Hsa_circ_0026628 promotes the development of colorectal cancer by targeting SP1 to activate the Wnt/β-catenin pathway

Abstract

Circular RNAs (circRNAs) have been reported to play crucial roles in the progression of various cancers, including colorectal cancer (CRC). SP1 (Sp1 transcription factor) is a well-recognized oncogene in CRC and is deemed to trigger the Wnt/β-catenin pathway. The present study was designed to investigate the role of circRNAs which shared the same pre-mRNA with SP1 in CRC cells. We identified that hsa_circ_0026628 (circ_0026628), a circular RNA that originated from SP1 pre-mRNA, was upregulated in CRC cells. Sanger sequencing and agarose gel electrophoresis verified the circular characteristic of circ_0026628. Functional assays including CCK-8, colony formation, transwell, immunofluorescence staining, and sphere formation assay revealed the function of circ_0026628. RNA pull-down and mass spectrometry disclosed the proteins interacting with circ_0026628. Mechanistic assays including RIP, RNA pull-down, CoIP, ChIP, and luciferase reporter assays demonstrated the interplays between molecules. The results depicted that circ_0026628 functioned as a contributor to CRC cell proliferation, migration, EMT, and stemness. Mechanistically, circ_0026628 served as the endogenous sponge of miR-346 and FUS to elevate SP1 expression at the post-transcriptional level, thus strengthening the interaction between SP1 and β-catenin to activate the Wnt/β-catenin pathway. In turn, the downstream gene of Wnt/β-catenin signaling, SOX2 (SRY-box transcription factor 2), transcriptionally activated SP1 and therefore boosted circ_0026628 level. On the whole, SOX2-induced circ_0026628 sponged miR-346 and recruited FUS protein to augment SP1, triggering the downstream Wnt/β-catenin pathway to facilitate CRC progression.

Wnt signaling in colorectal cancer: pathogenic role and therapeutic target

“…The results showed that circ_0026628 promoted the proliferation, migration, EMT and dryness of CRC cells. In terms of mechanism, circ_0026628, as the endogenous sponge of miR-346 and FUS, increases the expression of SP1 at the post-transcriptional level, thereby enhancing the interaction between SP1 and β-catenin to activate the Wnt/β-catenin pathway [ 17 ]. The prognosis of locally advanced colorectal cancer (CRC) is currently unsatisfactory.…”

circ_0052184 Promotes Colorectal Cancer Progression via Targeting miR-604/HOXA9 Axis

“…circRNAs form covalently closed loops by back-splicing. This structure makes them highly stable and conserved [ 19 ]. The role of circRNAs in colorectal cancer has received increasing attention.…”

Critical Roles of Circular RNA in Tumor Metastasis via Acting as a Sponge of miRNA/isomiR

“…CircRNA also contributes to the occurrence and development of CRC via acting as a sponge miRNA. CircRNA-102209 upregulates the RIN1 signal via sponging miR-761 [46], circ-0082182 can down-regulate the expression of miR-411 or miR-1205 [47] and circ_0026628 can activate Wnt/β-catenin pathway by enhancing the interaction between SP1 and β-catenin via sponging miR-346 [48], thus promote the proliferation, invasion, and EMT of CRC cells. Hsa_circ_0006732 regulates colorectal cancer cell proliferation, invasion, and EMT by miR-127-5p/RAB3D axis [49], circ_0085315 can promote cell proliferation, invasion, and migration in colon cancer through miR-1200/MAP3K1 signaling pathway [50], hsa_circ_0007843 can act as a miR-518c-5p sponge to regulate the migration and invasion of colon cancer SW480 cells [51], and circular RNA hsa_circ_0008285 inhibits cell proliferation and migration via the miR-382-5p/PTEN axis.…”