SMAD1 and colorectal cancer: Then, the same package was used to detect the differential expression of SMADs in 51 normal samples and 647 colorectal cancer samples (Figure 2), and the results showed that the expression levels of SMAD1-4, SMAD7, and SMAD9 were significantly downregulated, while the expression levels of SMAD5 and SMAD6 were significantly upregulated.