m6A-modified circFNDC3B inhibits colorectal cancer stemness and metastasis via RNF41-dependent ASB6 degradation

Abstract

Colorectal cancer (CRC) is the third most frequently diagnosed cancer with unfavorable clinical outcomes worldwide. circFNDC3B plays as a tumor suppressor in CRC, however, the mechanism of circFNDC3B in CRC remains ambiguous. The stem-like properties of CRC cells were detected by the evaluation of stemness markers, sphere formation assay and flow cytometry. qRT-PCR, FISH, IHC, and western blotting assessed the expression and localization of circFNDC3B, RNF41, ASB6, and stemness markers in CRC. The metastatic capabilities of CRC cells were examined by wound healing and Transwell assays, as well as in vivo liver metastasis model. Bioinformatics analysis, RNA immunoprecipitation (RIP), RNA pull-down assay and co-IP were used to detect the associations among circFNDC3B, FXR2, RNF41, and ASB6. Downregulated circFNDC3B was associated with unfavorite survival in CRC patients, and circFNDC3B overexpression suppressed CRC stemness and metastasis. Mechanistically, studies revealed that YTHDC1 facilitated cytoplasmic translocation of m6A-modified circFNDC3B, and circFNDC3B enhanced RNF41 mRNA stability and expression via binding to FXR2. circFNDC3B promoted ASB6 degradation through RNF41-mediated ubiquitination. Functional studies showed that silencing of RNF41 counteracted circFNDC3B-suppressed CRC stemness and metastasis, and ASB6 overexpression reversed circFNDC3B- or RNF41-mediated regulation of CRC stemness and metastasis. Elevated ASB6 was positively correlated with unfavorite survival in CRC patients. In vivo experiments further showed that circFNDC3B or RNF41 overexpression repressed tumor growth, stemness and liver metastasis via modulating ASB6. Taken together, m6A-modified circFNDC3B inhibited CRC stemness and metastasis via RNF41-dependent ASB6 degradation. These findings provide novel insights and important clues for targeted therapeutic strategies of CRC.

circFNDC3B Accelerates Vasculature Formation and Metastasis in Oral Squamous Cell Carcinoma

“…In this study, we found multiple circRNAs derived from the FNDC3B gene, and only hsa_circ_0001361 was overexpressed in OSCC, which might be due to the different biogenesis of these circRNAs. Several studies indicated that circFNDC3B (hsa_circ_0006156) could dramatically inhibit tumor progression including bladder cancer and colorectal cancer ( 36, 37 ). Furthermore, Yang and colleagues also found that high circFNDC3B (hsa_circ_0001361) expression in OSCC could repress cell ferroptosis (38 ).…”

m6A modification on the fate of colorectal cancer: functions and mechanisms of cell proliferation and tumorigenesis

“…Compared to normal bowel tissues, YTHDC1 was downregulated in colon cancer (53). A recent study demonstrated that YTHDC1 accelerated the cytoplasmic translocation of m6A-modified circFNDC3B, thereby inhibiting CRC stemness and metastasis via RNF41-dependent ASB6 degradation (81).…”

Emerging landscape of circFNDC3B and its role in human malignancies

“…Therefore, novel therapeutic targets for the diagnosis and prognosis of CRC are urgently needed. CircFNDC3B was an originally identified promising biomarker that regulated CRC development ( 30 , 81 , 82 ).…”

“…Zeng et al. also found circFNDC3B was down-expressed in CRC tissues and low expression was related to poor OS ( 82 ). Experiments in vitro confirmed circFNDC3B could modulate CRC stemness and metastasis.…”