PTEN and gastric cancer: For instance, circRNA C3P1 (circC3P1) regulates the miR-21/phosphatase and tensin homolog (PTEN) axis to restrain kidney cancer cell activity [16]; circRNA HIAT1 (circHIAT1) regulates miR-21 to inhibit epithelial–mesenchymal transition (EMT) of gastric cancer (GC) cell lines [17].