Preclinical evaluation of zoledronate using an in vitro mimetic cellular model for breast cancer metastatic bone disease.

BACKGROUND: The interactions between metastatic breast cancer cells and host cells of osteoclastic lineage in bone microenvironment are essential for osteolysis. In vitro studies to evaluate pharmacological agents are mainly limited to their direct effects on cell lines. To mimic the communication between breast cancer cells and human osteoclasts, a simple and reproducible cellular model was established to evaluate the effects of zoledronate (zoledronic acid, ZOL), a bisphosphonate which exerts antiresorptive properties. METHODS: Human precursor osteoclasts were cultured on bone-like surfaces in the presence of stimuli (sRANKL, M-CSF) to ensure their activation. Furthermore, immature as well as activated osteoclasts were co-cultured with MDA-MB-231 breast cancer cells. TRAP5b and type I collagen N-terminal telopeptide (NTx) were used as markers. Osteoclasts' adhesion to bone surface and subsequent bone breakdown were evaluated by studying the expression of cell surface receptors and certain functional matrix macromolecules in the presence of ZOL. RESULTS: ZOL significantly suppresses the precursor osteoclast maturation, even when the activation stimuli (sRANKL and M-SCF) are present. Moreover, it significantly decreases bone osteolysis and activity of MMPs as well as precursor osteoclast maturation by breast cancer cells. Additionally, ZOL inhibits the osteolytic activity of mature osteoclasts and the expression of integrin ß3, matrix metalloproteinases and cathepsin K, all implicated in adhesion and bone resorption. CONCLUSIONS: ZOL exhibits a beneficial inhibitory effect by restricting activation of osteoclasts, bone particle decomposition and the MMP-related breast cancer osteolysis. GENERAL SIGNIFICANCE: The proposed cellular model can be reliably used for enhancing preclinical evaluation of pharmacological agents in metastatic bone disease.

Expression of matrix macromolecules and functional properties of breast cancer cells are modulated by the bisphosphonate zoledronic acid.

BACKGROUND: The extracellular matrix (ECM) components play key roles in the multistep process of cancer growth and progression. Preclinical and clinical data show that bisphosphonates (BPs) may exert direct or indirect antitumoral effects. Despite proven efficiency in cancer treatment, the mechanism by which BPs can interfere with cancer progression remains elusive. METHODS: We investigated the effects of the third generation BP, zoledronate (zoledronic acid, Zometa®), in the expression of ECM macromolecules as well as the functional properties (proliferation, adhesion, migration and invasion) in two breast cancer cell lines (MDA-MB-231 and MCF-7) with different metastatic potentials. RESULTS: The data highlight that zoledronate effectively inhibits growth of breast cancer cells, functional invasion migration and adhesion to various matrices. At the level of ECM interacting molecules, the expression of specific heparan sulfate proteoglycans implicated in cancer progression, such as syndecan-1, -2 and glypican-1 is downregulated, whereas syndecan-4 expression is upregulated upon treatment with zoledronate. The levels of integrins ανß3, ανß5 and α5ß1 were significantly reduced following treatment with zoledronate which is in accordance with the reduced cell adhesion on various ECM matrices. The expression of hyaluronan and its receptor CD44 was also significantly suppressed. Moreover, ZOL suppressed the expression of metalloproteinases MMP-2, -9, the membrane type MT1- and MT2-MMP, whereas it increased the expression of their endogenous tissue inhibitors. CONCLUSIONS AND GENERAL SIGNIFICANCE: The obtained results demonstrate that zoledronate is a critical modulator of ECM gene expression and powerful anticancer agent inhibiting growth, migration and the matrix-associated invasion of breast cancer cells.

Monitoring serum chondroitin sulfate levels in patients submitted to coronary artery bypass surgery.

Glycosaminoglycans (GAGs) are functionally important molecules of the arterial wall and play a crucial role in atherogenesis. Chondroitin sulfate/dermatan sulfate proteoglycans (CS/DSPGs) participate in several biological events through their GAG chains, and are also involved in the development of atherosclerosis. The aim of this study was to compare the pre- and post-operative levels of CS in serum of patients after coronary artery bypass graft surgery using a highly sensitive reversed-polarity capillary electrophoresis method and to investigate the correlation of CS with common biochemical lipid markers. It was found that CS values were significantly higher for all patients post-operatively and, furthermore, CS levels were statistically correlated to apolipoprotein A and B levels. Notably, the pre-operational lipid profile of the patient may be indicative of the values of 4-sulfated CS post-operationally. Furthermore, the obtained results highlight the clinical significance of CS levels in serum, since they may provide complementary information for the latent inflammatory state of the patient.

Glycosaminoglycans as key molecules in atherosclerosis: the role of versican and hyaluronan.

Cardiovascular disease is the largest cause of death in Western societies and it primarily results from atherosclerosis of large and medium-sized vessels. Atherosclerosis leads to myocardial infarction, when it occurs in the coronary arteries, or stroke, when it occurs in the cerebral arteries. Pathological processes involved in macrovascular disease include the accumulation of lipids which are retained by extracellular matrix (ECM) molecules, especially by the chondroitin sulfate/dermatan sulfate (CS/DS) proteoglycans (CS/DSPGs), such as versican, biglycan and decorin. The sulfation pattern of CS is a key player in protein interactions causing atherosclerosis. Several studies have shown that lipoproteins bind CSPGs via their glycosaminoglycan chains. Galactosaminoglycans, such as CS and DS, bind low density lipoproteins (LDL), affecting the role of these molecules in the arterial wall. In this article, the role of CS and versican in atherosclerosis and hyaluronan in atherogenesis as well as the up to date known mechanisms that provoke this pathological condition are presented and discussed.

Expression and distribution of N-acetyl and N-glycolylneuraminic acids in secreted and cell-associated glycoconjugates by two human osteosarcoma cell lines.

N-acetylneuraminic acid (Neu5Ac) and N-glycolylneuraminic acid (Neu5Gc) are the dominant sialic acids (Sia) in mammals usually found in the non-reducing terminal of oligosaccharide side chains in glycoproteins and glycolipids. Their expression and distribution pattern have been correlated both with the malignant phenotype and tumor grade of human cancers. The aim of the present study was to determine by reversed-phase HPLC method the amounts of Neu5Ac and Neu5Gc as well as their distribution among the culture media and cell surface of MG-63 and Saos-2 human osteosarcoma cell lines of high and low metastatic potential. It was determined that MG-63 cells produce up to 5-fold more total sialic acid as compared with the Saos 2 cells. Neu5Ac accounts for ca 60% of the total sialic acids secreted by MG-63 cells, whereas Neu5Gc is the predominant sialic acid present on the MG-63 cell membrane. Saos 2 cells secrete considerable amounts of Neu5Ac to culture media. The obtained data indicate that the human osteosarcoma cells express both forms of Sia-containing glycoconjugates; the differences in the amounts of each of the two major Sia types and their distribution may be related to their differences in morphology and/or metastatic potentials.

Identification of the commonest cystic fibrosis transmembrane regulator gene DeltaF508 mutation: evaluation of PCR--single-strand conformational polymorphism and polyacrylamide gel electrophoresis.

In the present study we investigated whether single-strand conformational polymorphism (SSCP) and polyacrylamide gel electrophoresis (PAGE) could be used for the identification of the CFTR DeltaF508 gene mutation, which is commonest in the Greek population. Using DNA from patients carrying this mutation, the appropriate 98 bp region of the CFTR gene was amplified by PCR and the reaction products were analysed by non-radioactive SSCP-electrophoresis using silver staining for band visualization and non-denaturating PAGE to confirm the results. SSCP electrophoretic analysis has been optimized for several parameters in order to achieve the best resolution. Single-strand DNA fragments gave a reproducible pattern of bands, characteristic for the particular mutation. Comparison of the obtain patterns with control samples allowed the detection of the DeltaF508 mutation in the patients studied by SSCP assay and these results were confirmed by the independent method of PAGE. Although SSCP and PAGE can be used for detection of this mutation, PAGE resulted in more distinct patterns than SSCP. It is, therefore, proposed that PAGE can be reliably used for the detection and identification of such a mutation in patients provided that suitable controls are available. The applicability of PAGE to identification of the mutation in carriers, particularly useful for population screening, is also discussed.

Determination and distribution of N-acetyl- and N-glycolylneuraminic acids in culture media and cell-associated glycoconjugates from human malignant mesothelioma and adenocarcinoma cells.

Sialic acids containing glycoconjugates are very common in human neoplasias and their expression frequently correlates with malignant phenotype and the tumor grade. The majority of tumor markers containing sialic acids in man involve changes in the amount of total sialic acids and in the presence of the two main sialic acid types, Neu5Ac and Neu5Gc, and their derivatives. The aim of the present study was to examine whether malignant mesothelioma cell lines synthesize sialic acid containing glycoconjugates at both the extracellular and cell membrane levels and particularly whether the type and the content of Neu5Ac and Neu5Gc are of biological importance for mesothelioma cell differentiation and evaluation of its prognosis. The study was performed in three human malignant mesothelioma cell lines, two with a fibroblast like phenotype (STAV-FCS and Vester) and one of epithelial differentiation (STAV-AB), which developed from the pleural effusions of patients with malignant mesothelioma and in one human adenocarcinoma cell line (Wart). Neu5Ac and Neu5Gc were determined following a mild hydrolysis step and a sample clean-up procedure. The determination was performed by reversed-phase HPLC after the NeuAc and NeuGc had been converted to per-O-benzoylated derivatives. It was found that Neu5Gc is the major sialic acid in the culture media of all cell lines examined. Molar ratios of Neu5Ac to Neu5Gc showed that Neu5Gc is the predominant sialic acid in the culture medium of the fibroblast-like mesothelioma cells. Neu5Ac is almost undetectable in the cell membrane, whereas Neu5Gc is present in considerable amounts. The obtained results suggest that the type and the content of Neu5Ac and Neu5Gc in culture media are of biological importance for mesothelioma cell differentiation and may be of value in the evaluation of prognosis.

In vitro and in vivo antiresorptive effects of bisphosphonates in metastatic bone disease.

Bone metastases commonly occur in the course of malignant tumor disease. For many years, attempts have been made to identify factors for the management of cancer-induced skeletal complications. Nowadays, synthetic antiresorptive agents are considered to be indispensable for the treatment of cancer-related skeletal events, such as bone metastasis. The most common of these drugs are the bisphosphonates, which represent one of the most significant advances over the last 10 years in the field of supportive care and cancer. They are used for the treatment of cancer-induced hypercalcemia, for the prevention and treatment of postmenopausal osteoporosis, for patients with bone metastases secondary to breast cancer and multiple myeloma. A third-generation bisphosphonate, zolendronate, has been shown to minimize the destructive consequences of bone metastases and to exert a profound effect on tumor-induced osteolysis and tumor growth in bone. Zoledronate is already used for the treatment of hypercalcemia of malignancy, multiple myeloma-related osteolytic events and for patients with documented bone metastases from solid tumors in conjunction with standard antineoplastic therapy. The structure-function activity of the three generations of bisphosphonates developed to date, the in vitro models used for studying their effects on osteoclasts and osteoblasts, as well as the results of clinical trials obtained by the third generation bisphosphonate, zoledronic acid, are presented.

Determination and biological relevance of serum cross-linked type I collagen N-telopeptide and bone-specific alkaline phosphatase in breast metastatic cancer.

Bone metastasis is a frequent complication of cancer disease. The metastatic spread of cancer to bone is common to many different malignancies, particularly breast (ca. 73%), prostate (ca. 68%) and lung (ca. 36%) cancers. Metastases to bone cause increased bone resorption both from direct effects of the tumor itself and thought osteoclastic activation. The diagnosis and follow-up of bone metastatic cancer patients usually relies on skeletal X-ray and bone scintigraphy. However, the development of biochemical markers, used as indicators of bone metabolism, provides data useful in the clinical practice. The most important markers for bone remodeling process, bone formation and resorption, are bone-specific alkaline phosphatase (BAP) and N-telopeptide of type I collagen (NTx), respectively. In this report, we applied two solid-phase immunoassays used for the determination of BAP and NTx in serum of breast cancer (BC) post-menopausal women with bone metastasis and healthy individuals. BAP level in patients was found to be 45.72 +/- 12.92 U/l, while the normal range for healthy individuals was 14.2 - 42.7 U/l. The respective level of serum NTx was 19.20 +/- 8.87 nM bone collagen equivalents (BCE) for patients and 15.9 +/- 3.8 nM BCE for healthy women. Correlation of the obtained data showed elevated levels for both markers indicating high rate of bone degradation in breast metastatic cancer.

Capillary electrophoresis and enzyme solid phase assay for examining the purity of a synthetic heparin proteoglycan-like conjugate and identifying binding to basic fibroblast growth factor.

Interaction of basic fibroblast growth factor (bFGF) with heparin/heparan sulfate proteoglycans protects the growth factor against proteolytic degradation and is essential for its cellular activity. Although the structural requirements of heparin and heparan sulfate for the high-affinity binding to bFGF have been extensively examined, studies on intact heparin proteoglycans are limited. In this report, the purity and the binding ability of a heparin proteoglycan-like molecule-the heparin-bovine serum albumin (heparin-BSA) conjugate-was examined using capillary zone electrophoresis (CZE). Furthermore, the affinity of bFGF binding to the heparin-BSA conjugate was studied using an enzyme solid-phase assay. Chondroitin sulfate, dermatan sulfate, hyaluronan, heparan sulfate and variously sulfated disaccharides derived from heparin and heparan sulfate were also studied for their ability to compete with the binding of bFGF to heparin. Heparin-BSA conjugate was synthesized by reductive amination and, following precipitation with 1.5 vols of ethanol-sodium acetate, it was obtained free of contaminating heparin. Heparin-BSA-bFGF conjugate was obtained following incubation of heparin-BSA with bFGF for 2 h at 37 degrees C. Intact heparin, heparin-BSA and heparin-BSA-bFGF conjugates were completely resolved by CZE using 50 mM phosphate, pH 3.5, as operating buffer, reversed polarity (30 kV) and detection at 232 nm. Competitive solid phase assay showed that, among the glycosaminoglycans tested, heparin exhibits the highest affinity binding to bFGF (IC(50) = 6.4 nM). Heparan sulfate showed a lower affinity as compared with that of heparin, whereas all other glycosaminoglycans and heparin/heparan sulfate-derived disaccharides tested showed minute effects. The developed CZE method is rapid and accurate and can be easily used to identify bFGF-interacting heparin preparations of biopharmaceutical importance.