These findings indicated that circ_0000705 could promote proline metabolism and ESCC progression by targeting miR-621/PYCR1 axis, suggest a key role for circ_0000705 in proline metabolism in ESCC, and imply that circ_0000705 may be a potential biomarker or/and possible therapeutic target for ESCC. This evidence concerns the gene PYCR1 and esophageal squamous cell carcinoma.