ABCG2 and non-small cell lung carcinoma: In addition to the camptothecin-resistant HCT116 sublines discussed above, we also employed two NSCLC cell lines: H460, which express high levels of ABCG2 protein [10,23], and EKVX cells, which have undetectable levels of ABCG2 protein expression when assessed by Western blot (Figure 1B).