Circular RNA (circRNA) is a novel class of noncoding RNAs with functions in various pathophysiological activities. However, the expression profiles and functions of circRNAs in colorectal cancer (CRC) remain largely unknown. High-throughput RNA sequencing (RNA-seq) was performed to assess circRNA expression profiles in 4 paired CRC tissues, and significantly dysregulated circRNAs were validated by quantitative real-time polymerase chain reaction (qRT-PCR). Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analyses were performed to predict the potential functions of dysregulated circRNAs. Target miRNAs of circRNAs were predicted using miRanda software, and were further analyzed combining DIANA-miRPath v.3 platform (Reverse Search module) with KEGG pathways of COLORECTAL CANCER and MicroRNAs in cancer (Entry: map05210 and map05206). CircRNA-miRNA interaction networks were constructed using Cytoscape software. Expression levels of a significantly down-regulated circRNA, circDDX17 (hsa_circ_0002211), was detected by qRT-PCR in 60 paired CRC tissues. CircDDX17 was knockdown by siRNA, and the biological functions of circDDX17 were examined in CRC cell lines. Totally 448 differentially expressed circRNAs were identified, including 394 up-regulated and 54 down-regulated circRNAs. qRT-PCR validation confirmed the reliability of the RNA-Seq data. GO and KEGG analyses revealed that these dysregulated circRNAs were potentially implicated in CRC pathogenesis. Analyses by combining miRanda and miRPath softwares with KEGG pathways suggested that the miRNAs targeted by the top 10 dysregulated circRNAs were associated with the KEGG pathways of COLORECTAL CANCER and MicroRNAs in cancer, indicating that circRNA-miRNA interactions might play important functional roles in the initiation and progression of CRC. The results of qRT-PCR for circDDX17 in 60 paired CRC tissues showed that circDDX17 was significantly down-regulated in CRC tissues and associated with unfavorable clinicopathological parameters. In vitro experiments showed that silencing of circDDX17 promoted CRC cell proliferation, migration, invasion, and inhibited apoptosis. In conclusion, we have identified numerous circRNAs that are dysregulated in CRC tissues compared with adjacent normal mucosa tissues. Bioinformatic analyses suggested that these dysregulated circRNAs might play important functional roles in CRC tumorigenesis. CircDDX17 functions as a tumor suppressor and could serve as a potential biomarker and a therapeutic target for CRC.

Circular RNAs (circRNAs) are a novel class of non-coding RNAs with distinct properties and diverse physiological and pathological functions. However, the functions of circRNAs in colorectal cancer (CRC) remain elusive. This study aimed to investigate the functional roles of circVAPA in CRC. High-throughput RNA sequencing was performed in 4 paired CRC tissues, and circVAPA (hsa_circ_0006990), was identified as a potential functional circRNA. Using quantitative real-time polymerase chain reaction (qRT-PCR), circVAPA was found to be up-regulated in CRC patients' tissues and plasma. Furthermore, circVAPA level was associated with unfavorable clinicopathologic features in CRC. The area under curve (AUC) of ROC was 0.724, suggesting that plasma level of circVAPA could serve as a promising biomarker for CRC detection. Sanger sequencing confirmed the back-splice junction sequences of circVAPA. Actinomycin D and RNase R treatments suggested that circVAPA was highly stable compared with its linear counterpart, and qRT-PCR for the circVAPA level in nuclear and cytoplasmic fractions indicated that circVAPA was predominantly localized in the cytoplasm. Gain-of-function and loss-of-function studies in CRC cell lines indicated that circVAPA could promote CRC cell proliferation, migration, invasion, and inhibit apoptosis. miRanda software (v3.3a) was used to predict target miRNAs of circVAPA. Moreover, target miRNAs associated with the KEGG pathway of COLORECTAL CANCER (Entry: map05210; https://www.kegg.jp/) were screened using DIANA-miRPath v.3 platform (Reverse Search module; TarBase v7.0 method). The analyses by miRanda and miRPath suggested that circVAPA could potentially bind to hsa-miR-101-3p (miR-101) associated with the COLORECTAL CANCER pathway. Luciferase reporter assay confirmed a direct interaction between circVAPA and miR-101. Furthermore, circVAPA had no effect on the expression level of miR-101, and miR-101 over-expression had the similar tumor-suppressing effects as circVAPA silencing. The tumor-promoting effect of circVAPA over-expression could be reversed by the up-regulation of miR-101. These data demonstrated that circVAPA promoted CRC progression by sponging miR-101. In conclusion, we have verified that circVAPA is up-regulated in CRC patients' tissues and plasma, and exerts oncogenic properties by sponging miR-101 in CRC. CircVAPA could serve as a promising biomarker and a therapeutic target for CRC.

• circ-ZEB1 is highly expressed in colorectal cancer tissues. • circ-ZEB1 knocking down inhibits CRC cells proliferation and metastasis in vitro and in vivo. • circ-ZEB1 regulates EMT and chemotherapeutic resistance in CRC cells. • circ-ZEB1 exerts its regulatory effect through sponging miR-200c. • Our research provides new targets for colorectal cancer treatment.

Background: Colorectal cancer (CRC) represents a major global health challenge, characterized by rising incidence and mortality rates, necessitating improved diagnostic and therapeutic approaches. This study aimed to elucidate the expression and functional role of PAK6, a protein linked to cancer progression, as a potential biomarker for CRC. Methods: Utilizing comprehensive analyses of transcriptomic and clinical data from The Cancer Genome Atlas (TCGA) and Gene Expression Omnibus (GEO), we performed differential expression assessments, survival analyses, and functional enrichment studies. Results: Our findings demonstrate a significant upregulation of PAK6 in CRC tissues compared to adjacent normal tissues (p < 0.001), with a diagnostic AUC of 0.855, indicating its potential utility as a reliable biomarker for early detection. High PAK6 expression was significantly associated with aggressive clinicopathological features, including poor differentiation, residual tumor presence and reduced overall survival (HR = 1.72, p = 0.004). Functional enrichment analyses revealed PAK6’s involvement in critical biological processes such as cell cycle regulation, alongside its correlation with immune infiltration, particularly NK and CD8⁺ T cells. Moreover, PAK6 expression positively correlated with chemokines involved in immune cell recruitment, suggesting its role in modulating the tumor immune microenvironment. Conclusions: Our study underscores the significance of PAK6 as a diagnostic and prognostic biomarker in CRC, with the potential to inform targeted therapeutic strategies and enhance patient outcomes. Future research should focus on validating these findings in larger cohorts and exploring PAK6-targeted interventions to improve immunotherapeutic responses in CRC patients