Epigenetic Profiling Identifies LIF as a Super-enhancer-Controlled Regulator of Stem Cell-like Properties in Osteosarcoma.

Bing Lu,Jincan He,Zhuoxing Gao,Guohao Lu,Li Wang,Zhenguo Liu,Changye Zou,Yangyang He,Wei Zhao,Jiayan Yang

doi:10.1158/1541-7786.mcr-19-0470

Abstract

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. IMPLICATIONS: 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.

Highlights

Osteosarcoma is the most common primary bone tumor in childhood and adolescence
For defining the SE profiles in osteosarcoma, we investigated active enhancer landscapes defined by H3K27ac modification across a cohort of osteosarcoma cell lines (143B and SJSA1), primary osteosarcoma cells (ZOS and ZOSM) [10], primary osteosarcoma surgical specimens
Drug resistance is a common problem in the treatment of cancer and sarcoma, it is devastating for patients with osteosarcoma as nearly 50% of treatment responders develop recurrence due to drug resistance [12]

Summary

Introduction

Osteosarcoma is the most common primary bone tumor in childhood and adolescence. Despite several attempts to augment therapy in many large clinical trials through dose intensification, survival outcomes for advanced osteosarcoma patients remain mostly unchanged over the past 30 years [1]. The leading clinical complication of osteosarcoma is the unpredictable recurrence or metastasis due to intratumoral heterogeneity [2]. The osteosarcoma stem-like cells (OSC) are a rare subset of tumor clones related to treatment resistance, recurrence, and metastasis. Various OSC populations with different functional characteristics may coexist in osteosarcoma simultaneously. A comprehensive understanding of OSC-derived heterogeneity will

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Results

Conclusion