SOX2 and testicular germ cell tumor: Next, we compared the level of the top recognized stemness transcription factors, namely SRY (sex determining region Y)-box 2 (SOX2), Octamer-binding transcription factor 4 (OCT-3/4), Nanog Homeobox (Nanog), and Kruppel Like Factor 4 (KLF4), in highly stem-like testicular germ cell tumors (TGCT) divided into high and low mRNA-SI cohorts and observed a significant upregulation of OCT-3/4, Nanog, and KLF4 in the mRNA-SIHIGH phenotype (Figure 2J).