Abstract A15: Epigenetic up-regulation of ribosome biogenesis and more aggressive phenotype triggered by the lack of the histone demethylase JHDM1B in mammary epithelial cells

Abstract

Abstract Alterations of ribosome biogenesis and protein synthesis play a direct role in the development and the behavior of tumors. The accessibility and transcription of ribosomal genes are controlled at several levels, with their epigenetic regulation being one of the most important. Here we explored the JmjC domain-containing histone demethylase 1B (JHDM1B) function in the epigenetic control of rDNA transcription. Since JHDM1B is a negative regulator of gene transcription, we focused on the effects induced by its downregulation. We studied the consequences of inducible JHDM1B knock-down (KD) in cell lines derived from transformed (MDA-MB-231) and untransformed (MCF-10A) mammary epithelial cells. In these cellular models, sustained JHDM1B down-regulation triggered an increase in 45S pre-rRNA transcription and processing, associated with a re-modulation of the H3K36me2 levels at the rDNA loci. By means of the EpiTYPER assay, we observed that JHDM1B KD reproducibly induced quantitative changes in DNA methylation of specific CpG sites in rDNA genes. By polysomal profile analysis, we also found that JHDM1B KD induced an higher content of ribosomes in both the pre-polysomal and polysomal fractions indicating an increase in global protein synthesis. We then investigated in vitro and in vivo the behavior of cells after JHDM1B KD and the associated stimulation of ribosomes biogenesis. JHDM1B down-regulation conferred more aggressive features to the tested cellular models, which acquired a greater clonogenic and invasive potential in vitro. The study of tumors generated in nude Balb/c mice after xenografting MDA-MB-231 cells, indicated that JHDM1B KD triggered an incremental (although not statistically significant) trend in tumor growth. In addition, the selective nucleolar staining of sections from these tumors revealed a significant increase in the average nucleolar area after JHDM1B KD. Taken together, these data indicate that the reduction of JHDM1B leads to an increase in ribosome production and to a more aggressive cellular behavior in mammary gland cells. Citation Format: Alice Galbiati, Marianna Penzo, Maria Giulia Bacalini, Carmine Onofrillo, Ania Naila Guerrieri, Paolo Garagnani, Claudio Franceschi, Davide Treré, Lorenzo Montanaro. Epigenetic up-regulation of ribosome biogenesis and more aggressive phenotype triggered by the lack of the histone demethylase JHDM1B in mammary epithelial cells. [abstract]. In: Proceedings of the AACR Special Conference on Translational Control of Cancer: A New Frontier in Cancer Biology and Therapy; 2016 Oct 27-30; San Francisco, CA. Philadelphia (PA): AACR; Cancer Res 2017;77(6 Suppl):Abstract nr A15.