Increased EXT1 gene copy number correlates with increased mRNA level predicts short disease-free survival in hepatocellular carcinoma without vascular invasion

Exostosin-1 (EXT1) has been demonstrated to participate in the progression of many cancers. However, it has not been previously described in patients with hepatocellular carcinoma (HCC) without vascular invasion. In this study, we got the accurate data of EXT1 mRNA Z-score from the CBio data portal of The Cancer Genome Atlas (TCGA), which was used to express the level of EXT1 gene expression. We analyzed the EXT1 gene expression between HCC and normal liver tissue and compared the clinical significance of tumor tissue's EXT1 gene expression of HCC patients without vascular invasion based on data from TCGA database. The association between EXT1 gene expression and disease-free survival (DFS) was further analyzed. EXT1 gene copy number was also analyzed in this study. Univariate and multivariate analyses showed that high EXT1 gene expression group was significantly poorer than that of the low EXT1 gene expression group (P = .004). In addition, EXT1 gene expression was positively associated with α-fetoprotein (AFP), which is a well-known marker for HCC. There was a significant positive correlation between EXT1 copy number and upregulated EXT1 gene (P < .0001). In conclusion, upregulation of EXT1 could be an important indicator to the short DFS of HCC patients without vascular invasion. EXT1 gene copy number amplification is one of the mechanisms underlying the upregulation of EXT1.