BRD4/8/9 are prognostic biomarkers and associated with immune infiltrates in hepatocellular carcinoma

Bromodomain (BRD)-containing proteins are a class of epigenetic readers with unique recognition for N-acetyl-lysine in histones and functions of gene transcription and chromatin modification, known to be critical in various cancers. However, little is known about the roles of distinct BRD-containing protein genes in hepatocellular carcinoma (HCC). Most recently, we investigated the transcriptional and survival data of BRD1, BRD2, BRD3, BRD4, BRD7, BRD8, BRD9 in HCC patients through ONCOMINE, UALCAN, Human Protein Atlas, GEPIA, cBioPortal, STRING, TIMER databases. BRD1/2/3/4/7/8/9 were over-expressed in HCC and were significantly associated with clinical cancer stages and pathological tumor grades. High mRNA expressions of BRD4/8/9 were promising candidate biomarkers in HCC patients. The rate of sequence alternations in BRD1/2/3/4/7/8/9 was relatively high (52%) in HCC patients, and the genetic alternations were correlated with shorter overall survival and disease-free survival in HCC patients. Additionally, the mRNA expression levels of individual BRD genes were significantly positively associated with the immune infiltrating levels of B cells, CD8(+) T cells, CD4(+) T cells, macrophages, neutrophils, and dendritic cells. And the associations between BRD1/2/3/4/7/8/9 and diverse immune marker sets showed a significance. Overall, these results indicated that BRD4/8/9 could be potential prognostic markers and druggable epigenetic targets in HCC patients.