Redistribution of super-enhancers promotes malignancy in human hepatocellular carcinoma

Abstract

Introduction

Super-enhancers (SEs) are defined as the regulatory region where intensive transcriptional cofactors bind. Dysregulation of SEs is related to multiple diseases, however, its role in hepatocellular carcinoma (HCC) remains elusive.

Objectives

This work aimed to reveal the dysregulation of SEs in HCC and the therapeutic potential for HCC treatment.

Methods

Fifteen HCC and twelve paracancerous samples underwent chromatin immunoprecipitation (ChIP) sequencing targeting H3K27ac, and subsequently the SEs were identified by the Rank Ordering of Super-Enhancers algorithm. Differential SEs featured by tumor or paracancerous tissues were identified, and cross-referenced with the differential expression genes and prognosis-related genes in 2 independent public or in-house HCC cohorts. The SE region of HSPA4 was deleted in the genome of HCCLM3 cell by CRISPR-Cas9, named HSPA4-SE-KO cells. The potential druggable transcriptional factors were identified by CRCmapper, GeneMANIA and Drug Gene Interaction Database (DGID).

Results

Five targets, including CDKN2C, HSPA4, GGH, PDGFA, and CAP2, were identified as HCC-gain SEs with oncogenic potential, which were further validated experimentally by SE inhibitors and ChIP targeting H3K27ac and BRD4. Cell proliferation and migration assays further confirmed that silencing of these HCC-gain SEs significantly suppressed the malignant phenotype of HCC cell lines. HSPA4 appeared strongest oncogenic functions among these targets, which was further verified by HCC mouse xenograft models and clinical sample investigation. Moreover, HSPA4-SE-KO cells obtained significantly suppressed HSPA4 expression and retarded tumorigenic capability. Finally, dysregulation of transcriptional factors engaged in the oncogenic role of SEs, and Danthron that targeting RXRA were identified from DGID for HCC treatment.

Conclusion

The dysregulated SE landscape of HCC promoted the malignancy phenotype by the upregulation of oncogenes, and SE-regulatory network might be potential drug targets for HCC treatment. Our study deepened the insight of epigenetic dysregulation in HCC, offering the groundwork for SEs as potential therapeutic targets of HCC treatment.