P43: Endogenous inhibitors of cysteine proteases cystatin C and cystatin SN in biological fluids of patients with intraocular melanoma as possible biomarkers and therapy targets

Abstract

Cystatins are natural endogenous inhibitors of cysteine proteases universally involved into development of different tumors. Tumor growth and metastazing include increased consumption of these inhibitors, followed by decreased level of cystatins and dysregulation of proteases/protease inhibitors system. However, the biological role of individual cystatins is still not clear. The most known cystatin C was shown to relate to some types of tumor development. Cystatins include a group of intracellular cystatins (belonging to type 1) and extracellular cystatins (type 2), among them cystatins C, D, E/M, F, G, S, SN and SA, which functions were not studied enough. It was suggested that cystatin SN was responsible in regulation of tumor growth locally. To investigate cystatin C and cystatin SN concentrations in biological fluids of patients with intraocular melanoma as tumor biomarkers and possible therapy targets. The patients with melanoma chorioidea (57 patients; among them woman 36, men 21; aged from 28 to 80, of middle age of 56.6 ± 2.4 years) were under investigation. In all cases the pathological process involved one eye. The control group consisted of 37 healthy persons (volunteers), medical personnel in clinic and students, aged from 20 to 49 years; the middle age 31 ± 4.1 years); 7 patients with age-related cataract aged from 57 to 80 (middle age 71 ± 2.6 years; man 3, woman 4). The biological fluids studied: tears, intraocular fluid (obtained during operation) and blood serum. In all cases investigation was made according to informed agreement of patients and control group members. Cystatins concentration was measured by ELISA kits: for Cystatin C (BioVendor, Chechia) and for cystatin SN with help of Human Cystatin SN (CST1) Elisa Kit Cusabio, China. Statistical analysis was made by non-parametric statistic test of Kruskal–Wallis, for correlations – Spearman test. The difference between groups studied was considered significant p < 0.05. Increased serum level of cystatin C was revealed in patients with melanoma chorioides (1023.5 ± 78.9 ng/ml, p = 0.019) compared with the control (809.9 ± 146.8 ng/ml). In tears of patients with melanoma chorioidea, cystatin C concentration (441.7 ± 14.5 ng/ml) had a tendency to increase as compared to the data obtained in tears of the control group (287.5 ± 20.01 ng/ml) as well as the cystatin C level of intraocular fluid of these patients vs the control group (p < 0.1). Cystatin SN concentration in serum of patients with melanoma chorioidea (1.45 ± 0.30 ng/ml) was lower vs the control group (3.12 ± 0.32 ng/ml, p = 0.0038), as well as Cystatin SN level in intraocular fluid (1.43 ± 0.10 ng/ml) vs the control (2.60 ± 0.60 ng/ml, p < 0.05). There was no difference in cystatin SN concentration in tears of patients and control group. In serum of control (healthy) group, cystatin C concentration is significantly higher than cystatin SN level in serum, tears and intraocular fluid. The reverse correlation was revealed between the level of these inhibitors in serum, that is suggested their possible interaction. In melanoma patients the reciprocal changes in cystatin C and cystatin SN were shown: increased cystatin C and decreased cystatin SN level in all biological fluids studied. On the basis of cystatins distribution in biological fluids of patients one can suggest their involvement in pathological process as system reaction of organism on tumor development.