Since USP21 stimulated cell proliferation, migration, invasion, and stemness of GC, and could stabilize the expression of GATA3 by deubiquitinating GATA3, while MAPK1 was the transcription target of GATA3, it was further verified whether USP21 could play its oncogenic effect in GC through the GATA3/MAPK1 axis. The gene discussed is MAPK1; the disease is gastric cancer.