ERCC3-Related Genes May Aid in the Prognostic and Immunotherapeutic Analysis of Hepatocellular Carcinoma

Background: Hepatocellular carcinoma (HCC) has high morbidity and mortality worldwide. Excision repair cross-complement 3 (ERCC3), a key functional gene in the nucleotide excision repair (NER) pathway, is commonly mutated or overexpressed in cancers and is thought to be a key gene contributing to the development of HCC. The characteristics of immune cell infiltration in the global tumor microenvironment (TME) mediated by ERCC3 and its related key genes in HCC are still unclear. The aim of this study was to integrate the role of ERCC3-related key genes in assessing the TME cell infiltration characteristics, immunotherapy efficacy, and prognosis of HCC patients. This study provides a theoretical basis for the study of immunological mechanisms and prognosis prediction in HCC. Methods: The HCC cohort from the TCGA database included 50 normal samples and 374 tumor samples to compare the differences in ERCC3-related gene expression and prognosis between liver tumor tissues and normal liver tissues and to analyze the extent to which different genes infiltrated TME cells by quantifying the relative abundance of 24 cells through single-sample genome enrichment analysis (ssGSEA). A risk score associated with the ERCC3 gene was constructed using the least absolute shrinkage and selection operator (LASSO) Cox regression model. Results: The expression of 11 ERCC3-related genes was significantly upregulated in HCC tumor tissues compared to normal liver tissues, and high expression of these genes was significantly associated with poor prognosis in HCC patients. The key genes (11 ERCC3-related genes) were closely associated with the nucleic acid reduction signaling pathway in nucleic acid metabolism and the viral oncogenic pathway, suggesting that these key genes may play a role in tumor cell proliferation, migration, and invasion, as well as in the pathogenesis of virus-associated HCC. In addition, the infiltration characteristics of TME immune cells in normal and tumor tissues were different. Immune and mesenchymal activity was significantly lower in tumor tissues than in healthy liver tissues. This study revealed that key genes were significantly positively correlated with CTLA4 and enriched in central memory CD4 T cells, effector memory CD4 T cells, activated CD4 T cells, and type 2 T helper cells. The prognostic model constructed by regression analysis could better distinguish patients into high-risk and low-risk groups, and the survival analysis showed that the survival time of patients with high-risk score subtypes was significantly lower than that of patients with low-risk scores and that the high-risk group contained higher levels of immune-suppressive cells, which may be a mediator of immune escape. Moreover, multivariate analyses showed that the risk score profile is a reliable and unbiased biomarker for assessing the prognosis of HCC patients, and its value in predicting the outcome of immunotherapy was also confirmed. Conclusion: This study revealed a novel genetic signature that is significantly associated with TME cell infiltration and prognosis in HCC patients. It demonstrated that the combined action of multiple key genes associated with ERCC3 plays a crucial role in shaping the diversity and complexity of TME cell infiltrates. Evaluating the combined characteristics of multiple key genes associated with ERCC3 can help predict the outcome of immunotherapy in patients and provide new potential targets for immuno-individualized therapeutic studies on HCC.