The oncogenic role of YEATS4 in tumor growth and metastasis in hepatocellular carcinoma

Abstract

Hepatocellular carcinoma (HCC) is one of the most prevalent cancers worldwide with a poor prognosis, ranked as the third-highest cause of cancer-related death. Most HCC patients are diagnosed at the advanced stage because it has no obvious clinical symptoms in the early stage. With the advances in diagnosis and therapy, more and more HCC patients are benefited from the treatment. However, the understanding of the mechanisms behind the development and progression of HCC is still limited. Since surgery is the most effective way to cure HCC, early diagnosis becomes very important. In addition, due to the characteristics of liver cancer-prone to metastasis, liver cancer often metastasizes at an early stage. The recurrent tumors also show stronger tumorigenicity, aggressiveness, and stem cell characteristics. To find genes with pivotal clinical significance and application prospects in early diagnosis and recurrence prevention, we combined the sequencing data of embryonic cell differentiation models with the sequencing data of clinical samples to try to find genes that are highly expressed in the early stages of embryonic cell differentiation and upregulated in tumors. Through further analyzing the gene information in the TCGA database and literature review, we finally determined YEATS4 as our research object. The expression of YEATS4 was upregulated in a variety of cancers. GEO, HKU cohort, and TCGA data showed that YEATS4 expression in tumor tissues was higher than in normal tissues. The expression level of YEATS4 was negatively correlated with the overall survival rate, disease-free survival rate, and other poor prognosis clinical characters. XTT assay and foci formation assay showed that promoting YEATS4 expression can significantly enhance the proliferation of HCC cells. At the same time, increasing YEATS4 expression could also promote cell invasion and migration in vitro. The in vivo metastatic tumor formation assay also proved that the expression level of YEATS4 had a significant correlation with tumor growth ability and metastasis ability. The results of the nude mice subcutaneous tumor formation experiment and NOD/SCID mice liver orthotopic tumor formation experiment showed that YEATS4 could promote tumor formation and metastasis. Down-regulating the YEATS4 level could get the opposite results. In this study, we found that YEATS4 promoted cell proliferation by accelerating the cell cycle and stimulating the expression of CDK2 and Ki67. YEATS4 also enhanced EMT by upregulating Snail, Slug, MMP9, and Vimentin, while inhibiting the expression of epithelial markers E-cadherin and tight junction protein ZO-1, thereby promoting the invasion and migration of HCC cells. Bioinformatics and GO analysis based on the TCGA database provide more evidence for YEATS4 to regulate EMT and proliferation-related biomarkers. The results of protein-protein interaction analysis and CHIP-qPCR experiments also indicated that YEATS4 could interact with H3K27ac, which may induce chromatin modification and ultimately trigger the transcription of tumorigenesis genes.