HCC is a highly malignant disease with a poor prognosis. Currently, scholars have developed some scoring systems to predict the prognosis of HCC patients and guide the selection of treatment, such as the Barcelona Clinic Liver Cancer (BCLC), Child-Pugh score, and Cancer of the Liver Italian Program (CLIP). However, the utility of these scoring systems in predicting the survival rates of late-stage HCC patients is usually limited [15]. Therefore, establishing an accurate and effective HCC prognosis evaluation system is essential. Several studies have revealed that ISGs are closely related to the prognosis of various tumors and the effect of treatments such as radiotherapy and immunotherapy [5–7, 16]. However, the role of ISGs in HCC remains unclear. In this study, we constructed a novel prognostic model based on three ISGs, revealing the value of ISGs in predicting the survival outcomes of HCC patients for the first time.
As is well known, the accumulation of genomic alterations can alter the molecular and cellular biology processes of cells, driving the occurrence and development of HCC. At the same time, these changes can be used as biomarkers for predicting treatment response and evaluating tumor prognosis [17]. In our study, we identified three important genes (BUB1, NDC80, and SOCS2) that are differentially expressed in tumor tissue and adjacent normal tissue and are also correlated with the survival outcome of HCC patients. These genes play important roles not only in the interferon response but also in tumorigenesis and tumor progression. BUB1, a mitotic serine/threonine kinase, plays an important role in maintaining correct ploidy through mitosis [18] and it drives the occurrence and development of bladder cancer by mediating the STAT3 signaling pathway [19]. In addition, the abnormal expression of BUB1 is also associated with the prognosis of various tumors, such as sarcoma [20] and breast cancer [21]. SOCS2, a kind of adaptor protein that acts as the substrate recognition subunit of Cullin/Ring ubiquitin ligases [22], is closely related to somatic cell growth by regulating the GH/IGF-1 signal pathway [23]. Previous research has shown that overexpression of SOCS2 inhibits the growth of ovarian cancer cells and breast cancer cells [24], as well as the proliferation and migration of hepatocellular carcinoma cells [25]. Therefore, it is reasonable to consider SOCS2 as a tumor suppressor factor. NDC80 (also called Hec1) is a core component of the kinetochore and plays a critical role in chromosome segregation during mitosis[26]. It has been shown to promote the proliferation and migration of liver cancer [27], gastric cancer [28], and pancreatic cancer cells [29], but its exact mechanism of action in tumorigenesis is not clear.
Then, a risk score model based on these three genes was constructed, and the risk score was calculated by using the risk score formula. Patients were divided into the HR group and LR group according to the median risk score value. The results showed that patients with higher risk scores had poorer overall survival (OS). A high risk score was closely related to clinical pathological parameters representing poor prognoses, such as high AFP, vascular infiltration, low tumor differentiation, and advanced tumor stage. Univariate and multivariate analyses showed that this score was an independent risk factor affecting the prognosis of HCC patients. Furthermore, to verify its universal applicability, patients were stratified into several subgroups based on clinical and pathological features such as age, gender, race, AFP level, tumor T stage, TNM stage, Edmondson grade, and vascular invasion. Internal validation results showed that the model had good predictive ability in several subgroups of patients with different clinical characteristics. Moreover, in the TCGA database, this score demonstrated excellent predictive efficacy for patients’ OS, PFS, and DSS. External validation using the ICGC database confirmed the robustness of the score’s predictive ability. In summary, this risk score exhibits strong predictive power in the prognosis of HCC patients in both the training set and testing set.
It has been reported that the occurrence and development of tumors are associated with the accumulation of genetic mutations. In our study, we analyzed the differences in the genetic mutation profiles between the HR group and LR group and found that missense mutations were the most commonly observed form of mutation in both groups. The HR group had a higher proportion of gene mutations, such as TP53, TTN, CTNNB1, MUC16, and CSMD3. In particular, the proportion of TP53 mutations in the HR group was significantly higher than that in the LR group. Notably, previous studies have reported that TP53 mutations are closely associated with higher Edmondson grade, microvascular invasion [30], and a poorer prognosis [31]. Then, the GSEA results showed that the oxidative phosphorylation and adipogenesis signaling pathways were significantly activated in the HR group. Changes in mitochondrial oxidative phosphorylation function contribute to the proliferation, metastasis, and invasion of HCC [32]. Continuous de novo lipogenesis provides membrane building blocks, lipid signaling molecules, protein translation post-translational modifications, and energy supply to support the rapid proliferation of cancer cells [33]. In addition, the HR group also showed higher TMB levels and stemness scores, both of which are associated with a poorer prognosis. Consistent with our study, patients with high TMB in liver cancer have a significantly poorer overall prognosis [34] and high stemness scores are associated with malignant characteristics in many cancers [35]. In summary, these results explained the underlying reasons for the poorer prognosis represented by the HR group from the perspective of genetic alterations.
The tumor microenvironment is a unique environment that appears due to the interaction between the tumor and host during the progression of the disease, consisting of proliferating tumor cells, tumor stroma, blood vessels, infiltrating inflammatory cells, and various related tissue cells [36]. In our study, we found that the infiltration of common lymphoid progenitors, memory CD4 + T-cell, and CD4 + T-cell (Th2) was higher in the HR group, and the enrichment of these cells often led to a poor prognosis. Similarly, Yang et al.'s study showed that the infiltration of common lymphoid progenitor and CD4 + T-cell (Th2) cells is negatively correlated with the survival rate of pancreatic cancer patients, which also confirms our point [37]. In addition, our findings also revealed that the HR group had lower stroma scores and microenvironment scores compared to the LR group, which were strongly associated with a poorer prognosis. These results are consistent with the findings from Huo et al.'s study [38]. The immune microenvironment of HCC patients with a higher risk score is poorer, which may be one of the reasons for their poorer prognosis.
In order to better guide the selection of clinical treatment methods, we evaluated the sensitivity of patients in different risk groups to immunotherapy, targeted therapy, and chemotherapy. TIDE score is a novel biomarker for predicting response to immunotherapy. We found that the HR group had a lower TIDE score, which indicates a lower likelihood of tumor immune evasion [39]. Moreover, the HR group had significantly higher expression levels of immune checkpoint genes and higher TMB levels [40]. This suggests that patients in the HR group may have a better response to immunotherapy. Additionally, we also discussed the potential sensitivity of different risk groups to various drugs, and the results showed that the HR group had a higher sensitivity to multiple chemotherapeutic and targeted drugs. Therefore, although a higher risk score represents a poor prognosis, it also indicates a higher sensitivity to chemotherapy, targeted therapy, and immunotherapy. However, the ultimate efficacy of these drugs still needs to be verified in clinical trials.
To determine the differences in the mRNA expression of BUB1, NDC80, and SOCS2 genes in tumor cell lines and normal liver cell lines, we detected the mRNA levels of these genes using real-time PCR. Consistent with the results obtained in tumor tissues, we found that BUB1 and NDC80 were significantly more highly expressed in tumor cell lines, while SOCS2 was significantly more highly expressed in tumor cell lines compared with normal liver cell lines.
To sum up, we have developed an excellent stability and universality risk score model for HCC based on the analysis of high-throughput sequencing data, which consists of only three genes. This prognostic model is not only beneficial for clinical applications but also helps to reduce the sequencing cost. However, there are limitations to our study. On the one hand, this study is a retrospective analysis based on public data, and further validation in a large multi-center prospective study is needed. On the other hand, the selected genes have important prognostic value, and our study has not fully revealed their underlying mechanisms, which requires more in vitro and in vivo experiments for further verification.