DUSP9 and hepatocellular carcinoma: Furthermore, we performed immunohistochemical analysis to detect the expression of MKP-4, ERK1/2, p-ERK1/2 and Ki-67 in 160 HCC specimens and found that expression of MKP-4 was frequently downregulated while the expressions of ERK1/2, p-ERK1/2 and Ki-67 were elevated in tumorous samples compared with non-tumorous tissues (Fig. 5c, d).