Abstract. The present study aimed to determine the levels of cathepsin B (cath B), cathepsin L (cath L), cystatin C, urokinase plasminogen activator (u-PA) and urokinase plasminogen activator receptor (u-PAR) in the sera of patients with lung cancer compared to healthy controls using ELISA. Concomitantly, the relationship between the components and clinicopathological prognosis was analyzed. The study included 30 healthy volunteers and 105 lung cancer patients. Blood samples were collected and cath B, cath L, cystatin C, u-PA and u-PAR measurements were made using ELISA. Results showed that the levels of cath B, cath L, cystatin C, u-PA and u-PAR were significantly higher in the patient group compared to the healthy controls. The significance was marked for cath B and mild for u-PAR in correlation with lymph node metastasis. There was no significance for other parameters. Notably, patients with a combination of high cystatin C and high cath B levels had significantly lower survival probability as compared to those with cystatin C + /cath B -or with cystatin C -/cath B -. Similarly, patients with a combination of high u-PA and u-PAR experienced significantly shorter survival. Furthermore, the univariate analysis revealed that cath B, u-PAR, lymph node metastases, stage and grade were related to survival. However, findings of the multivariate Cox analysis indicated that the sera levels of cath B, u-PAR and lymph node metastases may serve as independent prognostic variables in patients with lung cancer.
IntroductionCathepsins are members of the lysosomal cysteine proteases family and are usually located inside a lysosome. Numerous studies showed a correlation of increased proteolytic activity of cysteine cathepsins with neoplastic transformation, tumor invasion and metastasis through the destruction of extracellular matrix components and basement membranes in tumor spread. Cathepsin B (cath B) is able to activate pro-urokinasetype plasminogen activator and enhance subsequent plasmin generation. Increased levels of cath B and L were observed in tissues of primary and metastatic tumors in a number of cancer types (1-3). The serum level of cath B may serve as a prognostic factor for patients with advanced melanoma. By contrast, the serum level of cath L was not statistically different in the control, non-metastatic and metastatic patient groups (3). Moreover, using immunohistochemical analysis, the overexpression of cath B and L was shown to correlate with more aggressive tumor behavior, early relapse and shorter survival (2). However, in lung cancer tissue, cath L did not reveal any association with prognosis (4).Cystatin C, an accurate marker of glomerular filtration rate and endogenous cysteine protease inhibitor, has been found in a variety of human tissues, but is mainly found in extracellular body fluid and serum. Increased levels of cystatin C in tumor tissues were shown to correlate with a favourable prognosis of cancer patients (5), whereas higher levels of cystatin C in body fluids have been associated with ...