Establishing a novel in vitro model of prostate cancer starting from stem-progenitor cells -

Abstract

Cell lines representing the progression of prostate cancer from an androgen-dependent to an androgen-independent state are scarce. Previously, we have established and characterized a new murine prostate luminal epithelial cell line (PLum), with Pten-TP53 deletions, derived from a prostate epithelial stem-progenitor-enriched cell population. The deprivation of androgens from established PLum-orthotopic tumors resulted in tumor regression and eventually castration-resistant growth. Cells derived from orthotopic tumors have been isolated to develop androgen-dependent versus androgen-independent model. In this study, several experiments were conducted to establish and investigate the functional differences of the newly isolated androgen-dependent (PLum- AD) and androgen-independent (PLum-AI) murine prostate cancer cell lines. Unlike PLum-AD cells that grew in serum-free medium, PLum-AI cells grew better in 5percent FBS-containing medium. Both cell lines remained faithful in morphology to their in vivo source, where PLum-AD showed a typical epithelial morphology (in vivo source: adenocarcinoma) and PLum-AI showed an epithelial-to-mesenchymal morphology (in vivo source: sarcomatoid carcinoma). Furthermore, upon immunofluorescent analysis, PLum-AD cell expressed mostly prostate epithelial markers while PLum-AI cells expressed mesenchymal cell markers. In addition, QRT-PCR and Western blot analysis confirmed the epithelial and mesenchymal morphology of PLum-AD and PLum-AI respectively. To assess for the presence of stem-progenitor cell population, the cells were subjected to sphere-formation assay. Both cell lines had the capacity to form spheres, where PLum-AD cells formed regular-shaped spheres and PLum-AI cells formed mostly large stellate shaped spheres consistent with their mesenchymal-like nature. Interestingly, and despite a lower level in PLum-AI, both cell lines showed expression of AR at the mRNA and protein levels. Although both cell lines showed tumorigenic abilities, PLum-AI was significantly more aggressive in t