Application of C60 Fullerene-Doxorubicin Complex for Tumor Cell Treatment In Vitro and In Vivo.

Development of nanocarriers for effective drug delivery to molecular targets in tumor cells is a real problem in modern pharmaceutical chemistry. In the present work we used pristine C60 fullerene as a platform for delivery of anticancer drug doxorubicin (Dox) to its biological targets. The formation of a complex of C60 fullerene with Dox (C60 + Dox) is described and physico-chemical characteristics of such complex are presented. It was found that Dox conjugation with C60 fullerene leads to 1.5-2-fold increase in Dox toxicity towards various human tumor cell lines, compared with such effect when the drug is used alone. Cytotoxic activity of C60 + Dox complex is accompanied by an increased level of cell produced hydrogen peroxide at early time point (3 h) after its addition to cultured cells. At the same time, cellular production of superoxide radicals does not change in comparison with the effect of Dox alone. Cytomorphological studies have demonstrated that C60 + Dox complexes kill tumor cells by apoptosis induction. The results of in vivo experiments using Lewis lung carcinoma in mice confirmed the enhancement of the Dox toxicity towards tumor cells after drug complexation with C60 fullerene. The effect of such complex towards tumor-bearing mice was even more pronounced than that in the in vitro experiment with targeting human tumor cells. The tumor volume decreased by 2.5 times compared with the control, and an average life span of treated animals increased by 63% compared with control. The obtained results suggest a great perspective of application of C60 + Dox complexes for chemotherapy of malignant tumors.

THE ROLE OF REACTIVE OXYGEN SPECIES IN TUMOR CELLS APOPTOSIS INDUCED BY LANDOMYCIN A.

Landomycin A (LA) is a new antitumor antibiotic of angucycline group, possessing high antitumor activity against cancer cells of different origin, which induces early apoptosis in target cells. It was shown that under LA action the level of reactive oxygen species (ROS) in human T-leukemia cells had increased 5.6 times in comparison to control already at the 1st hour after the addition of studied antibiotic to the culture medium. At the 6th hour after incubation of cells with LA the nucleosomal DNA cleavage, chromatin condensation and nucleus fragmentation were observed, indicating apoptotic cell death. Catalase (scavenger of hydrogen peroxide), mannitol (scavenger of hydroxyl radicals) and superoxide dismutase (scavenger of superoxide radicals) reduced the level of ROS production under LA, suggesting the generation of H2O2, OH* and O2- radicals, respectively. It was revealed that catalase and mannitol effectively inhibited LA-mediated tumor cell death, increasing 2.5 times the percentage of alive cells in comparison to LA. However, superoxide dismutase had no significant inhibitory effect on cytotoxic activity of LA, indicating the minor role of superoxide anions in the implementation of antitumor activity of this antibiotic. Combination of catalase, mannitol and superoxide dismutase with LA increased 4-fold the percentage of alive cells in comparison to the action of LA. Dynamics of ROS formation confirms that the increase of ROS is a very rapid process, but at the same time it is not a direct consequence of apoptosis triggering, mediated by mitochondria.