CD4 and renal carcinoma: Report on lung cell carcinomas prove that COX-2 derived PGE2 plays a significant role in the transformation of regulatory T cells (42), and researchers have found that COX-2 derived PGE2 in renal cancer can transform CD4+FOXP3− T cells into CD4+CD25+FOXP3+ regulatory T cells to escape the immune system (43).