Nucleolar organizer regions in prostate cancer

PPM1D controls nucleolar formation by up-regulating phosphorylation of nucleophosmin

An increase of nucleolar number and size has made nucleoli essential markers for cytology and tumour development. However, the underlying basis for their structural integrity and abundance remains unclear. Protein phosphatase PPM1D was found to be up-regulated in different carcinomas including breast cancers. Here, we demonstrate for the first time that PPM1D regulates nucleolar formation via inducing an increased phosphorylation of the nucleolar protein NPM. We show that PPM1D overexpression induces an increase in the nucleolar number regardless of p53 status. We also demonstrated that specific sequential phosphorylation of NPM is important for nucleolar formation and that PPM1D is a novel upstream regulator of this phosphorylation pathway. These results enhance our understanding of the molecular mechanisms that govern nucleoli formation by demonstrating that PPM1D regulates nucleolar formation by regulating NPM phosphorylation status through a novel signalling pathway, PPM1D-CDC25C-CDK1-PLK1.

Nucleolar and AgNOR-analysis of prostatic intraepithelial neoplasia (PIN), atypical adenomatous hyperplasia (AAH) and prostatic carcinoma

Atypical glandular proliferations of the prostate are found in combination with prostate carcinomas but also with benign prostatic hyperplasia (BPH). These atypical glandular lesions that mimic glandular carcinoma within the anterocentral part of the prostate (transition zone) are named "atypical adenomatous hyperplasia (AAH)." The term for atypical ductal and acinar mainly papillary and/or cribriform proliferations in the peripheral zone is "prostatic intraepithelial neoplasia (PIN)." In this study the significance of the status of nucleoli and the number of silver-stained nucleolar organizing regions (AgNOR) as a method for measuring proliferative activity was investigated in biopsies of AAH, PIN and carcinomas of different grades of malignancy. The aim was to prove whether there are relationships of AAH to low grade carcinomas on the one hand and of PIN to high grade carcinomas on the other hand. The frequency of nuclei with small nucleoli was low in BPH (0.6%). The values increased to 8.3% in AAH, and 28.7% in PIN. The frequency of nuclei with prominent nucleoli in low grade carcinomas was 41.7% and in high grade carcinomas 81.1%. Usually, one single nucleolus was found per nucleus. Multiple prominent nucleoli were found in high grade carcinomas and in some cases of high grade PIN only. The result of AgNOR-analysis was similar: low numbers in BPH, low to moderate values in AAH, moderate values in low grade carcinomas and high values in PIN, as well as high grade carcinomas. Besides correlation between topography, histology and cytology, the similarities of nucleolar and AgNOR-analysis between PIN and high grade carcinomas support the idea that PIN is the precursor of the peripheral prostatic carcinoma. The histological, cytological and cell kinetical features of AAH are intermediate between BPH and low grade carcinoma of the prostate. Therefore, the findings to date are inconclusive and further follow up studies are necessary to prove if AAH may be a precursor of transition zone carcinoma of the prostate.

Evaluation of three different AgNOR counting methods in advanced carcinoma of the prostate

We applied the silver staining of nucleolar organizer regions (AgNOR) technique to the pretreatment biopsies of 50 cases of advanced prostate cancer. Three different counting methods were utilized in the enumeration of AgNORs. All methods yielded statistically significant differences of mean AgNOR counts of groups defined by high and low WHO, and by Gleason grades. However, there was overlap among groups, and further analysis of counts by grouping of patients according to their stage, response to treatment, and prognosis was not conclusive. Replicate counts were performed in 10 cases. While intraobserver reproducibility was high by all methods, only the second counting method yielded nonsignificant interobserver variability. There was a significant intratumoral heterogeneity of AgNOR scores. Lack of technical standardization, low reproducibility, and lack of correlation with prognosis limit the use of AgNOR counts in advanced carcinoma of the prostate.