IHC staining was conducted as described previously [28]. Paraffin embeded samples were cut into 4 μm-thick sections, which were then deparaffinized in xylene and re-hydrated. The slices were incubated in 0.3% hydrogen peroxide for 30 min to block endogenous peroxidase activity and then antigen retrieval was performed in sodium citrate buffer for 45 s in a pressure cooker. After overnight blocking at 4°C, sections were incubated with primary antibodies against CtBP2 or GLI1 at 4°C overnight. Bound primary antibodies were detected using biotinylated secondary antibodies (Zhongshan Goldenbridge Biotechnology Lltd. Co., Beijing, China). Next, sections were incubated with diaminobenzidine before being counterstained with hematoxylin. Finally, sections were dehydrated in alcohol and xylene.
