Expression of silver-stained nucleolar organizing regions (Ag-NORs) in human cancer

Minichromosome maintenance (MCM) and AgNOR proteins expression in desmoid tumours: a tissue microarray analysis

In the present study, nuclear proliferative proteins: MCM2, MCM5, MCM7, Ki-67 and AgNORs expression was assessed in paraffin sections from sporadic desmoid tumours using a tissue microarray (TMA)-based immuno- and histochemistry, respectively. Nuclear expression of MCM7, where the percentage of positive cells was 0.87% (± 1.64) (range 0-5%), was found in 4/20 (20.0%) cases. In 32/32 (100%) of the examined desmoid cases no expression of nuclear proteins MCM2 and MCM5 was detected. Nuclear expression of Ki-67 was observed in 4/21 (19%) cases. Paraffin sections from 30 cases of desmoid tumours were silver-stained to visualize AgNORs. The following AgNOR parameters were calculated: mean AgNOR number per nucleus (N), mean AgNOR area per nucleus, mean AgNOR dot area per nucleus (A), and mean AgNOR content (C = N/A). In the investigated group the mean values of AgNOR parameters were the following number: 4.34 (± 0.11); area: 0.74 μm2 (± 0.19); dot area: 0.18 m2 (± 0.01), and AgNOR content: 23.73 (± 1.85). The mean AgNOR number per nucleus and mean AgNOR content in desmoid tumours were statistically significantly higher as compared to the controls (tonsil tissue) (p<0.001). This study observed low level of MCM7 and Ki-67 and lack of MCM2, MCM5 proteins expression which may explain commonly known low mitotic activity of desmoid tumour cells. The morphology of dots related to AgNORs (number, area) and their morphometric parameters point to elevated transcriptional activity of desmoid cells.

Ag-NOR staining and satellite association in lymphoproliferative disorders

The nucleolar organizer regions (NORs) activity and the frequency of satellite associations (SA) in peripheral blood lymphocytes from patients with two chronic lymphoproliferative disorders were studied: 10 cases with B-cell chronic lymphocytic leukemia (B-CLL) and 10 with mycosis fungoides (MF). Thirteen healthy individuals formed the MF control group, and the oldest 7 constituted the B-CLL control group. The mean of Ag-NORs per metaphase was increased in B-CLL patients (8.80 +/- 0.63) compared with their controls (7.99 +/- 0.90) (P less than 0.025), meanwhile MF patients' value did not differ from their controls. In both disorders, the frequency of Ag-NORs in the G chromosomes was increased. The analysis of SA in B-CLL patients only revealed an increase in the frequency of cells with more than 4 ASPs (association pairs). Meanwhile, a significant higher mean of ASPs per cell in MF patients (1.74 +/- 0.41) compared to controls (1.40 +/- 0.24) (P less than 0.05) was observed. Furthermore, a close correlation between cells with complexes of 3 or more chromosomes and the mean of ASPs per cell was also found in MF. In conclusion, an increase of the Ag-NORs expression in B-CLL patients and a modification in the degree of SA in MF patients were found.

AgNORs and myeloma prognosis

The argyrophilic nucleolar organizer regions (AgNORs) were analysed in bone marrow biopsies from 80 patients with multiple myeloma (MM) at presentation. The mean AgNOR number per MM cell (AgNOR counts) and their distribution within the nucleus (configuration) were assessed. AgNOR counts were significantly associated with several recognized prognostic factors: Durie and Salmon clinical staging system (p = 0.02), percentage of plasma cells (PCs) in aspirates (p = 0.01) and in bone marrow biopsies (p = 0.0000), pattern of bone marrow involvement (p = 0.0003), calcaemia (p = 0.0005) and creatininaemia (p = 0.0003). AgNOR counts were also associated with the degree of PC differentiation (p = 0.0000). A single central cluster of 2-3 large-sized AgNORs (configuration A) was evident in most G1 MM; one cluster of 4-5 medium-sized dots or two clusters of 2-4 dots (configuration B) were seen in most G2 MM; many small-sized, scattered dots were present in G3 MM (configuration C). AgNOR counts and configuration were related to the prognosis: in the univariate analysis, the 5 year survival rate was 7% for cases with > 4.5 AgNORs/cell and 46% for cases with < or = 4.5 AgNORs/cell (p = 0.01), 53% for configuration A, 12% for configuration B and 0% for configuration C (p = 0.0000). AgNOR counts (p = 0.02) and configuration (p = 0.000) were independent prognostic variables in the multivariate analysis. The AgNOR counts were significantly higher in "fulminant myeloma" than in less aggressive cases (p = 0.002). The plasma cell labelling index (LI%), evaluated in 44 MM patients, showed significant correlation with prognosis: the 5 year survival rate was 51% for LI% < or = 1 and 17% for LI% > 1 (p = 0.02). More than 70% of patients with low LI% had low AgNOR counts and more than 70% of patients with high LI% had high AgNOR counts (p = 0.007). AgNOR counts and configuration reflect the myeloma cell mass, the degree of differentiation and the kinetics of the myeloma cells. They offer an exact evaluation of the tumour characteristics and can be useful additional parameters for MM prognosis.

Progressive growth of rat bladder carcinomas after exposure to prolonged uracil-induced urolithiasis

Dietary uracil at the 3% level induces urinary bladder tumors in rats through urolithiasis-dependent mechanical irritation. In the present study, comparison of lesions induced by uracil administration over the different periods of 36 weeks (middle-term) and up to 103 weeks (long-term) revealed significant elevation of both incidences and multiplicity of transitional cell carcinomas (TCCs) in the long-term group. Histopathological assessment in terms of tumor biology further demonstrated significantly higher grading on the basis of the degree of cellular and structural atypia, and greater depth of invasion in the long-term group. Application of markers for cell proliferation activities including proliferating cell nuclear antigen (PCNA) and silver-binding nucleolar organizer regions (AgNORs) also revealed significantly elevated AgNOR counts in the long-term group TCC. AgNOR counts and PCNA rates in TCCs showed relation to the histological grades. Thus the present study demonstrated that prolonged uracil-induced urolithiasis causes more biologically aggressive bladder carcinomas with invasive potential. Continuous stimulation of cell proliferation presumably has the potential to facilitate multiple genetic alterations leading to development of more malignant carcinomas. However, it should be borne in mind that the difference in bladder cancer development might also be related to the fact that the animals survived longer and that the early lesions therefore had more time to progress to more advanced stages.

Expression of silver-stained nucleolar organizer regions is coupled to cell cycle in rat thymic cells

To directly analyze the relationship between the expression of silver-stained nucleolar organizer regions (AgNORs) and cell proliferation, thymic cells from newborn rats were separately sorted at the G0-G1-phase and early-mid and late-mid S-phase of the cell cycle according to their DNA content. Different AgNOR-derived parameters (mean area and numbers of AgNORs per cell and mean AgNOR-particle area) were evaluated after silver staining of cytospins. A linear correlation was observed between the mean area and numbers of AgNORs per cell, both parameters increasing progressively from G0-G1-phase to early-mid and late-mid S-phase. An increase of the mean AgNOR-particle area was also seen between G0-G1 and S-phase but this was not significant along the S-phase. A bias on the selection of S-phase cells linked to intrathymic maturation can be ruled out as S-phase cells labeled with bromodeoxyuridine were found throughout the thymus, and, moreover, the analysis of the frequency distribution of nuclear area did not show a bimodal pattern. It is concluded that the expression of AgNORs--evaluated as AgNOR area/cell or AgNOR numbers/cell--is causally or indirectly coupled to DNA synthesis and, thus, AgNORs can be considered as a cell proliferation marker.

Argyrophilic nucleolar organizer regions in neoplastic and non-neoplastic hepatocytes bearing Mallory bodies

The proliferative activity of Mallory bodies (MB)-positive hepatocytes (neoplastic and non-neoplastic) was examined by counting the argyrophilic nucleolar organizer regions (AgNORs). Among 19 cases of hepatocellular carcinoma, the mean number of AgNORs was lower in the MB-positive carcinoma cells than in the negative ones in nine cases, higher in six, and there was no difference in four. In non-neoplastic cases (seven cases of advanced primary biliary cirrhosis and seven cases of alcoholic or nutritional liver injury), the mean number of AgNORs was lower in the MB-positive hepatocytes than that in the negative ones in eight cases, and approximately equal in number in six cases. These findings imply that MB formation does not directly represent the level of proliferative activity of hepatocytes, regardless of whether they are malignant or not.

Cytogenetics of human malignant melanoma

There has been a tremendous recent resurgence of interest in examining chromosomal abnormalities in human cancers (particularly solid tumors). This interest has been stimulated by the molecular examination of recurring chromosome abnormalities, and the recognition that they may pinpoint the location of growth regulatory sequences (e.g. cellular oncogenes). This finding coupled with the clear recognition that specific chromosome abnormalities can also have important diagnostic and prognostic implications, have caused this avenue of research to expand at a significant rate. The following brief review will summarize the current state of knowledge regarding recurring chromosome abnormalities in human malignant melanoma. A discussion of chromosome changes in pre-malignant skin lesions, primary melanoma, and metastatic melanoma is described. Brief descriptions of the potential clinical utility, and biologic relevance of chromosome abnormalities in this disorder are also discussed.

Acrocentric interconnections and NOR variants in human lymphocytes

Acrocentric interconnections and NOR (nucleolus organizer region) variants are frequently observed in silver-stained metaphase preparations from lymphocytes of phenotypically normal individuals. The types of interconnections and of NOR variants are outlined. It is speculated that the satellite acrocentrics (both normal and variant) are the consequence of breakage and recoiling of these interconnections. Awareness of these two features of the human genome may facilitate understanding of the NOR/nucleolus interaction(s) in such important processes as nucleolus formation and in development and/or diagnosis of disease states (i.e., malignancy).

Nucleolar organiser regions: new prognostic variable in breast carcinomas

Nucleolar organiser regions (NORs), which are important for regulating protein synthesis, were identified in 20 breast carcinomas by means of a silver (Ag) staining technique. Infiltrating neoplasms with metastases in four or more axillary lymph nodes possessed, on average, a greater number of AgNORs per cell nucleus compared with neoplasms without nodal disease, or with one to three positive lymph nodes. The size, morphology, and distribution of AgNORs within the nucleus were also different in the two study groups. Overall, these findings suggest that breast carcinomas with multiple, irregular, and widely dispersed AgNORs tend to be of high grade malignancy.

Nucleolar organizer regions in normal, hyperplastic and neoplastic parathyroid glands

Using a one-stage silver staining technique, nucleolar organizer regions (AgNORs) were studied in paraffin sections of parathyroid glands (and in two lymph node metastases) from patients operated upon because of hyperparathyroidism or thyroid disease. The parathyroids were microscopically differentiated into normal, hyperplastic, adenomatous and carcinomatous glands. AgNORs were observed as distinct black dots of varying size and somewhat varying configuration in the nuclei of all glands. The mean number of AgNORs in the hyperplastic and adenomatous glands was not significantly different from that in the normal glands, whereas the carcinomatous glands exhibited significantly increased mean AgNOR number. No evidence was obtained for a role of AgNOR counting in the differentiation between normal and hyperplastic or adenomatous parathyroids, but the results suggest a potential role of enumeration of AgNORs in the discrimination between benign and malignant parathyroid neoplasms.

Silver-binding nucleolar organizer regions (AgNORs) in benign and malignant breast lesions: correlations with ploidy and growth phase by DNA flow cytometry

Silver-binding nucleolar organizer regions (AgNORs) have been counted in sections of routinely processed paraffin-embedded tissue blocks and have been shown to assist in the distinction between benign and malignant lesions. We have examined 214 benign and malignant breast lesions by this method. The AgNOR counts were fibroadenomas 1.87 +/- 0.20 (mean +/- SD; n = 39), papillomas 1.92 +/- 0.21 (n = 28), sclerosing adenosis 1.96 +/- 0.24 (n = 23), epitheliosis 2.21 +/- 0.30 (n = 38), lobular carcinoma in situ 2.67 +/- 0.54 (n = 9), intraduct carcinoma 3.75 +/- 1.33 (n = 37), and invasive carcinoma 4.22 +/- 1.18 (n = 40). However, the counts in 25-30 per cent of epitheliosis lesions and intraduct carcinomas overlapped in the region of 2-3 AgNOR dots per nuclear profile. The AgNOR counts in carcinomas were also compared with ploidy and growth phase fractions (S + G2 + M%) by flow cytometry. Thirty-three of the 46 cancers with counts over 3 AgNOR dots per nuclear profile contained aneuploid cells (greater than 10 per cent of the total), whereas 8 of the 12 with counts below 3 comprised diploid cells only (P less than 0.05). Similar trends were noted with regard to growth phase fractions which were 19.15 per cent +/- 12.31 and 13.98 per cent +/- 5.55, respectively, for the two groups (P greater than 0.10). We conclude that this method alone does not offer a reliable histological discriminant for malignancy in the breast. However, AgNOR counting may provide information on breast cancer prognosis supplementary to that obtained from DNA flow cytometric analyses.

Effects of age, sex and multiple endocrine neoplasia type-II on silver stained nucleolar organizer regions

Silver stained nucleolar organizer regions (AgNORs) were studied in phytohemagglutinin (PHA)-stimulated lymphocytes from 55 Caucasian control individuals (34 females with average age of 24 years and age range 19 weeks gestation to 87 years; 21 males with average age of 31 years and age range 29 weeks gestation to 72 years) and 13 individuals (7 females, 6 males; average age 38.8 years with age range 25-58 years) with multiple endocrine neoplasia-type II (MEN-II), an autosomal dominant malignancy with increased chromosome breakage. For the first time, AgNORs were examined in lymphocytes from normal fetuses and patients with MEN-II in order to determine the effects of age, sex or malignancy on the number of AgNORs. No significant difference in the average number of AgNORs were found in fetal cells (8.2 +/- S.D. 0.7/cell) when compared with cells from older individuals including those over 65 years of age (8.0 +/- S.D. 0.8/cell). There was a statistically significant negative correlation (P less than 0.05) between the modal number of AgNORs on G but not D chromosomes in both males and females. A negative correlation was also found between the mean number of AgNORs and age but was not statistically significant. The average number of AgNORs in the MEN-II individuals was 8.5 +/- S.D. 0.7/cell, which was not significantly different than 8.2 +/- S.D. 0.7/cell observed in age-matched control subjects.

Temporal variation in nucleolar organizer region expression in bone marrow cells of individuals with leukemia

Silver staining was used to study nucleolar organizer region (NOR) expression in bone marrow cells obtained at two or, in one case, three time points from each of six leukemia patients. Using three measures of silver positivity, we observed that NOR expression was influenced by both metaphase stage and time. Silver positivity decreased significantly from one metaphase stage to the next, from prometaphase through late metaphase. When this variable was controlled for, significant changes in NOR activity were documented in comparisons between disease stages in the patients examined. However, patterns of NOR expression were not consistently associated with disease stage. These results indicate that in previous reports both the metaphase stage effect and the temporally changing nature of NOR activity have, as unrecognized variables, influenced observations of heterogeneity in NOR expression.

Effect of differentiating agents on nucleolar organizer region activity in human melanoma cells

A human cell line established from a metastatic melanoma had both multiple numerical and structural chromosome aberrations including one to two copies of a submetacentric marker chromosome with an insertion of an active nucleolar organizer region (NOR). Treatment of this cell line with retinoic acid (RA) induced morphologic differentiation and reduced the cellular saturation density concomitant with a significant decrease in Ag-NOR activity. RA-treated cells grown in the absence of this differentiating agent, however, displayed a return to normal Ag-NOR activity, indicating the effect of this chemical on ribosomal genes is reversible.

Sister chromatid exchange in vivo, chromosomal characterization and NORs activity of leukemia cells during 5FU-treatments

A transplantable mouse leukemia model, the leukemia cell of which has a marker chromosome and the XX genome type which differ obviously from their male host cells provides a possibility to precisely identify the leukemia cells among their male host cells cytogenetically. A sister chromatid exchange (SCE) plus chromosomal C-banding technique that we report here is very useful. The SCE frequencies in vivo of both leukemia cells and host cells were twice as high as the normal mouse cells. The higher SCE frequencies of the host cells in the leukemia mice may be due to some toxicities from the leukemia cells or some biological large molecule exchanges between the leukemia cells and the host cells. There was no significant difference in SCE frequencies between cells from the spleen and from the bone marrow of the leukemia mice. The percentages of leukemia cells in both spleen and bone marrow were more than 90% when the mice had been injected with the leukemia cells for five days. The host cells in the leukemia mice did not become leukemia cells. The 5FU-treated leukemia mice survived very well for more than twenty-three days. After the 5FU-treatments, most of the leukemia cells died, subsequently, SCE frequencies decreased to a normal level. Both the number of Ag-NORs per cell and the number of chromosomes bearing Ag-NORs per cell in the leukemia mice decreased to 60% and 40%, respectively, of the level found in normal mouse cells.

Silver-stained nucleolar organizer regions in bone marrow cells and peripheral blood lymphocytes of Philadelphia chromosome-positive chronic myelocytic leukemia patients

Silver-stained nucleolar organizer regions (Ag-NOR) in bone marrow cells and/or phytohemagglutinin-stimulated peripheral blood lymphocytes were compared between six normal healthy persons as controls and 22 Philadelphia chromosome (Ph)-positive chronic myelocytic leukemia (CML) patients, to examine if any disease associated changes occur in the expression of Ag-NOR. Although the frequency of Ag-NOR-positive cells and the number of Ag-NOR per cell were generally greater in lymphocytes than in bone marrow cells in both controls and CML patients, the Ag-stainability of these cell types in CML patients was considerably heterogeneous, compared with that found in controls. The peripheral lymphocytes of CML patients in the chronic phase, but not in the blastic phase, exhibited a significantly lowered Ag-stainability when compared with those of controls. while no such difference was observed between bone marrow cells of controls and leukemia patients in both phases of CML. In the blastic phase, however, the occurrence of Ag-NOR on the Ph of CML bone marrow cells was significantly less than expected. The present findings are discussed in relation to the existing data on the Ag-NOR expression in both normal and neoplastic cells.

Nucleolar organizer regions in patients with precancerous and cancerous lesions of the uterine cervix

Nucleolar organizer regions (Ag-NORs) were studied in patients with cervical precancerous and cancerous lesions along with controls. The data revealed a statistically significant decrease of Ag-NORs in cancer patients, as well as in women with severe precancerous lesions as compared with controls. A similar decrease in the amount of Ag-staining was also observed in both cancer and severe dysplasia cases. The study suggests a possible relationship of Ag-NOR activity to malignancy.

Rearrangement and possible amplification of the ribosomal RNA gene sites in the human chronic myelogenous leukemia cell line K562

We have studied the location of the nucleolar organizer regions (NORs) in the human chronic myeloid leukemia cell line K562. In man, the NORs are normally found on the short arms of the acrocentric chromosomes. We show that in the K562 line, the NORs are substantially rearranged with both insertional and terminal NORs. In addition, the putative t(15;17) marker chromosome had three insertional NORs that may have arisen through gene amplification.

Comparison of metaphase and interphase nucleolar activity in Hela-CCL2 cells and PHA-stimulated human lymphocytes

Metaphase and interphase nucleolar activity in cultured Hela-CCL2 cells and PHA-stimulated human lymphocytes have been studied with silver nitrate staining. In metaphase, we examined the relationship between the actual number of active NORs (AgNORs) and total number of NOR-bearing acrocentrics. Interphase silver staining over the nucleus was analyzed cytodensitometrically and morphologically. From all investigations, Hela-CCL2 cells and lymphocytes were shown to have similar levels of nucleolar activity. Our results suggest that there is a form of regulation of nucleolar activity in malignant Hela-CCL2 cells as compared to PHA-stimulated human lymphocytes.

Heterochromatin and nucleolus organizer regions in cells of patients with malignant and premalignant lymphatic diseases

Peripheral blood lymphocytes (short-term cultures) and permanent lymphoid cell lines (long-term cultures) of patients with Hodgkin disease (5), lymphoma (1), plasma cell leukemia (1), angioimmunoblastic lymphadenopathy (1), and infectious mononucleosis (3) were investigated for C-band variants and nucleolus organizer region (NOR)-activities by C-banding and silver-staining, and compared to those of healthy adults (5) and newborn children (3). Heterochromatin polymorphisms were found in malignant diseases (33%) as well as in controls (29%). In the lymphoma patients, heterochromatin of class 3 (Patil and Lubs 1977) was seen more frequently than in the controls (83%:57%). No marker C-band variants could be detected in any of the lymphatic diseases. There was no difference in the heterochromatin polymorphism between short-term cultures (predominantly T-cells) and long-term cultures (B-cells), and there was little but inconsistant difference in the NOR-activities. Silver-staining showed differences between healthy adults (8.8 AgNORs; SD:0.5) and newborn children (6.9; SD:0.4). In the lymphoma patients we found 8.3 (SD:0.7) AgNORs. Thus, using silver staining there was no detectable increase in the number of active NORs in cells of patients with malignant diseases as an expression of increased nucleolus activation in malignancies. The remarkably low NOR-activity in infectious mononucleosis (6.7; SD:1.0) may reflect an influence of acute virus infection (Epstein-Barr virus) on NOR-activity.

Nucleolar silver-stained granules in maturing erythroid and granulocytic cells

Human and rabbit erythroid and granulocytic precursors in bone marrow have been investigated to provide information concerning the number of nucleolar silver-stained granules (SSGs), which represent active interphasic nucleolar organizer regions (NORs). The differentiation and maturation of precursor cells of both investigated cell lines are characterized by a gradual decrease in number of nucleolar SSGs. In advanced maturation stages of erythroblasts or granulocytes, which are known to lose the capacity to divide, the number of nucleolar SSGs is smaller than the reported average or maximal values of NORs determined for human or rabbit cells. Since committed stem cells from both cell lines contain several times the number of nucleolar SSGs than the last dividing maturation and differentiation stages, the number of active parts of interphasic NORs in committed stem cells seems to be increased and might represent a stock for the later stages. In addition, the number of nucleolar SSGs appear to be a very convenient marker of nucleolar biosynthetic activity in individual differentiating and maturing blood cells. The differences between erythroid and granulocytic stem cells with respect to the number of nucleolar SSGs disappear during the course of further differentiation and maturation.

Deoxycytidine reverses the suppression of nucleolar organizer regions' activity caused by BrdU

In this article we report that 5'-bromodeoxyuridine (BrdU) significantly suppresses the nucleolar organizer regions (NORs) activity of Chinese hamster cells (both dipliod cells and cell line Wg3-h) (P<0.001). One of the most obvious characteristics of the suppression is a significant decrease in the total number of the Ag-NORs per cell rather than in a frequency variation of the associated Ag-NORs. The decrease in the Ag-NORs number is mainly because of the decrease in number of chromosomes bearing 2 Ag-NORs. The degree of the suppression increases with increase in BrdU concentration in the culture medium. There is a close relationship between the suppression and the BrdU-treatment time, i.e. for a given concentration of the BrdU, the longer the BrdU-treatment time, the stronger the suppression. When the BrdU-treated cells are transferred into BrdU-free medium and allowed to grow in it for another 30 h, NORs activity can be restored. Therefore, the suppression of NORs activity may be due to BrdU toxicity. When deoxycytidine (dC) is added into medium containing 30 μg/ml of BrdU, the total number of both the Ag-NORs and the chromosomes bearing Ag-NORs per cell increases to the level of untreated cells. Our results thus indicate that the addition of dC reverses the suppression of the NORs activity caused by BrdU.