AFP and liver cancer: Clusters 1, 2, 3, 5, and 6 represented genes that were highly expressed in stages of embryonic development, but were expressed at low levels in adult livers (Fig. S1C), including oncofetal genes Afp, Gpc3, Sall4 (cluster 2), H19 (Cluster 3) and Igf2 (Cluster 5), which are re-expressed in liver cancer (ref. [18–22]).