Stem Cell Characteristics in Prostate Cancer Cell Lines

BackgroundRecent studies indicate the presence of a small, stem-like cell population in several human cancers that is crucial for the tumour (re)population.ObjectiveSix established prostate cancer (PCa) cell lines—DU145, DuCaP, LAPC-4, 22Rv1, LNCaP, and PC-3—were examined for their stem cell properties in vitro.Design, settings, and participantsThe colony-forming efficiency and self-renewal ability of morphologically distinguishable holoclones and paraclones were tested with low-density plating and serial passaging. Expression of the putative stem cell marker CD133 and breast cancer resistance protein (BCRP) was examined with flow cytometry, and immunohistochemical stainings were made for CD133, α2-integrin, nestin, BCRP, cytokeratin 5 (CK5), and cytokeratin 18 (CK18).Results and limitationsFive out of six cell lines formed clear holo-, mero-, and paraclones. Unlike paraclones, we can maintain DU145 holoclones in culture for several passages, which is indicative of self-renewal ability. Using fluorescence-activated cell sorting (FACS) analysis only in DU145 cells, a small fraction (0.01%) of CD133+ cells was detected. CD133+ cells; however, like DU145 BCRP+ (0.15%) cells, they were not more clonogenic, and they did not show more holoclone formation than the marker-negative cells or unselected cells. Immunohistochemistry revealed α2-integrin and BCRP as potential stem cell markers and CK5 with the combination of CK18 to distinguish transient amplifying cells.ConclusionsThese results indicate the possible presence of stem-like cells in several established PCa cell lines. CD133 selection does not enrich for stem-like cells in PCa cell lines.