ABCG2 and lung carcinoma: Similar results were observed when comparing HEK293 (immortalized kidney epithelial cells) with HEK293 cells stably transfected with an ABCG2 expression vector (Fig. S1A) and the lung carcinoma line H460 with its mitoxantrone selected subline H460/MX (Fig. S1B), indicating that this observation is not unique to the MCF-7 cell lines.