Elevation in FGF21 expression during DEN-induced hepatocarcinogenesis. A : Temporal changes of hepatic FGF21 mRNA levels in mouse livers following initial treatment with DEN. FGF21 and ALB mRNA levels were analyzed by quantitative PCR in the mouse liver tissues during different time courses of DEN-induced tumorigenic effect. mRNA levels are expressed as fold changes relative to that injected with PBS, which is assigned as an arbitrary unit 1. *p < 0.05 (n = 3-4 for each time point). B : Immunohistochemical analyses of FGF21 protein levels in mouse liver sections (cytosolic maroon stains) before DEN injection or 2, 4, 6, 8 and 12 month after DEN injection. There is only scattered staining in the sections from the livers at 12 months post-injection (green arrowheads). Data are representatives for FGF21 antigens from the livers of 3–5 mice at each time point. Green arrowhead: concentrated cytoplasmic FGF21 staining; Yellow arrow: enlarged or irregular nuclei; Black asterisk: lipid droplet; Blue arrow: fibrotic cirrhotic area.