Figure 4.

Sensitization of transfected and cancer cells overexpressing ABCG2 to SN-38. Cell viability was determined by MTT assay. (A) Cell viability of HEK293-ABCG2 and HEK293 (wild-type) control cells upon 72 h treatment with SN-38 at increasing concentrations, as indicated, and HEK293-ABCG2 cells upon co-treatment with SN-38 and inhibitors at either IC₅₀ values or 5 µM. (B) Cell viability of H460MX20 and H460 control cells upon 72 h treatment with SN-38 at 10 nM, as indicated, and H460MX20 cells upon co-treatment with SN-38 and inhibitors at either IC₅₀ values or 5 µM. The data are the mean ± SEM of three independent experiments performed in triplicate and compared using the Student's t test (2-sided) for independent samples. *p < 0.05 were considered significant for all tests.