The current study revealed that 10 CHGs, including TOP2A, CCNB1, CDK1, MAD2L1, RRM2, CCNA2, BUB1B, CDC6, AURKA, and BUB1, were associated with the prognosis of GIC. A prognostic model based on three common GIC CHGs, including CCNB1, MAD2L1, and BUB1, was established using LASSO-cox regression analysis to detect HCC prognosis. Moreover, the immune cell infiltration analysis showed a significant reduction in type I and type II IFN response pathways-related genes in high-risk HCC patients. These results were verified in the internal and ICGC cohorts.
Studies have shown that various prognostic-related hub genes, including integrin alpha subunit 5 (ITGA5), and microRNA, which are associated with the survival and clinicopathological features of GIC, might be potential biomarkers for the diagnosis and treatment of GIC [22, 23]. Studies investigating the role of the CHGs, which were identified in the current study in these GICs, are limited. The overexpression of TOP2A, a prognostic marker related to low survival rate, could induce the progression and recurrence of colorectal and liver cancers mainly through the regulation and replication of DNA topological state [24]. Wong et al. showed that TOP2A was overexpressed in HCC and was associated with histological grade, microvascular invasion, tumor progression, shortened survival, and resistance to chemotherapy [25]. CCNB1 could promote the phosphorylation of AKT and PI3K in liver cancer and play a crucial role in the abnormal cell cycle by promoting the ubiquitination of P53 as well as reducing its expression [26]. It has been reported that ellagic acid (EA), an important polyphenol compound, plays an anticancer role in various types of cancers, including colorectal, liver, and pancreatic cancers, by affecting different hub genes, such as CDK1, CCNA2, and CCNB1 [27]. MAD2L1, a pre-oncogene, with upregulated expression levels in gastric cancer, maintains the separation of chromosome and spindle during mitosis and acts as a checkpoint [28]. Wang et al. showed that the hepatitis B virus (HBV) could activate the expression of ribonucleoside reductase subunits M2 (RRM2) as well as the activity of the RR enzyme, thereby replicating viral DNA in host hepatocytes[29]. Moreover, RRM2 is also an important gene for Gemcitabine resistance in pancreatic cancer; therefore, RRM2 might be an important therapeutic target for HBsV-related HCC and pancreatic cancer [30].
Currently, studies on prognostic models related to HCC, such as copper death and cell senescence, have been successively conducted [31, 32]. The current study selected three genes among the 10 CHG genes to successfully construct a prognostic model of HCC. Recent studies suggested that the expression levels of CHGs, including CCNB1, MAD2L1, and BUB1, were greatly different in tumor and non-tumor tissues, and were greatly associated with the adverse survival rates of HCC patients [33]. These findings were consistent with the findings of the current study. Few studies have shown that CyclinB1 (CCNB1) is a key gene in the development of liver cancer [34]. Studies have shown that ncRNA-mediated upregulation of MAD2L1 is a predictor of adverse outcomes and tumor invasion in HCC [35]. MiR-200c-5p could inhibit the expression of the MAD2L1 gene, which led to inhibiting the migration, invasion, and proliferation of HCC cells [36]. In HCC, BUB1 is upregulated and is directly regulated by miR-490-5p, which leads to inhibiting the viability, proliferation, and migration of tumor cells and inducing cell cycle arrest and apoptosis [37]. Studies showed that these genes could significantly affect the progression and prognosis of HCC, thereby suggesting the prediction potential of the CHGs-based prognostic model.
Moreover, the functional enrichment analysis revealed that the common DEGs in the six GICs were mostly concentrated on the pathways related to cell proliferation and cell division. Studies have shown that the occurrence and development of both GIC and HCC are related to cell cycle disorders, and cyclin-dependent kinase 4/6 inhibitors are considered promising therapeutic strategies for GIC [38]. Therefore, CHGs might affect the cell cycle and promote the occurrence and progression of GIC by interfering with DNA or chromosome replication. Studies suggested that the changes in genomic and epigenomic DNA are present in almost all GICs [4]. Abnormal DNA methylation is a biomarker for the prognosis and diagnosis of GICs [39]. These findings were also consistent with those of the current study.
The treatment of HCC has been greatly changed by the use of ICIs [40, 41]. TIME performs an imperative part in the efficacy of ICIs [42]. IFN, a key factor of immune response in the TIME, is crucial for tumor immune surveillance, and the combination of type I and II IFNs could be regarded as a hopeful new anti-tumor therapy [43, 44]. In the current study, the immune functions of type I and II IFN response pathways were limited in the TIME of HCC. Studies have shown that ferroptosis and pyroptosis are significantly associated with the TIME of liver cancer. The low-risk group patients in the ferroptosis and pyroptosis models had a much better prognosis in predicting overall survival and anti-tumor immune function as compared to those in the high-risk group. In both internal and external cohorts of the ferroptosis and pyroptosis high-risk groups, the type I and II IFN response pathways were significantly lower than those in the low-risk group [45, 46]. This further validated the results of the current study and might be one of the specific mechanisms, by which, CHGs could affect the TIME of HCC. Moreover, a study reported that in tumor tissues, higher expression of IL-17 significantly inhibited IFN-γ-induced apoptosis in HCC cells and promoted HCC [47]. In NK cells in patients with chronic HBV infection, the secretion capacity of IFN-γ was reduced, which was involved in the progression of HCC. Moreover, the NK cell functions in HCC patients, including IFN-γ production, were downregulated as compared to those in healthy people [48]. IFIT3 could enhance the anti-tumor effects of IFN-α by promoting IFN-α response both in vitro and in vivo as well as could promote IFN-α response and therapeutic effects by enhancing IFN-α signaling in HCC [49]. These studies suggested that CHGs might inhibit the type I and II IFN response pathway and reduce the expression level of IFN, thereby, reducing its effects on HCC immunogenicity, immune infiltration, and adaptive immune attack as well as promoting the occurrence and progression of HCC. This also suggested that a decrease in the expression levels of IFN could disrupt the homeostasis of the cell cycle and cell death, mediated by the interaction of tumors with innate and adaptive immunity. The tumor cells that survive immune attacks are less sensitive to IFN; therefore, they are less immunogenic and are not detected easily by the adaptive immune system. Moreover, aged tumor cells can persist during this stage. Moreover, the cells that do not respond to IFN can acquire stem cell capabilities, such as self-renewal, to maintain the survival of this cell population, thereby promoting tumor survival [50]. In HCC, cytotoxic clearance of disseminated tumor cells is facilitated by the production of perforin by activated NK cells or by interactions between intrahepatic lymphocytes and Kupffer cells[51, 52]. CHGs might evade the role of immune effector cells, including liver-resident and liver-infiltrating NK cells, in the immune surveillance of HCC.
The current study built a reliable predictive prognostic model based on CHGs in HCC count using LASSO Cox regression analysis by searching for prognosis-related CHGs in GIC. Meanwhile, the model was verified using external and internal cohorts, which significantly improved the reliability of the data. However, there were certain limitations to the current study, such as the lack of experimental data to verify the correlations between CHGs and immune activity. Secondly, numerous prognostic genes and immune checkpoints of HCC were not considered, and only 19 immune cells were included, which might not be comprehensive enough; therefore, further research is needed.
In conclusion, the current study revealed 10 CHGs, including TOP2A, CCNB1, CDK1, MAD2L1, RRM2, CCNA2, BUB1B, CDC6, AURKA, and BUB1, in six GICs. A prognostic model was constructed based on three GIC CHGs, including CCNB1, MAD2L1, and BUB1 for HCC. Moreover, the results showed that the type I and II IFN response pathways were greatly reduced in the high-risk group of HCC patients. These findings might provide a novel perspective for targeted therapy of GIC as well as new ideas for immunotherapy of HCC.