Table 2

Potency of XR9576 and GG918 in enhancing cytotoxicity of various drugs in MDR cell linesa

Cytotoxic drugModulator EC50b (nm) for potentiating cytotoxicity
EMT6/AR1.0H69/LX42780AD
XR9576GG918XR9576GG918XR9576GG918
Doxorubicin15 ± 220 ± 616 ± 526 ± 2120 ± 332 ± 18
Vincristine22c36c38 ± 334d30 ± 1049d
Paclitaxel12d35d22 ± 1663d34 ± 1051d
Colchicine17 ± 1114 ± 1018 ± 134 ± 5NDeND
Actinomycin D12 ± 928 ± 1334 ± 1634 ± 6NDND
Etoposide14d19d18 ± 1044 ± 22NDND
  • a Values are mean ± SD, where n ≥ 3 separate experiments except where indicated.

  • b Concentration of modulator required to reverse resistance to cytotoxic drug by 50%. For method see “Drug Potentiation Assay” section in “Material and Methods.”

  • c Value from a single experiment.

  • d Mean values from two experiments.

  • e ND, not determined.