CD4 and cancer: High relative ratios of Treg cells to CD4+ or CD8+ Tconv cells within tumors are associated with poor prognoses in patients with a variety of cancers, including ovarian cancer (15, 16), breast cancer (17), non-small cell lung carcinoma (18), hepatocellular carcinoma (19), renal cell carcinoma (20), pancreatic cancer (21), gastric cancer (22), cervical cancer (23), intrahepatic cholangiocarcinoma (24) and colorectal carcinoma (25).