The characterization of epithelial and stromal subsets of candidate stem/progenitor cells in the human adult prostate

Abstract

Objectives: Questions regarding the cell source and mechanisms in the initiation and progression of prostate cancer are today still open for debate. Indeed, our knowledge regarding prostate cell regulation, self-renewal, and cytodifferentiation is presently rather limited. In this study, we investigated these processes in the normal adult human prostate.

Methods: Dynamic expression patterns in prostate stem/progenitor cells, intermediate/transit-amplifying cells, and cell lineages were immunohistochemically identified in an in situ explant renewal model of the human normal/benign adult prostate (n=6).

Results: Cells with a basal phenotype proliferated significantly in explant cultures, whereas luminal cells went into apoptosis. Results further show down-regulation in tissue cultures of the basal and hypothetical stem cell marker Bcl-2 in the majority of cells, except in rare putative epithelial stem cells. Investigation of established (AC133) and novel candidate prostate stem/progenitor markers, including the cell surface receptor tyrosine kinase KIT and its ligand stem cell factor (SCF), showed that these rare epithelial cells are AC133(+)/CD133(low)/Bcl-2(high)/cytokeratin(+)/vimentin(-)/KIT(low)/SCF(low). In addition, we report on a stromal population that expresses the mesenchymal marker vimentin and that is AC133(-)/CD133(high)/Bcl-2(-)/cytokeratin(-)/KIT(high)/SCF(high).

Conclusions: We provide evidence for epithelial renewal in response to tissue culture and for basal and epithelial stem/progenitor cell recruitment leading to an expansion of an intermediate luminal precursor phenotype. Data further suggest that SCF regulates prostate epithelial stem/progenitor cells in an autocrine manner and that all or a subset of the identified novel stromal phenotype represents prostate stromal progenitor cells or interstitial pacemaker cells or both.