Serum interleukin-6 in patients with metastatic bone disease: correlation with cystatin C.

The clinical significance of serum interleukin-6 (IL-6) and its correlation with cystatin C (Cyst C), an endogenous inhibitor of cysteine proteinase cathepsin K, was investigated by immunoassays in patients with bone metastasis from breast cancer (BCa) or prostate cancer (PCa). Additional studies were also performed in these patients to assess the effects of zoledronic acid (ZA) administration on the circulating levels of these molecules. Mean IL-6 and Cyst C serum concentrations were signifi- cantly increased in BCa patients and in patients with primary osteoporosis (PU) compared to healthy subjects (HS). However, Cyst C, but not IL-6, resulted significantly more elevated in BCa patients t…