Ilkiv M. Cytotoxic effect of thiazole derivative in complex with PEG-containing polymeric nanocarriers

This work is devoted to the study of the cytotoxic mechanism of the antitumor thiazole derivative N-(5-benzyl-1,3-thiazol-2-yl)-3,5-dimethyl-1-benzofuran-2-carboxamide (BF1) in a complex with PEG-containing polymeric nanocarriers (PEG-PN), that were used to improve the solubility of the investigated compound, towards to cancer cells in vitro and in vivo. Cancer is one of the most common causes of death worldwide characterized by uncontrolled cell proliferation and the absence of programmed cell death, which with the exception of hematological types of cancer, generates an abnormal cell mass or tumor. Unspecific damage of normal cells, high toxicity of chemotherapeutic compounds, their poor solubility in body fluids and insufficient selectivity towad tumor cells, as well as the development of multiple drug resistance confirm the need to find new effectively targeted cancer treatment and to improve existing therapeutic drugs used in clinical practice. The nanocarrier-based polymeric drug delivery systems (NDDSs) can deliver higher doses of chemotherapeutic agents to tumor due to enhanced permeability and retention effects, while reducing side effects of drugs, improve their solubility and ensure longer circulation of drug in the body. It was established that the thiazole derivative BF1 in the complex with PEG-PN were the more toxic to the human hepatocarcinoma HepG2 and the rat glioma C6 cell lines compared to the unconjugated thiazole derivative or Doxorubicin. However, it was found that unconjugated BF1, its complexes with PEG-PN and free PEG-PN did not show cytotoxic activity against non-tumor cells of HEK293 kidney embryos and NIH3T3 fibroblast cells whereas Doxorubicin exhibited a significant level of cytotoxicity. It was first demonstrated a significant increase in the content of reactive Oxygen species (ROS) in NK/Ly lymphoma cells under the influence of the thiazole derivative BF1 and its complexes with PEG-PN. The accumulation of ROS in tumor cells may be the main trigger of the cytotoxic mechanisms of the thiazole derivative BF1 and leads to the tumor cells' death. The effect of a thiazole derivative BF1 conjugated with PEG-PN on the lipid peroxidation (LPO) processes and the activity of antioxidant defense system (AOS) enzymes in lymphoma cells as markers of the cell damage caused by oxidative stress through the accumulation of ROS was investigated. It was established that both unconjugated BF1 and BF1+PEG-PN complexes increased the content of primary LPO products (lipid hydroperoxides), but only the complexes caused an increase in the content of TBARS-products (one of the secondary products of LPO) in lymphoma cells. The activity of superoxide dismutase (SOD), significantly increased under the influence of unconjugated BF1 and its complexes with PEG-PN, while the activity of catalase (CAT) and glutathione peroxidase (GPx) was reduced under the action of the studied compounds. This data indicates the accumulation of H2O2 in lymphoma cells. It was established that although none of the investigated compounds affected the rate of the glucose-fuelled basal respiration, Th4 and Th6 complexes significantly increased the maximum rate of cellular respiration when protonophore FCCP was added after glucose. It was established that only BF1 conjugated with PEG-PN were significantly reduced the mitochondrial membrane potential in murine lymphoma cells. It was first demonstrated that BF1 in a complex with PEG-PN causes significant ultrastructure changes in lymphoma cells, such as fragmentation, disintegration or/and disappearance of the cell nucleus, damage and destruction of the plasma membrane, an increase in the number of mitochondria and lysosomes. It was reported that neither BF1, PEG-PN nor their complexes changed the content of lipid peroxidation products, superoxide radicals or the activity of AOS enzymes in hepatocytes from mice with NK/Ly. This data characterizes BF1 in complex with PEG-PN as an effective antitumor DDS with minimal side effects on non-tumor cells. The antitumor effect of the thiazole derivative BF1 and its complex with PEG-PN Th1 was investigated on the experimental model of murine lymphoma NK/Ly in vivo. It was first established that the Th2 complex prolonged the survival of tumor-bearing mice compared to mice with NK/Ly lymphoma that did not receive treatment. In addition, unconjugated BF1 and Th2 complex did not cause significant cytotoxic effects on the blood cells of tumor-bearing mice compared to Doxorubicin. Therefore, the study of the effect of the thiazole derivative BF1 in a complex with PEG-PN on tumor and normal cells show that investigated compounds are promising chemotherapeutic DDS with effective antitumor effect with an acceptable safety profile and minimal side effects.