Table 2.
Relative drug resistance of HEK-293 cells expressing wild-type and mutant BCRP
| MX |
SN-38 |
Dox |
Rho-123 |
|||||
|---|---|---|---|---|---|---|---|---|
| IC50, nM | RR (ratio) | IC50, nM | RR (ratio) | IC50, nM | RR | IC50, nM | RR | |
| pcDNA control | 8.5 ± 0.6 | 2.3 ± 0.28 | 125.6 ± 32.0 | 1,881 ± 168.2 | ||||
| Wild-type BCRP | 64.8 ± 3.9 | 7.6 (1.0) | 89.7 ± 5.4 | 39.0 (1.0) | 168.0 ± 24.5 | 1.3 | 3,341 ± 267.4 | 1.8 |
| N387A | 54.8 ± 6.3 | 6.4 (0.2)* | 44.8 ± 6.3 | 19.5 (0.1)* | 120.4 ± 31.6 | 1.0 | 3,279 ± 436.8 | 1.7 |
| Q398A | 49.9 ± 4.6 | 5.9 (0.2)* | 71.6 ± 4.3 | 31.1 (0.2)* | 173.4 ± 36.5 | 1.4 | 2,534 ± 376.5 | 1.3 |
| T402A | 43.3 ± 7.6 | 5.1 (0.2)* | 63.0 ± 5.4 | 27.4 (0.2)* | 129.4 ± 31.4 | 1.0 | 2,140 ± 210.7 | 1.1 |
| N629A | 76.5 ± 12.3 | 9.0 (2.8)* | 108.3 ± 12.3 | 47.1 (2.9)* | 164.6 ± 14.8 | 1.3 | 3,051 ± 286.5 | 1.6 |
| T642A | 50.0 ± 9.5 | 5.9 (0.6) | 49.9 ± 9.9 | 21.7 (0.4)* | 156.1 ± 20.0 | 1.2 | 1,393 ± 221.6 | 0.7 |
| Y645F | 42.8 ± 6.8 | 5.0 (0.5)* | 44.8 ± 6.3 | 19.5 (0.3)* | 132.4 ± 18.4 | 1.1 | 1,846 ± 206.2 | 1.0 |
The IC50 values shown are means ± SD of 3 independent experiments. RR is the relative resistance factor. The ratios represent the relative levels of resistance of the mutants compared with wild-type BCRP after normalization for differences in BCRP protein levels. Relative BCRP protein levels of whole cell lysates shown in Fig. 2 were used for the calculations. Since wild-type and mutant BCRP did not confer resistance to doxorubicin hydrochloride (Dox) and rhodamine 123 (Rho-123); ratios for the two compounds were not calculated. MX, mitoxantrone hydrochloride. Differences between the IC50 values of wild-type and mutant BCRP after normalization to the BCRP protein levels are statistically significant:
P< 0.05 by the Student's t-test.