The present study was undertaken to provide missing information on the distribution of AgNORs in large nucleoli of human leukaemic early granulocytic precursors in vivo as well as in vitro. In vivo, the distribution of AgNORs was studied in early granulocytic precursors of patients suffering from chronic myeloid leukaemia who were both untreated and treated with imatinib mesylate. AgNORs were visualized by silver reaction under conditions which facilitated to see their distribution by light microscopy. In vitro, the distribution of AgNORs was studied in proliferating and ageing K 562 cells which originated from chronic myeloid leukaemia. In vitro, the ageing of K 562 cells produced intranucleolar translocation of AgNORs to the nucleolar periphery. Such translocation was also observed in some leukaemic early granulocytic precursors in vivo, e.g. in bone marrow myeloblasts and promyelocytes of leukaemic patients. As was expected, the intranucleolar translocation of AgNORs in early granulocytic precursors was more frequent in patients treated with the cytostatic therapy--imanitib mesylate. The abovementioned findings suggest that myeloblasts and promyelocytes with AgNORs translocated to the periphery of large nucleoli might be in the ageing state, similarly as blastic cells of leukaemic myeloid origin (K 562 cells) in ageing cultures. Thus, the translocation of AgNORs might be a useful marker of premature ageing in the future and might contribute to the evaluation of the single cell state under various experimental as well as clinical conditions. However, more clinically oriented studies are required in this direction.

Institute of Haematology and Blood Transfusion Prague Czech Republic