Circular RNA CCDC66 Improves Murine Double Minute 4 (MDM4) Expression through Targeting miR-370 in Colorectal Cancer

Abstract

Introduction. Colorectal cancer (CRC), a common digestive tract tumor that contains colon and rectal cancer, is one of the three most common cancers globally. circRNAs are involved in the occurrence and development of CRC, but the mechanism of how they participate in this process remains unclear. Methods. We adopted PCR for expression measure, CCK-8 for cell proliferation detection, Transwell for cell migration and invasion detection, and dual-luciferase reporter assays to detect the potential downstream targets of CCDC66 in CRC. Results. This study showed that circRNA CCDC66 was overexpressed in CRC tissues, and after knockdown, it inhibited the proliferation, migration, and invasion of CRC cells (RKO and HCT-116) in vitro. In addition, the dual-luciferase reporter assay showed that there was a binding site between circCCDC66 and miR-370, as well as between miR-370 and murine double minute 4 (MDM4). That is, circCCDC66 upregulated the expression of MDM4 through competitively binding to miR-370. The expression of circCCDC66 in CRC tissues was positively correlated with MDM4 and negatively correlated with miR-370. Conclusion. In summary, our results indicate that circCCDC66 is a key upregulation of CRC. circCCDC66 upregulates MDM4 through competitive binding to miR-370, thereby enhancing the metastatic ability of CRC cells and promoting the development of CRC.

CircCCDC66: Emerging roles and potential clinical values in malignant tumors

“…In addition, Mo et al. ( 47 ) showed that circCCDC66 up-regulated the expression of MDM4 by targeting miR-370 to promote cell proliferation, migration, and invasion in CRC. In conclusion, circCCDC66 acts as an oncogenic circRNA in CRC tumor development.…”

“…In NSCLC, circCCDC66 promoted cell proliferation through miR-211/SRCIN1 axis ( 17 ). Moreover, circCCDC66 was highly expressed in precancerous polyps and cancer tissues of colon cancer, and exacerbated the proliferation, migration and invasion of CRC cells by competitively binding miR-370 to upregulate MDM4 expression ( 15 , 47 ). And circCCDC66 could also exert oncogenic roles by binding miR-1238-3p and miR-452-5p in gastric and cervical cancers ( 19 , 49 ).…”

Recent findings on miR‑370 expression, regulation and functions in cancer (Review)

“…Mouse double minute 4 (MDM4) has been validated as an oncogene that can negatively regulate transcriptional activity of the tumor suppressor p53 (85). miR-370 functions as a suppressor to inhibit cell proliferation and promote apoptosis by targeting MDM4 in colorectal cancer (CRC) (22,86). Both zeste homologue 1 (EZH1), and its homolog EZH2, act as histone H3 lysine 27 (H3K27) methyltransferases that regulate target gene transcription.…”

“…In colon cancer, enforced miR-370-3p can inhibit EMT through modulating β-catenin (84). miR-370 can also downregulate MDM4 and inhibit the metastatic ability of CRC cells (86). EZH1 has been shown to facilitate CRC cell invasion and has been identified as a target of miR-370-5p (88).…”

“…In CRC, circCCDC66 facilitates cancer progression through regulating the miR-370/MDM4 axis (86). In addition, circ_0000714 acts as a sponge of miR-370-3p and influences cell paclitaxel resistance and the cell cycle in ovarian cancer cells (61).…”