Zoledronic acid inhibits visceral metastases in the 4T1/luc mouse breast cancer model

Adjuvant zoledronic acid therapy for patients with early stage breast cancer: an updated systematic review and meta-analysis

BACKGROUND

Zoledronic acid is a potent inhibitor of osteoclast-mediated bone resorption and has been widely used in bone metastasis malignancies and postmenopausal osteoporosis as a preventive therapy against skeletal-related events. The purpose of this study was to evaluate the clinical outcome of zoledronic acid as an adjuvant therapy for patients with early stage breast cancer.

PATIENTS AND METHODS

Entries in the PubMed and EMBASE databases up to 12 July 2013 were systematically reviewed. Online abstracts from the proceedings of the Annual Meetings of the American Society of Clinical Oncology (ASCO) (1992-2013) and the San Antonio Breast Cancer Symposium (SABCS) (2004-2013) were also reviewed. Primary endpoints included overall survival (OS) and disease-free survival (DFS), while secondary endpoints included bone metastasis-free survival (BMFS), distant metastasis-free survival (DMFS), and fracture-free rate (FFR).

RESULTS

A total of eight studies including 3,866 subjects and 3,864 controls met our search criteria and were evaluated. The use of zoledronic acid was found to improve OS (relative risk (RR), 0.88; 95% confidence interval (CI), 0.77-1.01; p-value = 0.06) and DMFS (RR, 0.77; 95% CI, 0.60-1.00; p-value = 0.05). Furthermore, statistically significant benefits were associated with BMFS (RR, 0.81; 95% CI, 0.66-0.99; p-value = 0.04) and FFRs (RR, 0.75; 95% CI, 0.61-0.92; p-value = 0.007). In contrast, there was no significant difference in DFS with the application of zoledronic acid (RR, 0.88; 95% CI, 0.72-1.09; p-value = 0.24). Sensitivity analysis further identified the improvement of 5-year OS for the adjuvant zoledronic acid therapy in early stage breast cancer patients (RR, 0.86; 95% CI, 0.75-0.99; p-value = 0.03), while a borderline statistically significant benefit was observed for 5-year DFS (RR, 0.90; 95% CI, 0.81-1.00; p-value = 0.06).

CONCLUSION

Zoledronic acid as an adjuvant therapy appears to improve the 5-year OS rate for early stage breast cancer patients, and was associated with a protective effect for the bone metastases and fractures evaluated in more than 7,000 patients. However, further research is needed to confirm our findings, and sub-group analyses according to menopause status or hormone status may provide further insight.

Influence of zoledronic acid on disseminated tumor cells in bone marrow and survival: results of a prospective clinical trial

Background

The presence of disseminated tumor cells (DTC) in bone marrow (BM) of breast cancer patients is associated with reduced clinical outcome. Bisphosphonate treatment was shown to eradicate DTC from BM in several studies. This controlled randomized open-label multi-center study aimed to investigate the influence of zoledronic acid (ZOL) on DTC and survival of breast cancer patients (Clinical Trial Registration Number: NCT00172068).

Methods

Patients with primary breast cancer and DTC-positive bone marrow were randomized to treatment with ZOL plus adjuvant systemic therapy (n = 40) or adjuvant systemic therapy alone (n = 46) between 03/2002 and 12/2004. DTC were identified by immunocytochemistry using the pancytokeratin antibody A45B/B3 and by cytomorphology. The change in DTC numbers at 12 months and 24 months versus baseline, as well as patient outcomes were evaluated.

Results

86 patients could be included into survival analysis (median follow-up: 88 months, range: 8–108 mths). Patients in the control group were more likely to die during follow-up than those in the ZOL-group (11% vs. 2%, p = 0.106). 15% of patients in the control group presented with relapse whereas only 8% of ZOL group patients developed metastatic or recurrent disease during follow-up (p = 0.205). At 24 months, 16% of patients from the control group were still DTC positive, whereas all patients treated with ZOL became DTC negative (p = 0.032). Patients presenting with persistent DTC 12 months after diagnosis had significantly shorter overall survival (p = 0.011).

Conclusions

Bisphosphonate therapy contributes to eradication of disseminated tumor cells. The positive influence of bisphosphonates on survival in the adjuvant setting may be due to their effects on DTC.

Trial registration

ClinicalTrials.gov Identifier: NCT00172068 [Zoledronic Acid in the Treatment of Breast Cancer With Minimal Residual Disease in the Bone Marrow (MRD-1)].

Estradiol increases ER-negative breast cancer metastasis in an experimental model

Breast cancer (BC) is the most common cancer affecting women in the United States and metastatic breast cancer is the leading cause of death. The role estradiol plays in ER-positive BC is well-documented, but the way it contributes to ER-negative BC remains unclear. In the present study, we utilized an experimental model of BC metastasis into lung by injecting ER-negative murine 4T1 cells into mice via the lateral tail vein. A 56 % metastasis occurrence rate following the injection of 5 × 10(3) cells was observed, thus this cell number was selected to study the potential stimulatory effect of estradiol on ER-negative BC metastasis. Female ovariectomized mice were randomized into estradiol and control groups with 16 mice per group, and estradiol pellets were implanted subcutaneously in the estradiol group. Results demonstrated that estradiol accelerated BC metastasis as indicated by bioluminescent imaging. In addition, estradiol enhanced metastatic tumor colony formation and increased the size of tumor nodules in the lungs, which were due, in part, to the increase in proliferative cells in the metastatic tumors. In vitro, estradiol increased the motility and invasion of 4T1 cells, and the stimulatory effect on cell motility was not blocked by ICI 182, 780, confirming that ER was not involved in the process. Results from the present study suggest that estradiol plays a role in ER-negative BC metastasis in whole animals.

Beyond aspirin-cancer prevention with statins, metformin and bisphosphonates

Cancer risk reduction using pharmacological means is an attractive modern preventive approach that supplements the classical behavioural prevention recommendations. Medications that are commonly used by large populations to treat a variety of common, non-cancer-related, medical situations are an attractive candidate pool. This Review discusses three pharmacological agents with the most evidence for their potential as cancer chemopreventive agents: anti-hypercholesterolaemia medications (statins), an antidiabetic agent (metformin) and antiosteoporosis drugs (bisphosphonates). Data are accumulating to support a significant negative association of certain statins with cancer occurrence or survival in several major tumour sites (mostly gastrointestinal tumours and breast cancer), with an augmented combined effect with aspirin or other non-steroidal anti-inflammatory drugs. Metformin, but not other hypoglycaemic drugs, also seems to have some antitumour growth activity, but the amount of evidence in human studies, mainly in breast cancer, is still limited. Experimental and observational data have identified bisphosphonates as a pharmacological group that could have significant impact on incidence and mortality of more than one subsite of malignancy. At the current level of evidence these potential chemopreventive drugs should be considered in high-risk situations or using the personalized approach of maximizing individual benefits and minimizing the potential for adverse effects with the aid of pharmacogenetic indicators.

Painful boney metastases

Boney metastasis may lead to terrible suffering from debilitating pain. The most likely malignancies that spread to bone are prostate, breast, and lung. Painful osseous metastases are typically associated with multiple episodes of breakthrough pain which may occur with activities of daily living, weight bearing, lifting, coughing, and sneezing. Almost half of these breakthrough pain episodes are rapid in onset and short in duration and 44% of episodes are unpredictable. Treatment strategies include: analgesic approaches with "triple opioid therapy", bisphosphonates, chemotherapeutic agents, hormonal therapy, interventional and surgical approaches, steroids, radiation (external beam radiation, radiopharmaceuticals), ablative techniques (radiofrequency ablation, cryoablation), and intrathecal analgesics.

Zoledronic acid but not somatostatin analogs exerts anti-tumor effects in a model of murine prostatic neuroendocrine carcinoma of the development of castration-resistant prostate cancer

BACKGROUND

Since neuroendocrine (NE) cells play an important role in the development of castration-resistant prostate cancer (CRPC), target therapy to NE cells should be considered for treating CRPC. We investigated the effects zoledronic acid (ZOL) and two somatostatin analogs (octreotide: SMS, and pasireotide: SOM) on an NE allograft (NE-10) and its cell line (NE-CS), which were established from the prostate of the LPB-Tag 12T-10 transgenic mouse.

METHODS

We examined the in vivo effects of ZOL, SMS and SOM as single agents and their combinations on subcutaneously inoculated NE-10 allografts and the in vitro effects on NE-CS cells. Apoptosis and cell cycle activity were assessed by immunohistochemistry using TdT-mediated dUTP-biotin nick-end labeling (TUNEL) and a Ki-67 antibody, respectively.

RESULTS

In vivo growth of NE-10 tumors treated with ZOL, ZOL plus SMS, or ZOL plus SOM was significantly inhibited compared to the control as a consequence of induction of apoptosis and cell cycle arrest. ZOL induced time- and dose-dependent inhibition of in vitro proliferation of NE-CS cells, but the somatostatin analogs (SMS and SOM) did not. ZOL also inhibited migration of NE-CS cells. These effects were caused by inhibition of Erk1/2 phosphorylation via impairment of prenylation of Ras.

CONCLUSIONS

ZOL, but not SMS or SOM, induced apoptosis and inhibition of proliferation and migration through impaired prenylation of Ras in NE carcinoma models. Our findings support the possibility that ZOL could be used in the early phase for controlling NE cells, which may trigger progression to CRPC.

Hyaluronan synthesis inhibitor supplements the inhibitory effects of zoledronic acid on bone metastasis of lung cancer

Hyaluronan is known to have pivotal roles in the growth, migration and invasion of malignant tumors. Bone metastases are critical lesions greatly impairing the quality of patients with malignancies. We investigated whether hyaluronan synthesis inhibitor supplements the inhibitory effects of zoledronic acid, which is a conventional therapeutic agent for bone metastasis. We examined the effects of methylumbelliferone, an inhibitor of hyaluronan synthesis and/or ZA on the tumorigenicity of one murine lung carcinoma and two human (A549, SK-MES-1) lung cancer cell lines in vitro. The interaction between methylumbelliferone and zoledronic acid was analyzed using Calcucyn software. With a murine bone metastasis model of lung cancer in vivo, we investigated the inhibitory effects and interaction of the two drugs on the progression of metastatic bone lesions. Methylumbelliferone or zoledronic acid treatment individually suppressed proliferation, migration and invasion of 3 cell lines, and combination treatment showed synergistic effects. Although methylumbelliferone as a single agent did not enhance apoptotic activity, it showed additive effects on apoptotic activity to those of zoledronic acid. Co-localization of CD44 and ezrin, which might be a pathway of hyaluronan signaling, was abrogated by methylumbelliferone treatment. Combination therapy showed additive inhibitory effects on metastatic bone lesions in vivo, which paralleled the inhibition of hyaluronan accumulation by methylumbelliferone, and inhibition of osteoclastogenesis. Although the detailed mechanisms underlying the synergistic or additive inhibitory effects of these two drugs should be further analyzed, inhibition of hyaluronan synthesis by methylumbelliferone is a promising novel therapeutic candidate for bone metastasis of lung cancer in addition to zoledronic acid.

Antagonism of inhibitor of apoptosis proteins increases bone metastasis via unexpected osteoclast activation

Inhibitor of apoptosis (IAP) proteins play a central role in many types of cancer, and IAP antagonists are in development as anticancer agents. IAP antagonists cause apoptosis in many cells, but they also activate alternative NF-κB signaling through NF-κB-inducing kinase (NIK), which regulates osteoclasts. In bone metastasis, a positive feedback loop between tumors and osteoclasts promotes tumor growth and osteolysis. We therefore tested the effect of IAP antagonists on the bone microenvironment for metastasis. In both drug-sensitive and drug-resistant tumors, growth in bone was favored, as compared with other sites during IAP antagonist treatment. These drugs also caused osteoporosis and increased osteoclastogenesis, mediated by NIK, and enhanced tumor-associated osteolysis. Cotreatment with zoledronic acid, a potent osteoclast inhibitor, reduced IAP antagonist-enhanced tumor growth in bone and osteolysis. Thus, IAP antagonist-based cancer treatment may be compromised by osteoporosis and enhanced skeletal metastasis, which may be prevented by antiresorptive agents.

SIGNIFICANCE

Although IAP antagonists are a class of anticancer agents with proven efficacy in multiple cancers, we show that these agents can paradoxically increase tumor growth and metastasis in the bone by stabilizing NIK and activating the alternative NF-κB pathway in osteoclasts. Future clinical trials of IAP antagonist-based therapy may require detailed examination of this potential for enhanced bone metastasis and osteoporosis, as well as possible combination with antiresorptive agents.

Bisphosphonates in the adjuvant treatment of breast cancer

Bisphosphonates, as potent inhibitors of osteoclast-mediated bone resorption, significantly reduce the risk of skeletal complications in metastatic bone disease and also prevent cancer treatment-induced bone loss (CTIBL). However, more recently, there has been increasing data indicating that bisphosphonates exhibit anti-tumour activity, possibly via both indirect and direct effects, and can potentially modify the metastatic disease process providing more than just supportive care. The evidence from previous studies of an anti-tumour effect of bisphosphonates was inconclusive, with conflicting evidence from adjuvant oral clodronate trials. However, more recent trials using zoledronic acid have shown benefits in terms of disease-free and overall survival outcomes in certain subgroups, most evidently in older premenopausal women with hormone-sensitive disease treated with ovarian suppression, and in women in established menopause at trial entry. In the adjuvant setting, the use of bisphosphonates has also been focused on the prevention and treatment of CTIBL and recent guidelines have defined treatment strategies for CTIBL. The role of bisphosphonates in CTIBL in early breast cancer is well defined. There have been mixed results from large adjuvant metastasis-prevention studies of bisphosphonates, but there are strong signals from large subgroups analyses of randomised phase III trials suggesting significant anti-tumour beneficial effects in specific patient populations.

The impact of menopause on bone, zoledronic acid, and implications for breast cancer growth and metastasis

Recent data from the AZURE, ABCSG-12, and ZO-FAST clinical trials have challenged our understanding of the potential anticancer activity of zoledronic acid (ZOL). Although the results of these studies may appear to be conflicting on the surface, a deeper look into commonalities among the patient populations suggest that some host factors (i.e. patient age and endocrine status) may contribute to the anticancer activity of ZOL. Indeed, data from these large clinical trials suggest that the potential anticancer activity of ZOL may be most robust in a low-estrogen environment. However, this may be only part of the story and many questions remain to be answered to fully explain the phenomenon. Does estrogen override the anticancer activity of ZOL seen in postmenopausal women? Are hormones other than estrogen involved that contribute to this effect? Does the role of bone turnover in breast cancer (BC) growth and progression differ in the presence of various estrogen levels? Here, we present a review of the multitude of factors affected by different endocrine environments in women with BC that may influence the potential anticancer activity of ZOL.

Bisphosphonate use and gastrointestinal tract cancer risk: Meta-analysis of observational studies

AIM: To perform a meta-analysis of observational studies to further elucidate the relationship between oral bisphosphonate use and gastrointestinal cancer risk.

METHODS: Systematic literature search was conducted in MEDLINE, EMBASE, and the Cochrane Library to identify studies through January 2011. Search terms were “bisphosphonates” or trade names of the drugs, and “observational studies” or “cohort studies” or “case-control studies”. Two evaluators reviewed and selected articles on the basis of predetermined selection criteria as followed: (1) observational studies (case-control or cohort studies) on bisphosphonate use; (2) with at least 2 years of follow-up; and (3) reported data on the incidence of cancer diagnosis. The DerSimonian and Laird random effects model were used to calculate the pooled relative risk (RR) with 95% confidence interval (CI). Two-by-two contingency table was used to calculate the outcomes not suitable for meta-analysis. Subgroup meta-analyses were conducted for the type of cancer (esophageal, gastric and colorectal cancers). Sensitivity analyses were performed to examine the effect sizes when only studies with long-term follow-up (mean 5 years; subgroup 3 years) were included.

RESULTS: Of 740 screened articles, 3 cohort studies and 3 case-control studies were included in the analyses. At first, 4 cohort studies and 3 case-control studies were selected for the analyses but one cohort study was excluded because the cancer outcomes were not categorized by type of gastrointestinal cancer. More than 124 686 subjects participated in the 3 cohort studies. The mean follow-up time in all of the cohort studies combined was approximately 3.88 years. The 3 case-control studies reported 3070 esophageal cancer cases and 15 417 controls, 2018 gastric cancer cases and 10 007 controls, and 11 574 colorectal cancer cases and 53 955 controls. The percentage of study participants who used bisphosphonate was 2.8% among the cases and 2.9% among the controls. The meta-analysis of all the studies found no significant association between bisphosphonate use and gastrointestinal cancer. Also no statistically significant association was found in a meta-analysis of long-term follow-up studies. There was no negative association between bisphosphonate use and the incidence of esophageal cancer in the overall analysis (RR 0.96, 95% CI: 0.65-1.42, I² = 52.8%, P = 0.076) and no statistically significant association with long-term follow-up (RR 1.74, 95% CI: 0.97-3.10, I² = 58.8%, P = 0.119). No negative association was found in the studies reporting the risk of gastric cancer (RR 0.89, 95% CI: 0.71-1.13, I² = 0.0%, P = 0.472). In case of colorectal cancer, there was no association between colorectal cancer and bisphosphonate use (RR 0.62, 95% CI: 0.30-1.29, I² = 88.0%, P = 0.004) and also in the analysis with long-term follow-up (RR 0.61, 95% CI: 0.28-1.35, I² = 84.6%, P = 0.011).

CONCLUSION: Oral bisphosphonate use had no significant effect on gastrointestinal cancer risk. However, this finding should be validated in randomized controlled trials with long-term follow-up.

Zoledronic acid produces antitumor effects on mesothelioma through apoptosis and S-phase arrest in p53-independent and Ras prenylation-independent manners

INTRODUCTION

We examined whether zoledronic acid (ZOL), the third generation of bisphosphonates, produced cytotoxic effects on human mesothelioma cells in vitro and in vivo, and investigated a possible involvement of p53, Ras, and extracellular signal-regulated kinase1/2 (ERK1/2) pathways.

METHODS

Cytotoxicity and cell cycles were assessed with a colorimetric assay and flow cytometry, respectively. Expression levels of apoptosis-linked proteins and prenylation of small guanine-nucleotide-binding regulatory proteins were tested with p53-small interfering RNA, an ERK kinase1/2-inhibitor, and prenyl alcohols. The antitumor activity was examined in an orthotopic animal model.

RESULTS

ZOL treatments suppressed growth of mesothelioma cells bearing the wild-type p53 gene through apoptosis induction accompanied by activation of caspases, or S-phase arrest by up-regulated cyclin A and B1. ZOL induced p53 phosphorylation and subsequent activation of the downstream pathways. Down-regulated p53 expression with the small interfering RNA, however, showed that both apoptosis and S-phase arrest were irrelevant to the p53 activation. Geranylgeranyl but not farnesyl pyrophosphate inhibited ZOL-induced apoptosis and S-phase arrest, and the geranylgeraniol supplement decreased ZOL-mediated Rap1A but not Ras unprenylation. Inhibition of ERK1/2 pathways suppressed ZOL-induced apoptosis but not S-phase arrest. We further demonstrated that ZOL, administrated intrapleurally, inhibited the tumor growth in the pleural cavity.

CONCLUSIONS

These data indicate that ZOL induces apoptosis or S-phase arrest, both of which are independent of p53 activation and Ras unprenylation, and suggest that ZOL is a possible therapeutic agent to mesothelioma partly through non-Ras- and ERK1/2-mediated pathways.

Zoledronic acid effectiveness against breast cancer metastases - a role for estrogen in the microenvironment?

Zoledronic acid (ZA) is an imidazole-containing bisphosphonate that has been extensively studied as an osteoclast inhibitor. ZA decreases bone turnover and has been effective in limiting osteolysis in metastatic cancers, including breast cancer. Recent clinical trials that demonstrated enhancement of disease-free survival by bisphosphonates have prompted interest in bisphosphonates as anti-cancer agents. ZA, for example, increased disease-free survival in postmenopausal and in premenopausal, hormone-suppressed breast cancer patients. Intriguingly, however, there was a lack of an anti-cancer effect of ZA in premenopausal women without ovarian suppression. These observations have prompted the conjecture that anti-cancer effects of ZA are limited to estrogen-poor environments. This review explores possible mechanisms compatible with differences in ZA activity in premenopausal women compared with postmenopausal (or hormone-suppressed) women.

Transcriptome analysis and in vivo activity of fluvastatin versus zoledronic acid in a murine breast cancer metastasis model

Statins and bisphosphonates are two distinct classes of isoprenoid pathway inhibitors targeting downstream enzyme to HMG-CoA reductase (upstream enzyme) and farnesyl-pyrophosphate synthase, respectively. Here, we studied fluvastatin (Fluva) and zoledronate (Zol), representative molecules of each class, respectively. In vivo metastatic potentials of both molecules were assessed. For the first time, we observed a significant reduction in progression of established metastases with Fluva treatment. Treatment with both Zol at 100 μg/kg and Fluva at 15 mg/kg inhibited 80% of the metastasis bioluminescence signal and increased survival of mice. The Zol and Fluva transcriptomic profiles of treated MDA-MB-231 cells revealed analogous patterns of affected genes, but each of them reached with different kinetics. The observable changes in gene expression started after 24 h for Fluva IC(50 72 h) and only after 48 h for Zol IC(50 72 h). To obtain early changes in gene expression of Zol-treated cells, a 3 times higher dose of Zol IC(50 72 h) had to be applied. Combining Fluva and Zol in vivo showed no synergy, but a benefit of several days in survival of mice. This study demonstrated that Zol or Fluva is of potential clinical use for the treatment of established metastasis.

Adjuvant bisphosphonate treatment for breast cancer: Where are we heading and can the pre-clinical literature help us get there?

Bisphosphonates have demonstrated anti-tumour activity in preclinical studies of bone metastatic disease, thus it was natural to transition these agents into the adjuvant cancer therapy setting. Surprisingly, the results of adjuvant breast cancer trials have shown either modest to no benefit or even harm. We sought to explore whether the preclinical results supporting bisphosphonate use provided clues to help explain the current clinical data. Interestingly, the majority of preclinical data suggested that bisphosphonate treatment was more efficacious when administered after the establishment of osseous metastases. This is similar to the findings of one clinical study whereby patients with biopsy evidence of osseous micrometastases derive greater survival benefit from bisphosphonate treatment. Another clinical study found bisphosphonates were associated with increased incidence of visceral metastases, similar to what has been previously published in preclinical models using “preventative” dosing strategies. While the current clinical data suggest bisphosphonates may be more efficacious in post-menopausal or oestrogen depleted patients, or those with hormone receptor positive tumours, to date no appropriately designed preclinical studies have evaluated these effects. Furthermore, putative mechanisms that regulate response to bisphosphonates in other tumour types remain to be evaluated in breast cancer. Despite the initial optimism regarding adjuvant bisphosphonate therapy, the conflicting clinical results from large trials suggest that we should return to the bench to further investigate factors that may influence response to bisphosphonate treatment or identify appropriate characteristics that would indicate the sub-groups of patients most likely to benefit from bisphosphonate treatment.

Location matters: osteoblast and osteoclast distribution is modified by the presence and proximity to breast cancer cells in vivo

Bone metastasis is a common incurable complication of breast cancer affecting around 70% of patients with advanced disease. In order to improve outcomes for these patients, the cellular and molecular mechanisms underlying bone metastasis need to be established. The majority of studies to date have focused on end-stage disease and little is known about the events taking place following initial tumour cell colonisation of bone. Here we report the results of a longitudinal study that provides detailed analysis of the spatial and temporal relationship between bone and cancer cells during progression of bone metastasis. Tumour growth in bone was initiated by intra-cardiac inoculation of MDA-MB-231-GFP breast cancer cells in immunocompromised mice. Differentiating between areas of bone in direct contact with the tumour and areas distal to the cancer cells but within the tumour bearing bone, we performed comprehensive analyses of the number and distribution of osteoclasts and osteoblasts. Tumour colonies were detectable in bone from day 10, while reduced trabecular bone volume was apparent from day 19 onwards. Cancer-induced changes in osteoblast and osteoclast numbers differed substantially depending on whether or not the cells were in direct contact with the tumour. Compared to naïve controls, areas of bone in direct contact with the tumour had significantly reduced osteoblast but increased osteoclast numbers, whereas the reverse was found in distal areas. Our data demonstrate that tumour cells induce substantial changes in the bone microenvironment prior to the appearance of bone lesions, suggesting that early therapeutic intervention may be required to oppose the tumour-induced changes to the microenvironment und thus tumour progression.

Zoledronic acid blocks the interaction between mesenchymal stem cells and breast cancer cells: implications for adjuvant therapy of breast cancer

BACKGROUND

Zoledronic acid (ZA) reduces locoregional and distant metastases in estrogen receptor (ER)-positive breast cancer patients. Since ZA rapidly concentrates in the bone following i.v. administration, we hypothesized that this phenomenon involves the mechanism of action of ZA in bone tissue.

MATERIALS AND METHODS

Migration assays were carried out in fibronectin-coated Boyden chambers. Activation of signaling proteins was analyzed with a phosphoprotein array. Chemokines and growth factors were measured by immunoassays and real-time PCR.

RESULTS

ZA significantly reduced in bone marrow-derived mesenchymal stem cells (MSCs) the activation of AKT and mitogen-activated protein kinase and their ability to migrate. Conditioned medium (CM) from ZA-treated MSCs showed a reduced capacity to promote the migration of ER-positive MCF-7 breast cancer cells as compared with CM from untreated MSCs. The levels of the chemokine (C-C motif) ligand 5 (CCL5, also known as RANTES - Regulated upon Activation, Normal T-cell Expressed, and Secreted) and interleukin (IL)-6 were significantly reduced in MSC-CM following treatment with ZA. Anti-RANTES and anti-IL-6 antibodies almost completely abolished the migration of MCF-7 cells induced by MSC-CM. Recombinant RANTES and IL-6 significantly induced MCF-7 cell migration and their combination showed a cooperative effect. Similar results were observed in different breast cancer cell lines.

CONCLUSION

ZA might exert its antitumor activity by inhibiting MSC migration and blocking MSCs' secretion of factors involved in breast cancer progression.

Bisphosphonates and other bone agents for breast cancer

BACKGROUND

Bone is the most common site of metastatic disease associated with breast cancer (BC). Bisphosphonates inhibit osteoclast-mediated bone resorption, and novel targeted therapies such as denosumab, inhibit key pathways in the vicious cycle of bone metastases.

OBJECTIVES

To assess the effect of bisphosphonates on skeletal-related events (SREs), bone pain, quality of life (QoL), recurrence and survival in women with breast cancer with bone metastases (BCBM), advanced breast cancer (ABC) without clinical evidence of bone metastases and early breast cancer (EBC).To assess the effect of denosumab on SREs, bone pain and (QoL) in women with (BCBM).

SEARCH METHODS

We searched the Specialised Register maintained by the Cochrane Breast Cancer Group (CBCGSR), MEDLINE, EMBASE and the WHO International Cancer Trials Registry Platform (WHO ICTRP) on 30 April 2011. We conducted additional handsearching of journals and proceedings of key meetings.

SELECTION CRITERIA

We included randomised controlled trials (RCTs) comparing: (a) bisphosphonates and control, or different bisphosphonates in women with BCBM; (b) denosumab and bisphosphonates in women with BCBM; (c) bisphosphonates and control in women with ABC; (d) bisphosphonates and control in women with EBC; and (e) early versus delayed bisphosphonate treatment in women with EBC.

DATA COLLECTION AND ANALYSIS

Two review authors (MW and NP) independently assessed the trials and extracted the data. We collected toxicity information from the trials.

MAIN RESULTS

We included thirty-four RCTs. In nine studies (2806 patients with BCBM), comparing bisphosphonates with placebo or no bisphosphonates, bisphosphonates reduced the SRE risk by 15% (risk ratio (RR) 0.85; 95% confidence interval (CI) 0.77 to 0.94; P = 0.001). This benefit was most certain with intravenous (i.v.) zoledronic acid (4 mg) (RR 0.59; 95% CI 0.42 to 0.82); i.v. pamidronate (90 mg) (RR 0.77; 95% CI 0.69 to 0.87); and i.v. ibandronate (RR 0.80; 95% CI 0.67 to 0.96). A direct comparison of i.v. zoledronic acid and i.v. pamidronate confirmed at least equivalent efficacy in a single large study. In three studies (3405 patients with BCBM), compared with bisphosphonates, subcutaneous (s.c.) denosumab was more effective in reducing the risk of SREs (RR 0.78; 95% CI 0.72 to 0.85; P < 0.00001).Bisphosphonates reduced the SRE rate in 12 studies (median reduction 28%, range 14% to 48%), with statistically significant reductions reported in 10 studies. Women with BCBM treated with bisphosphonates showed significant delays in the median time to SREs. Compared with placebo or no bisphosphonates, treatment with bisphosphonates significantly improved bone pain in six out of eleven studies. Improvements in global QoL with bisphosphonates compared to placebo were reported in two out of five studies (both ibandronate studies). Treatment with bisphosphonates did not appear to affect survival in women with BCBM. Compared to i.v. zoledronic acid, denosumab also significantly reduced the SRE rate, delayed the time to SREs and prolonged the time in developing pain for patients with no or mild pain at baseline; but there was no difference in survival between patients treated with denosumab and zoledronic acid.Bisphosphonates in women with ABC without clinically evident bone metastases did not reduce the incidence of bone metastases, or improve survival in three studies (320 patients).In seven studies (7847 patients with EBC), currently there is no evidence supporting bisphosphonates in reducing the incidence of bone metastases compared to no bisphosphonates (RR 0.94; 95% CI 0.82 to 1.07; P = 0.36). In three studies (2190 patients with EBC), early bisphosphonate treatment also did not significantly reduce the incidence of bone metastases compared to delayed bisphosphonate treatment (RR 0.73; 95% CI 0.40 to 1.33; P = 0.31). Currently, there is insufficient evidence to make a conclusion about the role of adjuvant bisphosphonates in reducing visceral metastases, locoregional recurrence and total recurrence, or improving survival. There was strong heterogeneity in EBC studies examining the outcomes of total recurrence and survival.Reported toxicity was generally mild. Renal toxicity and osteonecrosis of the jaw (ONJ) have been identified as potential problems with bisphosphonate use. ONJ was reported at similar rates for patients on denosumab compared to zoledronic acid. This highlighted a need for maintaining good oral care, prior to and during treatment, for patients who received long-term bone agents.

AUTHORS' CONCLUSIONS

In women with clinically evident BCBM, bisphosphonates (oral and i.v.) and denosumab (s.c.) reduced the risk of developing SREs, as well as delaying the time to SREs. Some bisphosphonates may also reduce bone pain and may improve QoL. The optimal timing and duration of treatment for patients with BCBM remains uncertain. There is currently insufficient evidence to support the routine use of bisphosphonates as adjuvant treatment for patients with EBC. However, a number of large clinical trials investigating bisphosphonates in EBC have completed accrual and are awaiting results.

Retrospective evaluation of the clinical benefit of long-term continuous use of zoledronic acid in patients with lung cancer and bone metastases

BACKGROUND

For patients with bone metastases, skeletal-related events including fracture are common, can cause considerable morbidity, and may reduce overall survival (OS). This retrospective analysis assessed the effect of Zometa (zoledronic acid, ZOL), an intravenous bisphosphonate (IV-BP), on fracture risk and OS in patients with bone metastases from lung cancer (LC). (Zometa is a registered trademark of Novartis Pharmaceuticals Corporation, USA.)

METHODS

A claims-based analysis using commercial and Medicare Advantage data from >45 US managed-care plans was used to evaluate the association between fracture risk and treatment persistency (31-90, 91-180, 181-365, and ≥366 days) and follow-up duration in LC patients diagnosed with bone metastases between 01/01/2001 and 12/31/2006 and treated with ZOL or without (no IV-BP). Persistency was defined as the absence of a >45-day gap between ZOL treatments. Analysis of variance tests were used to compare follow-up duration, a proxy for OS, between ZOL persistency groups. The effect of time to treatment with ZOL was also assessed.

RESULTS

In 9874 LC patients with bone metastases (n = 1090 ZOL; n = 8784 no IV-BP) the unadjusted relative fracture risk was reduced by 40% with ZOL vs no IV-BP; fracture risk decreased consistently with increasing duration of ZOL treatment. Even short-term (31-90 days) ZOL significantly reduced fracture risk (47%) vs no IV-BP (p = 0.005) with adjustment for differences in demographic and clinical characteristics. Delaying ZOL until after bone metastases were diagnosed significantly increased fracture risk (p = 0.0017). For a sub-set of patients included in a survival analysis (n = 550 ZOL; n = 4512 no IV-BP), mortality was significantly lower (mean, 38.6 vs 46.8 deaths/100 person-years; p = 0.038) in those treated with ZOL vs no IV-BP.

LIMITATIONS

Interpretation of this claims-based analysis must be tempered by the inherent limitations of observational data, such as limited clinical information and the ability to control for prognostic factors.

CONCLUSIONS

This retrospective analysis demonstrates that LC patients with bone metastases receiving ZOL had significantly reduced risk of fracture (p = 0.005) and death (p < 0.038) vs patients receiving no IV-BP. Longer ZOL persistency consistently yielded better outcomes, with ≥12 months' treatment producing the greatest benefit.

Combinations of bisphosphonates and classical anticancer drugs: a preclinical perspective

Bone metastases are frequent complications in advanced breast and prostate cancer among others, resulting in increased risk of fractures, pain, hypercalcaemia of malignancy and a reduction in patient independence and mobility. Bisphosphonates (BPs) are in wide clinical use for the treatment of cancer-induced bone disease associated with advanced cancer, due to their potent ability to reduce skeletal-related events (SREs) and improve quality of life. Despite the profound effect on bone health, the majority of clinical studies have failed to demonstrate an overall survival benefit of BP therapy. There is increasing preclinical evidence to suggest that inclusion of the most potent nitrogen-containing BPs (NBPs) in combination therapy results in increased antitumour effects and improved survival, but that the particular schedules used are of key importance to achieve optimal benefit. Recent clinical data have suggested that there may be effects of adjuvant NBP therapy on breast tumours outside the skeleton. These findings have led to renewed interest in the use of BPs in cancer therapy, in particular how they can be included as part of adjuvant protocols. Here we review the key data reported from preclinical model systems investigating the effects of combination therapy including BPs with particular emphasis on breast and prostate cancer.

Significance of combination therapy of zoledronic acid and gemcitabine on pancreatic cancer

In the present study, we examined the cytotoxic effects of combination therapy with zoledronic acid (ZOL) and gemcitabine (GEM) on pancreatic cancer cells in vitro and in vivo. Four human pancreatic cancer cell lines were treated with ZOL, GEM or a combination of both, and the effects of the respective drug regimens on cell proliferation, invasion and matrix metalloproteinase (MMP) expression were examined. A pancreatic cancer cell line was also intrasplenically or orthotopically implanted into athymic mice and the effects of these drugs on tumor metastasis and growth in vivo were evaluated by histological and immunohistochemical analyses. Combination treatment with low doses of ZOL and GEM efficiently inhibited the proliferation (P < 0.001) and invasion (P < 0.001) of pancreatic cancer cells in vitro. Western blotting assay revealed that MMP-2 and MMP-9 expression levels were decreased after ZOL treatment. In vivo, combined treatment significantly inhibited tumor growth (P < 0.05) and the development of liver metastasis (P < 0.05). These data revealed that ZOL and GEM, when used in combination, have significant antitumor, anti-metastatic and anti-angiogenic effects on pancreatic cancer cells. The present study is the first to report the significance of the combination treatment of ZOL and GEM in pancreatic cancer using an in vivo model. These data are promising for the future application of this drug regimen in patients with pancreatic cancer.

Retrospective analysis of antitumor effects of zoledronic acid in breast cancer patients with bone-only metastases

BACKGROUND

Bisphosphonates have been used successfully in the treatment of hypercalcemia and to reduce skeletal complications of bone metastasis, but have not been shown to prevent bone metastasis or to prolong survival time in metastatic breast cancer patients. The aim of this study was to determine whether the progression-free survival (PFS) and overall survival (OS) of patients with bone-only breast cancer metastasis differed based on whether patients received zoledronic acid, pamidronate, or no bisphosphonate upon diagnosis of their metastases.

PATIENTS AND METHODS

We retrospectively identified 314 patients diagnosed with bone-only metastasis at the time of initial staging or who developed bone metastasis as the first recurrence site during follow-up from January 1, 1997 to December 31, 2008, at The MD Anderson Cancer Center. Univariate and multivariate Cox hazards models were used to assess the effects of each treatment on PFS and OS.

RESULTS

Patients who had more than 1 bone metastasis and Eastern Cooperative Oncology Group (ECOG) performance status of 2 and 3 were more likely to receive zoledronic acid in this analysis. Compared with no bisphosphonate use, the use of zoledronic acid was not significantly associated with longer PFS (hazard ratio [HR] = 0.72, P = .058 in univariate analysis, and HR = 0.80, P = .235 in multivariate analysis) nor with longer OS (HR = 1.04, P = .863 in univariate analysis and HR = 1.34, P = .192 in multivariate analysis).

CONCLUSION

Our study demonstrates that for patients with bone-only metastases, zoledronic acid did not prolong PFS or OS. In patients with bone-only metastasis, we could not demonstrate antitumor effects of zoledronic acid.

Preventive effects of zoledronic acid on bone metastasis in mice injected with human breast cancer cells

Bisphosphonates are used routinely to reduce bone-related events in breast cancer patients with bone metastasis. We evaluated the effects of zoledronic acid, a third generation, nitrogen-containing bisphosphonate, to prevent bone metastasis in breast cancer. Zoledronic acid or vehicle alone was administered to nude mice either simultaneously or after intracardiac injection of human breast cancer MDA-MB-231 cells. Nude mice treated with zoledronic acid at early time points showed a lower incidence of bone metastases than did vehicle-treated nude mice, but these differences were not statistically significant. Only 37.5% of mice treated with zoledronic acid at the time of tumor cell inoculation developed bone metastases compared to over 51.8% of mice receiving vehicle alone (P = 0.304). Cell count of apoptosis confirmed by immunohistochemical staining in metastatic bone tissue significantly increased in the zoledronic acid-treated groups compared to non-treated group (1,018.3 vs 282.0; P = 0.046). However, metastatic tumor cells, which invade soft tissue around the bone, did not show extensive apoptosis; there were no differences between the zoledronic acid-treated and control groups. These results suggest that zoledronic acid increases apoptosis of metastatic breast tumor cells in the bone and could therefore reduce metastatic tumor burden. These results support the use of zoledronic acid to reduce the incidence of bone metastasis in breast cancer.

Geranylgeranyl diphosphate synthase: an emerging therapeutic target

Proteins modified post-translationally by geranylgeranylation have been implicated in numerous cellular processes related to human disease. In recent years, the study of protein geranylgeranylation has advanced tremendously in both cellular and animal models. The advances in our understanding of the biological roles of geranylgeranylated proteins have been paralleled by advances in the medicinal chemistry of geranylgeranylation inhibitors such as those that target geranylgeranyl transferases I and II and geranylgeranyl diphosphate synthase (GGDPS). Although these findings provide the rationale for further development of geranylgeranylation as a therapeutic target, more advanced studies on the efficacy of this approach in various disease models will be required to support translation to clinical studies. This article attempts to describe the advances in (and the challenges of) validation of GGDPS as a novel therapeutic target and assesses the advantages of targeting GGDPS relative to other enzymes involved in geranylgeranylation.

Tumour macrophages as potential targets of bisphosphonates

Tumour cells communicate with the cells of their microenvironment via a series of molecular and cellular interactions to aid their progression to a malignant state and ultimately their metastatic spread. Of the cells in the microenvironment with a key role in cancer development, tumour associated macrophages (TAMs) are among the most notable. Tumour cells release a range of chemokines, cytokines and growth factors to attract macrophages, and these in turn release numerous factors (e.g. VEGF, MMP-9 and EGF) that are implicated in invasion-promoting processes such as tumour cell growth, flicking of the angiogenic switch and immunosuppression. TAM density has been shown to correlate with poor prognosis in breast cancer, suggesting that these cells may represent a potential therapeutic target. However, there are currently no agents that specifically target TAM's available for clinical use.

Bisphosphonates (BPs), such as zoledronic acid, are anti-resorptive agents approved for treatment of skeletal complication associated with metastatic breast cancer and prostate cancer. These agents act on osteoclasts, key cells in the bone microenvironment, to inhibit bone resorption. Over the past 30 years this has led to a great reduction in skeletal-related events (SRE's) in patients with advanced cancer and improved the morbidity associated with cancer-induced bone disease. However, there is now a growing body of evidence, both from in vitro and in vivo models, showing that zoledronic acid can also target tumour cells to increase apoptotic cell death and decrease proliferation, migration and invasion, and that this effect is significantly enhanced in combination with chemotherapy agents. Whether macrophages in the peripheral tumour microenvironment are exposed to sufficient levels of bisphosphonate to be affected is currently unknown. Macrophages belong to the same cell lineage as osteoclasts, the major target of BPs, and are highly phagocytic cells shown to be sensitive to bisphosphonates in model studies; In vitro, zoledronic acid causes increased apoptotic cell death; in vivo the drug has been shown to inhibit the production of pro-angiogenic factor MMP-9, as well as most recent evidence showing it can trigger the reversal of the TAMs phenotype from pro-tumoral M2 to tumoricidal M1. There is thus accumulating evidence supporting the hypothesis that effects on TAMs may contribute to the anti-tumour effect of bisphosphonates. This review will focus in detail on the role of tumour associated macrophages in breast cancer progression, the actions of bisphosphonates on macrophages in vitro and in tumour models in vivo and summarise the evidence supporting the potential for the targeting of tumour macrophages with bisphosphonates.

Direct and indirect anticancer activity of bisphosphonates: a brief review of published literature

The bone marrow microenvironment provides a site for cancer cells to evade systemic anticancer therapy. Dormant tumor micrometastases are believed to be the source of disease persistence and relapse; however, the exact characteristics of cancer stem cells vs. cancer cells with limited metastatic potential have yet to be elucidated. Bisphosphonates inhibit osteoclast-mediated bone resorption, are approved for treating malignant bone disease from advanced cancers, and have shown efficacy for preventing cancer treatment-induced bone loss. Altering the bone marrow microenvironment to make it less conducive to cancer cell survival is now emerging as an important means to prevent cancer recurrence. This review aims to distill the diverse literature and provide a brief overview of the numerous preclinical and early clinical studies of bisphosphonates demonstrating a variety of direct and indirect anticancer activities that affect both the tumor cell (the "seed") and surrounding microenvironment (the "soil"). Recently, zoledronic acid was found to improve disease-free survival and overall survival in some adjuvant breast cancer settings and prolonged survival in patients with multiple myeloma and other advanced cancers. In the prostate cancer setting, antiresorptive therapy was reported to delay the development of overt bone metastases. Ongoing studies will provide further insight regarding the anticancer potential of bisphosphonates and other antiresorptive agents.

Bisphosphonates in oncology

Bone metastases result in considerable morbidity, often affecting quality of life and independence over years, and may place complex demands on health care resources. The bisphosphonates have been shown to reduce skeletal morbidity in multiple myeloma and solid tumours affecting bone by 30-50%. Quite appropriately, these agents are increasingly used alongside anticancer treatments to prevent skeletal complications and relieve bone pain. The use of bisphosphonates in early cancer has become increasingly important to prevent adverse effects of cancer treatments on bone health. These include chemotherapy induced ovarian failure and the use of aromatase inhibitors in breast cancer and androgen deprivation therapy in prostate cancer. Bisphosphonate strategies, similar to those used to treat post-menopausal osteoporosis, are the intervention of choice for patients with low bone mineral density or rapid bone loss, along with adequate calcium and vitamin D intake and a healthy lifestyle. There is a strong preclinical rationale for bisphosphonates to prevent metastasis, primarily through inhibition of the vicious cycle of metastasis within the microenvironment. Recent data suggest that adjuvant bisphosphonates, at least in some patient subgroups, may modify the course of the disease and disrupt the metastatic process, reducing the risks of disease recurrence. In comparison to most other cancer treatments, adverse events related to bisphosphonate therapy are generally mild and infrequent; thus, the benefits of treatment within licensed indications will almost always outweigh the risks.

Physiology of the aging bone and mechanisms of action of bisphosphonates

Fragility fractures, a major public health concern, are expected to further increase due to aging of the world populations because age remains a cardinal, independent determinant of fracture risk. With aging the balance between bone formation and resorption during the remodeling process becomes negative, with increased resorption and reduced formation. Bisphosphonates (BPs) are widely prescribed anti-resorptive agents that inhibit osteoclasts attachment to bone matrix and enhance osteoclast apoptosis. BPs can be divided into nitrogen-containing (N-BPs) and non-nitrogen-containing BPs (non-N-BPs). Both classes induce apoptosis but they evoke it differently. Several studies have examined the molecular mechanisms underlying BPs' effects on osteoclasts and bone remodeling. N-BPs (alendronate, risedronate, zoledronate) inhibit the intracellular mevalonate pathway and protein isoprenylation, via the enzyme farnesyl pyrophosphate synthase. N-BPs act by competition, binding to the natural substrate-binding site of the enzyme. The less potent non-N-BPs (etidronate, clodronate), do not inhibit the mevalonate pathway and protein isoprenylation, but are metabolized intracellularly to metabolites, which are cytotoxic analogs of ATP. N-BPs represent the first choice treatment for diseases associated with excessive bone resorption, such as fragility fractures (due to postmenopausal-, male, glucocorticoid- and transplant-induced osteoporosis), Paget's disease of bone, and bone metastasis. Better understanding of BPs' effects on osteoblasts/osteocytes (e.g., preventing apoptosis) and differential distribution may further help explain anti-fracture benefit and bone quality effects. Lower affinity BPs (e.g., risedronate) may allow better access to osteocyte network. Effects of BPs on bone senescence, cancer cells apoptosis and prevention of cardiovascular calcifications may open new avenues for biogerontological research.

Contemporary therapeutic approaches targeting bone complications in prostate cancer

Skeletal complications are major causes of morbidity in patients with prostate cancer. Despite the osteoblastic appearance of prostate cancer bone metastases, elevated serum and urinary markers of bone resorption are indicative of high osteoclast activity. Increased osteoclast activity is independently associated with subsequent skeletal complications, disease progression, and death. Osteoclast-targeted therapies aim to reduce the risk for disease-related skeletal complications, bone metastases, and treatment-related fractures. This review focuses on recent advances in osteoclast-targeted therapies in the treatment and prevention of bone complications in prostate cancer. Osteoclast-targeted therapies have been extensively studied in men with prostate cancer. The potent bisphosphonate zoledronic acid significantly decreased the risk of skeletal complications in men with castration-resistant prostate cancer and bone metastases, and is Federal Drug Administration approved for this indication. Denosumab is a human monoclonal antibody that inhibits receptor activator of nuclear factor-κB (RANK) ligand, a critical mediator of osteoclast differentiation, activation, and survival. Data from recent phase III clinic trials demonstrate the emerging role for denosumab in the treatment of prostate cancer bone metastases and prevention of fractures associated with androgen deprivation therapy.

Drugs which inhibit osteoclast function suppress tumor growth through calcium reduction in bone

Prostate carcinoma frequently metastasizes to bone where the microenvironment facilitates its growth. Inhibition of bone resorption is effective in reducing tumor burden and bone destruction in prostate cancer. However, whether drugs that inhibit osteoclast function inhibit tumor growth independent of inhibition of bone resorption is unclear. Calcium is released during bone resorption and the calcium sensing receptor is an important regulator of cancer cell proliferation. The goal of this investigation was to elucidate the role of calcium released during bone resorption and to determine the impact of drugs which suppress bone resorption on tumor growth in bone. To compare tumor growth in a skeletal versus non-skeletal site, equal numbers of canine prostate cancer cells expressing luciferase (ACE-1(luc)) were inoculated into a simple collagen matrix, neonatal mouse vertebrae (vossicles), human de-proteinized bone, or a mineralized collagen matrix. Implants were placed subcutaneously into athymic mice. Luciferase activity was used to track tumor growth weekly, and at one month tumors were dissected for histologic analysis. Luciferase activity and tumor size were greater in vossicles, de-proteinized bone and mineralized collagen matrix versus non-mineralized collagen implants. The human osteoblastic prostate carcinoma cell line C4-2b also grew better in a mineral rich environment with a greater proliferation of C4-2b cells reflected by Ki-67 staining. Zoledronic acid (ZA), a bisphosphonate, and recombinant OPG-Fc, a RANKL inhibitor, were administered to mice bearing vertebral implants (vossicles) containing ACE-1 osteoblastic prostate cancer cells. Vossicles or collagen matrices were seeded with ACE-1(luc) cells subcutaneously in athymic mice (2 vossicles, 2 collagen implants/mouse). Mice received ZA (5 μg/mouse, twice/week), (OPG-Fc at 10mg/kg, 3 times/week) or vehicle, and luciferase activity was measured weekly. Histologic analysis of the tumors, vossicles and endogenous bones and serum biochemistry were performed. Antiresorptive administration was associated with decreased serum TRAP5b, reduced osteoclast numbers, and increased tibia and vossicle bone areas. ZA significantly decreased bone marrow calcium concentrations without affecting serum calcium. ZA and OPG-Fc significantly inhibited tumor growth in bone but not in collagen implants. In conclusion, the inhibitory effects of ZA or OPG-Fc on prostate tumor growth in bone are mediated via blocking bone resorption and calcium release from bone.

Anti-tumour and anti-angiogenetic effects of zoledronic acid on human non-small-cell lung cancer cell line

OBJECTIVES

Although emerging data suggest that zoledronic acid (Zol) may have different anti-tumour activities against a broad range of cancers, its effects on lung cancer remain largely unknown. The aim of this study was to evaluate in vitro the anti-tumoural and anti-angiogenetic effect of zoledronic acid in non-small-cell lung cancer (NSCLC) cells.

MATERIAL AND METHODS

We treated A549 NSCLC cells with zoledronic acid to investigate survival, cell cycle activity, anti-angiogenic activity and apoptotic responses to it.

RESULTS

We observed that highest Zol concentration (100μm) caused arrest in G1 phase of the cell cycle and also induced different percentages of apoptosis in presence (0.9% versus 4.4%) or absence (2.4% versus 28.5%) of serum (P=0.0001). Zol concentration from 5 to 100μm for 2 days induced significant concentration-dependent cell death in adherent cells. Furthermore, Zol (10-100μm) induced dose-dependent reduction both of mRNA and protein expression of VEGF associated with parallel decrease in VEGF secretion in the culture medium.

CONCLUSION

Taken together, these results support a possible anti-cancer and anti-angiogenetic activity of Zol. Our data may not only provide a basis for the clinical use of this drug as preventive agent of bone metastases but also suggest that Zol deserves attention as an anti-cancer agent in non-small-cell lung cancer.

Zoledronic acid preserves bone structure and increases survival but does not limit tumour incidence in a prostate cancer bone metastasis model

BACKGROUND

The bisphosphonate, zoledronic acid (ZOL), can inhibit osteoclasts leading to decreased osteoclastogenesis and osteoclast activity in bone. Here, we used a mixed osteolytic/osteoblastic murine model of bone-metastatic prostate cancer, RM1(BM), to determine how inhibiting osteolysis with ZOL affects the ability of these cells to establish metastases in bone, the integrity of the tumour-bearing bones and the survival of the tumour-bearing mice.

METHODS

The model involves intracardiac injection for arterial dissemination of the RM1(BM) cells in C57BL/6 mice. ZOL treatment was given via subcutaneous injections on days 0, 4, 8 and 12, at 20 and 100 µg/kg doses. Bone integrity was assessed by micro-computed tomography and histology with comparison to untreated mice. The osteoclast and osteoblast activity was determined by measuring serum tartrate-resistant acid phosphatase 5b (TRAP 5b) and osteocalcin, respectively. Mice were euthanased according to predetermined criteria and survival was assessed using Kaplan Meier plots.

FINDINGS

Micro-CT and histological analysis showed that treatment of mice with ZOL from the day of intracardiac injection of RM1(BM) cells inhibited tumour-induced bone lysis, maintained bone volume and reduced the calcification of tumour-induced endochondral osteoid material. ZOL treatment also led to a decreased serum osteocalcin and TRAP 5b levels. Additionally, treated mice showed increased survival compared to vehicle treated controls. However, ZOL treatment did not inhibit the cells ability to metastasise to bone as the number of bone-metastases was similar in both treated and untreated mice.

CONCLUSIONS

ZOL treatment provided significant benefits for maintaining the integrity of tumour-bearing bones and increased the survival of tumour bearing mice, though it did not prevent establishment of bone-metastases in this model. From the mechanistic view, these observations confirm that tumour-induced bone lysis is not a requirement for establishment of these bone tumours.

Optimal management of bone metastases in breast cancer patients

Bone metastasis in breast cancer is a significant clinical problem. It not only indicates incurable disease with a guarded prognosis, but is also associated with skeletal-related morbidities including bone pain, pathological fractures, spinal cord compression, and hypercalcemia. In recent years, the mechanism of bone metastasis has been further elucidated. Bone metastasis involves a vicious cycle of close interaction between the tumor and the bone microenvironment. In patients with bone metastases, the goal of management is to prevent further skeletal-related events, manage complications, reduce bone pain, and improve quality of life. Bisphosphonates are a proven therapy for the above indications. Recently, a drug of a different class, the RANK ligand antibody, denosumab, has been shown to reduce skeletal-related events more than the bisphosphonate, zoledronic acid. Other strategies of clinical value may include surgery, radiotherapy, radiopharmaceuticals, and, of course, effective systemic therapy. In early breast cancer, bisphosphonates may have an antitumor effect and prevent both bone and non-bone metastases. Whilst two important Phase III trials with conflicting results have led to controversy in this topic, final results from these and other key Phase III trials must still be awaited before a firm conclusion can be drawn about the use of bisphosphonates in this setting. Advances in bone markers, predictive biomarkers, multi-imaging modalities, and the introduction of novel agents have ushered in a new era of proactive management for bone metastases in breast cancer.

Bisphosphonate anticancer activity

Bone metastases have a major impact on morbidity and on mortality in cancer patients. Despite its clinical relevance, metastasis remains the most poorly elucidated aspect of carcinogenesis. Different pathways or molecules such as RANK/RANKL/OPG, cathepsin K, endothelin-1, Wnt/DKK1 and Src have recently emerged as potential targets, and preclinical and clinical trials are now underway. The results from clinical trials indicate the importance of treating and preventing bone metastases in many different cancer populations.

Zoledronic acid use in cancer patients: more than just supportive care?

Bone is the most common site for metastasis from solid tumors, and the majority of patients will develop bone metastases during the natural course of their disease. Bisphosphonates are an effective treatment for preventing skeletal-related events in patients with bone metastases and may preserve functional independence and quality of life. Although several bisphosphonates have been investigated in patients with solid tumors, only zoledronic acid (ZOL) is approved by the US Food and Drug Administration and the European Medicines Agency for preventing skeletal-related events in patients across a broad range of solid tumors. In addition, bisphosphonates, notably ZOL, prevent cancer treatment-induced bone loss in breast and prostate cancer patients who are receiving endocrine therapy. It also has been demonstrated that ZOL directly and indirectly inhibits cancer cell growth in vitro and growth and tumorigenesis in animal model systems. These properties may produce clinically meaningful benefits. In recent clinical studies in patients with cancer, ZOL improved overall and prolonged disease-free survival. Ongoing clinical trials in patients with solid tumors will provide further insight into the potential of ZOL to prevent distant metastases and improve survival.

Breast cancer at bone metastatic sites: recent discoveries and treatment targets

Breast carcinoma is the most common cancer of women. Bones are often involved with breast carcinoma metastases with the resulting morbidity and reduced quality of life. Breast cancer cells arriving at bone tissues mount supportive microenvironment by recruiting and modulating the activity of several host tissue cell types including the specialized bone cells osteoblasts and osteoclasts. Pathologically activated osteoclasts produce osteolytic lesions associated with bone pain, pathological fractures, cord compression and other complications of metastatic breast carcinoma at bone. Over the last decade there has been enormous growth of knowledge in the field of osteoclasts biology both in the physiological state and in the tumor microenvironment. This knowledge allowed the development and implementation of several targeted therapeutics that expanded the armamentarium of the oncologists dealing with the metastases-associated osteolytic disease. While the interactions of cancer cells with resident bone cells at the established metastatic gross lesions are well-studied, the preclinical events that underlie the progression of disseminated tumor cells into micrometastases and then into clinically-overt macrometastases are just starting to be uncovered. In this review, we discuss the established information and the most recent discoveries in the pathogenesis of osteolytic metastases of breast cancer, as well as the corresponding investigational drugs that have been introduced into clinical development.

Treatment and prevention of bone complications from prostate cancer

Bone metastases and skeletal complications are major causes of morbidity in prostate cancer patients. Despite the osteoblastic appearance of bone metastases on imaging studies, patients have elevated serum and urinary markers of bone resorption, indicative of high osteoclast activity. Increased osteoclast activity is independently associated with higher risk of subsequent skeletal complications, disease progression, and death. Osteoclast-targeted therapies are therefore a rational approach to reduction of risk for disease-related skeletal complications, bone metastases, and treatment-related fractures. This review focuses on recent advances in osteoclast-targeted therapy in prostate cancer. Bisphosphonates have been extensively studied in men with prostate cancer. Zoledronic acid significantly decreased the risk of skeletal complications in men with castration-resistant prostate cancer and bone metastases, and it is FDA-approved for this indication. Denosumab is a human monoclonal antibody that binds and inactivates RANKL, a critical mediator of osteoclast differentiation, activation, and survival. Recent global phase 3 clinic trials demonstrated an emerging role for denosumab in the treatment of prostate cancer bone metastases and prevention of fractures associated with androgen deprivation therapy.

Anti-tumour activity of bisphosphonates in preclinical models of breast cancer

There is increasing evidence of anti-tumour effects of bisphosphonates from pre-clinical studies, supporting a role for these drugs beyond their traditional use in treatment of cancer-induced bone disease. A range of model systems have been used to investigate the effects of different bisphosphonates on tumour growth, both in bone and at peripheral sites. Most of these studies conclude that bisphosphonates cause a reduction in tumour burden, but that early intervention and the use of high and/or repeated dosing is required. Successful eradication of cancer may only be achievable by targeting the tumour cells directly whilst also modifying the tumour microenvironment. In line with this, bisphosphonates are demonstrated to be particularly effective at reducing breast tumour growth when used in combination with agents that directly target cancer cells. Recent studies have shown that the effects of bisphosphonates on breast tumours are not limited to bone, and that prolonged anti-tumour effects may be achieved following their inclusion in combination therapy. This has opened the field to a new strand of bisphosphonate research, focussed on elucidating their effects on cells and components of the local, regional and distal tumour microenvironment. This review highlights the recent developments in relation to proposed anti-tumour effects of bisphosphonates reported from in vitro and in vivo models, and summarises the data from key breast cancer studies. Evidence for effects on different processes and cell types involved in cancer development and progression is discussed, and the main outstanding issues identified.

Antitumor effects and anticancer applications of bisphosphonates

Bisphosphonates are firmly entrenched in the treatment of metastatic bone disease secondary to several tumor types, including breast cancer, prostate cancer, and myeloma. More recently, an emerging body of preclinical and clinical evidence indicates that bisphosphonates might also exhibit antitumor activity. This expanded role for bisphosphonates in the adjuvant setting might have profound clinical implications in many cancer types, particularly in the context of prevention of bone metastasis. Increased understanding of the mechanistic basis of the antitumor effects indicates that these might occur via direct mechanisms such as induction of apoptosis and inhibition of tumor cell adhesion and invasion, as well as indirect mechanisms such as inhibition of angiogenesis. There is also considerable evidence to suggest that nitrogen-containing bisphosphonates might exert additive or synergistic interactions with standard cytotoxic agents. However, mature clinical data with bisphosphonates are limited and, thus far, provide conflicting evidence regarding the antitumor role of bisphosphonates, but have mostly been conducted with first-generation bisphosphonates such as clodronate that are not as effective as next-generation bisphosphonates. Several large randomized clinical trials are ongoing with the next-generation bisphosphonate zoledronic acid to prospectively confirm an antitumor role for bisphosphonates in various tumor types. This review assesses the current body of preclinical and clinical evidence in favor of an antitumor effect of bisphosphonates in different cancer types.

How do bisphosphonates inhibit bone metastasis in vivo?

Bisphosphonates are potent inhibitors of osteoclast-mediated bone resorption and have demonstrated clinical utility in the treatment of patients with osteolytic bone metastases. They also exhibit direct antitumor activity in vitro and can reduce skeletal tumor burden and inhibit the formation of bone metastases in vivo. However, whether such effects are caused by a direct action of bisphosphonates on tumor cells or indirectly through inhibition of bone resorption remains unclear. To address this question, we used here a structural analog of the bisphosphonate risedronate, NE-58051, which has a bone mineral affinity similar to that of risedronate, but a 3000-fold lower bone antiresorptive activity. In vitro, risedronate and NE-58051 inhibited proliferation of breast cancer and melanoma cell lines. In vivo, risedronate and NE-58051 did not inhibit the growth of subcutaneous B02 breast tumor xenografts or the formation of B16F10 melanoma lung metastasis. In contrast to NE-58051, risedronate did inhibit B02 breast cancer bone metastasis formation by reducing both bone destruction and skeletal tumor burden, indicating that the antitumor effect of bisphosphonates is achieved mainly through inhibition of osteoclast-mediated bone resorption.

Microglia promote colonization of brain tissue by breast cancer cells in a Wnt-dependent way

Although there is increasing evidence that blood-derived macrophages support tumor progression, it is still unclear whether specialized resident macrophages, such as brain microglia, also play a prominent role in metastasis formation. Here, we show that microglia enhance invasion and colonization of brain tissue by breast cancer cells, serving both as active transporters and guiding rails. This is antagonized by inactivation of microglia as well as by the Wnt inhibitor Dickkopf-2. Proinvasive microglia demonstrate altered morphology, but neither upregulation of M2-like cytokines nor differential gene expression. Bacterial lipopolysacharide shifts tumor-educated microglia into a classical M1 phenotype, reduces their proinvasive function, and unmasks inflammatory and Wnt signaling as the most strongly regulated pathways. Histological findings in human brain metastases underline the significance of these results. In conclusion, microglia are critical for the successful colonization of the brain by epithelial cancer cells, suggesting inhibition of proinvasive microglia as a promising antimetastatic strategy.

Anticancer properties of zoledronic acid

Zoledronic acid effectively reduces/delays skeletal-related events in patients with metastatic disease or skeletal-related cancers. Emerging data suggest that zoledronic acid may also exhibit anticancer properties. Zoledronic acid ± anticancer therapies in animal models inhibits soft-tissue tumor growth, decreases tumor cell proliferation, increases apoptosis, inhibits angiogenesis, alters tumor-associated macrophage function, and enhances immune surveillance. Data from in vitro and pilot studies suggest that zoledronic acid inhibits tumor cell dissemination in bone marrow, and early clinical data show that it may improve disease-related outcomes. Ongoing studies will further elucidate the role of zoledronic acid in cancer patients.

Detection of Cancer Metastases with a Dual-labeled Near-Infrared/Positron Emission Tomography Imaging Agent

By dual labeling a targeting moiety with both nuclear and optical probes, the ability for noninvasive imaging and intraoperative guidance may be possible. Herein, the ability to detect metastasis in an immunocompetent animal model of human epidermal growth factor receptor 2 (HER-2)-positive cancer metastases using positron emission tomography (PET) and near-infrared (NIR) fluorescence imaging is demonstrated.

METHODS

((64)Cu-DOTA)(n)-trastuzumab-(IRDye800)(m) was synthesized, characterized, and administered to female Balb/c mice subcutaneously inoculated with highly metastatic 4T1.2neu/R breast cancer cells. ((64)Cu-DOTA)(n)-trastuzumab-(IRDye800)(m) (150 µg, 150 µCi, m = 2, n = 2) was administered through the tail vein at weeks 2 and 6 after implantation, and PET/computed tomography and NIR fluorescence imaging were performed 24 hours later. Results were compared with the detection capabilities of F-18 fluorodeoxyglucose ((18)FDG-PET).

RESULTS

Primary tumors were visualized with (18)FDG and ((64)Cu-DOTA)(n)-trastuzumab-(IRDye800)(m), but resulting metastases were identified only with the dual-labeled imaging agent. (64)Cu-PET imaging detected lung metastases, whereas ex vivo NIR fluorescence showed uptake in regions of lung, skin, skeletal muscle, and lymph nodes, which corresponded with the presence of cancer cells as confirmed by histologic hematoxylin and eosin stains. In addition to detecting the agent in lymph nodes, the high signal-to-noise ratio from NIR fluorescence imaging enabled visualization of channels between the primary tumor and the axillary lymph nodes, suggesting a lymphatic route for trafficking cancer cells. Because antibody clearance occurs through the liver, we could not distinguish between nonspecific uptake and liver metastases.

CONCLUSION

((64)Cu-DOTA)(n)-trastuzumab-(IRDye800)(m) may be an effective diagnostic imaging agent for staging HER-2-positive breast cancer patients and intraoperative resection.