Abstract
Introduction
p300 is a well-known coactivator of the androgen receptor (AR) and has been shown to play an important role in prostate cancer (PCa). The expression of p300 has been correlated to tumor volume and PCa progression. Therefore, we hypothesize that p300 may play an important role in tumor-initiating cells and therapy resistance. Due to its multifunctional role p300 may serve as a promising new therapeutic target for treatment of PCa. Ultimately, it is our aim to find new innovative therapeutic targets for castration resistant PCa.
Material & Methods
The tumor-initiating capacity of the AR-negative PCa cell lines PC3 and Du145, as well as primary prostate epithelial cells was characterized by seeding a limiting number of cells per flask. Colony formation efficiency, colony type and detailed morphological information about each colony were determined by an automated pipeline that we have developed. Stable cell lines with doxycycline inducible p300 sh RNAs were generated by lentiviral transduction. Knockdown of p300 was verified by Western Blot and reduced p300 activity was confirmed by measuring histone h3 acetylation.
Results
In concordance with the literature we identified three colony types (holo-, mero- and paraclones) in PC3 and Du145 cell lines as well as primary PCa cells. Serial clonogenic assays confirmed in both cell lines that holoclones show the highest colony formation potential and maintain their tumor-initiating capacity over numerous rounds. In PC3 we detected 10% and in Du145 30% holoclones. Under optimal growth conditions p300 was detected in all colony types, however no differences in protein expression of p300 as well as on mRNA level were observed. Knockdown of p300 did not alter colony formation efficiency or the relative distribution of colony types.
Conclusion
Taken together, we confirmed the presence of tumor-initiating holoclones in PCa cell lines and primary prostate epithelial cells and established stable cell lines with inducible knockdown of p300. In contrast to several other types of malignancies, p300 has no specific role in regulation of stemness in our PCa models at the tested conditions. As a next step we will determine the effects of p300 knockdown during chemotherapy and radiation therapy to evaluate if p300 depletion may enhance the treatment efficacy and which role p300 plays in therapy resistance.
Citation Format: Martina Gruber, Florian Handle, Zoran Culig. Transcriptional integrator p300 in human prostate tumor-initiating cells [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 2001.
RSS Feeds