MOR/0.4R has been developed from the parent line, MOR, by continuous exposure to increasing concentrations of doxorubicin (also known as adriamycin). This drug-resistant cell line accumulates lower levels of doxorubicin than the parent line and have been shown to overexpress multi drug resistance-associated protein (MRP). The expression of a 190kDa membrane protein associated with the degree of drug resistance has been indicated. Cells grow as easily detaching aggregates.