Nucleolar organizer regions in the normal, hyperplastic and carcinomatous epithelium of endometrium

Changes in ribosome biogenesis may induce cancer by down-regulating the cell tumor suppressor potential

Many human pathological conditions, not linked to genetic alterations of oncogenes or tumor suppressors, are nevertheless associated with an increased risk of developing cancer, and some of them are characterized by quantitative and/or qualitative changes in ribosome biogenesis. Indeed, there is evidence that both an up-regulation of ribosome biogenesis, such as that occurring during the abnormal stimulation of cell growth, and intrinsic dysfunctions of ribosomes, such as those characterizing a series of inherited disorders, show an increased incidence of tumor onset. Here we discuss some recent insights into the mechanisms by which these alterations in ribosome biogenesis may facilitate tumorigenesis.

Prognostic value of nucleolar organizer regions in supraglottic carcinoma

The relationship of nucleolar organizer regions (NORs) to proliferative activity and tumor progression was studied in 16 supraglottic carcinomas. The number of NORs stained by a silver colloid staining method (AgNOR staining method) was determined. The mean AgNOR number tended to be higher (but not significantly so) in poorly differentiated tumors. Moreover as T and N categories and stage of the tumor rose, the AgNOR number also rose, but not significantly. More interestingly, the mean AgNOR number was significantly higher in the presence than in the absence of lymph node metastasis. These studies indicate that the AgNOR number might be of clinical value as a predictor of lymph node metastasis of supraglottic carcinomas.

Nucleolar organizer regions in glottic carcinomas: comparison of DNA cytofluorometry and clinicopathological analysis

The significance of nucleolar organizer regions (NORs) and nuclear DNA content in 73 glottic carcinomas was assessed for proliferative activity and tumor progression. NORs stained with silver colloid were counted, and nuclear DNA content was assayed by cytofluorometry. The cytofluorometric study demonstrated that the percentage of tumors with aneuploidy tended to increase as histological differentiation decreased. Survival rates of patients with diploid and aneuploid tumors were not significantly different. AgNOR staining revealed that mean AgNOR numbers rose as histological differentiation of tumors decreased. Moreover, as T and N categories and stages showed advancing malignancy, mean AgNOR numbers tended to rise. However, there was no significant difference in survival rates between tumors with low and with high AgNOR counts. These studies indicate that while AgNOR staining is better than DNA cytofluorometry for determining histological differentiation of glottic carcinoma, neither is of prognostic value at the present time.

Nucleolar organizer regions as markers of endometrial proliferation: a study of normal, hyperplastic, and neoplastic tissue

Nucleolar organizer regions (NORs) are loops of DNA that transcribe to ribosomal RNA. They can be visualized as intranuclear black dots by histochemical staining with a colloid silver solution. We applied this method to 78 sections of endometrial tissue obtained either from curettage or from hysterectomy specimens. The histological diagnoses were as follows: normal proliferative (N = 9) or secretory (N = 5) endometrium, simple hyperplasia (N = 10), complex hyperplasia (N = 18), atypical hyperplasia (N = 8), and adenocarcinoma (N = 28). Mean silver-stained NOR (AgNOR) counts per cell were 3.2 (standard error of the mean [SEM], 0.2) in normal proliferative and 2.7 (SEM, 0.2) in normal secretory epithelium, and increased to 4.1 (SEM, 0.3) in simple hyperplasia, to 5.4 (SEM, 0.4) in complex hyperplasia, to 8.1 (SEM, 0.7) in atypical hyperplasia, and finally to 10.0 (SEM, 0.5) in endometrial carcinoma. The differences were significant (one-factor analysis of variance [ANOVA], P < .001). A slight increase but no significant difference was seen between the mean AgNOR counts in endometrial carcinomas of different histological grades. Our study suggests that AgNOR counts are reliable markers of endometrial proliferation and allow a clear distinction between benign, premalignant, and malignant epithelial changes. Our AgNOR findings in endometrial hyperplasia support the concept of various degrees of hyperplasia that can be differentiated on morphological grounds.

Potential criteria for cohort selection in chemoprevention trials of uterine adenocarcinoma

Women at risk of uterine cancer include those with one or more of the following characteristics: obesity, nulliparity, late menopause, diabetes mellitus, prolonged unopposed estrogen use, and tamoxifen therapy. Risk is additionally increased by the presence of endometrial hyperplasia. The incorporation of biomarkers into the selection criteria of cohort groups at risk for developing endometrial cancer offers an innovative approach to the clinical design of chemoprevention trials of endometrial adenocarcinoma. Biomarkers that may be useful in cohort selection include nuclear morphometry, specific genetic abnormalities, and markers of proliferation and differentiation.

Nucleolar organizer regions in tongue carcinomas induced in rats: comparison with DNA cytofluorometric analysis

Eleven papillomas and 25 carcinomas were induced in rat tongues by oral administration of 0.001% 4-nitroquinoline 1-oxide (4NQO) in drinking water, and the biological characteristics and proliferative activity of the tumors were investigated by both DNA cytofluorometry and the argyrophilic nucleolar organizer region (AgNOR) staining method. The histopathological characteristics, the mean number of AgNORs per cell and DNA ploidy patterns were compared. The mean AgNOR number was lowest in normal epithelium (1.65 +/- 0.10), and highest in squamous cell carcinomas (2.97 +/- 0.70) and intermediate in papillomas (1.87 +/- 0.28). The differences were statistically significant. All normal epithelium and all papillomas showed a diploid pattern. Eighteen (72%) of 25 squamous cell carcinomas showed a diploid pattern, while 7 (28%) showed a diploid plus tetraploid pattern. There was a significant difference in the mean AgNOR number between the two ploidy groups of squamous cell carcinomas. These results suggest that the mean AgNOR number may reflect the histological grade in the process of carcinogenesis and polyploidization of carcinomas.

Anionic sites in glomerular basement membrane of rats with serum sickness nephritis: quick-freezing and deep-etching study

Serum sickness nephritis was induced in male Fisher 344/JCL rats by injecting egg albumin into the foot pads and peritoneal cavity. The alteration of anionic sites in the glomerular basement membrane (GBM) of the rats with significant proteinuria was studied with a quick-freezing and deep-etching method using polyethyleneimine as a cationic probe. In control rats, anionic sites were located around the fibrils of the lamina rara externa, which radiated perpendicularly from the lamina densa to podocyte cell membranes. In the glomeruli of proteinuric rats, many electron-dense deposits were observed in the subepithelial side of the GBM, where the fibrils of the lamina rara externa were usually obscured and anionic sites around them could not be recognized. However, in some areas, a clear boundary could be observed between deposits and the lamina densa. Electron micrographs of freeze-fractured deposits showed that the fibrils radiated perpendicularly from the lamina densa and that anionic sites around them had been preserved. These results suggest that some of the deposits simply passed through the GBM and masked transiently the fibril structures of the GBM, but others probably destroyed these fibril structures, including anionic sites.

Classic, atypical, and anaplastic meningioma: three histopathological subtypes of clinical relevance

This study correlates the histopathological classification of meningiomas with clinicopathological features of biological activity. A retrospective evaluation of 1799 surgical specimens of meningiomas from 1582 patients was made. The classic histopathological type, atypical meningiomas defined by increased cellularity and at least five mitotic figures in 10 high-power fields, anaplastic (malignant) meningiomas, and hemangiopericytic or papillary meningiomas were seen in 87.6%, 7.2%, 2.4%, and 2.8% of operations, respectively. The rates of recurrence in surgically treated patients with classic, atypical, anaplastic, and hemangiopericytic or papillary meningiomas were 6.96%, 34.6%, 72.7%, and 68.2%, respectively. The extent of surgery and the tumor size and site were studied in detail in 252 tumors of all histopathological types. Recurrences were rare in classic meningiomas after complete resection, whereas atypical and anaplastic tumors recurred after complete resection much more frequently. Classic meningiomas, hemangiopericytomas, and papillary meningiomas were smaller at surgery than atypical and malignant meningiomas. Atypical and malignant tumors were operated on more often in falcine and lateral convexity regions than were classic meningiomas. To support the authors' subjective categorization by a quantitative parameter related to proliferation, 112 meningiomas comprising all histopathological subtypes were investigated for staining of argyrophilic nucleolar organizer region proteins (Ag-NOR's). The Ag-NOR counts showed significant differences between classic, atypical, and anaplastic tumors but no significant differences between primary and recurrent tumors. Hemangiopericytomas and papillary meningiomas had lower Ag-NOR values than anaplastic meningiomas. A correlation of Ag-NOR numbers with the authors' histopathological scale of malignancy supports the introduction of atypical meningiomas with intermediate biological behavior on the classification scale between classic and anaplastic meningiomas. Overlapping of Ag-NOR numbers among all groups of malignancy may restrict the prognostic value of Ag-NOR counting in the individual case.