Stem cell features of benign and malignant prostate epithelial cells.
OBJECTIVE
We present a new hypothesis suggesting that the different malignant potential of benign prostatic hyperplasia (BPH) and high grade prostatic intraepithelial neoplasia may be explained by distinct alterations in stem cell-like properties.


METHODS
We used our results and the recent literature to develop this hypothesis in the context of an updated prostate stem cell model.


RESULTS
While high grade prostatic intraepithelial neoplasia is a likely precursor lesion to many prostatic adenocarcinomas, BPH rarely if ever progresses directly to carcinoma. Prostate epithelium contains basal and secretory compartments. Secretory cells appear to differentiate from basal cells. Thus, prostatic stem cells most likely reside in the basal compartment. In BPH there is a slight increase in epithelial proliferation, yet most replicating epithelial cells within BPH maintain their normal restriction to the basal compartment. In high grade prostatic intraepithelial neoplasia there is a marked increase in cell proliferation. In contrast to BPH, the majority of proliferating cells in high grade prostatic intraepithelial neoplasia reside in the secretory compartment. The biological significance of this topographic infidelity of proliferation in high grade prostatic intraepithelial neoplasia remains unclear but may relate mechanistically to down regulation of the cyclin dependent kinase inhibitor, p27kip1. Normal basal cells express GSTP1, an enzyme that inactivates reactive electrophiles and organic hydroperoxides, and that may protect cells from deoxyribonucleic acid damaging agents. In contrast, normal secretory cells and high grade prostatic intraepithelial neoplasia cells do not express this enzyme.


CONCLUSIONS
We propose that topographic infidelity of proliferation produces a population of secretory cells replicating in the absence of key genome protective mechanisms, thus setting the stage for an accumulation of genomic alterations and instability in high grade prostatic intraepithelial neoplasia. This action occurs along with activation of telomerase, resulting in an immortal clone capable of developing into invasive carcinoma. The model predicts that genome protection remains intact in BPH, minimizing its malignant potential.
De Marzo
A M
AM
Department of Pathology, James Buchanan Brady Urological Institute, The Johns Hopkins University Medical Institutions, Baltimore, Maryland, USA.
Nelson
W G
WG
Meeker
A K
AK
Coffey
D S
DS
D000818:Animals; D014408:Biomarkers, Tumor; D018797:Cell Cycle Proteins; D050760:Cyclin-Dependent Kinase Inhibitor p27; D004249:DNA Damage; D005982:Glutathione Transferase; D006801:Humans; D008297:Male; D008869:Microtubule-Associated Proteins / Q000096:biosynthesis; D009687:Nuclear Proteins / Q000502:physiology; D010750:Phosphoproteins / Q000502:physiology; D011230:Precancerous Conditions / Q000473:pathology; D011467:Prostate / Q000166:cytology; D011470:Prostatic Hyperplasia / Q000235:genetics / Q000473:pathology*; D019048:Prostatic Intraepithelial Neoplasia / Q000235:genetics; D011471:Prostatic Neoplasms / Q000235:genetics / Q000473:pathology*; D051381:Rats; D013234:Stem Cells / Q000473:pathology*; D019098:Telomerase / Q000502:physiology; D025521:Tumor Suppressor Proteins
D014408:Biomarkers, Tumor; C493962:Cdkn1b protein, rat; D018797:Cell Cycle Proteins; D008869:Microtubule-Associated Proteins; D009687:Nuclear Proteins; D010750:Phosphoproteins; D025521:Tumor Suppressor Proteins; D050760:Cyclin-Dependent Kinase Inhibitor p27; D005982:Glutathione Transferase; D019098:Telomerase