WT1 and neoplasm: Another gene downregulated by ~nine-fold in GEN-treated TM4 cells is Usp18 (Ubiquitin specific protease 18), shown to promote proliferation and be negatively regulated by Wt1 (Wilms tumor gene), a transcription factor that plays a role in spermatogenesis [32,33] and in inhibiting interferon signaling [34].