Bone sialoprotein in serum of patients with malignant bone diseases

Bone sialoprotein (BS), a protein synthesized by osteoblasts and osteoclasts and highly modified posttranslationally, constitutes a predominant fraction of the noncollagenous organic matrix in human bone. We report an assessment of serum concentrations of BS in patients with malignant bone diseases. In patients with bone metastases (according to scintigraphic criteria), serum BS concentrations were greater than in patients without bone metastases (P <0.05). However, ROC curve analysis revealed that serum BS was inferior to serum bone alkaline phosphatase in discriminating between patients with and without bone metastases. Patients with bone metastases showed a weak correlation between serum BS concentrations and bone formation markers. Only “traditional” markers of bone formation—but not BS—were correlated with urinary deoxypyridinoline (P <0.01). Liver and kidney dysfunction had no significant influence on BS values in these patients (as assessed by analysis of variance; P >0.05). In multiple myeloma patients treated with corticosteroids and bisphosphonates, BS concentrations were lower than in tumor patients without bone metastases (P <0.001), and the correlation between BS concentrations and the number of bisphosphonate courses applied was significant (r = −0.578; P <0.05). In postmenopausal women, serum BS concentrations averaged 142% greater than in premenopausal women. Further studies should be done, therefore, to elucidate whether serum BS is able to predict high bone turnover after menopause.