A nucleic acid capable of driving the expression of a reporter gene in a cancer cell line is disclosed. A polypeptide able to confer multidrug-resistance on a cell is disclosed. Also disclosed are nucleic acids encoding the polypeptide, expression vectors, transformant host cell lines expressing the polypeptide, and antibodies binding to the polypeptide. Screening, diagnostic and treatment methods using the above polypeptide, nucleic acids, antibodies and host cell lines are also within the scope of this invention.