Building new in vivo models of human prostate cancer progression by manipulation of cyclin D1 and PTEN

Abstract

These studies examine the consequences of tissue-specific oncogene or a tumor suppressor gene expression in either human prostatic epithelial or stromal cells. This approach allows us to monitor the growth and differentiation status of such grafts in vivo. We utilized retroviral gene transfer to infect initiated epithelial cells (BPH-1 cells-SV40 immortalized human prostatic epithelial cells), benign prostate epithelial cells (PrE3) and primary cultures of normal prostatic fibroblasts (NPF) with either cyclin D1 overexpressing, PTEN shRNA or myr-AKT vectors. The resulting cells were then examined using tissue recombination approaches.

Overexpression of cyclin D1 in BPH-1 cells increased their proliferation rate, but did not elicit tumorigenicity in vivo. In contrast overexpression of cyclin D1 in NPF cells that were subsequently recombined with BPH-1 resulted in malignant transformation of the epithelial cells. DNA microarray analysis showed highly concordant profiles of gene expression between Carcinoma Associated Fibroblasts (CAFs) and NPF cells overexpressing cyclin D1 (NPFcyclin D1). Epithelial cells isolated from BPH-1 + NPFcyclin D1 recombinants (BPH-1NPF-cyclin D1) were permanently transformed in vivo, mirroring previously described results using BPH-1 + CAF recombinant-derived cells. Expression of the cell matrix protease cathepsin D was upregulated in NPFcyclin D1, CAFs and BPH-1NPF-cyclin D1 cells. Further work is needed to establish whether this molecule is an important paracrine mediator in this system.

A moderate (55%) suppression of PTEN expression elicited a tumorigenic response in BPH-1 cells converting benign epithelial cords into an invasive tumor. Partial suppression of PTEN in benign PrE3 cells caused high-grade PIN. The ability of human prostatic epithelial cells to induce and maintain smooth muscle differentiation in adjacent stroma was found to be negatively correlated to the level of genetic damage sustained by those epithelial cells.

This study examined several aspects of the molecular basis for the change in the relationship between stromal and epithelial cells in the transition from benign prostate to prostate cancer and provided new human models for prostate cancer research.