CircFBXW4 Suppresses Colorectal Cancer Progression by Regulating the MiR-338-5p/SLC5A7 Axis.

Dysregulated circular RNAs (circRNAs) contribute to tumourigenesis and cancer progression. However, the expression patterns and biological functions of circRNAs in colorectal cancer (CRC) remain elusive. Here, RNA sequencing and bioinformatics analyses are applied to screen for aberrantly expressed circRNAs. The expression of circFBXW4 in CRC tissues and cell lines is determined by quantitative real-time PCR. A series of in vitro and in vivo biological function assays are implemented to assess the functions of circFBXW4. The regulatory mechanisms linking circFBXW4, miR-338-5p, and SLC5A7 are explored by western blotting, dual luciferase reporter assays, and RNA pull-down assays. CircFBXW4 is dramatically downregulated in CRC tissues and cell lines. circFBXW4 downregulation is clearly correlated with malignant features and patient overall survival in CRC. Functionally, ectopic expression of circFBXW4 strikingly impairs the proliferation, migration, and invasion capacities of CRC cells in vitro and in vivo, whereas circFBXW4 knockdown has the opposite effects. Mechanistically, circFBXW4 competitively binds to miR-338-5p and prevents it from interacting with and repressing its target SLC5A7, thus suppressing the progression of CRC. This study reveals the specific critical role of circFBXW4 in inhibiting CRC progression via the miR-338-5p/SLC5A7 axis and provides an additional target for eradicating CRC.

Cross-Talk Between m6A- and m5C-Related lncRNAs to Construct a Novel Signature and Predict the Immune Landscape of Colorectal Cancer Patients.

Background: N6-methyladenosine (m6A) and 5-methylcytosine (m5C) can modify long non-coding RNAs (lncRNAs), thereby affecting tumorigenesis and tumor progression. However, there is a lack of knowledge regarding the potential roles and cross-talk of m6A- and m5C-related lncRNAs in the tumor microenvironment (TME) and their effect on prognosis. Methods: We systematically evaluated the expression patterns of m6A- and m5C-related lncRNAs in 1358 colorectal cancer (CRC) samples from four datasets. Consensus clustering was conducted to identify molecular subtypes of CRC, and the clinical significance, TME, tumor-infiltrating immune cells (TIICs), and immune checkpoints in the different molecular subtypes were analyzed. Finally, we established a m6A- and m5C-related lncRNA signature and a prognostic nomogram. Results: We identified 141 m6A- and m5C-related lncRNAs by co-expression analysis, among which 23 lncRNAs were significantly associated with the overall survival (OS) of CRC patients. Two distinct molecular subtypes (cluster A and cluster B) were identified, and these two distinct molecular subtypes could predict clinicopathological features, prognosis, TME stromal activity, TIICs, immune checkpoints. Next, a m6A- and m5C-related lncRNA signature for predicting OS was constructed, and its predictive capability in CRC patients was validated. We then constructed a highly accurate nomogram for improving the clinical applicability of the signature. Analyses of clinicopathological features, prognosis, TIICs, cancer stem cell (CSC), and drug response revealed significant differences between two risk groups. In addition, we found that patients with a low-risk score exhibited enhanced response to anti-PD-1/L1 immunotherapy. Functional enrichment analysis showed that these lncRNAs related to the high-risk group were involved in the development and progression of CRC. Conclusions: We conducted a comprehensive analysis of m6A- and m5C-related lncRNAs in CRC and revealed their potential functions in predicting tumor-immune-stromal microenvironment, clinicopathological features, and prognosis, and determined their role in immunotherapy. These findings may improve our understanding of the cross-talk between m6A- and m5C-related lncRNAs in CRC and pave a new road for prognosis assessment and more effective immunotherapy strategies.

Identification of pyroptosis-related subtypes, the development of a prognosis model, and characterization of tumor microenvironment infiltration in colorectal cancer.

Pyroptosis is a newly discovered programmed cell death that is associated with tumor progression, prognosis, and treatment response. However, the potential roles of pyroptosis-related genes (PRGs) in the tumor microenvironment (TME) remain unclear. We described the alterations of PRGs in 1109 colorectal cancer (CRC) samples from genetic and transcriptional fields and evaluated their expression patterns from four independent datasets. We identified two distinct molecular subtypes and found that multi-layer PRG alterations were correlated with patient clinicopathological features, prognosis, and TME cell-infiltrating characteristics. Then, a PRG_score for predicting recurrence-free survival (RFS) was constructed and its predictive capability in CRC patients was validated. Consequently, we constructed a highly accurate nomogram for improving the clinical applicability of the PRG_score. A low PRG_score, characterized by increased microsatellite instability-high (MSI-H), mutation burden, and immunity activation, indicated favorable odds of RFS. Moreover, the PRG_score was significantly associated with the cancer stem cell (CSC) index and chemotherapeutic drug sensitivity. Our comprehensive analysis of PRGs in CRC demonstrated their potential roles in the tumor-immune-stromal microenvironment, clinicopathological features, and prognosis. These findings may improve our understanding of PRGs in CRC and pave a new path for the assessment of prognosis and the development of more effective immunotherapy strategies.

N6-Methyladenosine-Related lncRNA Signature Predicts the Overall Survival of Colorectal Cancer Patients.

BACKGROUND: The N6-methyladenosine (m6A) RNA modification can modify long non-coding RNAs (lncRNAs), thereby affecting the tumorigenesis and progression of tumors. However, the underlying role of m6A-modified lncRNAs in colorectal cancer (CRC) remains largely unknown. Therefore, our aim was to assess the prognostic value of m6A-modified lncRNAs in CRC patients. METHODS: The gene expression and clinicopathological data of CRC were extracted from The Cancer Genome Atlas (TCGA) database. Pearson correlation analysis was used to investigate the m6A-modified lncRNAs. Consensus clustering was conducted to identify molecular subtypes of CRC, and the clinical significance of molecular subtypes was identified. The least absolute shrinkage and selection operator analysis (LASSO) was applied to establish a risk signature. Finally, a prognostic nomogram with risk score and clinicopathological variables was established. RESULTS: In total, 29 m6A-modified lncRNAs were identified as prognostic lncRNAs. Two molecular clusters were identified and significant differences were found with respect to clinicopathological features and prognosis. Cluster1 is associated with poor overall survival (OS), down-regulation of Programmed cell death ligand-1 (PD-L1) expression, lower immune score, and less immune cell infiltration. Then, an m6A-modified lncRNA signature for predicting OS was constructed in the TCGA training cohort. The signature demonstrated favorable prediction performance in both training and validation sets. Compared with low-risk patients, patients with high risk showed worse clinical outcomes, lower immune scores, and downregulated PD-L1 expression. Further analysis indicated that the signature was an independent prognostic indicator, and then a prognostic nomogram based on risk score, tumor location, and tumor stage was established. CONCLUSIONS: Our study identified a seven m6A-modified lncRNA signature and established a prognostic nomogram that reliably predicts OS in CRC. These findings may improve the understanding of m6A modifications in CRC and provide insights into the prognosis and treatment strategy of CRC.