LAUSR

Background The circular RNA (circRNA) antisense to the cerebellar degeneration-related protein 1 transcript (CDR1as)/micro RNA-7(miR-7) signal axis has been investigated in many diseases via regulation of the target genes of miR-7, which participates in the carcinogenesis and metastasis. However, the clinical role and function of CDR1as/miR-7 pathway in osteosarcoma (OS) remain to be identified. Materials and methods Noncancerous bone tissues (n=18) and OS tissues (n=38) were used to determine the expressions and roles of CDR1as and miR-7. We knocked down the expression of CDR1as via siRNAs in OS cell lines to analyze its function in vitro and in vivo. Results CDR1as was upregulated in OS tissues with significant diagnostic value (cutoff value: 1.613). OS patients with high tumor size, Enneking stage, and distant metastasis have high CDR1as levels, but the miR-7 as tumor suppressor negatively correlated with CDR1as. Inhibition of CDR1as in OS cell lines U2OS and MG63 with high CDR1as levels, leading to de-repressed miR-7 levels, impaired cell vitality and increased apoptosis and G1/S arrest in parallel with reduced ability of cell migration, which, however, could be restored by miR-7 inhibitor. Mechanistically, knockdown of CDR1as could restore the availability of miR-7 and inhibit the target genes of miR-7 including EGFR, CCNE1, PI3KCD, and RAF1. Moreover, CDR1as also upregulated N-cadherin and inhibited E-cadherin to promote the epithelial–mesenchymal transition via miR-7 for cell migration. CDR1as inhibition in vivo also induced tumor regression with decreased PCNA levels, and miR-7 inhibitor could reverse these effects via upregulation of EGFR, CCNE1, PI3KCD, and RAF1. The expressions of these genes were confirmed to be higher in CDR1as-high OS samples than in CDR1as-low OS samples. Conclusion These findings suggested that the CDR1as/miR-7 signal axis could be the molecular target for the treatment of OS.