Argyrophilic nucleolar organizer regions (AgNORs) in relation to p53 and bcl-2 protein expression in leukemia...

The aim of this study was to assess the possible relationship between the silver stained nucleolar organizer regions (AgNOR) and immunocytochemically detected p53 and bcl-2 proteins in ALL, AML, B-CLL and CML patients (adults and children) at the initial presentation. AgNORs are loops of DNA, correlated with proliferative potential of cells. Alteration in p53 and bcl-2 proteins expression may characterize the malignant potential of leukemic cells. The patients were subdivided according to the p53 positivity and negativity. The frequency of p53-positive patients was relatively low in T-ALL (29%) and B-CLL (16%). B-ALL, AML and CML patients revealed higher frequency of p53 protein (46%, 47% and 88%, respectively). The overall frequency of positive cytoplasmic staining for bcl-2 protein was demonstrated in the majority of patients. No significant differences in the percentage of p53-positive cells among leukemia subtypes were seen. The proportion of bcl-2 protein positive cells did not differ significantly among various leukemia subtypes, except for significant differences between p53-positive and p53-negative peripheral blood (p=0.0073) and bone marrow (p=0.0175) cells of B-CLL patients. The samples from healthy subjects used as controls exhibited relatively low numbers of AgNOR dots in both, peripheral blood and bone marrow cells. Highly significant differences in AgNOR quantities between healthy donors and p53 protein positive peripheral blood as well as bone marrow cells of distinct leukemia subtypes (except for bone marrow cells in B-CLL patients, p=0.1727) were observed. Significant differences in AgNOR count between p53 protein positive and p53 protein negative samples of peripheral blood cells of B-ALL (p=0.0099) as well as B-CLL (p=0.0117) cases were found. No significant differences (except for B-CLL, p=0.0558) were encountered in bone marrow cells. P53 protein positivity or negativity did not influence the amount of AgNOR proteins in cells of our T-ALL and AML cases. Mutual comparing the number of AgNOR dots among different leukemias showed that for both peripheral blood and bone marrow cells the differences between ALL and AML (p=0.0383 and p=0.0033, respectively) as well as for peripheral blood of AML and CML (p=0.0302) were statistically significant. The bcl-2 protein positivity did not affect significantly the AgNOR distribution either in p53 protein positive or p53-negative cases of our leukemia patients. However, an association between the lowest AgNOR quantity and highest bcl-2 protein expression in p53-negative B-CLL patients was seen for both peripheral blood and bone marrow cells. The correlation between relatively high AgNOR numbers and relatively increased percentage of bcl-2 protein in the p53-positive cases of CML patients was found in some cases. Regarding the age and sex, the AgNOR distribution in p53-positive and p53-negative leukemia cases in children and adults showed neither relationship nor dependence. The WBC count differed evidently among distinct leukemia subtypes, with enormous heterogeneity in range as well. Larger studies are needed in order to consolidate these preliminary results and characterize the possible prognostic value of AgNOR in association with p53 and bcl-2 proteins expression.