Multiple myeloma (MM) still is an uncurable cancer of the haematological system. The vast majority of patients will relapse after initial treatment and finally succumb to their disease. Thus, the development of drug resistance during the course of the disease is the major clinical problem to be solved in MM. Recently, we have identified an oncogene, designated YB-1, that is assumed to play a key role in the development of drug resistance. Therefore, we will now analyze the role of YB-1 establish in an MM animal in order to develop targeted therapeutic strategies to overcome drug resistance in MM.