Figure 6. CASC21 regulates CDK6 expression by sponging miR-539-5p in CRC. (A) GSEA results were plotted to visualize the correlation between the expression of CASC21 and genes related to cell proliferation (KEGG_CELL_CYCLE, GO_CELL_CYCLE_G1_S_PHASE_TRANSITION and WHITFIELD_CELL_CYCLE_G1_S). (B) Dual luciferase reporter assays conducted with wild type and mutant type (putative binding sites for miR-539-5p were mutated) luciferase report vectors of CDK6 3’UTR. Right panel, sequence alignment of miR-539-5p and their predicted binding sites (green) of CDK6 3’UTR. Predicted micorRNA target sequence (blue) in CDK6 3’UTR (Luc-CDK6-wt) and positions of mutated nucleotides (red) in CDK6 3’UTR (Luc-CDK6-mt). (C) Left panel: expression of CDK6 in CRC generated from RNA sequencing data from TCGA database. Right panel: qRT-PCR analysis of CDK6 expression in 80 pairs of CRC and corresponding adjacent normal tissues. (D) Upper panel: The correlation between CDK6 and miR-539-5p in 80 paired CRC samples (n= 80, r= 0.-530, P< 0.001). Lower panel: The correlation between CDK6 and CASC21 in 80 paired CRC samples (n= 80, r= 0.414, P< 0.001). (E, F) CDK6 expression was detected by qRT-PCR or western blot in HCT-116 cells with indicated treatment. All data represent mean ± SEM (n = 3-6). **P < 0.01 and ***P < 0.001.