Abstract

Prostate cancer (PCa) is the second most diagnosed type of cancer in men worldwide. Advanced PCa is resistant to conventional therapies and high recurrence has been associated with high rates of metastasis. Cancer stem cells (CSCs) have been proposed to be responsible for this, due to their ability of self-renewal and differentiation into other cell types. Zinc finger E-box-binding homeobox 1 (ZEB1), a transcription factor involved in the regulation of epithelial-mesenchymal transition (EMT), has been associated with the activation of several mechanisms that lead to resistance to treatment. As recent evidence has shown that CSCs may originate from non-CSCs during EMT, it was hypothesized that knocking down ZEB1 expression in PCa cell lines could revert some properties associated with CSCs. Using lentiviraltransduction, ZEB1 expression was silenced in the PCa DU145 and LNCaP cell lines. The mRNA and protein expression levels of key canonical CSC markers (Kruppel-like factor 4, SOX2, CD44 and CD133) were determined using reverse transcription-quantitative PCR and western blot analysis, respectively. In addition, the colony forming ability of the ZEB1-knockdown cells was evaluated, and the type of colonies formed (holoclones, paraclones and meroclones) was also characterized. Finally, the ability to form prostatospheres was evaluated in vitro. It was found that in ZEB1-knockdown DU145 cells, the expression levels of CSC phenotype markers (CD44, CD133 and SOX2) were decreased compared with those in the control group. Furthermore, ZEB1-knockdown cells exhibited a lower ability to form prostatospheres and to generate colonies. In conclusion, stable silencing of ZEB1 reversed CSC properties in PCa cell lines. Since ZEB1 is associated with malignancy, therapy resistance and a CSC phenotype in PCa cell lines, targeting ZEB1 may be a key factor to eradicate CSCs and improve the prognosis of patients with advanced PCa.