Fig 2: Expression level of SIK2 in CRC lines. (A) mRNA expression levels of SIK2 were notably increased in all types of cancer in the Cancer Cell Line Encyclopedia. The expression levels of SIK2 in the normal colonic epithelial cell line, NCM460, and different CRC cell lines (LoVo, SW480, SW620, CW2 and HCT116) were determined via (B) western blotting and (C) reverse transcription-quantitative PCR. ***P<0.001 vs. NCM460. CRC, colorectal cancer; SIK2, salt-inducible kinase 2.

Fig 3: SIK2 silencing attenuates the proliferation, migration and invasion of colorectal cancer cells. The transfection efficiency in HCT116 cells transfected with siRNA-SIK2 was evaluated via (A) western blot and (B) reverse transcription-quantitative PCR analyses. (C) A Cell Counting Kit-8 assay was used to determine the proliferative ability of HCT116 cells. Cell migration and invasion rates were measured using (D) wound healing and (E) Transwell assays, respectively. Scale bar, 100 µm. (F) MMP12 and MMP9 protein expression levels were detected using western blot analysis. ***P<0.001 vs. siRNA-NC group. SIK2, salt-inducible kinase 2; siRNA, small interfering RNA; NC, negative control.

Fig 4: SIK2 silencing attenuates glycolysis in colorectal cancer cell lines. The levels of (A) pyruvate kinase activity, lactate production and (B) glycolysis were detected using their corresponding kits. The mRNA and protein expression levels of the glycolysis-related genes, Glut1, HK2 and PKM2, were determined via (C) reverse transcription-quantitative PCR and (D) western blot analyses, respectively. **P<0.01, ***P<0.001 vs. siRNA-NC group. PKM2, pyruvate kinase M2; Glut1, glucose transporter 1; HK2, hexokinase 2; siRNA, small interfering RNA; NC, negative control.

Fig 5: Association between SIK2 and TRIM28. The mRNA and protein expression levels of TRIM28 in NCM460, LoVo, SW480, SW620, CW2 and HCT116 cells were measured using (A) reverse transcription-quantitative PCR and (B) western blot analyses, respectively. ***P<0.001 vs. NCM460. (C and D) Co-immunoprecipitation assays were conducted to verify the association between SIK2 and TRIM28. TRIM28 (E) mRNA and (F) protein expression levels in HCT116 cells. ***P<0.001 vs. siRNA-NC group. SIK2, RNA salt-inducible kinase 2; TRIM28, tripartite motif containing 28; siRNA, small interfering RNA; NC, negative control.