Abstract: A novel protein associated with multidrug resistance in living cells and capable of conferring multidrug resistance on a cell is disclosed. Nucleic acids encoding the novel multidrug resistance protein are also disclosed. Transformant cell lines which express the nucleic acid encoding the novel protein are also disclosed. Antibodies which bind the novel multidrug resistance protein are also disclosed. Diagnostic and treatment methods using the novel proteins, nucleic acids, antibodies and cell lines of the invention are also encompassed by the invention.