ABSTRACT
Hematological malignancies tend to respond reasonably well to chemotherapy. However, a number of patients do not achieve a complete remission or have relapsing disease. This poor response to chemotherapy has given rise to the question whether the tumor cells have the intrinsic (or acquired) property to detoxify these cytotoxic drugs. Clinically, there are patients who are refractory to a whole range of chemotherapeutic agents, even without prior exposure-this is called multidrug resistance (MDR). Some cellular mechanisms have been identified that are able to explain the clinical MDR phenotype. For instance, the detoxifying glutathione system is related to resistance for alkylating agents (1,2). Alteration of topoisomerase II leads to resistance to anthracyclines, epopodophylotoxins, mitoxantrone, and amsacrine (3).
