GFRA1 and leukemia: Transplantation of EL4 cells confirmed their tumorigenicity potential as tissuehistological examination revealed that the normal structure of the tubules haddisappeared, and the leukemia cells had penetrated the interstitial tissue (Fig .1C, D).SSC was confirmed by expression of Plzf, Gfrα-1 and Oct4by PCR (Fig .1E).