Both the precursor and mature forms of ADAM17 are downregulated by SKN. (A) Comparison across 12 analyses revealed the overexpression of ADAM17 transcripts in colon cancer. Blocks in red depict overexpression and blocks in blue represent underexpression. (B-E) Western blot analysis and quantification revealed that the expression of two forms of ADAM17 was reduced by SKN (concentration as indicated, 10 h of treatment) in HCT116 and SW480 colon cancer cells. Quantitative data of ADAM17 (precursor and mature) were normalized to GAPDH. The quantitative data of the DMSO group (0 µM SKN) were arbitrarily set as 1. All data represent the mean ± SEM. *P<0.05 vs. DMSO group. SKN, shikonin; ADAM17, A disintegrin and metalloproteinase 17; preA17, precursor form of ADAM17; matA17, mature form of ADAM17.