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<div>Abstract<p>Osteosarcoma is an aggressive malignancy with poor prognosis. Super-enhancers (SE) have been highlighted as critical oncogenic elements required for maintaining the cancer cell characteristics. However, the regulatory role of SEs in osteosarcoma properties has not yet been elucidated. In the current study, we found that osteosarcoma cells and clinical specimens shared a significant fraction of SEs. Moreover, leukemia-inhibitory factor (LIF) was identified as an essential factor under the control of osteosarcoma-specific SE. The expression of LIF was positively correlated with the stem cell core factor genes in osteosarcoma. Furthermore, LIF recombinant protein–treated osteosarcoma cells displayed enhanced stem cell–like characteristics, such as increased sphere-forming potential, stimulated self-renewal, upregulated metastasis ability, and increased stemness-related gene expression. Notably, the histone 3 lysine 27 tri-methylation (H3K27me3) demethylase UTX was found as a key activator of LIF transcription in osteosarcoma. The UTX inhibitor, GSK-J4, induced H3K27me3 accumulation and impaired histone 3 lysine 27 acetylation (H3K27ac) at LIF gene locus, leading to LIF signaling pathway inhibition. GSK-J4 treatment resulted in profound defects in stem cell-like characteristics and stemness-related gene activation in osteosarcoma by modulating the H3K27ac of NOTCH1 signaling pathway gene loci. The NOTCH1 inhibitor Crenigacestat (TargetMol, T3633) repressed LIF-mediated activation of the stemness-related genes in osteosarcoma patient-derived primary tissues.</p>Implications:<p>This study reveals osteosarcoma SE profiles and uncovers a distinct tumor–stemness epigenetic regulatory mechanism in which an osteosarcoma-specific SE-mediated factor, LIF, promotes osteosarcoma stemness gene activation via NOTCH1 signaling pathway.</p></div>

<p>Supplementary Figure 1. Super-enhancers (SEs) in osteosarcoma cells. Related to Figure 1. Supplementary Figure 2. LIF promotes epithelial-mesenchymal transition (EMT) gene expression. Related to Figure 2. Supplementary Figure 3. GSK-J4 inhibits stem cell-like properties of osteosarcoma cells. Related to Figure 3. Supplementary Figure 4. GSK-J4 treatment results in stemness related gene inactivation. Related to Figure 4. Supplementary Figure 5. LIF activates NOTCH1 signaling pathway. Related to Figure 5. Supplementary Figure 6. Crenigacestat suppresses NOTCH1 signaling pathway genes. Related to Figure 6. Supplementary Table 1. Primers used in this study</p>

<p>Supplementary Figure 1. Super-enhancers (SEs) in osteosarcoma cells. Related to Figure 1. Supplementary Figure 2. LIF promotes epithelial-mesenchymal transition (EMT) gene expression. Related to Figure 2. Supplementary Figure 3. GSK-J4 inhibits stem cell-like properties of osteosarcoma cells. Related to Figure 3. Supplementary Figure 4. GSK-J4 treatment results in stemness related gene inactivation. Related to Figure 4. Supplementary Figure 5. LIF activates NOTCH1 signaling pathway. Related to Figure 5. Supplementary Figure 6. Crenigacestat suppresses NOTCH1 signaling pathway genes. Related to Figure 6. Supplementary Table 1. Primers used in this study</p>