Serum cathepsin K and cystatin C concentration in patients with advanced non-small-cell lung cancer during chemotherapy

A pathogenic implication of cathepsin K (Cath K) and its inhibitor - cystatin C (Cyst C) occur to be of growing importance in the mechanisms of tumor invasiveness in lung cancer. This study was conducted to investigate the prognostic role and the effects of chemotherapy on serum Cath K and Cyst C (ELISA) in patients with advanced stage non-small cell lung cancer (NSCLC). The study entered 40 patients (32 men) and 15 healthy volunteers (control group). Peripheral blood samples were taken before and after four cycles of chemotherapy. The mean serum Cyst C levels were significantly higher in patients with advanced NSCLC than in controls (p=0.003). The levels of Cath K in serum of NSCLC are comparable to those in controls. No correlation was found between Cath K and Cyst C concentrations and the histological type and staging of lung cancer. Patients with T4-stage had a lower level of Cyst C, than those with T2 (p=0.033). No correlation was found between the concentrations of Cath K, Cyst C and the effect of chemotherapy. However, Cyst C level positively correlated with serum creatinine concentration (R=0.535; p=0.005) in patients who responded to chemotherapy and with patient's age (R=0.456; p=0.018) in whole group. When the cut-off values of serum Cath K and Cyst C (23.35 pmol/l, 1.29 mg/l, respectively) were used, the prognoses of high and low groups were not different. Concluding, patients with lung cancer have a higher serum concentration of Cyst C compared to healthy people. In our opinion, determination of Cath K and Cyst C concentrations has no clinical significance in the prognosis of the survival time in lung cancer.