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Colorectal cancer (CRC) is a common malignancy with high occurrence and mortality worldwide. In recent years, the overall survival rate of CRC patients has been improved because of the advances in early diagnosis and therapy. However, the prognosis of CRC patients at the advanced stage is still poor due to high recurrence rate and metastasis. The function of circular RNA (circRNA) ArfGAP with FG repeats 1 (circAGFG1) has been explored in non-small-cell lung cancer and triple-negative breast cancer. Nevertheless, its role in CRC is not clear. In this study, circAGFG1 was upregulated in CRC cell lines. CircAGFG1 silencing significantly suppressed cell proliferation, migration, invasion, and stemness, while promoted cell apoptosis in CRC. Meanwhile, we found that circAGFG1 also accelerated CRC tumor growth and metastasis in vivo. Importantly, circAGFG1 activated Wnt/β-catenin pathway through regulating CTNNB1. Afterwards, YY1 was found to transcriptionally activate CTNNB1. Furthermore, circAGFG1 directly sponged miR-4262 and miR-185-5p to upregulate YY1 expression. Eventually, rescue assays demonstrated that the effect of circAGFG1 silencing on CRC cell functions was observably reversed by upregulating YY1 or CTNNB1. In brief, our findings uncovered that circAGFG1 modulated YY1/CTNNB1 axis to drive metastasis and stemness in CRC by sponging miR-4262 and miR-185-5p.

The endophytic bacterium, MD-b1, was isolated from the medicinal plant Ophiopogon japonicas and identified as the Bacillus amyloliquefaciens sp. with 99% similarity based on the partial sequence analysis of 16S rDNA. Exopolysaccharides were extracted from the endophyte for the evaluation of its antitumor activity against gastric carcinoma cell lines (MC-4 and SGC-7901). 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assays and microscopy were performed to estimate the cell viability and morphological changes of the MC-4 and SGC-7901 cells following treatment with the exopolysaccharides at 14, 22 and 30 μg/μl. The results revealed that the exopolysaccharides displayed concentration-dependent inhibitory effects against the MC-4 and SGC-7901 cells, with an IC50 of 19.7 and 26.8 μg/μl, respectively. The exopolysaccharides also induced morphological abnormalities in the cells. These effects indicated the the exopolysaccharides had an antitumoral mechanism of action associated with the mitochondrial dysfunction of the treated cells. This is the first study to investigate the endophytic microorganism isolated from O. japonicas and also the first discovery of such antitumoral exopolysaccharides derived from the genus Bacillus. This provides a promising and reproducible natural product source with high therapeutic value for anticancer treatment, thereby facilitating the development of new anticancer agents.

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