Hypoxia-induced circCCDC66 promotes the tumorigenesis of colorectal cancer via the miR-3140/autophagy pathway

Circular RNAs (circRNAs) have been reported to be involved in the progression of colorectal cancer (CRC). However, the biological role of circCCDC66 in CRC remains unclear. Therefore, the present study aimed to elucidate the mechanisms through which circCCDC66 affects the hypoxia-induced progression of CRC. It was found that hypoxia promoted the progression of CRC and upregulated the expression of circCCDC66. Furthermore, circCCDC66-knockdown reduced viability, migration and invasion, and enhanced the apoptosis of hypoxia-exposed CRC cells. Using the starBase database, it was identified that circCCDC66 may bind to miR-3140. Subsequently, it was confirmed that circCCDC66 serves as a sponge of miR-3140 and the depletion of miR-3140 partly abolished the effects of circCCDC66 on the phenotype of hypoxia-exposed CRC cells. In addition, miR-3140 was validated to inhibit the autophagy pathway. The use of an autophagy inducer partially reversed the miR-3140 overexpression-induced inhibition of the viability and invasion, and the promotion of the apoptosis of hypoxia-exposed CRC cells. In summary, the findings of the present study demonstrated that circCCDC66 facilitates the development of CRC cells under hypoxic conditions via regulation of miR-3140/autophagy. These findings may provide a novel therapeutic option for patients with CRC.