Figure 4.

Characterization of DCV-SP cells using pharmacological inhibition and antibody-based costaining of SP-conferring drug transporters. A2780V cells containing ABCB1-positive SP (a) and parental A2780 cells harbouring an ABCG2-positive SP (b) were stained with 10 μM DCV (10⁶ cells/mL) and subjected to a set of control experiments. Specifically, the samples were inhibited using 50 μM verapamil (blocking several drug transporters) or 20 μM fumitremorgin C (blocking ABCG2 specifically) or, where indicated, both. In addition, noninhibited and inhibited cells were costained for the drug transporters ABCB1 and ABCG2 using respective monoclonal antibodies. This multimodal approach helped us to better define particularly A2780V cells, whose SP contains a major population of ABCB1-positive cells (~8–10%) and a minor population of ABCG2-expressing cells (~0.1%). Note that, at least in our model systems, verapamil does not inhibit the activity of ABCG2.