Appreciable levels of CCDC6 and USP7 proteins were detected in NTERA-2 human Embryonal Carcinoma and in the murine GC-1 spermatogonia cells, while nearly undetectable amount was observed in GC-2 spermatocytes and TM4 Sertoli cells (Fig. 1 E). This evidence concerns the gene USP7 and embryonal carcinoma.