Recently, an increasing number of studies focusing on the role of lncRNAs in CRC proved that lncRNAs exert a critical oncogenic role based on its dysregulated expression and localization18,19. Additionally, as the most abundant posttranscriptional modification in eukaryotic non-coding RNAs (ncRNAs), m6A has a huge effect on its stability and transport20–22. Previous studies have shown that m6A “writers” and “erasers” could adjust the levels of m6A modification in mRNAs and ncRNAs to regulate binding sites to m6A “reader” proteins. Different m6A “reader” proteins recognize and bind to methylated ncRNAs to realize different functions. For instance, the m6A mark increases the stability of lncRNA FAM225A, which promotes nasopharyngeal carcinoma progression by acting as ceRNA to sponge miR-590-3p/miR-127523. IGF2BP2 recognizes and binds to m6A-modified circRNA NSUN2 and increases its export to the cytoplasm24. Overexpression METTL3 can significantly increase lncRNA RP11 nuclear localization in CRC cells25. Thus, in consideration of the crucial role of lncRNAs and m6A RNA modification in COAD, these researches call our attention to investigate the gene profile of m6A-related lncRNAs and molecular mechanisms involved in COAD, explore whether m6A-related lncRNAs could serve as ideal biomarkers for COAD prognosis and participate in COAD initiation and progression.
In our study, a total of 437 samples, 385 patients with COAD, 24 m6A-related regulators and 3910 lncRNAs were included to exploit the specific role of m6A-related lncRNAs in COAD. 36 candidate lncRNAs that were highly correlated with OS of COAD were identified. Then, 11 of 36 m6A-related prognostic lncRNAs were used to establish a prognostic signature with the LASSO method in the training group. Kaplan-Meier analysis showed that the OS of patients with low risk scores was longer than those of patients with high risk scores. Additionally, the result of ROC curve analysis indicated that the 11-lncRNAs signature could serve as a highly specific and sensitive prognostic survival model in COAD. Moreover, the results were further validated in the test groups and the combined group. This signature can be used as an independent prognostic factor for COAD, suggesting that these 11 lncRNAs may be vital m6A-related lncRNAs and significant prognostic factors for patients with COAD. Furthermore, this m6A-related lncRNA prognostic model could serve as a prognostic indicator for OS in subgroups of patients with different clinical characteristics, especially age, gender, pathological stage, T stage, M0 stage and N stage.
To provide a comprehensive analysis of m6A-related lncRNAs, a ceRNA network consisting of 5 lncRNAs, 31 miRNAs and 216 mRNAs was constructed and differentially expressed genes between the high-risk group and low-risk group were identified for viewing the latent functions of m6A-related lncRNAs. With the 5 key m6A-related lncRNAs, LINC00174 and ZEB1-AS1 have been preliminarily studied so far in COAD. LncRNA ZEB1-AS1 acts as a sponge of miR-141-3p/miR-205/miR-455-3p/miR-181a-5p/miR-101 to promote COAD malignant progression25. LINC00174 was overexpressed in CRC tissues and cells, and promotes CRC progression via maintaining TAZ overexpression by sponging miR-1910-3p31. KEGG pathway and GO analysis showed that 216 target mRNAs were enriched in several biological processes and pathways associated with the occurrence and progression of COAD32,33, including “PI3K-Akt signaling pathway,” “MAPK signaling pathway,” “p53 signaling pathway,” “Cell cycle,” “Focal adhesion” and so on. Genes in high-risk group and low-risk group were functionally annotated using GSEA. Genes in high-risk group were also enriched in cancer-related pathway,such as “Focal adhesion,” “ECM-receptor interaction,” and “Wnt signaling pathway.”
However, a few limitations and shortcomings in our study should be acknowledged. First, it’s beneficial to perform external validation by other genes and clinical datasets. Second, the results of this study is purely computational, and further experimental studies are necessary.