Increased mediator complex subunit 15 expression is associated with poor prognosis in hepatocellular carcinoma

Mediator complex subunit 15 (MED15) is a coactivator involved in the regulated transcription of RNA polymerase II-dependent genes and serves an oncogenic role in numerous types of cancer. However, the expression and function of MED15 in hepatocellular carcinoma (HCC) remain unknown. In the present study, the aim was to investigate the expression and clinical significance of MED15 in HCC. Reverse transcription-quantitative polymerase chain reaction (RT-qPCR) and immunohistochemical analysis revealed that MED15 mRNA and protein levels were significantly upregulated in HCC tissues compared with those in the corresponding adjacent non-tumor liver tissues. Furthermore, analyzing data from The Cancer Genome Atlas-Liver Hepatocellular Carcinoma (TCGA-LIHC) and GSE14520 datasets revealed a significant correlation between MED15 expression and the tumor size (P=0.033), Barcelona Clinic Liver Cancer stage (P=0.031), α-fetoprotein levels (P=0.002) and metastasis risk (P=0.001). Furthermore, patients with high MED15 expression levels had a shorter survival time compared with those with low MED15 expression levels (P<0.05). Univariate and multivariate analyses further revealed that MED15 may be an independent prognostic factor for the overall survival of HCC patients (hazard ratio, 1.762; 95% confidence interval, 1.077–2.882; P<0.05). In addition, MED15 expression was positively associated with hypoxia-inducible factor 1α expression in the TCGA-LIHC and GSE14520 datasets (P<0.01). In conclusion, the data reported in the present study indicated that MED15 is overexpressed in HCC and may represent a novel prognostic biomarker for patients with HCC.