Fig. 1.

Induction of resistance to IFO. In A the MTT assay demonstrated that 26.77 μM of IFO inhibited approximately 50% of osteosarcoma U2OS cells. B indicates that after the resistance induction protocol, the IFO value necessary to inhibit 50% of the cells became 37.13 μM. In addition, the U2OS R+ group showed a significant difference in the rate of metabolic activity in relation to the U2OS S cells with *p < 0.05 and p < 0.0001 (****) at different drug concentrations. C- Significant difference between U2OS R+ and U2OS R-cells at all drug concentrations with p < 0.0001 (****). D – U2OS R- and U2OS S cells with significant differences in concentrations of 10 μM, 20 μM, and 30 μM (****); however, there was no difference in the higher concentrations of IFO, indicating the sensitivity to treatment in the two cell groups.