Figure 1. Smad4 is negatively related with phosphorylation of ERK in human metastatic CRCs. (A) Representative images of immunostained Smad4 and phospho-ERK in paired primary tumor and metastasis originated from single patient. (B) The expression of Smad4 in primary tumors was higher than that in liver metastases, (C) phospho-ERK in primary tumors was lower than that in liver metastases (P = 0.003 and P < 0.001, respectively, Mann–Whitney U-test).