To explore whether circ_0000705 promoted ESCC proline metabolism and malignant phenotype through the miR-621/PYCR1 axis, rescue assays were carried out by decreasing miR-621 expression via transfection with miR-621 inhibitor or increasing PYCR1 expression via transfection with p-PYCR1 in KYSE150 cells with circ_0000705 knockdown. The gene discussed is PYCR1; the disease is esophageal squamous cell carcinoma.