Fig. 1

Inhibitor of differentiation 4 (Id4) was frequently up-regulated in hepatocellular carcinoma (HCC) cancer tissues at the protein level but not at the mRNA level. a The relative Id4 mRNA expression in HCC tumor tissues is compared with the adjacent non-cancer tissues. b Compared with the adjacent non-cancer tissues, the mRNA expression of Id4 is not significantly up-regulated in HCC tumor tissues. Paired Student’s t test, P = 0.051. ns not significant. c The up-regulated protein expression of Id4 is observed in 63.0% (17/27) of tumor tissues. Densitometry of Western blotting (measured by Image J) showed the relative protein expression (the numbers, IntDen_Id4/IntDen_Actin). d The relative Id4 protein expression in HCC tissues is compared with that in the adjacent non-cancer tissues. Densitometry of Western blotting (measured by Image J) showed the relative protein expression (IntDen_Id4/IntDen_Actin). e Representative Id4 immunostaining in a HCC tissue array containing 57 samples: no positive immunostaining is detected in 10 cases; Id4-positive cells are scattered or focally clustered in 22 cases; and diffuse staining pattern is present in 25 cases. The number of cases in each subset is shown in the right corner of the upper panel. Original magnifications: up ×4 and down ×40. T: tumor tissues; N adjacent non-cancer tissues. f Kaplan–Meier survival curve showing the overall survival of 57 HCC patients according to the Id4 expression level. *P < 0.05