Although there are already lots of signatures utilizing ARGs or ARlncRNAs to predict LUAD patients’ survival outcomes, we are the first to explore the tumor immunity of the ARlncRNA model in detail17 18. We conducted a detailed study on the tumor immunity of the ARlncRNA signature, which renders the constructed signature applicable for guiding the clinical personalized treatment of LUAD patients.
First, the lncRNA and ARG transcriptome profiles were obtained, and ARlncRNAs related to prognosis of LUAD patients based on co-expression analysis and univariate Cox analysis were identified. Next, we calculated the AUC value of 1-, 3-, and 5-year to obtain an ideal signature and differentiated each patient into different groups based on median value. Then, the survival and clinicopathological characteristics was analyzed to assess the predictive value of the ARlncRNA signature. Subsequently, we conducted a comprehensive assessment of the tumor immunity of the ARlncRNA signature, including GO and KEGG function enrichment analyses, TMB, TME, infiltration of immune cells, expression of common ICI-related immunosuppressive molecules, and efficacy of ICIs.
Previous studies on LUAD have mostly focused on single genes or noncoding genes, which are unable to illustrate the complex tumorigenesis and development process19 20. In recent years, a combination of several genes to improve the predictive value of OS in LUAD patients were gradually identified. For example, Duan et al.18 constructed a prognostic signature based on ARGs, which served as a novel biomarker in LUAD. Meanwhile, Zhu et al.21 identified a ferroptosis-related gene signature and explored the immune cells infiltration. In this study, several ARlncRNAs included in the modeling process have been already reported in various malignant tumors, such as CARD8-AS122 23, AC060780.124, AC123595.125 26, UGDH-AS127, LINC0099628, LINC0086129 30 31, AL606489.117, HLA-DQB1-AS132, LINC0065433 LINC0084734 35. While others have not been discovered yet and may be potential novel biomarkers for further study.
Researchers found that autophagy played a vital role in tumorigenesis and development. Gu et al. confirmed that bupivacaine induced autophagy through Akt/mTOR signaling, inhibiting the progression of NSCLC36. Lin et al. proposed that high expression of miR-30a improved the prognosis of NSCLC after neoadjuvant chemotherapy by reducing autophagy caused by chemotherapy drugs37. In addition, Li et al. found that the dysfunction of autophagy mediated by c-myc/miR-150/EPG5 had a great impact on the progression of NSCLC38. Collectively, autophagy was probably involved in the occurrence and development of LUAD through a certain signaling pathway, having a significant impact on the prognosis of LUAD patients.
Then, GSEA enrichment analysis suggested that patients with low-risk had more autophagy and were enriched in B cell receptor signaling, natural killer cell mediated cytotoxicity, T cell receptor signaling pathway, and the VEGF signaling pathway. Recent searches confirmed the strong correlation between autophagy and VEGF. For example, Chen et al. found that VEGF promoted the occurrence of autophagy and VEGF knockdown decreased the autophagy level39. In addition, Spengler et al.40 discovered that VEGF signaling pathway regulated autophagy in endothelial cells. Taken together, we speculated that autophagy probably contributed to the occurrence and development of LUAD through VEGF signaling pathway, and that the ARlncRNA signature was closely associated with tumor immunity.
Recently, the interaction between autophagy and tumor immunity was investigated comprehensively. For example, TMB and TIME were identified as important determinants of the efficacy of ICIs and in the prognosis of cancer patients41. Moreover, Jena et al.42 have demonstrated that autophagy was closely related to TIME and participated in tumor progression. To explore the relationship between the ARlncRNA signature and tumor immunity thoroughly, we conducted ssGSEA to investigate the immune status in different groups. The patients in low-risk group had a higher abundance of immune cells and were more active in immune pathways, most of which were validated closely associated with autophagy. For example, Di et al.43 found that CALCOCO2, an autophagy receptor, was mainly expressed in B cells, which mediated autophagy. In addition, the function of DCs to secrete cytokines has been shown to be inhibited by autophagy44. Turan et al.45 proved through experiments that iDCs infected with TSV-1 could induce autophagy. Li et al.46 demonstrated that autophagy of mast cells could serve as a therapeutic target for allergic reactions. Ding et al.47 revealed that neutrophils were associated with autophagy. Autophagy has been validated to fuel pDCs48. Schmid et al.49 proposed that CD4(+) T helper cells could recognize MHCII molecules presented after autophagy. Lu et al.50 demonstrated that autophagy could mediate the function of Tregs. Samuel et al.51 proved that cellular metabolism facilitated autophagy to mediate the cytolytic effect. Zhang et al.52 confirmed the firm correlation between autophagy and HLA. These studies above suggest that autophagy is closely linked to tumor immunity, and autophagy probably participates in LUAD progression by regulating tumor immunity.
At present, PD-153 and CTLA-454 inhibitors have been validated to benefit patients with advanced NSCLC in clinical trials. Furthermore, research indicated that the autophagy of tumor cells increased the expression of ICI-related immunosuppressive molecules (e.g., PD-1 and CTLA-4), and affected anti-tumor immune responses directly. In this study, expression analyses was conducted to study the correlation between the ARlncRNA signature and the expression of common ICI-related immunosuppressive molecules, which revealed low-risk patients always had a higher expression of them and a better efficacy of ICIs. Subsequently, we analyzed the efficacy of ICIs and verified the results above; demonstrating that regardless of whether it is a PD-1 inhibitor alone, a CTLA-4 inhibitor alone or a combination of the two, the efficacy of patients in the low-risk group is better than that of the high-risk patients. Overall, the ARlncRNA signature could serve as a novel indicator for screening patients applicable for ICIs.
According to our data, we speculated that compared with high-risk patients, low-risk patients have more active autophagy, stronger tumor immunity, greater survival advantage and are more applicable for ICIs treatment. Autophagy could play an crucial part in the progression of LUAD by regulating the tumor immunity through VEGF signaling pathway, which had a great impact on prognosis of LUAD patients.
However, there are several limitations in our research. Firstly, bias of the information in the analysis process, as the profiles were obtained from public database. Secondly, it was difficult to find an ideal Gene Expression Omnibus (GEO) set including both 14 lncRNAs newly identified and detailed clinical information to validate the constructed ARlncRNA signature. Finally, external validation, such as quantitative real-time PCR and microarrays are necessary to increase credibility.
In conclusion, we constructed a novel ARlncRNAs signature and predicted the survival of LUAD patients, the state of TIME, and even the efficacy of ICIs accurately based on the expression of the 14 ARlncRNAs included in the modeling process, which may benefit patients with advanced NSCLC. Immunotherapy combined with TIME targeted therapy may improve individualized treatment of LUAD in the future.