A novel protein AXIN1-295aa encoded by circAXIN1 activates the Wnt/β-catenin signaling pathway to promote gastric cancer progression

Abstract

Background Circular RNA (circRNA), a subclass of non-coding RNA, plays a critical role in cancer tumorigenesis and metastasis. It has been suggested that circRNA acts as a microRNA sponge or a scaffold to interact with protein complexes; however, its full range of functions remains elusive. Recently, some circRNAs have been found to have coding potential. Methods To investigate the role of circRNAs in gastric cancer (GC), parallel sequencing was performed using five paired GC samples. Differentially expressed circAXIN1 was proposed to encode a novel protein. FLAG-tagged circRNA overexpression plasmid construction, immunoblotting, mass spectrometry, and luciferase reporter analyses were applied to confirm the coding potential of circAXIN1. Gain- and loss-of-function studies were conducted to study the oncogenic role of circAXIN1 and AXIN1-295aa on the proliferation, migration, invasion, and metastasis of GC cells in vitro and in vivo. The competitive interaction between AXIN1-295aa and adenomatous polyposis coli (APC) was investigated by immunoprecipitation analyses. Wnt signaling activity was observed using a Top/Fopflash assay, real-time quantitative RT-PCR, immunoblotting, immunofluorescence staining, and chromatin immunoprecipitation. Results CircAXIN1 is highly expressed in GC tissues compared with its expression in paired adjacent normal gastric tissues. CircAXIN1 encodes a 295 amino acid (aa) novel protein, which was named AXIN1-295aa. CircAXIN1 overexpression enhances the cell proliferation, migration, and invasion of GC cells, while the knockdown of circAXIN1 inhibits the malignant behaviors of GC cells in vitro and in vivo. Mechanistically, AXIN1-295aa competitively interacts with APC, leading to dysfunction of the “destruction complex” of the Wnt pathway. Released β-catenin translocates to the nucleus and binds to the TCF consensus site on the promoter, inducing downstream gene expression. Conclusion CircAXIN1 encodes a novel protein, AXIN1-295aa. AXIN1-295aa functions as an oncogenic protein, activating the Wnt signaling pathway to promote GC tumorigenesis and progression, suggesting a potential therapeutic target for GC.

ARL4C Regulates the Progression of Clear Cell Renal Cell Carcinoma by Affecting the Wnt/β-Catenin Signaling Pathway

“…By activating the Wnt signaling pathway, it increases the transcriptional activity of β -catenin and TCF [ 44 ]. In addition, related studies have found that Wnt agonist 1 can enhance β -catenin translocation to the nucleus in gastric cancer, thereby increasing the expression of β -catenin and Wnt signaling-dependent genes [ 45 ]. In recent years, there has been increasingly extensive exploration of the function of Wnt/ β -catenin in the initiation and progression of different cancers [ 46 ], and cyclin D1 and c-myc, which are downstream targets of Wnt/ β -catenin signaling, have been shown to affect tumor proliferation and metastasis [ 46 , 47 ].…”

Circular RNA circCSPP1 promotes the occurrence and development of colon cancer by sponging miR-431 and regulating ROCK1 and ZEB1

“…In addition, recently, many studies have reported that circRNAs may encode proteins or peptides to participate in tumor progression [ 40 ], such as cricAXIN1 [ 41 ], circMAPK14 [ 42 ] and circCUX1 [ 43 ]. However, we did not study the encoding ability of circCSPP1.…”

Identification and Characterization of the Roles of circCASP9 in Gastric Cancer Based on a circRNA-miRNA-mRNA Regulatory Network

“…circLARP4 inhibits GC development by sponging miR-424-5p [29]. Although a large number of circRNAs have been identified to be involved in GC progression [30][31][32], the mechanisms by which circRNAs contribute to GC remain largely unknown.…”