Neuroblastoma (NB) is a highly malignant pediatric cancer of the sympathetic nervous system with high biological and clinical heterogeneity. Possibly, the rearrangement of the “epigenetic machinery” and the reorganization of chromatin could have a crucial role in NB malignant transformation. In eukaryotic cells, DNA is packaged into chromatin fibers where the nucleosome is composed of a histone octamer (duplicates of H2A-H2B and H3-H4 dimers) wrapped by 147 base pairs of DNA. Therefore, we established a cellular model of malignancy where the neuroblastoma cell line SKNBE2 overexpressing the lncRNA NDM29 goes toward a retro-transformation from a highly malignant (Mock) into a neuron-like (S1.1) phenotype. To profile the chromatin epigenetic changes sustaining this retro-transformation, we assessed (1) global epigenetic modifications of H3 and H4 histone tails by ELISA assay and (2) H2B mono-ubiquitination (ubH2B-K120) by western blot and NSPARC fluorescence microscopy. Our preliminary analyses reveal epigenetic changes in neuron-like (S1.1) phenotype compared to malignant (Mock) cells. In detail, a rearrangement of H3 and H4 epigenetics was observed by ELISA assay when malignant cells assume a neuron-like phenotype together with a global increase in the level of H2B mono-ubiquitination. Furthermore, NSPARC imaging revealed a major reorganization of chromatin, marked by changes in the distribution of total and monoubiquitinated histone H2B during the retro-differentiation of neuroblastoma (NB) cells. Specifically, total H2B shifted from the nuclear periphery toward the center in S1.1 cells, indicating a more uniform chromatin distribution. Our findings clearly indicate dysregulated patterns of post-translational modifications of histones H2B, H3 and H4 that are associated to retro-transformation of highly malignant NB cells toward a neuron-like phenotype. These findings may suggest that epigenetic combination therapy may be a novel strategy for the future clinical treatment of neuroblastoma cancer.
Zbeeb et al. (Sun,) studied this question.