Circular RNA circITGA7 inhibits colorectal cancer growth and metastasis by modulating the Ras pathway and upregulating transcription of its host gene ITGA7

Circular RNAs (circRNAs) are significantly dysregulated in various cancer types. However, the roles and mechanisms of circRNAs in cancer remain largely unknown. In this study, we demonstrated that a novel circRNA (circITGA7) and its linear host gene ITGA7 are both significantly downregulated in colorectal cancer (CRC) tissues and cell lines. These decreased expression levels correlated with CRC progression. Functional assays demonstrated that ectopic circITGA7 expression suppressed the growth and metastasis of CRC cells in vitro and in vivo. Knockdown of circITGA7 or ITGA7 promoted the proliferation and migration of CRC cells in vitro, and enhanced CRC growth in vivo. Mechanistically, by using RNA-sequencing and KEGG enrichment analysis, we found that circITGA7 is a negative regulator of the Ras signalling pathway, and that ITGA7 is associated with cytokine-related signalling pathways. In addition, circITGA7 binds to miR-370-3p to antagonise its suppression of neurofibromin 1, which is a well-known negative regulator of the Ras pathway. Finally, circITGA7 upregulates the transcription of ITGA7 by suppressing RREB1 via the Ras pathway. In conclusion, our findings indicate a suppressor role of circITGA7 and ITGA7 in CRC, and reveal that circITGA7 inhibits the proliferation and metastasis of CRC cells by suppressing the Ras signalling pathway and promoting the transcription of ITGA7, suggesting that circITGA7 is a potential target for CRC treatment. Copyright (c) 2018 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.