Table 1

Effect of siRNA on sensitivity of MDR cells to chemotherapeutic drugs

Cells were plated in 60-mm cell culture dishes (200 cells/dish) and exposed to various concentrations of cytotoxic drugs for 12 days. At the end of incubation, cells were stained with 1% methylene blue and the colonies counted. IC50 is the concentration that produced 50% inhibition of colony formation compared to vehicle-treated controls. Results represent the mean of two or mean ± standard error of three separate experiments.

IC50
Vinblastine (nm)Doxorubicin (μm)Paclitaxel (nm)Hydroxyurea (μm)
MCF-70.0850.0020.09157
MCF-7/AdrRMock293 ± 280.60 ± 0.061450 ± 278165 ± 7.6
siRNA1.26 ± 0.40a (232)0.05 ± 0.01a (12)15.3 ± 1.1a (95)172 ± 3.0 (1)
MCF-7/BC-19Mock6.90 ± 0.800.03 ± 0.0121 ± 4.3
siRNA0.14 ± 0.05a (49)0.01 ± 0.00b (3)1.18 ± 0.42b (18)
A27800.160.011.15
A2780Dx5Mock65.3 ± 10.80.61 ± 0.142233 ± 338
siRNA15.0 ± 2.0b (4)0.12 ± 0.03b (5)247 ± 37a (9)
  • a P ≤ 0.01 versus mock treatment. Numbers in the parentheses represent fold-reversal.

  • b P < 0.05 versus mock treatment.