ABCG1 and synovial sarcoma: Additionally, we also found that the mRNA expression levels of key cholesterol efflux transporters ABCA1, ABCG1, and NR1H3 in CD4+T cells of SS patients were significantly lower than those from healthy controls (Supplementary File S3D), suggesting that a weakening of cholesterol efflux function of CD4+ T cells is involved in the pathophysiology of SS.