The study of AgNOR proteins in leukemias: diagnostic value and correlation to S-phase cell fraction

The study assessed the diagnostic value of silver staining method and its possible relevance as an alternative to DNA analysis for the study of cellular proliferation in various leukemias (ALL, AML, CML). Silver staining of nucleolar organizer region-related proteins (AgNORs) was applied to peripheral blood and bone marrow cells. The analysis of S-phase cells was carried out using a FACStar flow cytometer. The mean number of AgNOR dots per nucleus and the percentage of S-phase cells varied according to immunophenotype of leukemic cells, depending on the time of initial diagnosis, remission or relapse. Peripheral blood and bone marrow cells of healthy subjects exhibited less AgNOR dots than leukemic cells. The number of AgNORs in bone marrow cells was higher than that of AgNORs in peripheral blood. Significant differences between ALL and AML, as well as AML and CML in AgNOR quantity were observed. Important increase in AgNOR values was evident in relapsed leukemias and in the CML blast crisis. DNA flow cytometry analyses provided results comparable to those of AgNOR enumeration. The correlation between AgNOR dots and proportion of S-phase cells prompted us to consider that AgNOR count reflects cell proliferation capacity of leukemic cells.