FOXP3 and synovial sarcoma: Since the majority of SS patients with advanced disease have a colonization or infection of their skin with SE-producing S. aureus51, and SE induce FOXP3 expression in malignant cells as shown here in vitro, it is likely that SE may also induce FOXP3 expression in vivo through induction of cytokine expression by nonmalignant cells in the tumor microenvironment.