SPON2 and glioma: Further findings demonstrated that over-expression of SOX13 significantly increased the expression of SPON2 and that SOX13 promoted the angiogenesis of GECs by transcriptionally up-regulating SPON2. Moreover, our data indicated that miR-138-5p down-regulated the expression of SPON2 and inhibited the viability, migration, and tube formation of GECs by negatively regulating SOX13. Based on the above results, knockdown of circ_002136 negatively regulated the expression of SOX13 by targeting miR-138-5p and further down-regulated SPON2 expression to inhibit the glioma angiogenesis.