PGP and lung cancer: In four lung cancer cell lines, SK-MES-1, SPCA-1, NCI-H-460 and NCI-H-446, the expression of P-gp, MRP1 and GST-π was different; the level of GST-π in the SK-MES-1 cells was the highest, whereas the level of P-gp in the SPCA-1 cells was the lowest.