In our MTT assays, we observed that the addition of elacridar in concentrations of 0.1 μM and 1 μM results in the re-sensitization of PAC-resistant cell lines to PAC and DOX, a substrate of P-gp, but caused no change in resistance to CIS, which is not a P-gp substrate [53]. This evidence concerns the gene PGP and in situ carcinoma.