IS and RP designed experiments, analyzed data and wrote the paper. Conflict of Interest Statement The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest. Acknowledgments We are grateful to Dr. JMJD3 and p300, and it was required to preserve transcriptional permissive/active H3K27 marks and to sustain gene expression levels. Consistently, pharmacological inhibition of JMJD3 by GSKJ4 treatment or of p300 by A-485 decreased the levels of expression of and of the Notch target genes and c-Myc and abrogated cell viability in both Notch1- and Notch3-dependent T-cell contexts. Notably, re-introduction of exogenous Notch1, Notch3 as well as c-Myc partially rescued cells from anti-growth effects induced by either treatment. Overall our findings indicate JMJD3 and p300 as general Notch1 and Notch3 signaling co-activators in T-ALL and suggest further investigation on the potential therapeutic anti-leukemic efficacy of their enzymatic inhibition in Notch/c-Myc axis-related cancers and diseases. gene, which promote increased stability and ligand-independent release of the N1ICD (4). Notch3 receptor has been found overexpressed in most of the patients analyzed (3), and in primary samples, unlike Notch1, its activation was preferentially associated with high expression of full-length receptor rather than with gene mutations or rearrangements (9). These findings are in line with evidence demonstrating that Notch3 receptor is more susceptible than Notch1 to spontaneous basal transcriptional activity due to ligand-independent proteolysis, even though both receptors elicit comparable levels of ligand-dependent activities (11). Overall, these observations indicate machinery regulating over-expression among the major causes of its RFC4 oncogenic malfunction in this malignancy. However, molecular mechanisms sustaining expression remain mostly undefined and, although it is assumed that is a target gene of Notch1, to date it has not been clarified how its oncogenic expression/activation results to be aberrant even in T-ALL cases lacking Notch1 activation. Notably, recent studies indicated epigenetic modifications at gene locus to drive its expression in leukemia, as it has been demonstrated to be hypermethylated in B-ALL samples not expressing proximal AMG-176 promoter is critical to AMG-176 maintain active histone H3 tri-methylated lysine 4 chromatin mark (H3K4me3) (13). Other studies indicated the intron1 of as an enhancer region devoid of repressive H3 tri-methylated lysine 27 mark (H3K27me3) and associated with the active chromatin mark histone H3 acetylated lysine 27 (H3K27ac) in T-ALL cells, This gene region appears to be required for Notch1-dependent transcriptional activation of (14, 15). Levels of H3K27me3 mark at gene loci result from the balance between the methyltransferase activity of the Polycomb-Repressive Complex 2 (PRC2) component EZH2 (16) and of the enzymatic activity of the H3K27 demethylases JMJD3 (also referred to as KDM6B) and UTX (also referred to as KDM6A) (17). Recently, H3K27me3 modifiers have been linked to T-ALL onset and progression and have been demonstrated to be involved in transcriptional crosstalk with Notch1. Indeed, about 25% of T-ALL patients harbor loss-of-function-mutation or deletion of (18). Consistently, EZH2 acts as a tumor suppressor in T-ALL by antagonizing Notch signaling transcriptional activity (18). Similarly, inactivating gene lesions of characterize a group of T-ALL patients and it has been shown that deletion of accelerates leukemia growth in Notch1-dependent mice models (19, 20). Nevertheless, a more recent study proposed that UTX might act as a proto-oncogene in distinct subgroups of T-ALL characterized by the expression of the oncogenic transcription factor TAL1 (21). On the other hand, the H3K27 de-methylase JMJD3 has been found overexpressed in T-ALL samples when compared with physiological T-cell subsets, and it has been shown to sustain Notch1 oncogenic transcriptional program in murine models of T-ALL (19). In general, levels of H3K27ac mainly result from the balance between the enzymatic activity of the acetyltransferase p300 and of the Nucleosome Remodeling Deacetylase complex (NURD) subunits HDAC1 and HDAC2 (22). It is well accepted that p300 acts as a AMG-176 Notch1 transcriptional co-activator (23, 24). Here, we further explored the interplay between Notch signaling and the above-mentioned chromatin modifiers to gain further insights.