Forkhead box P3 (FOXP3) is a key gene in the immune system which also plays a role in tumor development. The Treg cell lineage-specification factor FOXP3 (forkhead box P3) is essential for Treg cells' ability to uphold immunologic tolerance. Forkhead box protein 3 (FOXP3) is expressed in numerous types of tumor cell and is associated with tumor progression and prognosis. which had been reported that FOXP3 inhibited cellular proliferation and induced apoptosis of gastric cancer (GC) cells by activating the apoptosis signaling pathway. The elevated expression of FOXP3 in blood and urine samples from kidney transplant recipients could be a useful noninvasive biomarker to diagnose graft dysfunction. Forkhead box P3 (FOXP3), an X-linked tumor suppressor gene, plays an important role in breast cancer.