Growth inhibition and sensitization to cisplatin by zoledronic acid in osteosarcoma cells

Bisphosphonates in common pediatric and adult bone sarcomas

The therapeutic strategies proposed currently for bone sarcomas are based on neo-adjuvant chemotherapy, delayed en-bloc wide resection, and adjuvant chemotherapy. Unfortunately, bone sarcomas are characterized by high rates of poor drug response, with a high risk of drug resistance, local recurrence and/or a high propensity for induced metastases. The pathogenesis of bone sarcomas is strongly associated with dysregulation of local bone remodeling and increased osteolysis that plays a part in tumor development. In this context, bisphosphonates (BPs) have been proposed as a single agent or in combination with conventional drugs to block bone resorption and the vicious cycle established between bone and sarcoma cells. Pre-clinical in vitro studies revealed the potential "anti-tumor" activities of nitrogen-bisphosphonates (N-BPs). In pre-clinical models, N-BPs reduced significantly primary tumor growth in osteosarcoma and Ewing sarcoma, and the installation of lung metastases. In chondrosarcoma, N-BPs reduced the recurrence of local tumors after intralesional curettage, and increased overall survival. In pediatric and adult osteosarcoma patients, N-BPs have been assessed in combination with conventional chemotherapy and surgery in randomized phase 3 studies with no improvement in clinical outcome. The lack of benefit may potentially be explained by the biological impact of N-BPs on macrophage differentiation/recruitment which may alter CD8⁺-T lymphocyte infiltration. Thanks to their considerable affinity for the mineralized extracellular matrix, BPs are an excellent platform for drug delivery in malignant bone sites with reduced systemic toxicity, which opens up new opportunities for their future use.

New insights into molecular and cellular mechanisms of zoledronate in human osteosarcoma

Osteosarcoma is the most common primary malignant tumor of the skeleton in teenagers and young adults and continues to confer a generally poor prognosis in patients who do not respond to chemotherapy or who present with metastatic diseases at diagnosis. The nitrogen-containing zoledronate, the third generation bisphosphonate (BP), effectively inhibits osteoclastic bone resorption and is widely utilized in the treatment of metabolic and metastatic bone diseases nowadays. Owing to an acceptable safety profile and tolerability, zoledronate is the only BP currently approved for the prevention and treatment of skeletal relevant events in patients with metastatic bone lesions, especially bone metastases from advanced renal cell carcinoma and prostate cancer, and breast cancer, due to all solid malignancy. Moreover, zoledronate possesses diverse anti-osteosarcoma properties and may have potential to become an adjunctive treatment for high-grade osteosarcoma to enhance survival rates and to obliterate complications of the chemotherapy. Herein we highlighted the pharmacology of BPs and its underlying molecular mechanisms in osteoclasts and various cancer cells. We further provided the available literature on in vitro studies to illustrate the new insights into the intracellular molecular mechanisms of zoledronate in human osteosarcoma cell lines and in vivo animal models that led to the development and regulatory approval of zoledronate in patients with human osteosarcoma. This review also addresses clinical trials to focus on the efficacy of zoledronate on human osteosarcoma.

Bisphosphonates-much more than only drugs for bone diseases

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

Cisplatin bioconjugated enzymatic GNPs amplify the effect of cisplatin with acquiescence

Enzymatic gold nanoparticles (B-GNPs) have been synthesized using a natural anticancer agent bromelain (a cysteine protease) and these nanoparticles were used to bioconjugate Cisplatin (highly effective against osteosarcoma and lung cancer). Cisplatin bioconjugated bromelain encapsulated gold nanoparticles (B-C-GNPs) were found profoundly potent against same cancers at much lower concentration with minimum side effects due to the synergistic effect of bromelain. The B-C-GNPs have been observed to inhibit the proliferation of osteosarcoma cell lines Saos-2 and MG-63 with IC₅₀ estimation of 4.51 µg/ml and 3.21 µg/ml, respectively, and against small lung cancer cell line A-549 with IC₅₀ 2.5 µg/ml which is lower than IC₅₀ of cisplatin against same cell lines. The B-GNPs/B-C-GNPs were characterized by TEM, UV-Visible spectroscopy, Zeta potential and DLS to confirm the production, purity, crystalline nature, stability of nanoemulsion, size and shape distribution. The change in 2D and 3D conformation of bromelain after encapsulation was studied by Circular Dichroism and Fluorometry, respectively. It was found that after encapsulation, a 19.4% loss in secondary structure was observed, but tertiary structure was not altered significantly and this loss improved the anticancer activity. The confirmation of bioconjugation of cisplatin with B-GNPs was done by UV-Visible spectroscopy, TEM, FTIR, 2D ¹H NMR DOSY and ICP-MS. Further, it was found that almost ~4 cisplatin molecules bound with each B-GNPs nanoparticle.

Biological effects of aromatic bis[aminomethylidenebis(phosphonic)] acids in osteoclast precursors in vitro

Nitrogen-containing bisphosphonates (N-BPs) inhibit bone resorption by preventing osteoclast activity. Most clinically used BPs are hydroxybisphosphonates with the exception of incadronate, which belongs to the class of aminomethylidenebisphosphonic acids. The aim of this study was to evaluate the antiproliferative activity of two previously reported aminobisphosphonates (WG8185B2 and WG9001B) in combination with doxorubicin and cisplatin toward J774E cells (a model of osteoclast precursors in vitro). WG8185B2 and WG9001B BPs enhanced the cytotoxic activity of doxorubicin and cisplatin, especially when applied 24 hr prior to cytostatics. The antiproliferative effect of studied BPs was related to the changes in cell cycle progression. WG8185B2 leads to significant accumulation of J774E cells in S phase, whereas WG9001B causes transient arrest in G₂ /M phase, followed by an increase in the percentage of cells in S phase. Moreover, WG8185B2 and WG9001B BPs showed enhanced proapoptotic activity in osteoclast precursors, which was manifested by an increase in caspase-3 activity and percentage of apoptotic cells. In addition, both compounds influenced the motility of J774E cells. The exact molecular mechanism of action of examined BPs remains to be determined; however, results show an interesting biological activity of these compounds, which may be of interest in the context of antiresorptive therapy.

The enhancing effect of a laser photochemotherapy with cisplatin or zolendronic acid in primary human osteoblasts and osteosarcoma cells in vitro

BACKGROUND

Photodynamic therapies (PDT) have become increasingly popular in the adjuvant treatment of different tumour entities. Chemotherapeutic agents, such as cisplatin may be used in combination with low-level laser therapy (LLLT) as laser photochemotherapy. The aim of this study was to investigate the effect of LLLT on cell bioviability of normal and malignant bone cells under chemotherapeutic conditions with either cisplatin or zolendronic acid in vitro.

METHODS

Primary human osteoblasts (HOB) and an osteosarcoma cell line (Saos-2) were treated with different concentrations of zolendronic acid or cisplatin and irradiated twice with a diode laser (wavelength 670 nm, 120 s, energy outputs of 100mW/cm² , continuous wave mode). Cell viability was tested by XTT-assay and via histomorphological analysis.

RESULTS

LLLT alone increased bioviability for both cell lines. LLLT lowered HOB viability at the three highest concentrations of cisplatin and zolendronic acid. For Saos-2, LLLT reduced cell viability at every concentration of cisplatin. In cases of incubation with zolendronic acid, similar to osteoblasts, LLLT lowered cell viability at the highest concentration only.

CONCLUSIONS

Based on the conditions of this study, laser photochemotherapy may be able to raise the cytotoxicity of cisplatin and zolendronic acid in benign and malignant bone cells. This could be of interest in the development of new therapeutic treatment modalities against neoplastic bone diseases like osteosarcoma.

Bone Tumor Environment as a Potential Therapeutic Target in Ewing Sarcoma

Ewing sarcoma is the second most common pediatric bone tumor, with three cases per million worldwide. In clinical terms, Ewing sarcoma is an aggressive, rapidly fatal malignancy that mainly develops not only in osseous sites (85%) but also in extra-skeletal soft tissue. It spreads naturally to the lungs, bones, and bone marrow with poor prognosis in the two latter cases. Bone lesions from primary or secondary (metastases) tumors are characterized by extensive bone remodeling, more often due to osteolysis. Osteoclast activation and subsequent bone resorption are responsible for the clinical features of bone tumors, including pain, vertebral collapse, and spinal cord compression. Based on the “vicious cycle” concept of tumor cells and bone resorbing cells, drugs, which target osteoclasts, may be promising agents as adjuvant setting for treating bone tumors, including Ewing sarcoma. There is also increasing evidence that cellular and molecular protagonists present in the bone microenvironment play a part in establishing a favorable “niche” for tumor initiation and progression. The purpose of this review is to discuss the potential therapeutic value of drugs targeting the bone tumor microenvironment in Ewing sarcoma. The first part of the review will focus on targeting the bone resorbing function of osteoclasts by means of bisphosphonates or drugs blocking the pro-resorbing cytokine receptor activator of NF-kappa B ligand. Second, the role of this peculiar hypoxic microenvironment will be discussed in the context of resistance to chemotherapy, escape from the immune system, or neo-angiogenesis. Therapeutic interventions based on these specificities could be then proposed in the context of Ewing sarcoma.

Clusterin inhibition using OGX-011 synergistically enhances zoledronic acid activity in osteosarcoma

Purpose

Despite recent improvements in therapeutic management of osteosarcoma, ongoing challenges in improving the response to chemotherapy warrants new strategies still needed to improve overall patient survival. Among new therapeutic approaches, zoledronic acid (ZOL) represents a promising adjuvant molecule to chemotherapy to limit the osteolytic component of bone tumors. However, ZOL triggers the elevation of heat shock proteins (Hsp), including Hsp27 and clusterin (CLU), which could enhance tumor cell survival and treatment resistance. We hypothesized that targeting CLU using siRNA or the antisense drug, OGX-011, will suppress treatment-induced CLU induction and enhance ZOL-induced cell death in osteosarcoma (OS) cells.

Methods

The combined effects of OGX-011 and ZOL were investigated in vitro on cell growth, viability, apoptosis and cell cycle repartition of ZOL-sensitive or -resistant human OS cell lines (SaOS2, U2OS, MG63 and MNNG/HOS).

Results

In OS cell lines, ZOL increased levels of HSPs, especially CLU, in a dose- and time-dependent manner by mechanism including increased HSF1 transcription activity. The OS resistant cells to ZOL exhibited higher CLU expression level than the sensitive cells. Moreover, CLU overexpression protects OS sensitive cells to ZOL-induced cell death by modulating the MDR1 and farnesyl diphosphate synthase expression. OGX-011 suppressed treatment-induced increases in CLU and synergistically enhanced the activity of ZOL on cell growth and apoptosis. These biologic events were accompanied by decreased expression of HSPs, MDR1 and HSF1 transcriptional activity. In vivo, OGX-011, administered 3 times a week (IP, 20mg/kg), potentiated the effect of ZOL (s.c; 50μg/kg), significantly inhibiting tumor growth by 50% and prolonging survival in MNNG/HOS xenograft model compared to ZOL alone.

Conclusion

These results indicate that ZOL-mediated induction of CLU can be attenuated by OGX-011, with synergistic effects on delaying progression of osteosarcoma.

Skeletal consequences of RANKL-blocking antibody (IK22-5) injections during growth: mouse strain disparities and synergic effect with zoledronic acid

High doses of bone resorption inhibitors are currently under evaluation in pediatric oncology. Previous works have evidenced transient arrest in long bone and skull bone growth and tooth eruption blockage when mice were treated with zoledronic acid (ZOL). The question of potential similar effects with a RANKL-blocking antibody (IK22.5) was raised. Sensitivity disparities in these inhibitors between mouse strains and synergic effects of zoledronic acid and a RANKL-blocking antibody were subsidiary questions. In order to answer these questions, newborn C57BL/6J and CD1 mice were injected every two or three days (4 injections in total so 7 or 10 days of treatment length) with high doses of a RANKL-blocking antibody. The consequences on the tibia, craniofacial bones and teeth were analyzed by μCT and histology at the end of the treatment and one, two and three months later. The results obtained showed that RANKL-blocking antibody injections induced a transient arrest of tibia and skull bone growth and an irreversible blockage of tooth eruption in C57BL/6J mice. In CD1 mice, tooth eruption defects were also present but only at much higher doses. Similar mouse strain differences were obtained with zoledronic acid. Finally, a synergic effect of the two inhibitors was evidenced. In conclusion as previously observed for bisphosphonates (ZOL), a RANKL-blocking antibody induced a transient arrest in long bone and skull bone growth and a blockage of tooth eruption with however disparities between mouse strains with regard to this last effect. A synergic effect of both bone resorption inhibitors was also demonstrated.

Mevalonates restore zoledronic acid-induced osteoclastogenesis inhibition

Bisphosphonate-related osteonecrosis of the jaw (BRONJ) is likely to be caused by continuous imperfection of bone healing after surgical treatments in patients with long-term administration of nitrogen-containing bisphosphonates (NBPs). NBPs inhibit osteoclastic bone resorption by impairing the mevalonic acid sterol pathway in osteoclasts. Thus, we hypothesized that exogenous mevalonic acid metabolites restore the inhibitory effects of NBPs on osteoclastogenesis and bone remodeling. To clarify the effects of mevalonic acid metabolites, especially geranylgeranyl pyrophosphate (GGPP) and geranylgeranyl transferase substrate geranylgeranyl acid (GGOH), we examined the effects of zoledronic acid with or without GGOH or GGPP on osteoclast differentiation, multinucleation, and bone mineral deposition in tooth-extracted sockets. Zoledronic acid decreased the number of tartrate-resistant acid phosphatase (TRAP)-positive multinuclear cells derived from mouse osteoclast precursors treated with receptor activator of nuclear factor-κB ligand and macrophage colony-stimulating factor. Zoledronic acid simultaneously suppressed not only the expressions of osteoclastic differentiation-related molecules such as TRAP, cathepsin K, calcitonin receptor, and vacuolar H-ATPase but also those of multinucleation-related molecules such as dendrocyte-expressed 7 transmembrane proteins and osteoclast stimulatory transmembrane protein. Treatment with GGOH or GGPP, but not farnesyl acid, restored the zoledronic acid-inhibited number of TRAP-positive multinuclear cells together with the expressions of these molecules. Although intraperitoneal administration of zoledronic acid and lipopolysaccharide into mice appeared to induce BRONJ-like lesions with empty bone lacunae and decreased mineral deposition in tooth-extracted socket, both GGOH and GGPP partially restored the inhibitory effects on zoledronic acid-related mineral deposition. These results suggest the potential of mevalonic acid metabolites as therapeutic agents for BRONJ.

The synergistic anticancer effect of artesunate combined with allicin in osteosarcoma cell line in vitro and in vivo

BACKGROUND

Artesunate, extracted from Artemisia annua, has been proven to have anti-cancer potential. Allicin, diallyl thiosulfinate, the main biologically active compound derived from garlic, is also of interest in cancer treatment research. This object of this report was to document synergistic effects of artesunate combined with allicin on osteosarcoma cell lines in vitro and in vivo.

METHODS

After treatment with artesunate and allicin at various concentrations, the viability of osteosarcoma cells was analyzed by MTT method, with assessment of invasion and motility, colony formation and apoptosis. Western Blotting was performed to determine the expression of caspase-3/9, and activity was also detected after drug treatment. Moreover, in a nude mouse model established with orthotopic xenograft tumors, tumor weight and volume were monitored after drug administration via the intraperitoneal (i.p.) route.

RESULTS

The viability of osteosarcoma cells in the combination group was significantly decreased in a concentration and time dependent manner; moreover, invasion, motility and colony formation ability were significantly suppressed and the apoptotic rate was significantly increased through caspase-3/9 expression and activity enhancement in the combination group. Furthermore, suppression of tumor growth was evident in vivo.

CONCLUSION

Our results indicated that artesunate and allicin in combination exert synergistic effects on osteosarcoma cell proliferation and apoptosis.

In vitro and in vivo effects of photodynamic therapy on metastatic breast cancer cells pre-treated with zoledronic acid

BACKGROUND

Photodynamic therapy (PDT), a non-ionizing, minimally invasive drug-light treatment, has recently been shown to successfully ablate tumor within rat vertebrae with concurrent improvements in bone strength and architecture. The bisphosphonate zoledronic acid (zol), a current drug for patients with skeletal metastases, primarily works by inhibiting osteoclast activity, but direct anti-tumor effects have also been reported. However, it is unknown if or how pre-treatment with zol may alter the tumorcidal effect of PDT. The aim of this study was to evaluate the effect of PDT, both in vitro and in vivo, on zol-pretreated cancer cells.

MATERIALS AND METHODS

Human metastatic breast cancer cells (MT-1) were cultured in vitro and treated with zol (10μM) for 24h, followed by PDT treatment. Cell viability was assessed by fluorescence microscopy and flow cytometry. In vivo, MT-1 cells were injected (intracardiac) into athymic rats. On day 7, zol (60μg/kg) was administered subcutaneously. On day 14, PDT was applied (1mg/kg verteporfin; 75J; 690nm) to lumbar vertebrae. Histomorphometric assessment of tumor burden was evaluated on day 21.

RESULTS

The cell viability measured in vitro after PDT treatment decreased in cells pre-incubated with zol up to 20% compared to treatment with PDT alone. Zol alone had no influence on the MT-1 cell viability. In vivo, all treatments, either alone or combined, had a tumorcidal effect.

CONCLUSIONS

Pre-treatment with zol in vivo did not yield a synergistic effect on tumor ablation in contrast to the in vitro results, but neither did it abrogate the positive tumorcidal effect of PDT, so that those therapies may be applied in combination.

Zoledronic acid produces combinatory anti-tumor effects with cisplatin on mesothelioma by increasing p53 expression levels

We examined anti-tumor effects of zoledronic acid (ZOL), one of the bisphosphonates agents clinically used for preventing loss of bone mass, on human mesothelioma cells bearing the wild-type p53 gene. ZOL-treated cells showed activation of caspase-3/7, -8 and -9, and increased sub-G1 phase fractions. A combinatory use of ZOL and cisplatin (CDDP), one of the first-line anti-cancer agents for mesothelioma, synergistically or additively produced the cytotoxicity on mesothelioma cells. Moreover, the combination achieved greater anti-tumor effects on mesothelioma developed in the pleural cavity than administration of either ZOL or CDDP alone. ZOL-treated cells as well as CDDP-treated cells induced p53 phosphorylation at Ser 15, a marker of p53 activation, and up-regulated p53 protein expression levels. Down-regulation of p53 levels with siRNA however did not influence the ZOL-mediated cytotoxicity but negated the combinatory effects by ZOL and CDDP. In addition, ZOL treatments augmented cytotoxicity of adenoviruses expressing the p53 gene on mesothelioma. These data demonstrated that ZOL-mediated augmentation of p53, which was not linked with ZOL-induced cytotoxicity, played a role in the combinatory effects with a p53 up-regulating agent, and suggests a possible clinical use of ZOL to mesothelioma with anti-cancer agents.

Cisplatin in combination with zoledronic acid: a synergistic effect in triple-negative breast cancer cell lines

Zoledronic acid (ZA) is the most widely used bisphos-phonate to treat cancer-induced bone disease. There is evidence that bisphosphonates have direct antitumor activity and that their combination with anticancer agents can significantly enhance the effect of treatment. We evaluated whether the combination of ZA with different platinum compounds exerts a synergistic effect in breast cancer cell lines and we investigated the mechanisms of action involved. This study was performed on four breast cancer cell lines, MCF-7, SKBR3, MDA-MB-231 and BRC-230, and confirmed on a primary culture obtained from a breast cancer bone metastasis specimen. ZA (50 µM) was administered for 72 h alone or in combination with cisplatin (Cis) or carboplatin. Drug-induced growth inhibition was detected by sulforhodamine B assay, apoptosis and cell cycle regulation were detected by flow cytometry, and protein expression was evaluated by western blot analysis. MCF-7 and SKBR3 showed very low sensitivity to the three drugs tested. The ZA + Cis combination exerted a high antitumor activity in the two triple-negative lines MDA-MB-231 and BRC-230. An important synergistic effect was obtained in MDA-MB-231 and an additive effect was observed in BRC-230. The p21, pMAPK and m-TOR pathways were regulated by this combined treatment, particularly at lower Cis doses. Carboplatin did not show antitumor activity either alone or in combination with ZA. In conclusion, the potential novel treatment schedule identified for triple-negative breast cancer could prove beneficial in view of the limited therapeutic options available for patients and also since the synergism with ZA would enable lower Cis doses to be used, thus reducing toxicity. Although further research in a clinical setting is warranted, our results on cell lines has been confirmed on a human primary bone metastasis culture.

The Current and Future Therapies for Human Osteosarcoma

Osteosarcoma (OS) is the most common non-hematologic malignant tumor of bone in adults and children. As sarcomas are more common in adolescents and young adults than most other forms of cancer, there are a significant number of years of life lost secondary to these malignancies. OS is associated with a poor prognosis secondary to a high grade at presentation, resistance to chemotherapy and a propensity to metastasize to the lungs. Current OS management involves both chemotherapy and surgery. The incorporation of cytotoxic chemotherapy into therapeutic regimens escalated cure rates from <20% to current levels of 65-75%. Furthermore, limb-salvage surgery is now offered to the majority of OS patients. Despite advances in chemotherapy and surgical techniques over the past three decades, there has been stagnation in patient survival outcome improvement, especially in patients with metastatic OS. Thus, there is a critical need to identify novel and directed therapy for OS. Several Phase I trials for sarcoma therapies currently ongoing or recently completed have shown objective responses in OS. Novel drug delivery mechanisms are currently under phase II and III clinical trials. Furthermore, there is an abundance of preclinical research which holds great promise in the development of future OS-directed therapeutics. Our continuously improving knowledge of the molecular and cell-signaling pathways involved in OS will translate into more effective therapies for OS and ultimately improved patient survival. The present review will provide an overview of current therapies, ongoing clinical trials and therapeutic targets under investigation for OS.

Taurine chloramine induces apoptosis in human osteosarcoma cell lines

Although combination of surgery with chemotherapy has noticeably improved the survival rate of osteosarcoma patients, the application of anticancer drugs is still associated with significant adverse reactions, for instance acquisition of drug-resistant phenotypes, necessitating the development of new chemotherapeutical agents. Therefore, the aim of this study was to research, if taurine chloramine (NCT) induces apoptosis in the osteosarcoma cell lines HOS, MG-63, and SAOS-2. Proliferation of osteosarcoma cells was detected with the "EZ4U Cell Proliferation and Cyotoxicity Assay" showing a time- and dose-dependent cytotoxic effect of NCT on these cell lines. After 3 h of incubation all cell lines showed significantly less cells at 5.5 mM NCT solutions, after 6 h at concentrations of 1.1 and 2.2 mM. Acridine-orange fluorescence nuclear staining showed characteristic features of apoptosis. DNA fragmentation was detected via ELISA, showing significant results for HOS and MG-63 after 6 h at an NCT concentration of 3.3 mM. Results of JC-1 mitochondrial FACS analysis presented a significant increase in apoptotic cells after 6 h at 3.3 mM for the tested cell lines. Summarized, the results of this study indicate that NCT is a promising agent in osteosarcoma therapy.

Bone sarcomas: from biology to targeted therapies

Primary malignant bone tumours, osteosarcomas, and Ewing sarcomas are rare diseases which occur mainly in adolescents and young adults. With the current therapies, some patients remain very difficult to treat, such as tumour with poor histological response to preoperative CT (or large initial tumour volume for Ewing sarcomas not operated), patients with multiple metastases at or those who relapsed. In order to develop new therapies against these rare tumours, we need to unveil the key driving factors and molecular abnormalities behind the malignant characteristics and to broaden our understanding of the phenomena sustaining the metastatic phenotype and treatment resistance in these tumours. In this paper, starting with the biology of these tumours, we will discuss potential therapeutic targets aimed at increasing local tumour control, limiting metastatic spread, and finally improving patient survival.

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.

Bisphosphonates regulate cell proliferation, apoptosis and pro-osteoclastic expression in MG-63 human osteosarcoma cells

Bisphosphonates are well established in the management of cancer-induced skeletal complications. Recent studies suggest that nitrogen-containing bisphosphonates (N-BPs) promote the apoptosis of cancer cells as well as osteoclasts in bone metastatic sites. To investigate whether N-BPs exhibit a direct antitumor effect on osteoclasts, the current study investigated the effects of zoledronic acid (ZOL) on MG-63 cells in vitro. MG-63 cells were treated with ZOL. The inhibitory effect of ZOL on the growth of MG-63 cells was measured by MTT assay. ZOL-induced apoptosis of the MG-63 cells was examined by Hoechst 33258 staining, electron microscopy, Annexin V-FITC and propidium iodide staining. Reverse-transcription polymerase chain reaction (RT-PCR) and western blotting analysis were employed to assess the expression of osteoprotegerin (OPG) and receptor activator of nuclear factor-κB ligand (RANKL). The MTT assay showed that ZOL induced a distinct dose- and time-dependent reduction of cell viability with an IC(50) value of 52.37±1.0 μM for 72 h. Flow cytometric analysis further revealed that the cell apoptosis was induced by arrest of the cell cycle in the G(1) phase. RT-PCR and western blot analysis demonstrated that ZOL upregulated OPG expression. These results suggest that ZOL has direct effects on osteosarcoma cell growth and apoptosis. Increased OPG expression is an indirect effect, possibly via changes in the local microenvironment.

Impact of oncopediatric dosing regimen of zoledronic acid on bone growth: preclinical studies and case report of an osteosarcoma pediatric patient

Osteosarcoma and Ewing sarcoma represent the two most frequent primary bone tumors that arise in the pediatric population. Despite recent improvement in their therapeutic management, no improvement in survival rate has been achieved since early 1980 s. Among new therapeutic approaches, bisphosphonates are promising candidates as potent inhibitors of bone resorption. However, their effects on bone growth must be studied at dosing regimen corresponding to pediatric protocols. To this aim, several protocols using zoledronic acid (ZOL) were developed in growing mice (50 µg/kg every 2 days × 10). Parameters of bone remodeling and bone growth were investigated by radiography, micro-computed tomography, histology, and biologic analyses. Extramedullar hematopoiesis was searched for in spleen tissue. A transient inhibitory effect of ZOL was observed on bone length, with a bone-growth arrest during treatment owing to an impressive increase in bone formation at the growth plate level (8- to 10-fold increase in BV/TV). This sclerotic band then shifted into the diaphysis as soon as endochondral bone formation started again after the end of ZOL treatment, revealing that osteoclasts and osteoblasts are still active at the growth plate. In conclusion, endochondral bone growth is transiently disturbed by high doses of ZOL corresponding to the pediatric treatment of primary bone tumors. These preclinical observations were confirmed by a case report in a pediatric patient treated in the French OS2006 protocol over 10 months who showed a growth arrest during the ZOL treatment period with normal gain in size after the end of treatment.

Addition of pamidronate to chemotherapy for the treatment of osteosarcoma

BACKGROUND

This study evaluated the safety and feasibility of the addition of pamidronate to chemotherapy for treatment of osteosarcoma.

METHODS

The authors treated 40 patients with osteosarcoma with cisplatin, doxorubicin, and methotrexate with the addition of pamidronate 2 mg/kg/dose (max dose 90 mg) monthly for 12 doses. Survival, event-free survival (EFS), and durability of orthopedic reconstruction were evaluated.

RESULTS

For patients with localized disease, event-free survival (EFS) at 5 years was 72% and overall survival 93%. For patients with metastatic disease, EFS at 5 years was 45% and overall survival 64%. Toxicity was similar to patients treated with chemotherapy alone. Thirteen of 14 uncemented implants demonstrated successful osteointegration. Among allograft reconstructions, there were 2 graft failures, 4 delayed unions, and 6 successful grafts. Overall, 5 of 33 reconstructions failed. There were no stress fractures or growth disturbances.

CONCLUSIONS

Pamidronate can be safely incorporated with chemotherapy for the treatment of osteosarcoma. It does not impair the efficacy of chemotherapy. Pamidronate may improve the durability of limb reconstruction.

Zoledronic acid as a new adjuvant therapeutic strategy for Ewing's sarcoma patients

Ewing's sarcoma (ES) is the second most frequent pediatric bone tumor also arising in soft tissues (15% of cases). The prognosis of patients with clinically detectable metastases at diagnosis, not responding to therapy or with disease relapse, is still very poor. Among new therapeutic approaches, bisphosphonates represent promising adjuvant molecules to chemotherapy to limit the osteolytic component of bone tumors and to protect from bone metastases. The combined effects of zoledronic acid and mafosfamide were investigated on cell proliferation, viability, apoptosis, and cell cycle distribution of human ES cell lines differing in their p53 and p16/ink4 status. ES models were developed to reproduce both soft tissue and intraosseous tumor development. Mice were treated with 100 μg/kg zoledronic acid (two or four times per week) and/or ifosfamide (30 mg/kg, one to three cycles of three injections). ES cell lines showed different sensitivities to zoledronic acid and mafosfamide at the cell proliferation level, with no correlation with their molecular status. Both drugs induced cell cycle arrest, but in the S or G(2)M phase, respectively. In vivo, zoledronic acid had no effect on soft tissue tumor progression, although it dramatically inhibited ES development in bone. When combined with ifosfamide, zoledronic acid exerted synergistic effects in the soft tissue model: Its combination with one cycle of ifosfamide resulted in an inhibitory effect similar to three cycles of ifosfamide alone. This very promising result could allow clinicians to diminish the doses of chemotherapy.

Past, present and future of therapies in pediatric sarcomas

Limited progress has been made over the past 30 years in improving the outcome of patients with high-risk pediatric sarcomas. The 5-year overall survival rate remains at 20% or less with metastatic sarcomas. Therefore, current and future research is focused on the identification and development of molecular or biological agents targeting the pathogenic pathways in sarcomas, either alone or in combination with conventional chemotherapy. To this end, the most promising activity has been seen with IGF-1 receptor antibodies and mTOR inhibitors. Other agents of interest are oncolytic viruses, epigenetic modulators (e.g., histone deacetylase inhibitors), immune modulators (e.g., muramyl tripeptide phosphatidylethanolamine) and other biological agents (e.g., trabectedin). In addition to the development of novel drugs, the other major area of recent focus is developing immune therapies, such as dendritic cell vaccines and adoptive immunotherapy for treating pediatric sarcomas. This article discusses the successes, the failures and the future direction of these therapies.

Emerging drugs for high-grade osteosarcoma

IMPORTANCE OF THE FIELD

Osteosarcoma (OS) is the most common primary malignant bone tumour in children and adolescents. This review focuses on the most promising therapeutic markers and drugs which may potentially be considered for innovative high-grade OS treatments.

AREAS COVERED IN THIS REVIEW

The list of drugs and compounds reviewed has been generated by taking into account those which target markers of potential clinical interest for high-grade OS and have been included in Phase I, II or III clinical trials. The literature search covers the last 40 years, starting from the first OS chemotherapy reports of the early 1970s. Particular relevance was given to reports and reviews on new targeted therapies of possible clinical usefulness for high-grade OS.

WHAT THE READER WILL GAIN

This review gives an updated overview of novel therapeutic approaches which have been or are going to be evaluated in Phase I/II/III clinical studies for high-grade OS.

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On the basis of the information that has emerged so far, it can be predicted that in the next 5 - 10 years, new agents to be included in innovative treatment strategies for selected subgroups of high-grade OS patients may become available.

Zoledronic acid protects against osteosarcoma-induced bone destruction but lacks efficacy against pulmonary metastases in a syngeneic rat model

Osteosarcoma (OS) is the most common primary malignant tumor of bone in children and adolescents. In spite of successful control of the primary tumor, death from lung metastasis occurs in more than a third of patients. To investigate the efficacy of zoledronic acid (ZOL) on the development, progression and metastatic spread of OS, we used a rat model of OS, with features of the disease similar to human patients, including spontaneous metastasis to lungs. Rat OS cells were inoculated into the tibial marrow cavity of syngeneic rats. OS development was associated with osteolysis mixed with new bone formation, adjacent to the periosteum and extended into the surrounding soft tissue. Metastatic foci in the lungs formed 3-4 weeks postcancer cell transplantation. Treatment with a clinically relevant dose of ZOL was initiated 1 week after tumors were established and continued once weekly or as a single dose. ZOL preserved the integrity of both trabecular and cortical bone and reduced tumor-induced bone formation. However, the overall tumor burden at the primary site was not reduced because of the persistent growth of cancer cells in the extramedullary space, which was not affected by ZOL treatment. ZOL treatment failed to prevent the metastatic spread of OS to the lungs. These findings suggest that ZOL as a single agent protects against OS-induced bone destruction but lacks efficacy against pulmonary metastases in this rat model. ZOL may have potential value as an adjuvant therapy in patients with established OS.

Osteosarcoma treatment: state of the art

Osteosarcoma (OS) is a class of cancer originating from bone, mainly afflicting children or young adults. It is the second highest cause of cancer-related death in these age groups, mainly due to development of often fatal metastasis, usually in the lungs. Survival for these patients is poor despite the aggressive use of surgery, chemotherapy, and/or radiotherapy. Thus, new effective drugs and other forms of therapy are needed. This article reviews the biology and the state of the art management of OS. New experimental drugs and potential therapies targeting molecular pathways of OS are also discussed.

Zoledronic acid inhibits osteosarcoma growth in an orthotopic model

Zoledronic acid (ZOL) has been shown to reduce osteolysis in bone metastasis. Its efficacy in osteosarcoma has not been convincingly proved in a clinically relevant model for the disease. In vitro, ZOL decreased osteosarcoma cell proliferation, mainly due to an increase in apoptosis in a dose-dependent fashion. There was a decrease in cell migration at >or=10 micromol/L concentrations, but invasion was inhibited at a much lower dose of 0.1 micromol/L. Reverse transcription-PCR showed that ZOL overall caused an increased expression of osteocalcin and decreased expression of alkaline phosphatase, osteopontin, osteonectin, and vascular endothelial growth factor, with no change in expression of osteoprotegerin. ZOL administration s.c. twice weekly at 0.12 mg/kg to SaOS-2 tumor-bearing mice resulted in primary tumor growth inhibition, reduction in lung metastases, and dramatic decrease in osteolysis. Furthermore, in the ZOL cohort, there was a clear reduction in the number of osteoclasts in bone exposed to tumor and a lower tumor vessel density. These data point to the adjuvant potential of ZOL in the management of osteosarcoma not only for its antiosteolytic properties but also for its ability to directly halt tumor cell growth and metastasis via its effects on viability, invasion, differentiation, and angiogenesis.

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.