B-109 METALLOTHIONEIN AND ITS LEVELS DURING TREATMENT WITH PLATINUM-BASED CYTOSTATICS

Abstract

Background Metallothionein (MT) is a low-molecular-weight intracellular protein whose primary function is heavy metal homeostasis. Several studies have already demonstrated a correlation between increasing MT concentrations in body fluids and cancer progression. The increased metabolic rate of cancer leads to higher consumption of metal ions. In cases where metal-based drugs are used for treatment, these MTs bind the drugs, subsequently leading to a decrease in therapeutic concentration. Methods Samples from patients following the administration of platinum cytostatics were analyzed in the experimental group. Patient anonymity was maintained at all times, and the entire study was approved by the Ethics Committee of Motol University Hospital. The observed group of evaluated data was from the years 2025–2026. A total of 20 probands were analyzed: 58 % female and 42 % male. The age range was from 16 to 81 years, with a mean age of 59 years (median 61 years). The frequency histogram clearly shows a skewness toward higher age categories. Electrochemical determination of MT was performed using the Brdicka reaction. Plasma was obtained from these probands and stored at -20 °C until processing. Samples were prepared according to our proposed procedure by thermal denaturation (99 °C, 20 min, 450 rpm). MT was determined via electrochemistry (differential pulse voltammetry, initial potential -0.7 V, final potential -1.85 V, scan rate 25 mV/s in Brdicka solution, 4 °C). For platinum analysis, GT-AAS determination was used (Pt 265.9 nm, lamp current 10 mA, argon flow 0.3 l/min, atomization 2850 °C, 1 s). Each studied sample was analyzed in 5 replicates. The obtained data were stored and processed in the laboratory information system QUINSLAB. Results During the optimization steps, the dependence on platinum concentration in plasma was studied. From the obtained data, a linear dependence of platinum concentration on absorbance was found (r = 0.9949). Analytical characteristics were calculated from all available data: LOD 40 ng/ml, LOQ 120 ng/ml, RSD up to 15%. In probands, concentrations upon drug administration were found between 2,000 – 1,500 ng/ml, and by 168 h, plasma concentrations were below the LOQ. MT levels were studied in these probands. The electrochemical study yielded MT voltammetric curves with typical signals (Cat1, Cat2, and Cat3). For each proband, the average curve was mathematically calculated and the area under the curve (AUC) was determined. Control sera from healthy probands (n = 40) were used to compare normal and abnormal MT levels, with a determined mean MT amount of 1.28±0.05 µg/l. In the group of probands, the mean MT amount at the time of cytostatic treatment administration was 18 ± 5.5 µg/l. During subsequent monitoring over time, MT levels gradually increased (by 20 – 80%) relative to the time since drug administration. Conclusion A pilot study was conducted focusing on monitoring the dynamics of platinum cytostatic levels and the electrochemical determination of metallothionein levels. It was demonstrated that MT levels increase slightly during monitoring. The work was carried out with the support of the League Against Cancer Prague and CA COST Action CA22125.