HCC tends to be diagnosed in advanced stages and is associated with high mortality rates, and the prognosis of these patients after therapy is poor[24]. Immunotherapy as a promising strategy may expected to bring new hope for HCC treatment[25]. Clinically, immunotherapy for HCC has a good effect, but the benefit population only is 20%[26]. How to improve the benefit group of immunetherapy has become a big problem. LncRNAs regulated immune response in HCC had been widely reported[27–29]. Pyroptosis, which induces inflammatory by activates the classical signaling pathway, which may lead to inflammatory and immune in HCC[30, 31]. Few reports have indicated that PRlncRNAs directly regulate HCC progression, and their prognostic roles have not been adequately demonstrated. The relevance of the pyroptosis process and the immune infiltration of tumor is not clear.
In this study, we established a PRlncRNA prognostic signature for HCC patients, found that this model is more accurate in predicting the prognosis of patients than other clinical features and risk score can be used as an indicator to predict survival. We also preliminarily identified molecular function, pyroptosis process and the immune status of AC009283.1 and LINC00942. This model may offer guiding effect on evaluating the immune status of patients and improved clinical utility for immunotherapy strategies in HCC patients.
First, 76 PR-DEGs were enriched mainly in NOD-like receptor signalling pathway and NF-κB signalling pathway by KEGG analysis. Studies have suggested that NK-κB signalling pathway also plays a significant role in poptosis and pyroptosis, which can activate NLRP3/Caspase-1 signalling pathway[32, 33]. The results indicated that PR-DEGs may regulate HCC progression by triggering inflammasome and activating the NLRP3/Caspase-1-dependent pyroptosis pathway and may influencing the NF-κB signalling pathway.
Next, 8 DE-PRlncRNAs were identified and used to construct a risk signature via Cox regression and LASSO regression. Patients were grouped into high- and low-risk groups based on their median risk scores. The high-risk group exhibited shorter OS and DFS than the low-risk group. The ROC areas at 1-, 3- and 5-years indicated that the signature showed a certain level of accuracy and consistency in predicting survival. The risk score exhibited a good prognosis value than other different clinicopathological indexes. These results revealed that risk score can be served as an independent prognostic factor in predicting HCC patient prognosis.
The immune microenvironment mainly related to the changes of immune checkpoints, the proportions and functions of immune cell subpopulations. Therefore, we performed GSEA to research the potential path differences in the low-risk and high-risk groups, found that B-cell and T-cell receptor signalling pathway were mainly enriched in the high-risk group. The higher level of immune function in the high-risk group maybe mainly attribute to immune checkpoints[18]. Immune checkpoint-related genes (PDCD1, CTLA-4, TIGIT, HAVCR2, TNFRSF14) were highly expressed in the high-risk group, which may result in the changes of tumor cells, including decreased the infiltrating levels of immunoreactive cells and increased immunosuppressive cell. PDCD1 can protect against autoimmunity through promoting apoptosis of antigen-specific T cells in the lymph nodes and reducing apoptosis of regulatory T cells[34, 35]. TIGIT can inhibit the NK cell effect by preventing the initial death of tumor cells and releasing tumor antigens, also directly inhibit CD8 + T cell effects, or TIGIT + Treg can inhibit CD8 + T cells and prevent cancer cell clearance. High expression levels of inhibitory immune checkpoints in the high-risk group suggested that PRlncRNAs could evaluate the immune status in tumor microenvironment and improved clinical decision-making in cancer treatment.
ssGSEA analysis also showed that the low-risk group had greater infiltration of mast cells, and NK cells. NK cells and B cells are vital regulators in pyroptosis[36]. Activated NK cells have been reported to promote the production and release of GZMB, activating the Caspase-3-independent pyroptosis pathway, which leads to the death of tumour cells. Low levels of NK cells and B cells in the high-risk group reduced the inflammatory response and pyroptosis rate, leading to fewer immune cells infiltrating tumours and worsening the HCC prognosis. CCR, APC-costimulated pathway, check point and MHC class I showed greater activity in the high-risk group, and both Type I and Type II INF were lower in the high-risk group. CCRs and their receptors play significant roles in HCC cell proliferation, the tumour inflammatory microenvironment, immune evasion of tumour cells and angiogenesis[37–49].Type I IFN induces autophagy in a variety of cancer cells and regulates viral clearance and antigen presentation and the inhibition of cell proliferation[40]. The lower expression of Type I and Type II IFN decreased response in the high-risk group inhibited immune system activation and weakened antitumour immunity. The results also suggested that lower immunoreactivity in the TME may be pivotal factors contributing to poor prognosis of high-risk HCC patients.
AC009283.1 and LINC00942 were chosen to verify the function of PRlncRNA. Our studies indicated that AC009283.1 as a tumor-suppressor gene inhibited HCC development, the downregulation of AC009283.1 can reduce the expression of NLRP3, Caspase-1 and CD3, while si-LINC00942 had opposite effect, that indicating that PRlncRNA can be used to assess the pyroptosis and immune status of the patient's tumor cells.
In this study, we identified eight PRlncRNAs that were associated with HCC prognosis and then constructed a novel prognosis-predictive risk signature. We found that the risk score in the PRlncRNA signature heightened the predictive reliability of prognosis than clinical factors, which can be server as an independent predictor in our signature model and may undergo routine application in the future. In addition, lncRNAs were identified in the risk signature to evaluate the immune infiltration changes of patients, may helpful for the development of targeted kits to evaluate the prognosis and immune infiltration status of patients, predict the benefit groups of immune therapy, and improve the immunotherapy effect of liver cancer patients.
Although our risk model achieved better results, still has some shortcomings to point out. We only obtain data from the TCGA database and need to verify our model with other different databases. We examined the relation between lncRNA and pyroptosis and immune markers together for the first time beyond previous research based on the identification of the role of lncRNA and the changes of pyroptosis genes. However, more clinical samples are essential to verify the accuracy of our model.