosphonates, surgical intervention to improve structural integrity and palliative focal radiotherapy. This article focuses on the role of bisphosphonate therapy in metastatic breast cancer. Bisphosphonate therapy significantly reduces the impact of skeletal-related events, reduces bone pain and increases patient quality of life. Our current understanding is that bisphosphonates may also disrupt the metastatic process and reduce the development of bone lesions. Ultimately, this may lead to further expansion of bisphosphonate-based therapy in the future.

Metastatic bone pain: treatment options with an emphasis on bisphosphonates

INTRODUCTION

One of the key targets for metastatic cancer cells is the skeleton. Once metastatic cells are established within the bone matrix, skeletal integrity becomes increasingly compromised. Bone lesions lead to various complications, including bone pain, fractures and spinal cord compression.

MECHANISMS OF BONE PAIN

Bone pain is debilitating and affects quality of life of the patient. In addition, it increases the use of health care resources. Many patients with metastatic bone disease experience substantial bone pain despite state-of-the-art systemic analgesic treatment. Incident pain is the predominant pain syndrome.

TREATMENT OPTIONS FOR BONE PAIN

Typically, this syndrome requires moderate baseline analgesia with increased on-demand doses. Other techniques for treating bone pain, including radiation therapy, neuraxial application of analgesics, nerve blocks and local stabilisation procedures, should be considered. In addition, therapy with bisphosphonates targeting bone-specific pain is an important strategy. This review discusses the various management options for bone pain arising from metastatic bone disease.

The osteoclast: friend or foe?

Bone is a dynamic organ constantly remodeled to support calcium homeostasis and structural needs. The osteoclast is the cell responsible for removing both the organic and inorganic components of bone. It is derived from hematopoietic progenitors in the macrophage lineage and differentiates in response to the tumor necrosis factor family cytokine receptor activator of NF kappa B ligand. alpha v beta 3 integrin mediates cell adhesion necessary for polarization and formation of an isolated, acidified resorptive microenvironment. Defects in osteoclast function, whether genetic or iatrogenic, may increase bone mass but lead to poor bone quality and a high fracture risk. Pathological stimulation of osteoclast formation and resorption occurs in postmenopausal osteoporosis, inflammatory arthritis, and metastasis of tumors to bone. In these diseases, osteoclast activity causes bone loss that leads to pain, deformity, and fracture. Thus, osteoclasts are critical for normal bone function, but their activity must be controlled.

Advances in treating metastatic bone cancer: summary statement for the First Cambridge Conference

The First Cambridge Conference on Advances in Treating Metastatic Bone Cancer, a symposium held in Cambridge, Massachusetts, October 28 to 29, 2005, was convened to discuss recent advances and research related to the natural history of bone metastases and skeletal complications, bone cancer biology, treatment of myeloma and other solid tumors, and treatment-induced bone loss. The conference format combined brief presentations with extended periods of discussion. The conclusions reached during the 2-day meeting are summarized in this article and presented in more detail in the individual articles and accompanying discussion sessions that comprise the conference proceedings.

Zoledronic acid (Zometa) enhances the cytotoxic effect of gemcitabine and fluvastatin: in vitro isobologram studies with conventional and nonconventional cytotoxic agents

OBJECTIVES

To identify synergistic combinations of clinically available agents with zoledronic acid which would enhance antitumor activity as measured by median effect isobologram analysis and apoptosis assays in vitro.

METHODS

The interaction of zoledronic acid as a doublet with either carboplatin, cisplatin, 5'DFUR, docetaxel, epirubicin, fluvastatin, gemcitabine, imatinib, paclitaxel, trastuzumab, or vinorelbine was studied in a 72-hour in vitro system using defined human cancer cell lines grown as a monolayer in exponential phase. Drug effect on growth was measured by a standard MTT assay. Median effect isobologram analysis was applied to the results to determine the presence of synergism, additive effects, or antagonism of drug combinations. Synergistic combinations were also assayed by a cytoplasmic histone-associated DNA fragmentation apoptosis assay to verify that the effect was not cytostatic.

RESULTS

Zoledronic acid with gemcitabine demonstrated global cytotoxic synergy across 7 of 8 cell lines. Clinically achievable concentrations of fluvastatin with zoledronic acid also demonstrated synergy in 7 of 8 cell lines. All the breast cancer cell lines were sensitive. Zoledronic acid and epirubicin were antagonistic in all 4 breast cell lines studied.

CONCLUSIONS

Combinations of zoledronic acid with either gemcitabine or fluvastatin may have a therapeutic role in treatment of bone metastasis of selected malignancies.

Ibandronate: pharmacology and preclinical studies

Over the past three decades, changes to the chemical structures of the bisphosphonates have resulted in progressive improvements in their antiresorptive potencies. Ibandronate is a potent, nitrogen-containing bisphosphonate that possesses a tertiary nitrogen group on its R2 side chain and a hydroxyl group on its R1 side chain, which together confer one of the highest antiresorptive potencies of all bisphosphonates. In common with other nitrogen-containing bisphosphonates, ibandronate is a strong inhibitor of farnesyl pyrophosphate synthase, which probably accounts for its major effects on osteoclast activity. In addition, it binds strongly to hydroxyapatite. The pharmacological efficacy and safety of various continuous and intermittent regimens of ibandronate have been extensively investigated in experimental models of osteoporosis in several animal species, including rats, dogs, and monkeys. In ovariectomized (OVX) rats, intermittent (dosing interval 2, 4, and 6 weeks) and continuous ibandronate regimens provided equivalent results per total dose irrespective of the dosing regimen. Similar results were obtained in OVX dogs and monkeys. High doses of ibandronate many times those used therapeutically were well tolerated and did not impair bone quality or mineralization in rats. Moreover, bone mass, architecture, and strength were maintained or improved, and bone healing was not adversely affected in animal models, regardless of whether ibandronate was administered intermittently or daily. The findings from all these studies demonstrate the efficacy and safety of intermittent ibandronate regimens and support the development of such regimens for the clinical management of postmenopausal osteoporosis.

Ibandronic Acid

Ibandronic acid (Bondronat) is a potent, new-generation, nitrogen-containing bisphosphonate, available in both intravenous and oral formulations, which effectively inhibits osteoclast-mediated bone resorption. In clinical trials, the two formulations were equally effective in preventing skeletal-related events and improving quality of life in patients with bone metastases of breast cancer. Both intravenous and oral ibandronic acid reduced metastatic bone pain scores below baseline levels for up to 2 years. Oral ibandronic acid is administered as a single 50 mg tablet taken once daily. It suppressed bone resorption in breast cancer patients with bone metastases to an extent similar to that observed with intravenous zoledronic acid. Both intravenous and oral ibandronic acid were well tolerated with no evidence of renal toxicity. Ibandronic acid is therefore a valuable addition to the bisphosphonates used in the treatment of bone metastases of breast cancer, offering high potency and the convenience of oral administration, combined with the absence of renal toxicity.

Additive growth inhibitory effects of ibandronate and antiestrogens in estrogen receptor-positive breast cancer cell lines

INTRODUCTION

Bisphosphonates are inhibitors of osteoclast-mediated tumor-stimulated osteolysis, and they have become standard therapy for the management of bone metastases from breast cancer. These drugs can also directly induce growth inhibition and apoptosis of osteotropic cancer cells, including estrogen receptor-positive (ER+) breast cancer cells.

METHODS

We examined the anti-proliferative properties of ibandronate on two ER+ breast cancer cell lines (MCF-7 and IBEP-2), and on one ER negative (ER-) cell line (MDA-MB-231). Experiments were performed in steroid-free medium to assess ER regulation and the effect of ibandronate in combination with estrogen or antiestrogens.

RESULTS

Ibandronate inhibited cancer cell growth in a dose- and time-dependent manner (approximate IC50: 10(-4) M for MCF-7 and IBEP-2 cells; 3 x 10(-4) M for MDA-MB-231 cells), partly through apoptosis induction. It completely abolished the mitogenic effect induced by 17beta-estradiol in ER+ breast cancer cells, but affected neither ER regulation nor estrogen-induced progesterone receptor expression, as documented in MCF-7 cells. Moreover, ibandronate enhanced the growth inhibitory action of partial (4-hydroxytamoxifen) and pure (ICI 182,780, now called fluvestrant or Faslodex) antiestrogens in estrogen-sensitive breast cancer cells. Combination analysis identified additive interactions between ibandronate and ER antagonists.

CONCLUSION

These data constitute the first in vitro evidence for additive effects between ibandronate and antiestrogens, supporting their combined use for the treatment of bone metastases from breast cancer.

Ibandronate in metastatic bone disease: a review of preclinical data

Bisphosphonates are widely used to prevent and treat skeletal complications of metastatic bone disease. There is increasing evidence that, besides inhibiting osteoclast activity and reducing bone resorption, bisphosphonates also have an anti-tumor effect. This paper reviews the preclinical data for ibandronate. Ibandronate increased the proportion of apoptotic tumor cells in vitro and in vivo, possibly following activation of caspase-like proteases. In vitro, ibandronate also prevented adhesion and spreading of tumor cells to bone, and tumor cell invasion. These inhibitory effects were additive when ibandronate was given with paclitaxel or docetaxel. In animal models of tumor-induced osteolysis, ibandronate significantly reduced the development of osteolytic lesions. Efficacy for the prevention and reduction of bone metastases was related to the timing of treatment; ibandronate treatment initiated prior to or shortly after tumor cell inoculation inhibited the growth of bone metastases and preserved skeletal integrity most effectively. As with other bisphosphonates, the influence of ibandronate on soft tissue metastases has been inconsistent. Overall, preclinical evidence supports the rationale for adjuvant treatment with ibandronate for patients at risk of metastatic bone disease. The renal safety profile of ibandronate supports its suitability for long-term adjuvant use, even with intermittent high dosing. Adjuvant clinical trials have been initiated. The ability of bisphosphonates to preserve skeletal integrity is also of benefit in other clinical settings. Recent studies in rat models demonstrate improved osseointegration of joint implants following ibandronate therapy, with potential application in patients with conditions such as degenerative arthritis or osteoporosis.

Analytical methods for the quantification of ibandronate in body fluids and bone

The accurate determination of bisphosphonate levels in bone and biological fluids is important in both clinical and pharmacological/toxicological studies. Ibandronate is a potent nitrogen-containing bisphosphonate containing a tertiary amine group, which does not easily form chromophore derivatives that can be detected by UV light or fluorescence emissions. The current report describes the methodology and validation of a GC-MS assay for ibandronate in serum/plasma and urine, a similar, modified GC-MS method for measurement of bone ibandronate levels, and an ELISA for ibandronate determination in serum/plasma. The range of quantification for the GC-MS was 1-100 ng/ml and 2-7500 ng/ml in plasma or serum and urine, respectively, and 50-1600 pg/ml (potentially 10-320 pg/ml depending on sample size) for the ELISA in plasma or serum. These assays were comparable. The practical application of the assays in preclinical and clinical studies is briefly reviewed.

Detection and molecular characterisation of disseminated tumour cells: Implications for anti-cancer therapy

Haematogenous distant metastasis is the leading cause of cancer-related death in solid tumours. By applying sensitive immunocytochemical and molecular assays, disseminated tumour cells (DTC) in bone marrow (BM) can be detected in 20-40% of cancer patients without any clinical or even histopathological signs of metastasis, and the presence of these DTC at primary diagnosis predicts the subsequent occurrence of overt metastases in bone and other organs. The detection and characterisation of DTC in BM may lead to a better understanding of the biology initiating metastatic spread in cancer patients and will eventually contribute to the development of more effective strategies to eliminate DTC. In this review, we will therefore discuss the detection and characterisation of DTC in the light of new therapeutic strategies targeting tumour-associated molecules and signalling pathways.

Review of ibandronate in the treatment of metastatic bone disease: experience from phase III trials

BACKGROUND

Metastatic bone disease is a serious clinical problem in patients with advanced cancer. Bisphosphonates inhibit the activity of osteoclasts and are the treatment of choice for bone metastases.

OBJECTIVE

This article reviews the efficacy and safety data from Phase III trials of ibandronate in metastatic bone disease.

METHODS

Phase III data (available as of June 2004) for ibandronate were reviewed. Literature searches using the MEDLINE database and abstracts from scientific meetings were used to obtain data from Phase III trials of ibandronate.

RESULTS

Compared with placebo, patients with bone metastases from breast cancer receiving IV ibandronate (6 mg infused over 1-2 hours every 3-4 weeks) or oral ibandronate (50 mg/d for up to 96 weeks) had a statistically significant reduction in skeletal complications, as measured by the Skeletal Morbidity Period Rate (P = 0.004 vs placebo). Multivariate Poisson regression analysis of the data showed that the risk of a new bone event was reduced by 40% with IV ibandronate 6 mg and by 38% with oral ibandronate 50 mg, compared with placebo (P < or = 0.003). Both formulations also reduced bone pain below baseline levels over 2 years (P < or = 0.001 vs placebo). IV and oral ibandronate were well tolerated, with adverse-event profiles comparable to placebo and no significant renal toxicity.

CONCLUSIONS

IV and oral ibandronate provide meaningful clinical benefits in patients with bone metastases from breast cancer. Both formulations reduce the risk of skeletal events and provide sustained relief from metastatic bone pain. With its favorable efficacy and safety profile, and the added convenience of the oral formulation, ibandronate provides improved treatment options for managing metastatic bone disease.

Ibandronate: a clinical pharmacological and pharmacokinetic update

Ibandronate is a potent nitrogen-containing bisphosphonate. It has a strong affinity for bone mineral and potently inhibits osteoclast-mediated bone resorption. Ibandronate is effective for the treatment of hypercalcemia of malignancy, metastatic bone disease, postmenopausal osteoporosis, corticosteroid-induced osteoporosis, and Paget's disease. Oral ibandronate is rapidly absorbed (t(max) < 1 hour), with a low bioavailability (0.63%) that is further reduced (by up to 90%) in the presence of food. Ibandronate has a wide therapeutic index and is not metabolized and, therefore, has a low potential for drug interactions. Given its metabolic stability, ibandronate is eliminated from the blood by partitioning into bone (40%-50%) and through renal clearance (CL(R) approximately 60 mL/min). The CL(R) of ibandronate is linearly related to creatinine clearance. The sequestration of ibandronate in bone (V(D) > 90 L) results in a multiphasic elimination (t((1/2)) range approximately 10-60 hours), characterized by the slow release of ibandronate from the bone compartment. The potency of ibandronate and its sequestration into bone allow ibandronate to be developed as oral and intravenous injection formulations that can be administered with convenient extended between-dose intervals.

Non-peptide antigens activating human Vγ9/Vδ2 T lymphocytes

Various non-peptidic ligands which specifically activate most of circulating human Vgamma9/Vdelta2 T lymphocytes are now known. Most of these are so-called phosphoantigens and directly trigger the Vgamma9/Vdelta2 TCR expressing cells, without need for MHC-restricted presentation molecules. Although some potent phosphoantigens currently involved in clinical trials are chemically-synthesized molecules, most of the natural antigens were isolated from microbial cultures. The structures and biosynthesis of phosphoantigens are reviewed here and the possible physiological significance of their recognition by gammadelta T lymphocytes is discussed.

Efficacy and Safety of Ibandronate in the Treatment of Opioid-Resistant Bone Pain Associated With Metastatic Bone Disease: A Pilot Study

Purpose

Bone metastases are associated with severe and sometimes intractable pain, compromising patient quality of life (QOL). This open-label pilot study investigated the effects of short-term intensive treatment with intravenous (IV) ibandronate on opioid-resistant bone pain in patients with skeletal metastases.

Patients and Methods

Eighteen patients with advanced tumors and metastatic bone disease received nonstandard treatment with 4 mg of ibandronate administered IV (2-hour infusion) for 4 consecutive days (16-mg total dose). Baseline opioid analgesic use was equivalent to 400 mg/d of morphine. Patients were assessed for 6 weeks or until death. Changes from baseline were determined for bone pain, opioid consumption, patient functioning, QOL, performance status, and biochemical markers of calcium metabolism and bone turnover. Renal function was assessed by serum urea and creatinine measurement.

Results

Short-term, intensive ibandronate treatment significantly reduced bone pain scores within 7 days (P < .001). Pain reductions were sustained over the study period. Ibandronate significantly improved QOL, patient functioning, and performance status (P < .05). Mean values of the urinary cross-links pyridinoline and deoxypyridinoline tended to increase after day 21, returning close to baseline values by day 42. There was no correlation between the change in crosslinks values and the change in pain scores after ibandronate treatment. Ibandronate was well tolerated, with no evidence of renal toxicity.

Conclusion

Nonstandard, intensive treatment with IV ibandronate seems to have a marked analgesic effect in patients with opioid-resistant bone pain from metastatic bone disease. Further investigation is warranted.

Extracellular calcium downregulates estrogen receptor alpha and increases its transcriptional activity through calcium-sensing receptor in breast cancer cells

Skeleton is the most common organ targeted by breast cancer cells, especially from estrogen receptor alpha (ER)-positive neoplasms. Metastatic cells can stimulate directly or indirectly osteoclast-mediated bone resorption. Tumor-induced osteolysis is often extensive and leads to the release of large quantities of calcium. Metastatic cancer cells can be thus exposed to high calcium concentrations (40 mM has been reported at the resorption site). However, the effects of Ca2+ on breast cancer cells have been minimally examined. We showed that 20-mM extracellular Ca2+ induced a downregulation of ER protein in MCF-7 cells and caused ER-mediated transactivation of a reporter gene by 55 +/- 10% (mean +/- SD) in MVLN cells (MCF-7 cells stably transfected with ERE and luciferase reporter gene). Moreover, 3 mM Ca2+ increased progesterone receptor (PgR) expression by 45 +/- 8%. Mg2+ tested at up to 20 mM did not exert any effects, while 17beta-estradiol downregulated ER, transactivated the reporter gene, and enhanced PgR expression. The pure antiestrogen ICI 182,780 was able to abrogate the transactivation of the reporter gene and the increase in PgR levels induced by Ca2+, indicating that Ca2+ may exert a weak and specific estrogenic effect in MCF-7 cells. Ca2+ effects on ER probably start at the cell membrane level since a large Ca2+ influx caused by the ionophore A23187 failed to activate ER. We have thus studied the involvement of the membrane calcium-sensing receptor (CaR) that is known to be expressed notably in MCF-7 cells. We first tested the effects of a specific activator of CaR. Exposure to 10(-4) M calcimimetic NPS R-467 mirrored the changes observed with extracellular Ca2+ by inducing a marked decrease in ER protein levels, increasing the transcriptional activity of ER (67 +/- 12%) and stimulating PgR expression (41 +/- 4%). As expected, the NPS S-467 isomer was less effective. Furthermore, a highly selective CaR antagonist partly suppressed the downregulation of ER as well as transactivation of the reporter gene induced by Ca(2+). Our results suggest that the effects of extracellular Ca2+ on ER expression and activity are mediated, at least in part, by the CaR. In summary, calcium released during the process of metastatic bone destruction could modulate the functions of the estrogen receptor, a key receptor involved in breast cancer cells growth and function, and thus participate in the pathogenesis of tumor-induced osteolysis.

Bisphosphonates antagonise bone growth factors' effects on human breast cancer cells survival

Bone tissue constitutes a fertile 'soil' for metastatic tumours, notably breast cancer. High concentrations of growth factors in bone matrix favour cancer cell proliferation and survival, and a vicious cycle settles between bone matrix, osteoclasts and cancer cells. Classically, bisphosphonates interrupt this vicious cycle by inhibiting osteoclast-mediated bone resorption. We and others recently reported that bisphosphonates can also induce human breast cancer cell death in vitro, which could contribute to their beneficial clinical effects. We hypothesised that bisphosphonates could inhibit the favourable effects of 'bone-derived' growth factors, and indeed found that bisphosphonates reduced or abolished the stimulatory effects of growth factors (IGFs, FGF-2) on MCF-7 and T47D cell proliferation and inhibited their protective effects on apoptotic cell death in vitro under serum-free conditions. This could happen through an interaction with growth factors' intracellular phosphorylation transduction pathways, such as ERK1/2-MAPK. In conclusion, we report that bisphosphonates antagonised the stimulatory effects of growth factors on human breast cancer cell survival and reduced their protective effects against apoptotic cell death. Bisphosphonates and growth factors thus appear to be concurrent compounds for tumour cell growth and survival in bone tissue. This could represent a new mechanism of action of bisphosphonates in their protective effects against breast cancer-induced osteolysis.