Enhanced cytotoxicity of рhotoexcited fullerene C60 and cisplatin combination against drug-resistant leukemic cells

Abstract

Aim: To evaluate the viability of leukemic cells sensitive (L1210S) and resistant (L1210R) to cisplatin, ROS production and free cytosolic Ca²⁺ concentration under treatment with cisplatin or its combination with photoexcited fullerene C₆₀. Methods: Cell viability was assessed by the MTT reduction assay. Light-emitting diode lamp (2.45 J/сm2) was used for photoexcitation of intracellular accumulated fullerene C₆₀. Free cytosolic calcium concentration ([Ca²⁺]i) and ROS production in cells were estimated with the use of fluorescent probes Indo-1 and 2′,7′-dichlorodihydrofluorescein diacetate (DCF-DA), respectively. Results: It is shown that viability of L1210R cells wasn’t changed under treatment with cisplatin in concentration range 0.1–10 μg/ml. 50% and 30% decrease of L1210S cells were observed after 24 h of incubation with cisplatin at concentrations 5 and 1 μg/ml, respectively. Intensification of extranuclear cytotoxic effects (ROS production and [Ca²⁺]iincrease) after treatment with 1 μg/ml was detected in L1210S, but not in L1210R cells. The most strongly pronounced increase of ROS production and [Ca²⁺]i in both L1210 cell lines was revealed in dynamics after combined treatment with cisplatin (1 μg/ml) and photoexcited fullerene C₆₀ (10⁻⁵ M) and was followed by decreased viability of not only L1210S, but of L1210R cells as well.. Conclusion: Combined treatment with photoexcited C₆₀ and cisplatin allowed to decrease effective concentration of cisplatin against parental L1210 cells and to increase sensibility of resistant cells to the drug. Key Words: cisplatin, L1210 cells, photoexcited fullerene C₆₀, ROS, cytosolic Ca²⁺, cell viability.