POU5F1 and cancer: As a close resemblance between testicular GCTs and embryonic stem cells has been shown [7] particular focus was on stem cell-related factors including KIT (also known as c-Kit, tyrosine kinase receptor for stem cell factor (SCF)), OCT-3/4 (POU5F1, a POU-family transcription factor), NANOG, and AP-2γ (TFAP2C, transcription factor activator protein-2), and focus was also on germ cell-specific proteins (including MAGE-A4 and NY-ESO-1 belonging to the cancer/testis gene family) with a cell differentiation related biological function or a developmentally regulated expression pattern [8].