Correlation between nucleolar organizer region staining and Ki-67 immunostaining in human gliomas

Analysis of a Surgical Series of 21 Cerebral Radiation Necroses

BACKGROUND

There is no standard approach to differentiate cerebral radiation necrosis from tumor recurrence and no standard treatment pathway for symptomatic lesions. In addition, reports on histology-proven radiation necrosis and the underlying pathophysiology are scarce and highly relevant.

METHODS

Our monocentric, retrospective analysis included 21 histology-proven cerebral radiation necroses. Our study focused on 1) potential risk factors for the development of radiation necrosis, 2) radiologic and histopathologic features of individual necroses, and 3) the suitability of previously reported magnetic resonance imaging (MRI)-based methods to identify radiation necroses based on specific structural image features.

RESULTS

Average time between radiation treatment and development of necrosis was 4.68 years (95% confidence interval, 0.19-9.55 years). Matching available MRI data sets with those of patients with tumor lesions, we compared specificity and sensitivity of 3 previously reported methods to identify radionecrosis based on imaging criteria. In our hands, none of these methods reached a sensitivity ≥70%. Radionecrosis presented with large edema and showed increased levels of cell proliferation, as inferred by Ki-67 staining. Surgical removal of radiation necrosis proved to be a safe approach with low permanent morbidity (<5%) and no mortality.

CONCLUSIONS

Although the overall incidence of cerebral radiation necrosis is low, our data suggest an increasing incidence over the last 2 decades, which is likely associated with the use of stereotactic radiotherapy. There are no imaging standards to identify radiation necrosis on standard MRI with structural sequences. Surgical removal of radiation necrosis is associated with low morbidity and mortality.

IMP dehydrogenase-2 drives aberrant nucleolar activity and promotes tumorigenesis in glioblastoma

In many cancers, high proliferation rates correlate with elevation of rRNA and tRNA levels, and nucleolar hypertrophy. However, the underlying mechanisms linking increased nucleolar transcription and tumorigenesis are only minimally understood. Here we show that IMP dehydrogenase-2 (IMPDH2), the rate-limiting enzyme for de novo guanine nucleotide biosynthesis, is overexpressed in the highly lethal brain cancer glioblastoma. This leads to increased rRNA and tRNA synthesis, stabilization of the nucleolar GTP-binding protein nucleostemin, and enlarged, malformed nucleoli. Pharmacological or genetic inactivation of IMPDH2 in glioblastoma reverses these effects and inhibits cell proliferation, whereas untransformed glia cells are unaffected by similar IMPDH2 perturbations. Impairment of IMPDH2 activity triggers nucleolar stress and growth arrest of glioblastoma cells even in the absence of functional p53. Our results reveal that upregulation of IMPDH2 is a prerequisite for the occurance of aberrant nucleolar function and increased anabolic processes in glioblastoma, which constitutes a primary event in gliomagenesis.

Correlation between argyrophilic nucleolar organizer region staining and brain tumor classification and grading

Distinctions between benign and malignant tumors are less evident in the central nervous system than in other tissues. Since the level of cell proliferation is an important feature in tumor grading, we applied AgNOR in 50 cases of brain tumors with different grades and histological origins in order to check its efficiency in discriminating between benign and malignant cases. We found significant differences between the means of grade I (1.76) and grade IV (2.46) tumors. No significant differences were observed considering the same grading with distinct histological types or age of patients, reinforcing the efficiency of AgNOR.

Possible involvement of Fas system in the induction of apoptosis in human astrocytic brain tumors

1. For a better understanding of the biological features of astrocytic tumors, we investigated apoptosis and its pathway, especially in the interaction between Fas and Fas ligand (FasL). 2. We examined the presence of apoptosis in human astrocytic brain tumors by terminal deoxynucleotidyl transferase (TdT)-mediated d-UTP-biotin nick end labeling (TUNEL) and then apoptotic index (AI) was calculated. We also examined the distribution of Fas and FasL-positive tumor cells immunohistochemically. Labeling index (LI) for Fas and FasL was calculated as Fas-LI and FasL-LI, respectively, and compared to AI. 3. Tumor cells expressing both Fas and FasL were TUNEL positive. Such cells were distributed sparsely in low-grade astrocytomas, but focally in glioblastomas. There was a close correlation among AI, Fas-LI, and FasL-LI, and astrocytic tumors with higher Al were associated with a longer survival time than that with lower Al. 4. It was concluded that the Fas system may be involved in the apoptosis of astrocytic tumors, and Al can be a useful parameter for assessing prognosis of astrocytic tumors.

Cell proliferation and tumors of the central nervous system, part II: radiolabeling, cytometric, and immunohistochemical techniques

A variety of techniques have been developed to evaluate cell proliferation. Many of these methods provide a more accurate means of assessing the true proliferation rate of a given neoplasm, as compared with the simple assessment of mitotic activity. Similar to the evaluation of mitotic activity, these methods are also subject to limitations associated with tumor heterogeneity and interobserver variability. This paper reviews a variety of methodologies including radiolabeling, flow cytometric, and immunohistochemical that have been used in recent years to evaluate cell proliferation in brain neoplasms. Factors that affect these methodologies and their practical application to routine practice of diagnostic neuropathology will be explored.

Enhanced apoptosis in pilocytic astrocytoma: a comparative study of apoptosis and proliferation in astrocytic tumors

Both cell proliferation and cell death occur simultaneously in tumor tissue, and extent of tumor growth reflects the net balance of these events. We correlated cell proliferation, spontaneous cell death, and alterations in tumor suppressor proteins with one another and with survival of patients with primary astrocytic tumors. In 39 astrocytic tumor specimens (6 pilocytic astrocytomas, 14 fibrillary astrocytomas, 9 anaplastic astrocytomas, and 10 glioblastomas), we determined the MIB-1 labeling index, the apoptotic ratio according to nick end labeling with morphologic confirmation, the p53 labeling index, and the presence of p53 or PTEN mutations. MIB- I labeling indices of pilocytic astrocytomas, fibrillary astrocytomas, anaplastic astrocytomas, and glioblastomas were 0.30+/-0.32; 1.84+/-1.87; 19.3+/-6.42; and 28.0+/-14.5 (mean +/- SD), respectively. Corresponding apoptotic ratios were 17.9+/-5.16; 3.96+/-3.57; 1.18+/-0.93; and 2.11+/-1.60 (mean +/- SD). The apoptotic ratio in pilocytic astrocytomas was significantly higher than in other astrocytic tumors (fibrillary astrocytomas, p < 0.05; anaplastic astrocytomas and glioblastomas, p < 0.01). MIB-1 showed a significant negative correlation with apoptosis (p < 0.01). MIB- I and apoptosis showed significant negative and positive correlations with patient survival (p < 0.01). Mutations of p53 and PTEN show no correlation with survival and apoptotic ratio. The apoptotic ratio can clearly distinguish pilocytic astrocytomas from other tumors, and this biological feature may reflect less aggressive growth of pilocytic astrocytomas.

Standardized in situ AgNOR analysis in breast pathology: diagnostic and cell kinetic implications

The aim of the present study was to assess the diagnostic value of the recently standardized morphometric analysis of silver-stained nucleolar organizer region-associated proteins (AgNORs) [30] in a variety of 155 routinely processed benign and malignant breast lesions. 5 normal breast samples, 21 adenoses, 20 ductal hyperplasias, 10 atypical ductal hyperplasias, 20 in situ and 43 invasive ductal carcinomas, 10 in situ and 26 invasive lobular carcinomas were investigated. A statistically highly significant difference was found between normal/ordinary hyperplastic and neoplastic breast lesions with all 4 consensus AgNOR parameters (mean area, mean number, CV of area, CV of number) evaluated. AgNOR quantity was significantly related to histological grade of both in situ and invasive carcinomas. However, variable overlap was found between AgNOR values in different diagnostic groups. We conclude that standardized AgNOR analysis is a prerequisite for objective and reproductible AgNOR assessment in archival tissues. Despite its limited diagnostic utility for individual breast lesions, standardized AgNOR analysis bears a significant potential for characterizing cell kinetic and metabolical activity of breast lesions. This may give insight into the biological background of breast carcinogenesis, differentiation and tumor progression and may also underlie the independent prognostic value of AgNORs in breast cancer.

Ki-67 (clone MIB-1) proliferation index in recurrent glial neoplasms: no prognostic significance

BACKGROUND

To determine if the Ki-67 (MIB-1 clone) proliferative index (PI) has prognostic potential in patients with recurrent astroglial neoplasms.

METHODS

We conducted a retrospective review of 27 patients whose initial and recurrent specimens were available. Histopathology was determined according to the World Health Organization classification. Proliferation index was calculated on formalin-fixed tissue using the Ki-67 (MIB-1 clone) antibody. Morphometric data were analyzed in conjunction with clinical data and Cox Proportionate Hazards Analysis, Spearman's correlation coefficient and Mann-Whitney Test.

RESULTS

Initial histopathology included 14 glioblastoma multiforme, 7 anaplastic astrocytoma, 3 oligoastrocytoma, and 3 astrocytoma. Recurrent specimens showed changes consistent with treatment. While univariate analysis shows initial histology correlated with survival (p<0.036), PI did not correlate with survival after either initial (p = 0.86) or recurrent (p = 0.46) surgery for any tumor type. PI difference between specimens also did not correlate with survival (p = 0.91). Initial PI did not correlate with recurrent PI either (p = 0.43).

CONCLUSIONS

Ki-67 PI does not confer additional prognostic information for patients with recurrent astroglial neoplasms. One possible explanation for this observation is that treatment may alter the PI independent of its effect on tumor growth.

MIB-1 labeling index in nonpilocytic astrocytoma of childhood: a study of 101 cases

BACKGROUND

The prognosis of pediatric patients with nonpilocytic astrocytoma, and in particular those with anaplastic astrocytoma, is somewhat unpredictable. This study used MIB-1 monoclonal antibody, a proliferative marker that can be used in formalin fixed paraffin embedded tissues, to study nonpilocytic pediatric astrocytoma.

METHODS

Astrocytoma, anaplastic astrocytoma, and glioblastoma specimens excised from a total of 101 pediatric patients during the period from January 1975 to September 1996 were retrieved from the authors' surgical pathology file. Histologic grading of the specimens was performed based on a modified Ringertz system. The proliferative potential of the tumors was estimated by using the MIB-1 labeling index (LI), which was evaluated with morphologic grades of tumors and survival of the patients.

RESULTS

Of the 101 patients, 34 had astrocytoma, 33 had anaplastic astrocytoma, and 34 had glioblastoma. Their mean survival times were 165.2+/-14.9 months (mean+/-standard error; SE), 46.1+/-9.9 months, and 21.8+/-5.6 months, respectively. The mean MIB-1 LI of different tumor grades were as follows: astrocytoma, 3.9+/-4.3 (mean+/-standard deviation; range, 0.0-21.6); anaplastic astrocytoma, 24.3+/-15.6 (range, 1.7-62.8); and glioblastoma, 35.9+/-16.4 (range, 7.36-63.3). The mean survival of the entire group of patients with LIs < or = 11 was 173.2+/-12.2 months (mean+/-SE), and the mean survival of those with LIs > 11 was 20.3+/-4.1 months. The survival of anaplastic astrocytoma patients with LIs < or = 11 was similar to that of astrocytoma patients, whereas the survival of anaplastic astrocytoma patients with LI > 11 was similar to that of patients with glioblastoma.

CONCLUSIONS

The results of the current study show that histopathologic grading can predict the outcome for patients with astrocytomas and glioblastomas, whereas MIB-1 LI can separate better and worse prognostic groups in patients with anaplastic astrocytoma.

The proliferative potential of the pilocytic astrocytoma: the relation between MIB-1 labeling and clinical and neuro-radiological follow-up

The proliferative potential of 39 pilocytic and 5 low grade astrocytomas was studied in relation to the Ki-67 activity as measured by the MIB-1 Labelings Index. The results were correlated to the biological behaviour of the tumor as measured by clinical and neuro-radiological (CT- or MRI-scans) follow-up of the patient. This study was undertaken to answer the question whether MIB-1 expression reflects differences in biological behaviour of these tumors, such as rapid progression of residual tumor or stable remaining tumor. MIB-1 LI values ranged from 0 to 19% in the group of pilocytic astrocytomas (mean 4.2%) and from 0 to 15% in the 5 low grade astrocytomas (mean 4,2%). All patients were operated and 23 of them had incomplete tumor resection as proven on postoperative neuro-imaging studies. Those 23 patients could be subdivided into two groups; one without progression of residual tumor during follow-up (n=12) and the other with tumor progression (n=11). mean MIB-1 LI in the group with 'quiescent' tumor tended to be lower than in the group with progressive tumor: 3,3% vs. 6,6%. Residual tumors which were negative for MIB-1 staining showed fewer progressions of residual tumor compared to those being positive for MIB-1 staining, however this difference was not significant (p=0, 15, Fisher exact test). Tumor samples of a second operation of the same patient had lower MIB-1 LI values than those of the samples taken at first operation. The proliferating potential seemed to be decreased after part of the tumor was resected. Pilocytic astrocytomas with a negative MIB-1 LI are unlikely to show progression of residual tumor after partial resection. MIB-1 staining might be an additional tool in determining the frequency and duration of follow-up and in making decisions regarding further treatment of a patient operated for a pilocytic astrocytoma with residual tumor.

p120 and AgNOR nucleolar protein expression: a comparison with nuclear proliferation markers in oral pathology

To find a better method for predicting the biological behavior of certain oral cavity lesions, the expression of nucleolar protein p120 and nucleolar organizer region counts (AgNOR) was compared with that of nuclear proliferation markers MIB-1 and PCNA in 10 cases of keratotic epithelial hyperplasia (KEH), 10 cases of epithelial dysplasia (ED), and 15 cases of squamous cell carcinoma (SCC). Significant differences in p120 and AgNOR mean area values and PCNA labeling index (LI) were recorded between KEH and ED, as well as ED and SCC (Student-Neumann-Keuls test). All markers significantly differed between SCC grades I and III. Significant differences were also noted in AgNOR mean area values between grade I and II SCC and in p120 mean area values. MIB-1 and PCNA LI differed significantly when grade II and III SCC were compared (SNK test). There were significant correlations between p120 and AgNOR (Pearson correlation coefficients) and between both of them and the proliferative indexes. AgNOR correlated with tumor grade, stage, and lymph node status (Spearman correlation coefficients), suggesting a prognostic role for that marker.

Clinical and biological considerations regarding glioma based on the TUNEL method and immunohistochemical staining using apoptosis-related antibodies

We examined 36 gliomas both by the terminal deoxynucleotidyl transferase-mediated dUTP-digoxigenin nick-end-labeling (TUNEL) technique and by immunostaining of antibodies against apoptosis-related antigens. The apoptotic index (AI) obtained by the TUNEL method was 10.77 +/- 3.78% in astrocytomas, 6.19 +/- 1.81% in anaplastic astrocytomas, and 5.21 +/- 1.14% in glioblastomas. The AI of anti-Fas antibody and Le(Y) antibody in gliomas also showed a similar tendency as the results with the TUNEL method. As a result, statistically significant differences were observed in the distribution of survival between the two groups according to the AI obtained by the TUNEL method. Therefore, an analysis of the AI is considered to be useful for prognosis.

Argyrophilic nucleolar organizer regions and bromodeoxyuridine and 3[H]-thymidine labelling indices in colorectal cancer

The count of argyrophilic nucleolar organizer regions (AgNORs) has been proposed as a useful method for evaluating cell replication in human tumours. The current study was undertaken to compare AgNOR values in colorectal cancers with two better established methods for investigating cell proliferation such as bromodeoxyuridine (BrdUrd) and 3[H]-thymidine (3[H]dT) labelling indices (LIs). Because some concern still exists regarding accuracy and reproducibility of AgNOR quantifying methods, we carried out a control study by independently repeating the same measurements (number, area and area per silver-stained NOR particle) in two centres with different operators and computer-assisted image analysers on 40 colorectal carcinomas. AgNOR values recorded in the two centres were strictly correlated (r = 0.75; P < 0.001 for number; r = 0.62, P < 0.01 for area; r = 0.63, P < 0.001 for area per silver-stained NOR particle) and the range of values were almost identical. Then, AgNOR values were compared with BrdUrd and 3[H]dT LIs, respectively obtained by in vivo incorporation and in vitro incubation in the same series of colorectal carcinomas. No correlation was found between AgNOR values and BrdUrd or 3[H]dT LIs. BrdUrd and 3[H]dT LIs were instead reciprocally significantly correlated. No evident correlation was seen between LIs or AgNOR values and clinico-pathological parameters of the tumour. In conclusion, in colorectal neoplasms, AgNOR values did not appear to relate with more direct parameters of cell proliferation. It follows that AgNOR reliability as a biomarker of cell proliferation remains questionable.

Effectiveness of intraoperative radiation therapy for recurrent supratentorial low grade glioma

Twelve adult patients in the records of 38 patients with histologically verified supratentorial low grade glioma showed recurrence at the Gifu University Hospital between 1980 and 1992. A mean period to recurrence from the initial surgery and postoperative radiation was 38 months. Six of these patients underwent intraoperative radiation therapy. The other six patients received chemotherapy with conventional cytoreductive surgery in three cases and additional external irradiation in three cases. The 2-year survival rate of the former patients was 83.8% and significantly higher than that of the latter ones, 16.7% (p < 0.05). Most cases showing recurrence of supratentorial low grade glioma were occurred locally, and dissemination or remote metastasis of the lesion were rare. The results revealed that the local control is important for recurrent tumors of supratentorial low grade gliomas. The effectiveness of the intraoperative radiation therapy as the second operation for the recurrent supratentorial benign glioma is discussed.

Regional differences in bromodeoxyuridine uptake, expression of Ki-67 protein, and nucleolar organizer region counts in glioblastoma multiforme

To investigate intratumoral differences in indices of tumor cell proliferation, we measured the bromodeoxyuridine labeling index (BrdUrd LI), the Ki-67 protein proliferating cell indices (PCIs) determined by monoclonal antibody MIB 1 in microwave-processed paraffin sections (MIB 1 PCI) and in some cases by monoclonal antibody in frozen sections (Ki-67 PCI), and counts of argyrophilic nucleolar organizer regions (AgNORs) in 20 glioblastomas. In the most actively proliferating areas, MIB 1 and Ki-67 PCIs correlated well with the BrdUrd LI and with each other, while AgNOR counts correlated less strongly with these indices. In less active areas, the MIB 1 PCI and BrdUrd LI changed concomitantly from one area to another within a tumor except in areas of pseudopalisading with necrosis; in these areas the BrdUrd LI decreased significantly compared with neighboring tumor tissue, while the MIB 1 PCI did not. There was very little staining of gemistocytic nuclei with either anti-BrdUrd or MIB 1 monoclonal antibodies; this supports the concept that gemistocytes are mainly quiescent cells. AgNORs in all of the above-mentioned areas varied from tumor to tumor, which suggests that they may indicate some cellular activity other than proliferation. The close correlation between the BrdUrd LI and Ki-67 protein PCIs in corresponding regions of glioblastomas suggests that MIB 1 staining of microwave-processed paraffin sections can be used to evaluate the growth potential of individual glioblastomas and possibly of other gliomas as well.

Central neurocytoma: proliferative assessment by nucleolar organizer region staining

Proliferative potential of four cases of central neurocytoma were assessed by a silver colloid staining technique for argyrophilic protein associated with nucleolar organizer regions (AgNORs). All but one tumor had an Ag-NOR score of less than 2 and were regarded as a benign entity. However, one tumor tissue from a patient suffering from a recurrent central neurocytoma after 13 years from the first operation possessed a 2.06 AgNOR score, which is not significantly different from others. It is considered that central neurocytoma is an essentially benign neoplasm, even though the tumor is recurrent. The present study revealed the usefulness of AgNOR staining for a retrospective assessment of the proliferative potential of central neurocytomas.

Importance of interphase nucleolar organizer regions in tumor pathology

The importance of the distribution of silver-stained nucleolar organizer regions (Ag-NORs) in interphase nuclei for diagnostic and prognostic purposes in tumor pathology has been reviewed. The available data demonstrated that interphase Ag-NOR evaluation may be of help in distinguishing malignant from hyperplastic or normal cells. On the other hand, there is increasing evidence that a relationship exists between the quantity of interphase Ag-NORs and the prognosis of malignant tumors: the greater the number of interphase Ag-NORs, the worse is the prognosis. This can be explained by the observation that the interphase Ag-NOR quantity is strictly related to the cell proliferation rate. The procedures used for the measurement of the interphase Ag-NOR quantity are also critically discussed.

Argyrophilic nucleolar organizer region counts in multiple myeloma: a histopathological study on bone marrow trephine biopsies

Argyrophilic nucleolar organizer region (Ag-NOR) analysis was performed on bone marrow biopsies from 90 patients with multiple myeloma (MM) at presentation. The pattern of AgNOR expression and its relationship to histological features were evaluated. The mean AgNOR number per plasma cell was directly correlated with the degree of MM differentiation (3.18 for G1, 4.36 for G2, 6.13 for G3; P less than 0.0001), with the percentage of bone marrow plasma cells (BMPC%) (3.06 for BMPC% less than or equal to 20, 4.28 for BMPC% 21-50, 5.14 for BMPC% greater than 50; P less than 0.0001), with the pattern of medullary involvement (3.63 for interstitial, 4.44 for nodular, 5.17 for diffuse involvement; P less than 0.001) and with medullary fibrosis (5.23 for cases with fibrosis, 4.29 for cases without fibrosis; P less than 0.05). The plasma cells of G1 MM showed 2-3 large AgNORs, tightly grouped in a central nuclear cluster; those of G2 MM showed a central nuclear cluster composed of 4-5 medium-size dots and/or two clusters of 2-3 dots; the G3 MM plasma cells showed many small dots scattered in the nucleolus or dispersed in the nucleus. Our results indicate the diagnostic value of AgNOR analysis in MM and suggest the use of this method for identifying clones of atypical plasma cells with different proliferative activity in bone marrow biopsies. It allows simultaneous evaluation of the morphology and kinetics of MM cells in routinely fixed, decalcified, paraffin-embedded material.

Glial fibrillary acidic protein (GFAP) expression and nucleolar organizer regions (NORs) in human gliomas

The frequency of nucleolar organizer regions (NORs) in each glioma tissue and the relation between the expression of glial fibrillary acidic protein (GFAP) and the frequency of NORs was investigated. The number of Ag-NORs per cell for glioblastoma multiforme was significantly higher than that for anaplastic astrocytoma (P less than 0.05) and that for astrocytoma (P less than 0.01). The number of Ag-NORs per cell for GFAP-positive cells was significantly lower than that for GFAP-negative cells in each histopathological grade (P less than 0.01). Moreover, the linear relationship was demonstrated between the Ag-NORs numbers of GFAP-negative cells and bromodeoxyuridine (BUdR) labeling indices. From these results, it is concluded that many GFAP-positive glioma cells may have low growth potential in glioma tissue and GFAP-negative cells may have a close relation to cell proliferation. The combination of immunohistochemical and silver colloid staining is a useful method for investigating the biological characteristics of brain tumors.

Standardization of interphase Ag-NOR measurement by means of an automated image analysis system using lymphocytes as an internal control

Using an automated image analysis system, we have developed a procedure for standardizing the measurement of silver-stained proteins of the nucleolar organizer regions (NORs) in cancer cells, irrespective of the fixative employed and the time of the staining reaction. We observed that the area of Ag-NOR proteins from the same tumour was smaller in samples fixed with formalin-containing solutions, buffered formalin, and Bouin liquid, compared with those fixed with absolute ethanol and 'methcarn' solution (1.77 +/- 0.26micron 2 and 2.36 +/- 0.35 micron2 versus 3.34 +/- 0.54 micron2 and 3.72 +/- 0.61 micron2). Increased values of the Ag-NOR area were also observed after lengthening the silver staining reaction. However, in both cases no difference was observed in the ratio between Ag-NOR area of cancer cells and that of the lymphocytes infiltrating the stroma. The value of the ratio, which is called the 'Ag-NOR index', was in fact very similar, for the same cancer, after employing different fixatives or staining times. The use of lymphocyte Ag-NOR area as an internal control for the standardization of Ag-NOR evaluation in cancer tissues was made possible by the fact that lymphocyte Ag-NOR area is almost constant in human tumours independent of sex and age.

Rapid detection of proliferating potential in human brain tumors by nucleolar organizer region staining on squash preparations

Rapid detection of the proliferating potential of 37 human brain tumors was attempted using squash preparations stained by a silver colloid technique for argyrophilic protein associated with nucleolar organizer regions (AgNORs). Less than 1 h was required for staining. The mean number of AgNORs in cell nuclei of malignant or recurrent brain tumors (16 cases) including meningeal sarcoma, recurrent meningioma, recurrent craniopharyngioma, anaplastic astrocytoma, glioblastoma multiforme and metastatic brain tumor was 3.18, and the number for benign brain tumors (21 cases) including meningioma, neurinoma, pituitary adenoma, benign astrocytoma, ependymoma, and adenoma of lachrymal gland was 1.85. The former value was significantly greater than the latter value (P less than 0.001). These results indicate that quantitative analysis of AgNORs in brain neoplastic cells, using squash preparations, is useful to differentiate malignant from benign tumors within 1 h. Thus, this method provides rapid and useful information about the proliferative potential of human brain tumors even during operation.

Correlation between nucleolar organizer region score and bromodeoxyuridine labeling index in C6 glioma cell line

Correlation between the mean number of nucleolar organizer region-associated argyrophilic proteins (AgNORs) per cell and BrdU labeling index (LI), the percentage of S-phase cells, was investigated in vitro using rat C6 glioma cells under several different conditions such as increased concentration of fetal calf serum (FCS) in a stepwise manner in medium. In addition, the effect of dibutyryladenosine cyclic monophosphate (d-cAMP) on the mean number of AgNORs and the BrdU LI was examined. C6 glioma cells cultured with no FCS showed 5.1% BrdU LI and 3.46 AgNOR score. BrdU LI and AgNOR score of the cells cultured with 1% FCS were 26.5% and 6.25, respectively. Those with 5% FCS were 44.7% and 8.41, with 10% FCS; 49.8% and 10.85, and with 20% FCS; 48.4% and 10.64. Treatment of d-cAMP with 10% FCS induced morphological differentiation and reduced BrdU LI (9.4%) and AgNORs score (4.90), compared with C6 cells cultured in medium containing 10% FCS without d-cAMP. Thus, the BrdU LI and AgNOR score of the C6 cells cultured under several different concentration of FCS were shown to be well linearly related (r = 0.97) and both values were decreased with morphological alteration of C6 glioma cells in the presence of 1 mM d-cAMP.

AgNOR area in interphase nuclei of human tumours correlates with the proliferative activity evaluated by bromodeoxyuridine labelling and Ki-67 immunostaining

The area of silver-stained proteins associated with interphase nucleolar organizer regions (AgNORs) was compared with labelling data obtained by bromodeoxyuridine (BrdU) incorporation and Ki-67 immunostaining in 25 tumours of different origins and two non-neoplastic lesions of the thyroid. Our data demonstrate a highly significant correlation between the mean area occupied by the AgNOR proteins measured by an image processing system and the proliferative indices evaluated by BrdU labelling (r = 0.89, P less than 0.001) and Ki-67 immunostaining (r = 0.86, P less than 0.001). AgNOR protein area measurement is therefore proposed as a simple, inexpensive, and reliable method of evaluating the proliferative activity in routinely processed tumour samples.

Proliferating cell nuclear antigen expression in central nervous system neoplasms

Proliferating cell nuclear antigen (PCNA) is a cell-cycle-regulated protein, which can be demonstrated in routinely fixed specimens. Studies on various tissues, cell cultures and neoplasms have shown that PCNA labelling index (LI) correlates with flow cytometry, tritiated thymidine LI, bromodeoxyuridine (BrdU) incorporation and Ki67 LI. PCNA LI may have prognostic value in various neoplasms. The present study concerns PCNA immunostaining in a series of neuroglial tumours. We demonstrate that there is a relation between PCNA LI and histological grade, and between PCNA LI and reported thymidine LI, BrdU LI and Ki67 LI. Pleomorphic xanthoastrocytomas and low-grade astrocytomas had the lowest LI, whereas metastases of small cell lung cancer and medulloblastomas had the highest LI. Glioblastomas sometimes showed a certain degree of intratumoral heterogeneity of distribution of immunostained cells. Intratumoral heterogeneity underscores the critical importance of representative sampling of central nervous system neoplasms for kinetic studies. As expected, PCNA LI are somewhat higher than tritiated thymidine LI, BrdU LI and Ki67 LI because PCNA is a marker of G1, S, G2 and M-phases of the cell cycle and not of S-phase only. In addition, because of its long half-life, PCNA may be detected immunohistochemically in cells that have recently left the cell cycle. The immunohistochemical evaluation of PCNA LI is easy to perform on routinely processed material, allowing retrospective studies. PCNA LI may be a useful tool in grading gliomas. However, its prognostic value must be validated by comparing PCNA LI with the follow-up of the neoplasms, and possibly with the responsiveness to anti-proliferative therapy.

Proliferative assessment of GFAP-positive and GFAP-negative glioma cells by nucleolar organizer region staining

The proliferative potential of two types of tumor cells that did or did not express glial fibrillary acidic protein (GFAP) in 19 cases of high-grade gliomas, including nine anaplastic astrocytomas (WHO criteria, grade 3) and 10 glioblastoma multiforme (grade 4), was investigated by a combined staining technique, one-step silver colloid method for nucleolar organizer region-associated argyrophilic protein (Ag-NOR) and immunocytochemistry for GFAP. The mean numbers of Ag-NORs in GFAP-positive cells and GFAP-negative cells of high-grade gliomas were 2.68 and 3.74, respectively. The value of GFAP-negative cells was significantly greater than that of GFAP-positive cells (p less than 0.01). Our results show that, by means of the immunocytochemistry for GFAP, tumor cells in human high-grade gliomas can be divided into two groups expressing GFAP or not, and that the mean number of Ag-NORs of GFAP-negative cells is more representative of the degree of histological malignancy than that of positive cells. It is considered that the proliferative assessment of GFAP-negative tumor cells in high-grade gliomas by combined staining of Ag-NOR silver staining and GFAP immunocytochemistry is useful for understanding the histological malignancy of high-grade gliomas.

Variations in the occurrence of silver-staining nucleolar organizer regions (AgNORs) in non-proliferating and proliferating tissues

Previous studies on the subject of silver-staining nucleolar organizer regions (AgNORs) as indicators of precise proliferative status of tissues have sometimes resulted in ambiguity. The studies, however, have most frequently addressed themselves to the prognosis of neoplasias, with the aim of using AgNORs principally to distinguish between benign and malignant tumours. This investigation was to determine a base-line relationship of AgNOR clusters to proliferation and thus concentrated on normally proliferative tissues and conditionally renewing tissues after appropriate stimulation. Two murine transplantable tumours were also examined as examples of frank malignancy. As an example of the former, variations in AgNOR clusters were noted in the small intestine of man, mouse, and rat. The conditionally renewing systems of liver, prostate, and salivary glands were stimulated into proliferation by two-thirds partial hepatectomy, castration followed by treatment with testosterone, and isoproterenol treatment, respectively, in rat models; the murine sarcoma SaF and carcinoma CaNT provided relatively simple malignant tumours for AgNOR investigation. Proliferation was monitored by noting labelling indices after injection with bromodeoxyuridine (BrdUrd) in vivo followed by immunocytochemical visualization of S-phase cells. In all tissues, an increase in the size of AgNOR clusters rather than their number correlated positively with elevated labelling, particularly with the emergence of silver-staining regions of 2-3 microns visible diameter. Thus, increased AgNOR cluster size (diameter) as representative of AgNOR cluster/nucleolus volume was found to be dependent on proliferative activity in a range of normal and neoplastic tissues.

Assessment of proliferative potential in gliomatosis cerebri

The proliferative potential of neoplastic cells in two cases of gliomatosis cerebri was investigated by a combined staining technique, a one-step silver colloid method for nucleolar organizer region-associated protein (AgNOR) and immunohistochemistry for fibrillary acidic protein (GFAP). The neoplastic cells in the two cases had an abnormal shape and showed positive GFAP immunostaining in their cytoplasm. The numbers of AgNORs were counted in central and peripheral lesions of the neoplastic field in each case. The mean AgNOR scores in neoplastic cells were almost the same as those of nonneoplastic astrocytes in both the central and the peripheral lesions. These values were almost equal to the AgNOR score of low-grade gliomas. These findings indicate that gliomatosis cerebri has an invasive character in the central nervous system and often shows a malignant tendency, but its proliferative potential is significantly lower than that of high-grade gliomas.

Nucleolar organizer region score and Ki-67 labelling index in high-grade gliomas and metastatic brain tumours

Sixteen cases of malignant brain tumours comprising 6 anaplastic astrocytomas, 3 glioblastoma multiforme, 1 medulloblastoma and 6 metastatic brain tumours were investigated independently by a silver colloid method for nucleolar organizer regions (NORs) and an immunohistochemistry using a monoclonal antibody against a nuclear antigen. Ki-67, in proliferating cells. The correlation between the mean number of NORs and the percentage of Ki-67 labelled cells (Ki-67 labelling index) was examined. In addition, four normal brain tissue samples without neoplastic cells were stained for NOR. The mean number of NORs in these malignant brain tumours was significantly greater than that in normal astrocytes (p less than 0.001). Moreover, both the mean number of NORs and the Ki-67 labelling index in metastatic brain tumours were significantly greater than those in high-grade gliomas (p less than 0.001). The Ki-67 labelling index and the mean number of NORs in malignant brain tumours including metastatic brain tumours were found to be linearly related (r = 0.86). These results suggest that the proliferative potential of malignant brain tumours could be evaluated by NOR score as well as Ki-67 labelling index and that such indices provide clear discrimination between high-grade gliomas and metastatic brain tumours.

The relationship between Ki-67 labeling and mitotic index in gliomas and meningiomas: demonstration of the variability of the intermitotic cycle time

The monoclonal antibody (mAb) Ki-67 is a marker for the growth fraction (GF) of tumor cells. The exact relationship between the Ki-67 labeling index (LI) and the conventional diagnostic criterion of the proliferative activity of brain tumors, the mitotic index (MI), is unknown except for some general references. On serial frozen sections Ki-67 LI and MI were determined in nearly identical areas of 32 glioblastomas, 20 grade III astrocytomas, 21 grade II astrocytomas and 20 selected cases of meningioma. The data not only clearly showed different median values of LI and MI for the various malignancy grades, but also similar regression coefficients for each glioma type. A non-linear relationship between the two indices was found for all glioma cases with high significance and high correlation coefficient; (LI) = 5.6 (MI)0.59. This results from differing intermitotic cycle times, the variability of which can be estimated from the data given.