circ_0005615 affects the radiosensitivity of CRC cells via regulating miR-665. LOVO and SW480 cells were transfected with si-NC, si-circ_0005615, si-circ_0005615 + inhibitor NC, or si-circ_0005615 + miR-665 inhibitor and then exposed to 6 Gy irradiation. Cell viability (a), apoptosis (b), colony number (c), migration and invasion (d and e), and migratory rate (f) were examined using CCK-8 assay, flow cytometry, colony formation assay, transwell, and scratch assay, respectively. Data are shown as mean ± SD, n = 3. *P < 0.05.