The revertant lung cancer cell line COR-L23/R23- was generated by growing the doxorubicin-selected, resistant variant COR-L23/R without drug exposure for 24-28 weeks. The cell line, also known as COR-L23/Rev, overexpresses multidrug resistance -associated protein (MRP), but to a lesser extent than the parent line. It was shown that the cell line has the ability to recover quickly, similar levels of MRP expression and resistance as COR-L23/R after a transient exposure to the MDR-drugs doxorubicin and vincristine.