Background Prostate stem cells, responsible for the development, maturation, and function of the prostate, have been implicated in the aetiology of both benign prostate hyperplasia (BPH) and prostate cancer (CaP). However, research has been hampered by the lack of a definitive stem cell marker. We have adapted the protocol for differential Hoechst 33342 uptake by hemopoietic stem cells to enable isolation of putative stem cells from the prostate. Methods Prostate epithelial cells isolated from prostate tissue obtained from patients with BPH after transurethral resection of the prostate were stained with Hoechst 33342. The Hoechst 33342 Red/Blue flow cytometry profile was then determined. Hoechst 33342 and Pyronin Y staining was used to determined the cell cycle status. Results A verapamil‐sensitive side population (SP) can be isolated from primary prostate tissue accounting for 1.38% ± 0.07% of prostate epithelial cells. Cell cycle analysis of this SP population revealed that the majority of SP cells are in either G0 (12.38 ± 0.31%) or G1 (63.19 ± 2.13%). Conclusions The Hoechst 33342 dye efflux protocol can be adapted for the isolation of a SP from primary prostate tissue. Cytometry Part A 54A:89–99, 2003. © 2003 Wiley‐Liss, Inc.

Our observations are consistent with the Hoechst 33342 dye efflux assay isolating a stem cell enriched population which can be further sub-fractionated by CD133 selection. Moreover, the loss of the CDK inhibitor in malignancy is consistent with the hypothesis that neoplastic change originates in the stem cell compartment.