Exosome-transported of circ_0081069 induces SPIN1 production by binding to miR-195-5p to inhibit radiosensitivity in esophageal squamous cell carcinoma.

Circ_0081069 plays a key role in tumor growth; however, its effect on radiosensitivity in esophageal squamous cell carcinoma (ESCC) remains unknown. The study is performed to reveal the association of circ_0081069 expression and radiosensitivity in ESCC and the underlying mechanism. Circ_0081069, miR-195-5p, and spindlin 1 (SPIN1) RNA expression were detected by quantitative real-time polymerase chain reaction. Protein expression was checked by Western blot analysis or immunohistochemistry assay. Cell viability, proliferation, cell apoptosis, migration, and invasion were investigated by cell counting kit-8, 5-Ethynyl-29-deoxyuridine, flow cytometry analysis, scratch test, and transwell assays, respectively. The sensitivity of ESCC cells to radiation was investigated by cell colony formation assay. The interactions among circ_0081069, miR-195-5p, and SPIN1 were identified by dual-luciferase reporter assay and RNA Immunoprecipitation assay. Xenograft mouse model assay was performed to determine the effect of circ_0007841 on radiosensitivity in vivo. Circ_0081069 and SPIN1 expression were upregulated, whereas miR-195-5p was downregulated in ESCC tissues, ESCC cells, and radiation-stimulated ESCC cells. Circ_0081069 silencing inhibited ESCC cell proliferation, invasion, and migration but improved cell apoptosis. In addition, circ_0081069 knockdown enhanced ESCC cell radiosensitivity in vitro and in vivo. Circ_0081069 bound to miR-195-5p and regulated radiosensitivity by binding to miR-195-5p in ESCC cells. Moreover, SPIN1, a target of miR-195-5p, rescued miR-195-5p-mediated effects in ESCC cells. Circ_0081069 was secreted from ESCC cells by being packaged into exosomes. Further, circ_0081069-Exo inhibited radiosensitivity in ESCC cells. Exosome-mediated transfer of circ_0081069 induced SPIN1 production by binding to miR-195-5p, further inhibiting radiosensitivity in ESCC.