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Background: The effects of the bisphosphonate derivative zoledronic acid (ZA) on the > circulating levels of matrix metalloproteinase-2 (MMP-2), matrix metallo-proteinases-9 > (MMP-9), cathepsin B (Cath B) and urokinase-type plasminogen activator (uPA) in > patients with bone metastasis (BMTS) and the possible correlation with the symptomatic > response induced by this drug in these patients were evaluated. Patients and Methods: > Proteinase levels were determined by enzyme-linked immunosorbent assay (ELISA) in the > plasma of 30 patients with painful bone metastases from breast or prostate cancer > undergoing multiple treatment with ZA (4 mg i.v., every 4 weeks). Healthy subjects > (HS) of both genders (12 female and 30 male) served as the control group. The > symptomatic response to ZA was assessed by the visual analog scale score (VAS). > Results: The median MMP-2 and MMP-9 pretreatment levels were more elevated in BMTS as > compared to HS (p¡Ü0.0001). Conversely, uPA levels were lower in BMTS p=0.0033; no > significant difference was observed for Cath B. ZA administration was associated with > a symptomatic response (VAS score¡Ü4) in 25/30 patients (83.3%) (p phenomenon paralleled a decrease of Cath B and MMP-2 plasma concentrations from > baseline values on week 12 (p=0.05). A similar trend, although not statistically > significant, was also noted for MMP-9 and uPA. However, no direct relationship was > observed between the analgesic effect induced by ZA and changes in the circulating > levels of these enzymes. Conclusion: These data show that ZA administration may > provide relief from bone pain in patients with diffuse skeletal metastases and confirm > a possible implication of cysteine proteinases and matrix metalloproteinases in bone > metastasis formation, but not in the pathogenesis of metastatic bone pain.

This study was directed to assess the clinical impact of the circulating cathepsin L, cystatin C, activin A, and follistatin in breast cancer patients. The serum concentrations of these molecules were determined by immunoenzymatic assays, and their association with some clinico-pathological parameters of breast cancer progression was evaluated. Our results identified cystatin C and activin A as predictive markers for the presence of breast cancer and bone metastasis, respectively. Therefore, these proteins may have a clinical role as circulating biomarkers in the diagnosis and therapeutic monitoring of breast cancer patients.

Cathepsin L is a lysosomal cysteine proteinase primarily devoted to the metabolic turnover of intracellular proteins. However, accumulating evidence suggests that this endopeptidase might also be implicated in the regulation of other important biological functions, including bone resorption in normal and pathological conditions. These findings support the concept that cathepsin L, in concert with other proteolytic enzymes involved in bone remodeling processes, could contribute to facilitate bone metastasis formation. In support of this hypothesis, recent studies indicate that cathepsin L can foster this process by triggering multiple mechanisms which, in part, differ from those of the major cysteine proteinase of osteoclasts, namely cathepsin K. Therefore, cathepsin L can be regarded as an additional target in the treatment of patients with metastatic bone disease. This review discusses the clinical and therapeutic implications related to these findings.

The clinical significance of circulating fol- listatin (FLST), an inhibitor of the multifunctional cytokine activin A (Act A), was investigated in patients with prostate cancer (PCa). The serum concentrations of this molecule were determined by an enzyme-linked immunosorbent assay (ELISA) in PCa patients with (M?) or without (M0) bone metastases, in patients with benign prostate hyperplasia (BPH) and in healthy sub- jects (HS). The effectiveness of FLST in detecting PCa patients with skeletal metastases was determined by the receiver operating characteristic (ROC) curve analysis. Serum FLST was significantly higher in PCa patients than in BPH patients (P = 0.001) or HS (P = 0.011). Conversely, in BPH patients, FLST levels resulted lower than in HS (P = 0.025). In cancer patients the serum concentrations of FLST significantly correlated with the presence of bone metastases (P = 0.0005) or increased PSA levels (P = 0.04). Interestingly, significant differ- ences in the ratio between FLST and Act A serum concentrations (FLST/Act A) were observed between HS and BPH patients (P = 0.001) or PCa patients (P = 0.0005). Finally, ROC curve analysis, highlighted a sound diagnostic performance of FLST in detecting patients (P = 0.0001). However, the diagnostic effectiveness of FLST did not result significantly supe- rior to that of Act A or PSA. These findings suggest that FLST may be regarded as a potential, molecular target in the treatment of metastatic bone disease while its clinical role as soluble marker in the clinical management of PCa patients with bone metastases needs to be better defined.

The clinical significance of serum cathepsin K and cystatin C was assessed in patients with breast cancer (BCa) or prostate cancer (PCa) with confined disease (M0) or bone metastasis (BM). Cathepsin K and cystatin C circulating levels were determined by ELISAs in 63 cancer patients, in 35 patients with nonmalignant diseases and in 42 healthy blood donors (control group). In BCa patients, cathepsin K serum levels were significantly lower than in sex matched control group (HS; p = 0.0008) or in patients with primary osteoporosis (OP; p = 0.0009). On the contrary, cystatin C levels were significantly higher in BCa patients than in HS ( p = 0.0001) or OP ( p = 0.017). In PCa patients, cathepsin K concentrations did not significantly differ from those measured in sex matched HS or in patients with benign prostatic hyperplasia (BPH). Conversely, cystatin C was more elevated in cancer patients than in controls ( p = 0.0001) or BPH patients ( p = 0.0078). Furthermore, in PCa patients, a positive correlation was observed between cystatin C and cathepsin K ( r S = 0.34; p = 0.047). No further relationship was highlighted between these molecules and the clinicobiological parameters of BCa or PCa progression including the number of bone lesions. Moreover, ROC curve analysis showed a poor diagnostic performance of cathepsin K and cystatin C in the detection of BM patients. Interestingly, the administration of zoledronic acid (ZA), a bisphosphonate derivative endowed with a potent antiosteoclastic activity, induced in BM patients a marked increase of cathepsin K and cystatin C serum levels compared to baseline values. However, this phenomenon was statistically significant only in the PCa group. In conclusion Cystatin C and cathepsin K may be regarded as possible markers to monitor the therapeutic response to bisphosphonate treatments. Nevertheless, their clinical value as specific gauges of skeletal metastasis remains questionable.

Recent studies have highlighted that Activin A, a member of the transforming growth factor-beta (TGF-beta) superfamily, may be involved in the regulation of osteoblastic activity and in osteoclast differentiation. Therefore, we have investigated the clinical significance of its circulating levels in patients with bone metastasis. Activin A serum concentrations were determined, by a commercially available enzyme-linked immunosorbent assay kit, in 72 patients with breast cancer (BC) or prostatic cancer (PC) with (BM+) or without (BM-) bone metastases, in 15 female patients with age-related osteoporosis (OP), in 20 patients with benign prostatic hypertrophy (BPH) and in 48 registered healthy blood donors (HS) of both sex (25 female and 23 male). Activin A serum concentrations were significantly increased in BC or PC patients as compared to OP (P < 0.0001) or BPH (P = 0.045), respectively, or to sex matched HS (P < 0.0001). Additionally, these levels resulted more elevated in PC patients as compared to BC patients (P = 0.032). Interestingly, Activin A was significantly higher in BM+ patients than in BM- patients (BC, P = 0.047; PC, P = 0.016). In BC patients, a significant correlation was observed only between Activin A and number of bone metastases (P = 0.0065) while, in PC patients, Activin A levels were strongly correlated with the Gleason score (P = 0.011) or PSA levels (P = 0.0001) and, to a lessen extent, with the number of bone metastases (P = 0.056). Receiver operating characteristic curve (ROC) analysis showed a fair diagnostic accuracy of Activin A to discriminate between BM+ and BM- patients (BC: AUC = 0.71 +/- 0.09, P = 0.03; PC: AUC = 0.73 +/- 0.081, P = 0.005). These findings indicate that Activin A may be implicated in the pathogenesis of bone metastasis. Therefore, this cytokine may be considered a novel potential target for a more selective therapeutic approach in the treatment of skeletal metastasis and may be also useful as additional biochemical marker of metastatic bone disease.