Bone invasion by Walker 256 carcinoma, line A in young and adult rats: effects of etidronate

Pharmacologic inhibitors of IkappaB kinase suppress growth and migration of mammary carcinosarcoma cells in vitro and prevent osteolytic bone metastasis in vivo

The NF-kappaB signaling pathway is known to play an important role in the regulation of osteoclastic bone resorption and cancer cell growth. Previous studies have shown that genetic inactivation of IkappaB kinase (IKK), a key component of NF-kappaB signaling, inhibits osteoclastogenesis, but the effects of pharmacologic IKK inhibitors on osteolytic bone metastasis are unknown. Here, we studied the effects of the IKK inhibitors celastrol, BMS-345541, parthenolide, and wedelolactone on the proliferation and migration of W256 cells in vitro and osteolytic bone destruction in vivo. All compounds tested inhibited the growth and induced apoptosis of W256 cells as evidenced by caspase-3 activation and nuclear morphology. Celastrol, BMS-345541, and parthenolide abolished IL1beta and tumor necrosis factor alpha-induced IkappaB phosphorylation and prevented nuclear translocation of NF-kappaB and DNA binding. Celastrol and parthenolide but not BMS-345541 prevented the activation of both IKKalpha and IKKbeta, and celastrol inhibited IKKalpha/beta activation by preventing the phosphorylation of TAK1, a key receptor-associated factor upstream of IKK. Celastrol and parthenolide markedly reduced the mRNA expression of matrix metalloproteinase 9 and urinary plasminogen activator, and inhibited W256 migration. Administration of celastrol or parthenolide at a dose of 1 mg/kg/day suppressed trabecular bone loss and reduced the number and size of osteolytic bone lesions following W256 injection in rats. Histomorphometric analysis showed that both compounds decreased osteoclast number and inhibited bone resorption. In conclusion, pharmacologic inhibitors of IKK are effective in preventing osteolytic bone metastasis in this model and might represent a promising class of agents to the prevention and treatment of metastatic bone disease associated with breast cancer.

A pilot study of antitumor effect of gallium ethylenediaminetetramethylene phosphonate [Ga(III)-EDTMP] in tumor-bearing rats

The inhibitory effects of gallium ethylenediamine-N,N,N',N'-tetrakismethylene phosphonate [Ga(III)-EDTMP] was studied on a malignant tumor and metastatic bone lesion model induced with Walker carcinosarcoma 256 (WCS 256) in Wistar rats weighing 120 to 135 g. A water-soluble chelate, Ga(III)-EDTMP, was prepared for injection in a tumor-bearing model. Radiographic analysis at 14 days indicated that the bone invasion and osteolysis were markedly reduced in animals treated with Ga(III)-EDTMP. The calculated tumor inhibitory rates were 33.16+/-0.38% at a dosage of 5 mg/kg and 47.75+/-0.74% at 10 mg/kg. Biochemical markers such as serum calcium decreased by 23% (P<.05) and by 31% (P<.01) at dosages of 5 mg/kg and 10 mg/kg, respectively, whereas serum alkaline phosphatase (ALPase) activity decreased by 47% (P<.01) and 69% (P<.01) at the 2 dosages.

Rationale for the use of alendronate in osteoporosis

Bisphosphonates are being used in disorders associated with accelerated resorption of bone, particularly Paget's disease of bone and the bone disease of malignancy. Their undoubted biological efficacy and relatively low apparent toxicity make them attractive candidates for the management of osteoporosis. The bisphosphonate alendronate has many characteristics which suggest that it is suitable for use in osteoporosis. It is a potent inhibitor of osteoclast-mediated bone resorption with no adverse effect on the mineralization of bone. Earlier studies have shown it to be one of the most active bisphosphonates in Paget's disease and the hypercalcemia of malignancy. In common with other bisphosphonates tested thus far, alendronate appears to inhibit bone loss in a variety of experimental models of osteoporosis. Long-term studies are needed to determine its steady-state effects on bone mass in man. Most data indicate that alendronate is capable at least of decreasing the rate of bone loss, and might even induce increments in bone mass for many years. Since the experimental studies show that the increase in bone mass observed with alendronate is associated with an increase in bone strength, its use is likely to decrease the frequency of fractures. However, direct clinical evidence for this requires the outcome of well-designed long-term prospective studies.

Etidronic acid. A review of its pharmacological properties and therapeutic efficacy in resorptive bone disease

Etidronic acid is an orally and intravenously active bisphosphonate, which is believed to inhibit resorption of bone via a number of cellular mechanisms, including alteration of osteoclastic activity. In studies of patients with symptomatic Paget's disease, etidronic acid 5 to 20 mg/kg/day administered orally rapidly decreased the biochemical indices of bone turnover. Mineralisation defects in forming bone may be avoided by the use of an initial dosage of 5 mg/kg/day for up to 6 months; dosages above 10 mg/kg/day should be limited to 3 months' duration, and dosages greater than 20 mg/kg/day should be avoided. Although 3-day intravenous therapy with etidronic acid 7.5 mg/kg/day has shown superior efficacy to rehydration and forced diuresis in the management of hypercalcaemia of malignancy, the efficacy of the drug is lower than that of the newer bisphosphonates, pamidronic acid and clodronic acid. Clinical studies involving postmenopausal women with established osteoporosis have indicated that oral etidronic acid 400 mg/day for 14 days as part of a 90-day cycle, repeated for up to 3 years, increases the bone mineral density (BMD) of the lumbar vertebrae and appears to reduce the incidence of vertebral fracture. Published data suggest that etidronic acid shows similar efficacy to hormone replacement therapy (HRT) in these respects. The above dosage also appears to be effective in preventing corticosteroid-induced osteoporosis when administered as part of an intermittent, cyclical regimen. Etidronic acid in higher dosages (10 to 20 mg/kg/day orally) is effective in reducing the incidence of heterotopic ossification and its ensuing complications in both neurological and post-surgical patients. Etidronic acid is well tolerated by the majority of patients, with gastrointestinal complaints reported most commonly, but tends to delay the normal mineralisation of forming bone when administered continuously at higher dosages for prolonged periods. This is of little consequence where short term treatment is involved, but may be detrimental to those patients receiving longer courses of therapy. This effect may be minimised or avoided by using the lowest effective dosage for as short a time as possible (as in the above recommendations for Paget's disease), or by the use of intermittent cyclical therapy (as in the management of osteoporosis). Etidronic acid therefore retains a role in the management of resorptive bone disease, particularly in the treatment of Paget's disease, the prevention of heterotopic ossification, and as a second-line option in postmenopausal osteoporosis. However, the development of newer bisphosphonates requires that these compounds be continually compared and re-evaluated.

Effect of the bisphosphonate risedronate on bone metastases in a rat mammary adenocarcinoma model system

Risedronate (NE-58095) is a third-generation bisphosphonate with very potent antiresorptive activity but few toxic effects. The purpose of this work was to evaluate the effect of risedronate treatment on bone metastases produced in a rat breast cancer model. Berlin Druckrey IV rats inoculated with ENU1564 mammary adenocarcinoma cells were treated daily with risedronate or a saline placebo. Survival times, dictated by extraskeletal metastases (lung, heart, and brain), were not affected by risedronate treatment. Risedronate-treated animals had skeletal changes associated with decreased remodeling of bones undergoing endochondral ossification, most prominently affecting the appendicular skeleton. Despite the skeletal alterations induced by the treatment, the distribution of bone metastases throughout the surveyed skeletal sites was similar for treated and untreated animals. Bone metastases were enumerated in histologic sections of distal femur, spine, and skull. Tumor size was estimated from area measurements obtained from histologic lesions in distal femoral metaphyses and vertebral bodies. A greater number of treated rats had no bone metastases in any of the examined sections (30 versus 16.1% of untreated rats). Multiple bone metastases were observed less frequently in treated rats (33.3 versus 71% of untreated rats). Treated rats had fewer observed bone metastases in each examined site than untreated rats (p < or = 0.025). Mean tumor areas in femora and vertebrae were smaller in treated rats (p < or = 0.05), due to the less frequent presence of very large lesions. In untreated animals, osteoclasts appeared to be active at the tumor/bone interface and osseous structures were often completely replaced by expanding tumors. In contrast, metastases in treated animals caused less disruption of skeletal histoarchitecture. The apparent lack of osteoclastic activity and retention of bone within lesions suggested a decreased contribution of osteoclasts to the bone resorptive process. An in vivo immunohistochemical cell proliferation assay failed to reveal differences in the percentage of dividing tumor cells in bone metastatic sites in treated versus untreated animals. The results demonstrate significant effects of risedronate treatment on the incidence and size of observed skeletal metastases in this model.

New bisphosphonates in the treatment of bone metastases

Normal skeletal integrity is maintained by physiological bone turnover through a coupled process of bone resorption, mediated by osteoclasts, followed by new bone formation, mediated by osteoblasts. Major features of the pathogenesis of cancer-associated skeletal destruction are enhanced osteoclast-mediated bone resorption and disruption of normal bone formation. In this article, the literature on the pathogenesis and clinical manifestations of metastatic bone disease is discussed. Animal and clinical trials investigating novel bone targeted agents, emphasizing the bisphosphonates, are critically assessed. The most frequent clinical manifestations of bone metastases are pain, fracture, immobility, spinal cord compression, and hypercalcemia. New treatments under study for patients with bone metastases include agents specifically targeted to the skeleton such as bone-seeking radioisotopes and bisphosphonates. Studies in animal models of metastatic bone disease show that these bisphosphonates are able to inhibit tumor-induced osteolysis and are potentially useful in this condition. Bisphosphonates have been investigated in several clinical trials of patients with skeletal metastases from breast cancer, prostate cancer, and multiple myeloma. Overall, the studies investigating bone targeted radioisotopes or bisphosphonates for the treatment of morbidity due to skeletal metastases have been inconclusive. An improved understanding of the pathogenesis of metastatic bone disease and preclinical studies with bisphosphonates suggest that these agents may have a role in the treatment of this disorder. Additional trials of new generation bisphosphonates, employing a rigorously controlled, randomized study design with adequate numbers of subjects, are needed to demonstrate the safety and efficacy of this class of agents in this setting.

Mechanisms involved in the metastasis of cancer to bone

The metastasis of cancer to bone is a frequent outcome of common malignancies and is often associated with significant morbidity due to osteolysis. Bone metastasis is also selective in that a disproportionately small number of malignancies account for the majority of tumors which spread to bone. While the mechanisms of bone destruction have been studied, those responsible for the site-specific nature of bone metastasis are poorly understood. As a metastatic target, bone is unique in that it is continuously being remodelled under the influence of local and systemic growth factors, many of which are embedded in the bone matrix. This review summarizes evidence for the hypothesis that the formation of metastatic tumors in bone is the consequence of a unique microenvironment where metastatic cells can alter the metabolism of bone, thereby regulating the release of soluble bone-derived growth factors as a consequence of bone resorption. These, in turn, can modulate the malignant phenotypic properties of receptive cells. Transforming growth factor-beta is one factor which can promote the growth and motility of Walker 256 cells, a rat cell line with a propensity to metastasize spontaneously to bone.

A quantitative model for spontaneous bone metastasis: evidence for a mitogenic effect of bone on Walker 256 cancer cells

A new model for the study of spontaneous bone metastasis has been developed which allows for the quantification of metastatic tumor burden and cancer cell growth rate, and which describes the progressive changes in bone morphology. Walker 256 (W256) cells or vehicle were injected into the left upper thigh muscle of male Fischer rats, which were killed 7, 10 or 14 days later. By day 7, metastases had appeared in the distal femur, in the glomeruli of the kidney, and diffusely throughout the liver and lungs. The extent of tumor burden in these organs increased over time. In the femur, 14 days of tumor burden was associated with a 53 +/- 10% decrease in trabecular bone content, a 61 +/- 15% increase in osteoclast surface, and a 95 +/- 10% decrease in osteoblast surface, as compared with non-tumor-bearing controls. By autoradiography, metastatic tumor cells in all organs were determined to have greater growth rates than did cells in the primary tumor. However, within the femur, W256 cells located adjacent to trabecular bone surfaces had a 33 +/- 7% greater growth rate than did W256 cells located > 50 microns from bone surfaces (P < 0.05), suggesting a mitogenic effect of bone.

Bisphosphonates. Pharmacology and use in the treatment of tumour-induced hypercalcaemic and metastatic bone disease

The geminal bisphosphonates are a new class of drugs characterised by a P-C-P bond. Consequently, they are analogues of pyrophosphate, but are resistant to chemical and enzymatic hydrolysis. The bisphosphonates bind strongly to hydroxyapatite crystals and inhibit their formation and dissolution. This physicochemical effect leads in vivo to the prevention of soft tissue calcification and, in some instances, inhibition of normal calcification. The main effect is to inhibit bone resorption, but in contrast to the effect on mineralisation, the mechanism involved is cellular. These various effects vary greatly according to the structure of the individual bisphosphonate. The half-life of circulating bisphosphonates is very brief, in the order of minutes to hours. 20% to 50% of a given dose is taken up by the skeleton, the rest being excreted in the urine. The half-life in bone is far longer and depends upon the turnover rate of the skeleton itself. Bisphosphonates are very well tolerated; the relatively few adverse events that have been associated with their use are specific for each compound. Bisphosphonates have been used to treat various clinical conditions, namely ectopic calcification, ectopic bone formation, Paget's disease, osteoporosis and increased osteolysis of malignant origin. The three compounds commercially available for use in tumour-induced bone disease are in order of increasing potency, etidronate, clodronate and pamidronate. Most data have been obtained with the latter two agents. By inhibiting bone resorption, they correct hypercalcaemia and hypercalciuria, reduce pain, the occurrence of fractures, as well as the development of new osteolytic lesions, and in consequence improve the quality of life. In view of these actions, of their excellent tolerability and of the fact that they are active for relatively long periods, these compounds are, after rehydration, the drugs of choice in tumour-induced bone disease and an excellent auxiliary to the drugs used in oncology.