Abstract B225: Short activating RNA (saRNA) targeting C/EBPA significantly inhibits cell proliferation of undifferentiated cancer cells.

In general, ‘poorly’ differentiated tumours have a worse prognosis when compared to more ‘well’ differentiated ones. Therefore, the use of a biological agent that could promote differentiation might have a therapeutic advantage. CCAAT enhancer binding protein alpha (C/EBPα) is a transcription factor known to be involved in the regulation of cell differentiation in a number of tissue types. Loss of C/EBPα expression, for example, causes abnormal levels of biliary transcription factors, impaired hepatocyte maturation and liver fibrosis. In contrast C/EBPα overexpression inhibits the development of hepatocellular carcinoma, restores myeloid differentiation and prevents hyperproliferation of hematopoietic cells in acute myeloid leukemia. In this study, we tested the effect of stimulation of C/EBPα expression by a specific small activating RNA (saRNA) on a panel of cell lines representing both well-differentiated and poorly-differentiated cancer cell types. The C/EBPα-saRNA inhibited proliferation of poorly differentiated small cell lung cancer and pancreatic cancer cell lines compared to treatment with scrambled double-stranded RNA controls. However C/EBPα-saRNA was not as effective in suppressing proliferation in well-differentiated insulinoma and breast cancer (MCF7) cell lines. Comparison of endogenous levels of C/EBPα, using qPCR and Western blots, showed that undifferentiated tumour cell lines expressed lower levels of C/EBPα when compared to the well-differentiated tumor types. Gene expression analysis in tumours from xenografts and cirrhotic DEN treated HCC rats, demonstrated that saRNA mediated stimulation of C/EBPα expression, could suppress the steady-state transcript levels for KLF4, OCT3, SOX2, C-Myc and C-Kit. The inhibited expression of these transcription factors correlated with greater expression of differentiation markers and reduced epithelial mesenchymal transition by the C/EBPα saRNA treated cells. Our results suggest that saRNA mediated stimulation of C/EBPα, could be of potential therapeutic value, especially in poorly differentiated cancers. Furthermore, intracellular expression levels of C/EBPα could be an important prognostic factor for predicting the therapeutic response in poor or un-differentiated tumors. Citation Information: Mol Cancer Ther 2013;12(11 Suppl):B225. Citation Format: K W. Huang, Vikash Reebye, Paul J. Mintz, Pal Saetrom, Piotr Swiderski, L Peng, C Liu, X X. Liu, Steen Lindkaer Jensen, Dimitris Zacharoulis, Nikos Kostomitsopoulos, Noriyaki Kasahara, Joanna Nicholls, Long R. Jiao, Madhava Pai, Duncan Spalding, Farzin Farzaneh, Malkhaz Mizandari, Tina Chikovani, Mohammed Emara, Abdelali Haoudi, Don Tomalia, John J. Rossi, Nagy A. Habib. Short activating RNA (saRNA) targeting C/EBPA significantly inhibits cell proliferation of undifferentiated cancer cells. [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2013 Oct 19-23; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2013;12(11 Suppl):Abstract nr B225.