CircSAMD4A regulates cell progression and epithelial-mesenchymal transition by sponging miR-342-3p via the regulation of FZD7 expression in osteosarcoma

Osteosarcoma (OS) is a primary malignant tumor with a complex etiology. Therefore, research into the pathogenesis of osteosarcoma is considered a priority. Circular RNAs play important roles in cell metabolism and in the immune response and are closely associated with cancer treatment. However, research into the association of circular RNAs with osteosarcoma is limited. In the present study, CircSAMD4A was validated by RT-qPCR and agarose gel electrophoresis. CircSAMD4A and miR-342-3p expression was detected by RT-qPCR. The relative protein expression levels were measured by western blot analysis. MTT assay and flow cytometry were used to detect cell cytotoxicity and apoptosis, respectively. Transwell assay was applied to assess cell migration and invasion. Dual-luciferase reporter assay was used to determine the association among CircSAMD4A, Frizzled-7 (FZD7) and miR-342-3p. In vivo, subcutaneous tumor formation assay was performed in an experiment with nude mice. The results revealed that the expression levels of CircSAMD4A and FZD7 were upregulated, while those of miR-342-3p were downregulated in OS tissues and cells. The inhibition of CircSAMD4A suppressed cell progression and epithelial-mesenchymal transition (EMT), and promoted cell apoptosis in OS. The reduction of miR-342-3p reversed the effects of CircSAMD4A downregulation on cell cytotoxicity, migration, invasion, apoptosis and EMT in OS, while FZD7 overexpression blocked the effect of miR-342-3p upregulation on OS progression. The suppressive effect of sh-CircSAMD4A on tumor growth was thus verified in OS. Overall, the present study demonstrated that CircSAMD4A affected cell cytotoxicity, invasion, apoptosis, migration and EMT by regulating the miR-342-3p/FDZ7 axis in OS, thereby providing a novel regulatory mechanism and a potential therapeutic target for OS.