Super-silencer perturbation by EZH2 and REST inhibition leads to large loss of chromatin interactions and reduction in cancer growth [Hi-C]

Human silencers have been shown to exist and regulate developmental gene expression. However, the functional importance of human silencers need to be elucidated such as the working mode and whether they can form “super-silencers”. Here, through interrogating two putative silencer components of FGF18 gene, we found that two silencers can cooperate via compensated chromatin interactions to form the “super-silencer”. Furthermore, double knock-out of two silencers exhibited synergistic upregulation of FGF18 expression and changes of cell identity. To disturb the “super-silencers”, we applied the combinational treatment of GSK343 and X5050 (“GR”). We found that GR led to severe loss of TADs and loops, while any single treatment only had mild changes. Such changes of TADs and loops may due to the decreased CTCF proteins upon the GR treatment. Moreover, GSK343 and X5050 can work synergistically to upregulated the super-silencer controlled apoptotic genes, thus gave rise to antitumor effects including apoptosis, cell cycle arrest and tumor growth inhibition. Overall, our data demonstrated the first example of “super-silencer” and showed that combinational usage of GSK343 and X5050 maybe the potential drug to curing cancers through disruption of “super-silencers”.