PTEN and esophageal squamous cell carcinoma: For example, circ-Foxo3 upregulates PTEN expression via the circ-Foxo3/miR-23a/mRNA PTEN and circ-Foxo3/miR-155/mRNA AKT/PTEN axes in ESCC and NSCLC, respectively (Zhang Y. et al., 2018; Karimi et al., 2019).