Figure 2.

Cross-resistance of DX-R bone sarcoma cell lines to other chemotherapeutic drugs. (A–D) Cell viability (WST-1 assay) measured after the treatment of parental and DX-R bone sarcoma cell lines with increasing concentrations of cisplatin (CIS) (A), methotrexate (MTX) (B), mithramycin (MTM) (C) and EC-8042 (D) for 72 h. IC₅₀ values (µM) for each condition are shown. Error bars represent the SD. Asterisks indicate statistically significant differences between IC₅₀ concentrations calculated from three independent experiments (ns: p > 0.05; *: p < 0.05; **: p < 0.01; ***: p < 0.001; ****: p < 0.0001; two-sided Student’s t test). (E) Resistance index (RI) for the different drugs calculated as the ratio of the IC₅₀ values of the resistant cells and the corresponding parental cells. The dotted line represents a resistance index of 1, which indicates equal sensitivity in DX-R and parental cells.