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Circ_RUSC2 Sequesters miR-661 and Elevates TUSC2 Expression to Suppress Colorectal Cancer Progression
Yixin Shi1, Dingru Li2, Yunchao Xu3
1Liaoning Laboratory of Cancer Genomics, Department of Cell Biology, College of Basic Medical Sciences, Dalian Medical University, Dalian 116044, China.
Background:
Despite advancements in diagnostic efficiency, colorectal cancer (CRC) remains a leading cause of cancer-related mortality, with increasing incidence rates. Circular RNA (circRNA) is a closed-loop, generally stable noncoding RNA that functions as a sponge for microRNAs in CRC. The purpose of this study was to investigate the function and underlying mechanism of circ_RUSC2, a new circRNA, in CRC. The expression levels of circ_RUSC2, miR-661, and TUSC2 were assessed using qRT-PCR, Western blot, and immunohistochemistry. Functional assays, including CCK-8, Transwell, and scratch wound healing, were performed to evaluate cell proliferation, migration, and invasion. RNA pull-down and actinomycin D assays were used to study RNA interactions and stability. In both CRC cells and tissues, miR-661 was markedly elevated, while circ_RUSC2 expression was considerably reduced. Poor differentiation, distant metastases, lymph node metastases, and an advanced stage were all strongly correlated with either miR-661 overexpression or circ_RUSC2 downregulation. circ_RUSC2 was more stable compared to its linear RUSC2 mRNA. CRC cell invasion, migration, and proliferation were suppressed by circ_RUSC2 ectopic expression; this inhibitory effect was restored by a miR-661 mimic. Circ_RUSC2 served as miR-661's sponge. TUSC2 counteracted the effects of miR-661, which stimulated CRC cell proliferation, migration, and invasion. At the post-transcriptional level, miR-661 controlled the expression of TUSC2 in CRC cells. In comparison to the negative control, circ_RUSC2 expression was markedly reduced, and its half-life was shortened by methyltransferase-like 3 (METTL3) knockdown. Circ_RUSC2 is a stable cytoplasmic circRNA. Circ_RUSC2 inhibits CRC cell malignant phenotypes via the miR-661/TUSC2 axis. The onset and progression of CRC are linked to the downregulation of Circ_RUSC2. circ_RUSC2 might become more stable through N6-methyladenosine (m6A) methylation regulated by METTL3. According to our research, circ_RUSC2 might be a new biomarker and treatment target for CRC.
Insights
Circular RNA RUSC2 (circ_RUSC2) inhibits colorectal cancer (CRC) progression by sponging miR-661, downregulating TUSC2. Reduced circ_RUSC2 expression correlates with advanced CRC, suggesting its potential as a therapeutic target.
Area of Science:
- Molecular Biology
- Oncology
- RNA Biology
Background:
- Colorectal cancer (CRC) remains a significant cause of cancer mortality with increasing incidence.
- Circular RNAs (circRNAs) are emerging as key regulators in cancer, including CRC.
- The specific role of circ_RUSC2 in CRC pathogenesis requires elucidation.
Purpose of the Study:
- To investigate the function and molecular mechanism of circ_RUSC2 in colorectal cancer.
- To determine the relationship between circ_RUSC2, miR-661, and TUSC2 in CRC.
Main Methods:
- Quantitative real-time PCR (qRT-PCR) and Western blot for expression analysis.
- Cellular assays (CCK-8, Transwell, scratch wound healing) for proliferation, migration, and invasion.
- RNA pull-down and actinomycin D assays to elucidate RNA interactions and stability.
Main Results:
- circ_RUSC2 was downregulated, while miR-661 was upregulated in CRC tissues and cells.
- circ_RUSC2 suppressed CRC cell proliferation, migration, and invasion, acting as a sponge for miR-661.
- miR-661 targets TUSC2, promoting CRC cell malignancy; circ_RUSC2 reverses this effect.
- METTL3 knockdown reduced circ_RUSC2 stability, suggesting m6A methylation involvement.
Conclusions:
- circ_RUSC2 inhibits CRC progression via the miR-661/TUSC2 axis.
- Downregulation of circ_RUSC2 is linked to CRC onset and progression.
- circ_RUSC2 shows potential as a novel biomarker and therapeutic target for CRC.
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