Effect of MK571 on the chemosensitivity of three human stomach cancer cell lines to etoposide
Three human stomach cancer cell lines (St-4, MKN45, and MKN1) were exposed for 72 hours to various concentrations of etoposide with or without 50 μM MK571, a multidrug resistance–associated protein (MRP) inhibitor. Control was etoposide exposure without MK571. The IC50 value was determined by plotting the percentage cell viability versus the concentration of etoposide. Each value of MRP1 expression represents the mean ± S.E.M. (n = 4).
| Cell Line | IC50 | Control/MK571 Ratio of IC50 | MRP1 Expression | |
|---|---|---|---|---|
| Control | 50 μM MK571 | |||
| μM | fmol/μg protein of membrane fraction | |||
| St-4 | 63.2 | 6.15 | 10.3 | 2.45 ± 0.29 |
| MKN45 | 34.3 | 2.97 | 11.5 | 1.36 ± 0.13 |
| MKN1 | 12.6 | 2.23 | 4.24 | 0.588 ± 0.072 |