FOXO3 and cancer: CircFOXO3 is formed from the exon 2 of FOXO3 and it can not only increase the protein level of FOXO3, but also participate in the post-transcriptional regulation of transcription products through the competitive endogenous RNAs (ceRNAs) network, thus having a dual effect on the development of cancers (Tay et al., 2014; Du et al., 2017a; Zhou et al., 2019).