BREAST CANCER RESISTANCE PROTEIN - Drug Transporters: Molecular Characterization and Role in Drug Disposition - page 327

FIGURE 12.1. Effect of amino acid 482 mutations on ABCG2 substrate specificity. HEK293
cells transfected with mutant (R482G, R482T) or wild-type (R482) ABCG2 were incubated
in phosphate-buffered saline with 2% BSA with phycoerythrin-labeled negative control anti-
body (solid line) or phycoerythrin-labeled anti-ABCG2 antibody (clone 5D3, dashed line) for
30 minutes, washed, and subsequently analyzed by flow cytometry to generate the top row of
histograms. Cells were also incubated in medium containing 20 M mitoxantrone (second row
of histograms), 250 nM BODIPY-prazosin (third row), 5 g/mL daunorubicin (fourth row),
0.5 g/mL rhodamine 123 (fifth row), or 10 M Hoechst 33342 (bottom row) in the presence
(dashed line) or absence (solid line) of 10 M FTC.
a as a specific ABCG2 substrate. 84 Subsequently, the porphyrins chlorin e6 and py-
ropheophorbide a methyl ester were also found to be ABCG2-specific substrates. 85
Figure 12.1 demonstrates the effect of amino acid 482 on substrate specificity.
HEK293 cells expressing mutant R482G or R482T ABCG2 (left and right columns,
respectively) are able to transport mitoxantrone, BODIPY-prazosin, daunorubicin,
rhodamine 123, and Hoechst 33342, while cells expressing wild-type ABCG2 (cen-
ter column) transport only mitoxantrone, BODIPY-prazosin, and Hoechst 33342. All