LUAD is a high mortality rate of primary lung cancer. Although LUAD has made good progress in diagnosis and treatment, it has a high degree of malignancy and poor survival prognosis. Exploring the detailed mechanisms of LUAD pathogenesis and identifying promising diagnostic and prognostic biomarkers for LUAD may help to provide effective therapeutic targets and improve patient outcomes17,18. The TME is considered to be an important influence on tumor growth and development. The TME contains many types of cells, including CD4 + T cells, CD8 + T cells, macrophages, CAFs, B cells, and so on. In recent years, there have been more and more studies on CAFs. Many studies believed that CAFs in the tumor microenvironment were an important factor affecting tumor invasion and metastasis. Therefore, we hope to screen the biomarkers that affect the prognosis and diagnosis of LUAD from the perspective of CAFs in the tumor microenvironment. The results of our study support that COL11A1 derived from CAFs in the TME of LUAD may serve as a novel diagnostic and prognostic biomarker for LUAD.
The WGCNA and EPIC algorithm in immune infiltration were used to analyze the sample data of LUAD in TCGA, and finally 13 hub genes with a strong correlation with CAFs were obtained. They were ADAM12, ADAMTS12, COL11A1, COL1A1, COL1A2, COL3A1, COL5A1, COL5A2, ITGA11, LRRC15, POSTN, THBS2, THY1. To clarify the prognosis of 13 hub genes in LUAD, the GEPIA database was used for analysis and finally found that the COL11A1 gene was highly expressed in LUAD and had a poor prognosis. We further verified the COL11A1 on the prognosis of LUAD patients by using GSE72094 and Kaplan-Meier plotter database, and confirmed that the prognosis of LUAD patients with high expression of COL11A1 was poor. Therefore, COL11A1 has the potential as a prognostic biomarker in LUAD.
Collagen type XI alpha 1 (COL11A1) is a component of XI collagen and is found mainly in the cartilage19. The lack of type XI collagen leads to abnormal thickening of the tissues in cartilage20,21. Importantly, emerging evidence indicates that COL11A1 is a gene associated with cancer progression that can promote tumor growth, migration, invasion, metastasis, and chemotherapy resistance22. In addition, upregulation of COL11A1 is associated with cancer recurrence and poor survival and serves as a diagnostic indicator in some types of cancer, such as breast cancer, colorectal cancer, gastric cancer, ovarian cancer, and so on23–26. Several reports also validate that COL11A1 is an oncogene in the progression of non-small cell lung cancer27–30. However, there is still a lack of reports on studying COL11A1 from the perspective of CAFs in the LUAD.
In our study, we used to TCGA + GTEx, GSE32863, and GSE75037 to confirm that the expression of COL11A1 was significantly higher in tumor tissues than that in normal tissues, which was verified by our own samples in IHC experiment. Besides, the corresponding AUC value of ROC curves was all greater than 0.86, which revealed that COL11A1 exhibited excellent diagnostic efficiency for LUAD and adjacent normal tissues. Therefore, COL11A1 has the potential as a diagnostic biomarker in LUAD. To explore the reasons for the high expression of COL11A1 in LUAD, we used the cBioPortal database to study the mutation of the COL11A1 gene. We found that the gene mutation rate of COL11A1 in LUAD was as high as 18%, which may be one of the reasons for the high expression of the COL11A1 gene. In addition, Gene promoter methylation is an important factor affecting gene expression. The ULCAN database was used to explore the promoter methylation of the COL11A1 gene in LUAD. We found that the tumor tissues was hypermethylated compared with the adjacent normal tissues, which could not explain why the COL11A1 gene was highly expressed in LUAD. Therefore, it is suggested that promoter methylation is not the cause of the high expression of the COL11A1 gene in LUAD. In addition to gene mutation and promoter methylation, the expression of COL11A1 at the transcriptional level may also be affected by many other factors, such as histone modification and m6A RNA methylation modification31–33, which have not been discussed in our study.
To explore the mechanism by which COL11A1 affects the proliferation and invasion of LUAD, we performed GO and KEGG analyses. We found that the genes co-expressed with COL11A1 (greenyellow module) were mainly enriched in some signal pathways related to the extracellular matrix in the TME of LUAD. These results further suggested that COL11A1 played an indispensable role in influencing tumor proliferation and invasion through the TME. In recent years, the technology of single-cell RNA sequencing has developed rapidly, which allows us to master much information that is not available by bulk RNA sequencing34. Single-cell RNA sequencing (scRNA-seq) is a technique to analyze complex tissue transcripts at the single-cell level, identifying differences in gene expression and epigenetic factors associated with unicellular genomes mutations, as well as novel cell-specific markers and cell types35. scRNA-seq plays an important role in all aspects of tumor research. In our study, using single-cell analysis related database, we found that the expression of COL11A1 was mainly secreted by CAFs in the TME rather than from LUAD cancer cells. Therefore, we believed that CAFs in the TME might affect the growth and development of LUAD cells by secreting COL11A1.
There are some limitations to our study that should be noted when promoting our findings. First, our results were mainly generated from bioinformatics analysis. To increase the reliability of the conclusion, we performed IHC experiment, and the results also confirmed that COL11A1 was highly expressed in LUAD. However, more in vivo/in vitro experiments are needed to prove our results on the potential function of COL111A1 in LUAD. Second, the data used in this study was retrospective. Our results should thus be further confirmed by prospective studies in the future. Third, no anti-COL11A1 therapeutic monoclonal antibodies have been evaluated in clinical trials. Therefore, we have no specific and complete cases with data to identify the benefit of anti-COL11A1 targeting drugs in the survival of LUAD.