We conducted immunohistochemical experiments to further clarify the biological functions of circRREB1 in vivo and found that in tumour tissues with stable circRREB1 silencing, the expression levels of the proliferation-related protein Ki67, the cycle-related protein cyclin D1, the apoptosis-related protein BCL2, and the migration-related protein RhoA were reduced (Fig. 4D‒G, Supplementary Fig. S2I‒L). Here, CCND1 is linked to neoplasm.