ABCB1 and squamous cell lung carcinoma: To further evaluate the ability of AIF-1 to inhibit ABCB1 activity and increase intracellular calcein content in tumor cells, we tested AIF-1 at concentrations between 1 and 10 μM in A549 and in a NSCLC cell line (SKMES-1) derived from squamous cell lung carcinoma (SQCLC), which expresses a high level of ABCB1 (Figure S1).