Differential inhibition of invasion and proliferation by bisphosphonates: anti-metastatic potential of Zoledronic acid in prostate cancer

Disseminated carcinomatosis of the bone marrow caused by prostate cancer diagnosed with only bone marrow biopsy

INTRODUCTION

Disseminated carcinomatosis of the bone marrow caused by prostate cancer is a rare condition with poor prognosis. Diagnosis has mostly been by primary prostate biopsy.

CASE PRESENTATION

A 60-year-old man had malaise, low platelet count (9000/μL), and high prostate-specific antigen (1382 ng/mL). Bone marrow biopsy showed strongly positive immunostaining NKX3.1, leading to diagnosis of prostate cancer bone marrow metastasis, cT3aN1M1b. Definitive diagnosis by prostate biopsy was difficult because of the sparsity of atypical glands. He had progression to castration-resistant prostate cancer after 3 months of hormonal therapy, and received 27 courses of docetaxel and six courses of cabazitaxel as chemotherapy, but finally died of respiratory failure 33 months after the start of treatment.

CONCLUSION

Aggressive biopsy of the metastatic sites should be considered if a prostate biopsy at the primary site cannot be diagnosed definitively.

A Systematic Review and Meta-Analysis about the Effect of Bisphosphonates on the Risk of Skeletal-Related Event in Men with Prostate Cancer

BACKGROUND

Although the adjuvant therapy of bisphosphonates in prostate cancer is effective in improving bone mineral density, it is still uncertain whether bisphosphonates could decrease the risk of Skeletal- Related Event (SRE) in patients with prostate cancer. We reviewed and analyzed the effect of different types of bisphosphonates on the risk of SRE, defined as pathological fracture, spinal cord compression, radiation therapy to the bone, surgery to bone, hypercalcemia, bone pain, or death as a result of prostate cancer.

METHODS

A systemic literature search was conducted on PubMed and related bibliographies. The emphasis during data extraction was laid on the Hazard Ratio (HR) and the corresponding 95% Confidence Interval (CI) from every eligible Randomized Controlled Trial (RCT). HR was pooled with the fixed effects model, and preplanned subgroup analyses were performed.

RESULTS

5 RCTs (n = 4651) were included and analyzed finally after screening 51 articles. The meta-analysis of all participants showed no significant decrease in the risk of SRE when adding bisphosphonates to control group (HR = 0.968, 95% CI = 0.874 - 1.072, p = 0.536) with low heterogeneity (I2 = 0.0% (d.f. = 4) p = 0.679). There was no significant improvement on SRE neither in the subgroups with Metastases (M1) or Castration-Sensitive Prostate Cancer (CSPC) (respectively HR = 0.968, 95% CI = 0.874 - 1.072, p = 0.536, I2 = 0.0% (d.f. = 4) p = 0.679; HR = 0.954, 95% CI = 0.837 - 1.088, p = 0.484, I2 = 0.0% (d.f. = 3) p = 0.534).

CONCLUSION

Our study demonstrated that bisphosphonates could not statistically significantly reduce the risk of SRE in patients with prostate cancer, neither in the subgroups with M1 or CSPC.

Role of zoledronic acid in nasopharyngeal carcinoma patients with bone-only metastasis at diagnosis

OBJECTIVE

We aimed to investigate whether zoledronic acid (ZA) can prevent skeletal-related events (SREs) and offer survival benefits for nasopharyngeal carcinoma (NPC) patients with bone-only metastasis at diagnosis.

MATERIALS AND METHODS

A total of 228 newly diagnosed NPC cases with bone-only metastasis were eligible for this retrospective study. Using the propensity score method (PSM) method, a well-balanced cohort was created for further analysis. Overall survival (OS) was the primary endpoint. The difference in survival was evaluated using the log-rank test. Hazard ratios (HRs) and 95% confidence intervals (CIs) for all-cause mortality were derived from a Cox regression model. Cumulative incidence competing risk analyses using Fine and Gray's method was used to test the cumulative incidence of SREs between the different treatment groups.

RESULT

In the PSM cohorts, patients in the platinum-based palliative chemotherapy (PCT) + ZA group and PCT alone group achieved similar 3-year OS (57.3% vs. 46.4%; log rank P = 0.188). Multivariate analysis indicated that ZA administration was not an independent prognostic factor (HR, 0.783; 95% CI, 0.267-2.300; P = 0.657). There was no significant difference in acute treatment toxicity between the 2 treatment groups, although the cumulative incidence of bone-related events (SREs) was significantly lower in the PCT + ZA group (Fine-Gray P = 0.026).

CONCLUSION

ZA combined with PCT could not improve OS in NPC patients with bone-only metastasis at diagnosis. However, the incidence of SREs could be effectively prevented via ZA application.

Effect of bisphosphonates on overall survival in subgroups of patients with prostate cancer

Adjuvant therapy with bisphosphonates in prostate cancer is effective in improving bone mineral density and thus reducing fractures and skeletal-related events. We analyzed the effect of bisphosphonates on overall survival (OS) in subgroups of patients with prostate cancer. A systematic literature search was conducted of the PubMed database and the bibliographies of related studies. The long-term OS rates were extracted from every eligible trial. The hazard ratio (HR) was pooled with the fixed effects model, and preplanned subgroup analyses were performed. The search yielded 112 articles, of which 10 articles with 13 patient subgroups met the eligibility criteria. The meta-analysis of all 13 subgroups showed that adjuvant bisphosphonate therapy did not significantly improve OS versus the control group (HR = 0.961, 95% CI 0.899-1.026, p = 0.233) with low heterogeneity (I² = 13.47%, degrees of freedom = 12, p = 0.336). There was no significant improvement in OS with the addition of bisphosphonates in the major subgroup analyses (metastatic (M1) versus non-metastatic, clodronate versus zoledronic acid, castration-sensitive prostate cancer (CSPC) versus castration-refractory prostate cancer). When the subgroups were further divided, adjuvant bisphosphonate therapy significantly improved OS in patients with CSPC + M1 (HR = 0.874, 95% CI 0.778-0.982, p = 0.023; I² = 0.0%, degrees of freedom = 3, p = 0.579). Our study demonstrated that bisphosphonates do not significantly improve long-term OS in patients with prostate cancer. However, adjuvant bisphosphonate therapy significantly improves OS in the subgroup of patients with CSPC + M1.

Adding Celecoxib With or Without Zoledronic Acid for Hormone-Naïve Prostate Cancer: Long-Term Survival Results From an Adaptive, Multiarm, Multistage, Platform, Randomized Controlled Trial

Purpose Systemic Therapy for Advanced or Metastatic Prostate Cancer: Evaluation of Drug Efficacy is a randomized controlled trial using a multiarm, multistage, platform design. It recruits men with high-risk, locally advanced or metastatic prostate cancer who were initiating long-term hormone therapy. We report survival data for two celecoxib (Cel)-containing comparisons, which stopped accrual early at interim analysis on the basis of failure-free survival. Patients and Methods Standard of care (SOC) was hormone therapy continuously (metastatic) or for ≥ 2 years (nonmetastatic); prostate (± pelvic node) radiotherapy was encouraged for men without metastases. Cel 400 mg was administered twice a day for 1 year. Zoledronic acid (ZA) 4 mg was administered for six 3-weekly cycles, then 4-weekly for 2 years. Stratified random assignment allocated patients 2:1:1 to SOC (control), SOC + Cel, or SOC + ZA + Cel. The primary outcome measure was all-cause mortality. Results were analyzed with Cox proportional hazards and flexible parametric models adjusted for stratification factors. Results A total of 1,245 men were randomly assigned (Oct 2005 to April 2011). Groups were balanced: median age, 65 years; 61% metastatic, 14% N+/X M0, 25% N0M0; 94% newly diagnosed; median prostate-specific antigen, 66 ng/mL. Median follow-up was 69 months. Grade 3 to 5 adverse events were seen in 36% SOC-only, 33% SOC + Cel, and 32% SOC + ZA + Cel patients. There were 303 control arm deaths (83% prostate cancer), and median survival was 66 months. Compared with SOC, the adjusted hazard ratio was 0.98 (95% CI, 0.80 to 1.20; P = .847; median survival, 70 months) for SOC + Cel and 0.86 (95% CI, 0.70 to 1.05; P =.130; median survival, 76 months) for SOC + ZA + Cel. Preplanned subgroup analyses in men with metastatic disease showed a hazard ratio of 0.78 (95% CI, 0.62 to 0.98; P = .033) for SOC + ZA + Cel. Conclusion These data show no overall evidence of improved survival with Cel. Preplanned subgroup analyses provide hypotheses for future studies.

Adoptive transfer of ex vivo expanded Vγ9Vδ2 T cells in combination with zoledronic acid inhibits cancer growth and limits osteolysis in a murine model of osteolytic breast cancer

Bone metastases occur in over 75% of patients with advanced breast cancer and are responsible for high levels of morbidity and mortality. In this study, ex vivo expanded cytotoxic Vγ9Vδ2 T cells isolated from human peripheral blood were tested for their anti-cancer efficacy in combination with zoledronic acid (ZOL), using a mouse model of osteolytic breast cancer. In vitro, expanded Vγ9Vδ2 T cells were cytotoxic against a panel of human breast cancer cell lines, and ZOL pre-treatment further sensitised breast cancer cells to killing by Vγ9Vδ2 T cells. Vγ9Vδ2 T cells adoptively transferred into NOD/SCID mice localised to osteolytic breast cancer lesions in the bone, and multiple infusions of Vγ9Vδ2 T cells reduced tumour growth in the bone. ZOL pre-treatment potentiated the anti-cancer efficacy of Vγ9Vδ2 T cells, with mice showing further reductions in tumour burden. Mice treated with the combination also had reduced tumour burden of secondary pulmonary metastases, and decreased bone degradation. Our data suggests that adoptive transfer of Vγ9Vδ2 T cell in combination with ZOL may prove an effective immunotherapeutic approach for the treatment of breast cancer bone metastases.

A microalga, Euglena tuba induces apoptosis and suppresses metastasis in human lung and breast carcinoma cells through ROS-mediated regulation of MAPKs

Background

Euglena tuba, a microalga, is known for its excellent antioxidant and iron-chelation activities; however its anticancer efficacies have not been reported yet. This study investigates the antitumor and antimetastatic activities of 70 % methanolic extract of Euglena tuba (ETME) against human lung (A549) and breast cancer (MCF-7) cells in vitro. Moreover, we had examined ETME’s role in inducing intracellular ROS with the regulation of antioxidants and MAPK pathway.

Methods

Anticancer activity of ETME was thoroughly studied using flow cytometry, confocal microscopy and western blotting; along with various biochemical assays for analysing ROS-induced regulation of antioxidant enzymes. Inhibition of invasion and migration of malignant cells by ETME were investigated by wound healing and zymographic studies. DNA–Protein interaction with ETME was also studied.

Results

ETME inhibited the growth of both A549 (IC₅₀ 92.14 µg/ml) and MCF-7 cells (IC₅₀ 50.27 µg/ml) by inducing apoptosis, while remained non-toxic against nomral WI-38 cells (IC₅₀ 911.43 µg/ml). ETME treatment resulted in increasing Bax/Bcl-2 ratio, BID truncation and activation of caspase cascade. This ultimately leads to PARP degradation and apoptosis through the intrinsic and extrinsic pathway in both A549 and MCF-7 cells. Wound healing and gelatin zymography studies revealed that ETME significantly inhibited the invasion and migration of both A549 and MCF-7 cells dose-dependently through the downregulation of MMP-9. Further investigations showed that ETME selectively induces intracellular ROS, regulated the levels of intracellular antioxidants and suppresses the activation of ERK1/2, JNK, P38 mitogen-activated protein kinase pathways in both type of malignant cells. Further DNA and protein binding studies revealed that ETME strongly interact with DNA as well as protein attributing the possibilities of presence of components which are targeting the macromolecules in cancer cells. Moreover, when the identified compounds from ETME were examined for their cytotoxicities individually, it was found that they lost their specificities towards cancer cells and also attacked normal cells.

Conclusions

Our study suggests that ETME retards the growth of both lung and breast cancer cells, in vitro, through multivariate mechanisms, proving its candidature for the development of better and safer drugs against these cancers.

Addition of docetaxel or bisphosphonates to standard of care in men with localised or metastatic, hormone-sensitive prostate cancer: a systematic review and meta-analyses of aggregate data

BACKGROUND

Results from large randomised controlled trials combining docetaxel or bisphosphonates with standard of care in hormone-sensitive prostate cancer have emerged. In order to investigate the effects of these therapies and to respond to emerging evidence, we aimed to systematically review all relevant trials using a framework for adaptive meta-analysis.

METHODS

For this systematic review and meta-analysis, we searched MEDLINE, Embase, LILACS, and the Cochrane Central Register of Controlled Trials, trial registers, conference proceedings, review articles, and reference lists of trial publications for all relevant randomised controlled trials (published, unpublished, and ongoing) comparing either standard of care with or without docetaxel or standard of care with or without bisphosphonates for men with high-risk localised or metastatic hormone-sensitive prostate cancer. For each trial, we extracted hazard ratios (HRs) of the effects of docetaxel or bisphosphonates on survival (time from randomisation until death from any cause) and failure-free survival (time from randomisation to biochemical or clinical failure or death from any cause) from published trial reports or presentations or obtained them directly from trial investigators. HRs were combined using the fixed-effect model (Mantel-Haenzsel).

FINDINGS

We identified five eligible randomised controlled trials of docetaxel in men with metastatic (M1) disease. Results from three (CHAARTED, GETUG-15, STAMPEDE) of these trials (2992 [93%] of 3206 men randomised) showed that the addition of docetaxel to standard of care improved survival. The HR of 0·77 (95% CI 0·68-0·87; p<0·0001) translates to an absolute improvement in 4-year survival of 9% (95% CI 5-14). Docetaxel in addition to standard of care also improved failure-free survival, with the HR of 0·64 (0·58-0·70; p<0·0001) translating into a reduction in absolute 4-year failure rates of 16% (95% CI 12-19). We identified 11 trials of docetaxel for men with locally advanced disease (M0). Survival results from three (GETUG-12, RTOG 0521, STAMPEDE) of these trials (2121 [53%] of 3978 men) showed no evidence of a benefit from the addition of docetaxel (HR 0·87 [95% CI 0·69-1·09]; p=0·218), whereas failure-free survival data from four (GETUG-12, RTOG 0521, STAMPEDE, TAX 3501) of these trials (2348 [59%] of 3978 men) showed that docetaxel improved failure-free survival (0·70 [0·61-0·81]; p<0·0001), which translates into a reduced absolute 4-year failure rate of 8% (5-10). We identified seven eligible randomised controlled trials of bisphosphonates for men with M1 disease. Survival results from three of these trials (2740 [88%] of 3109 men) showed that addition of bisphosphonates improved survival (0·88 [0·79-0·98]; p=0·025), which translates to 5% (1-8) absolute improvement, but this result was influenced by the positive result of one trial of sodium clodronate, and we found no evidence of a benefit from the addition of zoledronic acid (0·94 [0·83-1·07]; p=0·323), which translates to an absolute improvement in survival of 2% (-3 to 7). Of 17 trials of bisphosphonates for men with M0 disease, survival results from four trials (4079 [66%] of 6220 men) showed no evidence of benefit from the addition of bisphosphonates (1·03 [0·89-1·18]; p=0·724) or zoledronic acid (0·98 [0·82-1·16]; p=0·782). Failure-free survival definitions were too inconsistent for formal meta-analyses for the bisphosphonate trials.

INTERPRETATION

The addition of docetaxel to standard of care should be considered standard care for men with M1 hormone-sensitive prostate cancer who are starting treatment for the first time. More evidence on the effects of docetaxel on survival is needed in the M0 disease setting. No evidence exists to suggest that zoledronic acid improves survival in men with M1 or M0 disease, and any potential benefit is probably small.

FUNDING

Medical Research Council UK.

Pathophysiology of Osteonecrosis of the Jaws

Osteonecrosis of the jaw (ONJ) is a multifactorial disease in patients with primary or metastatic bone malignancy or osteoporosis undergoing systemic antiresorptive therapy, where pathophysiology has not yet been fully determined. The staging of ONJ is based on severity of symptoms and extent of clinical and radiographic findings. Treatment strategies range from conservative local wound care to aggressive resective surgery of all necrotic bone. The first ONJ cases were reported in 2003 and 2004, and although significant progress has been made in our understanding of the disease, much more work needs to be done to completely explain its pathophysiology.

Oral squamous cell carcinoma arising in a patient after hematopoietic stem cell transplantation with bisphosphonate-related osteonecrosis of the jaws

A 55-year-old man with a history of acute myeloid leukaemia treated with hematopoietic stem cell transplantation and with a 5-year history of bisphosphonate-related osteonecrosis of the jaws, following 12 cycles of intravenous zoledronic acid therapy, presented in December 2009 with a history of increasingly severe unilateral lower jaw pain. Oral examination revealed, as previously, exposed bone in the left mandible, but also a new exophytic mass on the lower-left buccal mucosa. Biopsy confirmed a diagnosis of oral squamous cell carcinoma. To the best of our knowledge, this is the first report of an oral squamous cell carcinoma that appeared adjacent to an area of osteochemonecrosis.

Development of a preclinical orthotopic xenograft model of ewing sarcoma and other human malignant bone disease using advanced in vivo imaging

Ewing sarcoma and osteosarcoma represent the two most common primary bone tumours in childhood and adolescence, with bone metastases being the most adverse prognostic factor. In prostate cancer, osseous metastasis poses a major clinical challenge. We developed a preclinical orthotopic model of Ewing sarcoma, reflecting the biology of the tumour-bone interactions in human disease and allowing in vivo monitoring of disease progression, and compared this with models of osteosarcoma and prostate carcinoma. Human tumour cell lines were transplanted into non-obese diabetic/severe combined immunodeficient (NSG) and Rag2^−/−/γc^−/− mice by intrafemoral injection. For Ewing sarcoma, minimal cell numbers (1000–5000) injected in small volumes were able to induce orthotopic tumour growth. Tumour progression was studied using positron emission tomography, computed tomography, magnetic resonance imaging and bioluminescent imaging. Tumours and their interactions with bones were examined by histology. Each tumour induced bone destruction and outgrowth of extramedullary tumour masses, together with characteristic changes in bone that were well visualised by computed tomography, which correlated with post-mortem histology. Ewing sarcoma and, to a lesser extent, osteosarcoma cells induced prominent reactive new bone formation. Osteosarcoma cells produced osteoid and mineralised “malignant” bone within the tumour mass itself. Injection of prostate carcinoma cells led to osteoclast-driven osteolytic lesions. Bioluminescent imaging of Ewing sarcoma xenografts allowed easy and rapid monitoring of tumour growth and detection of tumour dissemination to lungs, liver and bone. Magnetic resonance imaging proved useful for monitoring soft tissue tumour growth and volume. Positron emission tomography proved to be of limited use in this model. Overall, we have developed an orthotopic in vivo model for Ewing sarcoma and other primary and secondary human bone malignancies, which resemble the human disease. We have shown the utility of small animal bioimaging for tracking disease progression, making this model a useful assay for preclinical drug testing.

Selaginella tamariscina (Beauv.) possesses antimetastatic effects on human osteosarcoma cells by decreasing MMP-2 and MMP-9 secretions via p38 and Akt signaling pathways

Selaginella tamariscina is a traditional medicinal plant for treatment of some advanced cancers in the Orient. However, the effect of S. tamariscina on metastasis of osteosarcoma and the underlying mechanism remain unclear. We tested the hypothesis that S. tamariscina suppresses cellular motility, invasion and migration and also investigated its signaling pathways. This study demonstrates that S. tamariscina, at a range of concentrations (from 0 to 50 μg/mL), concentration-dependently inhibited the migration/invasion capacities of three osteosarcoma cell lines without cytotoxic effects. Zymographic and western blot analyses revealed that S. tamariscina inhibited the matrix metalloproteinase (MMP)-2 and MMP-9 enzyme activity, as well as protein expression. Western blot analysis also showed that S. tamariscina inhibits phosphorylation of p38 and Akt. Furthermore, SB203580 (p38 inhibitor) and LY294002 (PI3K inhibitor) showed the similar effects as S. tamariscina in U2OS cells. In conclusion, S. tamariscina possesses an antimetastatic activity in osteosarcoma cells by down-regulating MMP-2 and MMP-9 secretions and increasing TIMP-1 and TIMP-2 expressions through p38 and Akt-dependent pathways. S. tamariscina may be a powerful candidate to develop a preventive agent for osteosarcoma metastasis.

Advances in prevention and treatment of bone metastases in prostate cancer. Role of RANK/RANKL inhibition

BACKGROUND

Bone metastases are a common complication of prostate cancer, so treatment and prevention are essential to slow the progression of the disease and the occurrence of skeletal related events (SREs), which have devastating consequences for the quality of life of patients.

SUMMARY OF EVIDENCE

Bone metastases are characterized by increased bone turnover and altered balance between osteogenesis and osteolysis, with activation of the RANK and its ligand (RANKL). In patients with metastatic prostate cancer, bisphosphonates have been the bone-targeted agents most commonly used to date. Zoledronic acid has demonstrated efficacy in the reduction and delay of SREs in patients with bone metastases. Denosumab, a RANKL inhibitor, has been demonstrated to be superior to zoledronic acid in the prevention of SREs in castration-resistant prostate cancer (CRPC). Both agents are being considered, along with other new bone-targeted agents, for the prevention of bone metastases in patients with nonmetastatic CRPC, where denosumab has already demonstrated superiority over placebo.

CONCLUSIONS

Denosumab and zoledronic acid prevent SREs in patients with prostate cancer and bone metastases. Denosumab also has a potential role in delaying bone metastases in nonmetastatic patients. Advances in the treatment of CRPC include an increasing focus on prevention of the progression of bone disease.

Zoledronic acid reverses the epithelial-mesenchymal transition and inhibits self-renewal of breast cancer cells through inactivation of NF-κB

Zoledronic acid, a third-generation bisphosphonate, has been shown to reduce cell migration, invasion, and metastasis. However, the effects of zoledronic acid on the epithelial-mesenchymal transition (EMT), a cellular process essential to the metastatic cascade, remain unclear. Therefore, the effects of zoledronic acid on EMT, using triple-negative breast cancer (TNBC) cells as a model system, were examined in more detail. Zoledronic acid treatment decreased the expression of mesenchymal markers, N-cadherin, Twist, and Snail, and subsequently upregulated expression of E-cadherin. Zoledronic acid also inhibited cell viability, induced cell-cycle arrest, and decreased the proliferative capacity of TNBC, suggesting that zoledronic acid inhibits viability through reduction of cell proliferation. As EMT has been linked to acquisition of a self-renewal phenotype, the effects of zoledronic acid on self-renewal in TNBC were also studied. Treatment with zoledronic acid decreased expression of self-renewal proteins, BMI-1 and Oct-4, and both prevented and eliminated mammosphere formation. To understand the mechanism of these results, the effect of zoledronic acid on established EMT regulator NF-κB was investigated. Zoledronic acid inhibited phosphorylation of RelA, the active subunit of NF-κB, at serine 536 and modulated RelA subcellular localization. Treatment with zoledronic acid reduced RelA binding to the Twist promoter, providing a direct link between inactivation of NF-κB signaling and loss of EMT transcription factor gene expression. Binding of Twist to the BMI-1 promoter was also decreased, correlating modulation of EMT to decreased self-renewal. On the basis of these results, it is proposed that through inactivation of NF-κB, zoledronic acid reverses EMT, which leads to a decrease in self-renewal.

Zoledronic acid inhibits proliferation and impairs migration and invasion through downregulating VEGF and MMPs expression in human nasopharyngeal carcinoma cells

To demonstrate the effect of zoledronic acid in proliferation, invasion, and migration of human nasopharyngeal carcinoma cell HNE-1 and explore the potential role of VEGF, MMP-2, and MMP-9 proteins in vitro. Human nasopharyngeal carcinoma cell HNE-1 was exposed to various concentrations (0-40 μmol/l) of zoledronic acid. Zoledronic acid inhibited proliferation of HNE-1 cells though not in a dose-dependent manner. Zoledronic acid had exerted a dose-dependent effect on the migration and invasion of HNE-1 cells. Both expressions of mRNA and protein of MMP2, MMP9, and VEGF were reduced, respectively, detected by RT-PCR and Western blot assays. These data suggested that zoledronic acid not only inhibited growth but also invasion and migration of HNE-1 cells in vitro. The anti-cancer action of zoledronic acid was partially associated with the suppression of VEGF expression and secretion and downregulating the expression of MMP2 and MMP9.

Recent developments in treatments targeting castration-resistant prostate cancer bone metastases

BACKGROUND

Prostate cancer is the most common male cancer and one of the top causes of male cancer-related death. Most patients with prostate cancer respond to initial androgen deprivation therapy before progressing to castration-resistant prostate cancer (CRPC) and eventually developing bone metastases. Growth of prostate cancer metastases in the bone microenvironment produces numerous factors that disrupt the dynamic equilibrium of osteogenesis and osteolysis existing in healthy bone, leading to progressive morbidity, poor quality of life, and increased treatment costs.

MATERIALS AND METHODS

Relevant studies of CRPC and targeted therapies were identified from literature and clinical trial databases, websites, and conference abstracts.

RESULTS

Available data on agents potentially targeting bone metastatic CRPC or the bone microenvironment in patients with CRPC are discussed, including inhibitors of tumor growth/survival and bone turnover (SRC family kinase inhibitors, endothelin-1 inhibitors, MET inhibitors, and thalidomide and its derivatives), inhibitors of bone turnover (bisphosphonates and receptor activator of nuclear factor-kB ligand inhibitors), antiangiogenic agents (vascular endothelial growth factor receptor and platelet-derived growth factor blockers), prostate cancer vaccines, and bone-directed radiopharmaceuticals.

CONCLUSIONS

With increasing data availability demonstrating tumor-bone microenvironment interactions and routine incorporation of bone-related end points into CRPC trials, bone microenvironment-targeted agents are likely to become an increasingly important component of CRPC treatment.

Antiresorptive therapies in oncology and their effects on cancer progression

Bone health is an emerging concern in the early breast cancer setting. Current adjuvant therapies, especially hormonal therapies in premenopausal patients (e.g. goserelin) and aromatase inhibitors in postmenopausal patients, have been associated with substantial decreases in bone mineral density that may place patients at risk for fractures. Bisphosphonates--and the recently approved anti-RANKL antibody, denosumab--have both demonstrated activity for the treatment of postmenopausal osteoporosis and cancer treatment-induced bone loss (CTIBL) in breast cancer patients, although neither has received widespread approval specifically for CTIBL. However, some bisphosphonates, especially the nitrogen-containing bisphosphonate zoledronic acid, have also demonstrated clinically meaningful anticancer effects in patients receiving adjuvant hormonal therapy for breast cancer and in other oncology settings. The effects of denosumab on cancer disease outcomes in the adjuvant setting remain to be established. This discrepancy has created a dilemma in terms of how to evaluate the complete benefit:risk profile of bone-health management options in the adjuvant breast cancer setting. This review summarises the current data on the course of cancer in clinical trials of the antiresorptive agents and provides important insight into the relative anticancer potential of the various therapies.

Zoledronic acid combined with chemotherapy bring survival benefits to patients with bone metastases from nasopharyngeal carcinoma

PURPOSE

Bone is the most common site of metastases from nasopharyngeal carcinoma (NPC). Zoledronic acid (ZA) used to prevent skeletal-related events (SREs) of bone metastases has shown anti-tumor effects; yet, no report has been found on the survival benefit of ZA in NPC. This study aimed to evaluate whether ZA can bring survival benefits to patients with bone metastases from NPC.

METHODS

A total of 307 patients with of NPC who had bone metastases were analyzed retrospectively. The differences of survival between patients treated with chemotherapy combined with ZA and those with chemotherapy alone were evaluated by the log-rank test. The Cox multivariate analyses of clinical features and different treatment methods of the 307 patients were conducted.

RESULTS

The prevalence of SREs in the combined approach group was lower than that with chemotherapy alone (34% vs. 48%, X (2) = 7.003, P = 0.008). The combined approach group had better progression-free survival (PFS) (11.5 vs. 5.5 months, P < 0.001) and overall survival (OS) (23.5 vs. 17.5 months, P < 0.001) than chemotherapy alone group. Cox multivariate analysis identified the following independent prognostic factors: ZA treatment, bone metastatic sites, baseline serum alkaline phosphatase (ALP) level, SREs and cycles of chemotherapy.

CONCLUSIONS

ZA treatment combined with chemotherapy could reduce SREs and improve PFS and OS for NPC patients with bone metastases.

Antimetastatic effects of Phyllanthus on human lung (A549) and breast (MCF-7) cancer cell lines

Background

Current chemotherapeutic drugs kill cancer cells mainly by inducing apoptosis. However, they become ineffective once cancer cell has the ability to metastasize, hence the poor prognosis and high mortality rate. Therefore, the purpose of this study was to evaluate the antimetastatic potential of Phyllanthus (P. niruri, P. urinaria, P. watsonii, and P. amarus) on lung and breast carcinoma cells.

Methodology/Principal Findings

Cytotoxicity of Phyllanthus plant extracts were first screened using the MTS reduction assay. They were shown to inhibit MCF-7 (breast carcinoma) and A549 (lung carcinoma) cells growth with IC₅₀ values ranging from 50–180 µg/ml and 65–470 µg/ml for methanolic and aqueous extracts respectively. In comparison, they have lower toxicity on normal cells with the cell viability percentage remaining above 50% when treated up to 1000 µg/ml for both extracts. After determining the non-toxic effective dose, several antimetastasis assays were carried out and Phyllanthus extracts were shown to effectively reduce invasion, migration, and adhesion of both MCF-7 and A549 cells in a dose-dependent manner, at concentrations ranging from 20–200 µg/ml for methanolic extracts and 50–500 µg/ml for aqueous extracts. This was followed by an evaluation of the possible modes of cell death that occurred along with the antimetastatic activity. Phyllanthus was shown to be capable of inducing apoptosis in conjunction with its antimetastastic action, with more than three fold increase of caspases-3 and -7, the presence of DNA-fragmentation and TUNEL-positive cells. The ability of Phyllanthus to exert antimetastatic activities is mostly associated to the presence of polyphenol compounds in its extracts.

Conclusions/Significance

The presence of polyphenol compounds in the Phyllanthus plant is critically important in the inhibition of the invasion, migration, and adhesion of cancer cells, along with the involvement of apoptosis induction. Hence, Phyllanthus could be a valuable candidate in the treatment of metastatic cancers.

Potential pathophysiological mechanisms in osteonecrosis of the jaw

Bisphosphonates are used in the treatment of hypercalcemia of malignancy, skeletal complications associated with metastastic bone disease, Paget's disease, and osteoporosis. Osteonecrosis of the jaw (ONJ) is a recently described clinical condition that has been associated with the use of nitrogen-containing bisphosphonates. Reports describing this entity first appeared in the literature in 2003. While there have been significant numbers of case reports and a limited number of retrospective and prospective studies examining risk factors associated with ONJ, the pathophysiology of this condition remains elusive. In this review, we explore proposed mechanisms underlying ONJ development and identify potential areas for future investigation.

Zoledronic acid induces autophagic cell death in human prostate cancer cells

PURPOSE

Bisphosphonates are potent inhibitors of bone resorption. In vitro studies show that zolendronic acid inhibits prostate cancer cell growth by activating apoptosis. We investigated whether zolendronic acid also inhibits prostate cancer cell growth by autophagy (type II programmed cell death).

MATERIALS AND METHODS

We investigated the induction of autophagy in the PC-3, DU-145, LNCaP and CRW22Rv1 cell lines upon zolendronic acid treatment. LC3-II protein formation was detected by Western blot. LC3-II incorporation into autophagosomes was detected by immunofluorescence staining. Acidic organelle formation was detected by acridine orange staining. Rescue experiments using an apoptosis inhibitor and/or an autophagy inhibitor were performed by MTT assay.

RESULTS

Autophagy induction was detected by formation of the LC3-II protein after exposure to 100 μM zolendronic acid. LC3-II and caspase-3 processing was detected 6 days after treatment. Acidic organelles were detectable by acridine orange staining and immunofluorescence showed round-up and condensed staining of LC3-II, suggesting autophagosome formation in the cytoplasm during autophagic cell death. Cell growth was rescued only by administering an apoptosis and autophagy inhibitor during zolendronic acid treatment, indicating that zolendronic acid induces prostate cancer death by apoptotic and autophagic cell death.

CONCLUSIONS

To our knowledge we report the first study showing that zolendronic acid markedly inhibits human prostate cancer cell growth through autophagic cell death. Zolendronic acid shows its anticancer activity via apoptosis and autophagy. These findings can potentially contribute to the beneficial use of zolendronic acid for prostate cancer treatment.

Zoledronic acid impairs myeloid differentiation to tumour-associated macrophages in mesothelioma

Background:

Suppressive immune cells present in tumour microenvironments are known to augment tumour growth and hamper efficacy of antitumour therapies. The amino-bisphosphonate Zoledronic acid (ZA) is considered as an antitumour agent, as recent studies showed that ZA prolongs disease-free survival in cancer patients. The exact mechanism is a topic of debate; it has been suggested that ZA targets tumour-associated macrophages (TAMs).

Methods:

We investigate the role of ZA on the myeloid differentiation to TAMs in murine mesothelioma in vivo and in vitro. Mice were intraperitoneally inoculated with a lethal dose of mesothelioma tumour cells and treated with ZA to determine the effects on myeloid differentiation and survival.

Results:

We show that ZA impaired myeloid differentiation. Inhibition of myeloid differentiation led to a reduction in TAMs, but the number of immature myeloid cells with myeloid-derived suppressor cell (MDSC) characteristics was increased. In addition, ZA affects the phenotype of macrophages leading to reduced level of TAM-associated cytokines in the tumour microenvironment. No improvement of survival was observed.

Conclusion:

We conclude that ZA leads to a reduction in macrophages and impairs polarisation towards an M2 phenotype, but this was associated with an increase in the number of immature myeloid cells, which might diminish the effects of ZA on survival.

Molecular mechanisms of metastasis in prostate cancer

Prostate cancer (PCa) preferentially metastasizes to the bone marrow stroma of the axial skeleton. This activity is the principal cause of PCa morbidity and mortality. The exact mechanism of PCa metastasis is currently unknown, although considerable progress has been made in determining the key players in this process. In this review, we present the current understanding of the molecular processes driving PCa metastasis to the bone.

Systemic therapy for advancing or metastatic prostate cancer (STAMPEDE): a multi-arm, multistage randomized controlled trial

There is a need to improve the outcomes for men with high-risk localised, nodal or metastatic prostate cancer, or with aggressively relapsing disease after initial therapy for local disease. This group of men is currently managed with long-term hormone therapy. Thus we aim to evaluate the toxicity and efficacy of three different systemic therapies (docetaxel, zoledronic acid and celecoxib) used alone or combined at the initiation of hormone manipulation for high-risk prostate cancer. A novel statistical design (multi-arm, multistage method) simultaneously tests multiple distinct strategies in parallel against a single control arm. The trial has several 'stages', from initial confirmation of safety to a phase III assessment of survival, with a series of intervening activity stages. This method provides a means of assessing several agents more quickly and efficiently, and allows inactive treatments to be dropped from further study at an early stage. STAMPEDE has been designed to address in parallel the activity and efficacy of these agents for this patient group. It is a flagship randomized clinical trial for academic research into prostate cancer in the UK. More than 500 patients have been recruited on schedule, confirming the acceptability of this complex trial design to patients and clinicians. The trial targets a population of approximately 3000 patients. STAMPEDE is a major new trial with a novel design applicable to the synchronous testing of several agents. It is hoped that the results will improve outcomes for patients with high-risk prostate cancer. The design could be applicable to the study of new therapies in other cancer types. Continued efforts are required by the urological cancer community to maintain the excellent recruitment shown to date.

Antitumor effects of bisphosphonates: promising preclinical evidence

The majority of patients with advanced cancer will ultimately develop bone metastases. The bone microenvironment provides fertile soil for a cycle of tumor growth and bone destruction that increases the risk of debilitating and potentially life-limiting skeletal-related events. Therefore, developing appropriate strategies to prevent bone metastases is critical. Bisphosphonates used to treat and prevent skeletal-related events resulting from multiple myeloma and bone metastases secondary to solid tumors, may also have direct and indirect antitumor effects. Emerging evidence from in vitro and in vivo preclinical studies in several tumor types suggests that bisphosphonates can reduce tumor burden in bone and soft tissue, inhibit angiogenesis, prevent tumor cell invasion and adhesion in bone, and induce tumor cell apoptosis. The powerful antiresorptive properties of bisphosphonates appear to directly prevent tumor cell growth and angiogenesis; in addition, combining bisphosphonates with cytotoxic chemotherapy may provide further antitumor synergies. Sequential application of cytotoxic chemotherapy (e.g., doxorubicin, paclitaxel, and gemcitabine) followed by bisphosphonates has been shown to induce significantly more tumor cell apoptosis than either agent alone in vitro and effectively inhibits tumor growth in vivo. Furthermore, in vivo data suggest that optimizing the dosing schedule may significantly increase survival. Overall, preclinical data suggesting that bisphosphonates have antitumor potential are promising and have provided the impetus for several ongoing clinical studies.

The role of bisphosphonates in the management of patients that have cancer

Bisphosphonates are pharmacologic agents widely used in people for managing pathologic bone resorptive conditions. Based on their physicochemical properties, bisphosphonates concentrate within areas of active bone remodeling and induce osteoclast apoptosis. Appropriate use of bisphosphonates for treating companion animals requires a thorough understanding of how bisphosphonates exert their biologic effects. This review article highlights general properties of bisphosphonates, including their pharmacology, mechanisms of action, adverse side effects, anticancer mechanisms, surrogate markers for assessing response, and potential clinical utility for treating dogs and cats diagnosed with malignant skeletal tumors.

Bisphosphonates in cancer therapy

Bisphosphonates are the standard of care in the treatment of malignant bone diseases, because of their ability to inhibit osteoclast-mediated bone destruction. We review here preclinical evidence that bisphosphonates also exert direct antitumour effects and antiangiogenic properties. Furthermore, we describe new insights on how bisphosphonates may act synergistically in combination with antineoplastic drugs or gammadelta T cells to exhibit antitumour activity. These findings reveal new exciting possibilities to fully exploit the antitumour potential of bisphosphonates in the clinical practice.

Biphosphonates in Advanced Prostate and Renal Cell Cancer – Current Status and Potential Applications

OBJECTIVE

This review summarizes recent findings on the therapeutic benefits of biphosphonates in patients with advanced prostate or renal cell carcinoma (RCC). The role of biphosphonates in ADT-induced osteoporosis and delay of skeletal-related events (SREs) in metastatic bone disease is discussed. A brief overview on the proposed modes of action is given.

METHODS

Literature search of PubMed documented publications and abstracts from meetings.

RESULTS

Among the biphosphonates currently available, zoledronic acid is the only one known to be capable of delaying SREs in RCC and prostate cancer patients. Zoledronic acid counteracts cancer treatment-induced osteoporosis in men with prostate malignancies. The antitumor activity of biphosphonates found in vitro and in vivo is intriguing and has to be further assessed in clinical studies.

CONCLUSION

Due to its unique properties, zoledronic acid is a breakthrough in the management of metastatic bone disease in patients with advanced prostate cancer and RCC. It significantly improves the patients' quality of life, drastically prolongs time to first SRE, and showed a positive but not significant effect on survival.

Administration of zoledronic acid enhances the effects of docetaxel on growth of prostate cancer in the bone environment

Background

After development of hormone-refractory metastatic disease, prostate cancer is incurable. The recent history of chemotherapy has shown that with difficult disease targets, combinatorial therapy frequently offers the best chance of a cure. In this study we have examined the effects of a combination of zoledronic acid (ZOL), a new-generation bisphosphonate, and docetaxel on LuCaP 23.1, a prostate cancer xenograft that stimulates the osteoblastic reaction when grown in the bone environment.

Methods

Intra-tibial injections of LuCaP 23.1 cells were used to generate tumors in the bone environment, and animals were treated with ZOL, docetaxel, or a combination of these. Effects on bone and tumor were evaluated by measurements of bone mineral density and histomorphometrical analysis.

Results

ZOL decreased proliferation of LuCaP 23.1 in the bone environment, while docetaxel at a dose that effectively inhibited growth of subcutaneous tumors did not show any effects in the bone environment. The combination of the drugs significantly inhibited the growth of LuCaP 23.1 tumors in the bone.

Conclusion

In conclusion, the use of the osteolysis-inhibitory agent ZOL in combination with docetaxel inhibits growth of prostate tumors in bone and represents a potential treatment option.

Lack of Prophylactic Effect of Incadronate on Skeletal Lesions Associated with Implants of Prostate Cancer

OBJECTIVES

To evaluate prophylactic effects of bisphosphonate (BP) on skeletal lesions induced by prostate cancer (CaP).

METHODS

Incadronate, a third-generation BP, was administered weekly for 4 weeks, with or without 4-week pre-administration, to rats whose calvaria had been inoculated with syngeneic CaP tissue.

RESULTS

The transplanted CaP grew up and caused bone resorption with osteoblastic changes regardless of incadronate treatment. Although decrease in bone resorption accompanied by reduced number of osteoclasts was shown by incadronate administration, pre-administration had no additional inhibitory effect on bone destruction and Ki-67 labeling indices of CaP cells were not altered.

CONCLUSIONS

These results indicate that application of BP alone is not sufficient to prevent skeletal lesions due to CaP in patients with high risk of bone metastases although it is useful in inhibition of cancer-induced bone resorption with osteoblastic changes.

Invasive characteristics of human prostatic epithelial cells: understanding the metastatic process

Prostate cancer has a predilection to metastasise to the bone marrow stroma (BMS) by an as yet uncharacterised mechanism. We have defined a series of coculture models of invasion, which simulate the blood/BMS boundary and allow the elucidation of the signalling and mechanics of trans-endothelial migration within the complex bone marrow environment. Confocal microscopy shows that prostate epithelial cells bind specifically to bone marrow endothelial-to-endothelial cell junctions and initiate endothelial cell retraction. Trans-endothelial migration proceeds via an epithelial cell pseudopodial process, with complete epithelial migration occurring after 232±43 min. Stromal-derived factor-1 (SDF-1)/CXCR4 signalling induced PC-3 to invade across a basement membrane although the level of invasion was 3.5-fold less than invasion towards BMS (P=0.0007) or bone marrow endothelial cells (P=0.004). Maximal SDF-1 signalling of invasion was completely inhibited by 10 μM of the SDF-1 inhibitor T140. However, 10 μM T140 only reduced invasion towards BMS and bone marrow endothelial cells by 59% (P=0.001) and 29% (P=0.011), respectively. This study highlights the need to examine the potential roles of signalling molecules and/or inhibitors, not just in single-cell models but in coculture models that mimic the complex environment of the bone marrow.