EPO and hepatocellular carcinoma: The erythropoietin-producing hepatocellular carcinoma receptor B2 (EPHB2), an essential member of the erythropoietin-producing hepatocellular carcinoma (EPH) receptor family, has been confirmed to be highly expressed in various tumors, such as breast cancer, meningioma, colorectal cancer, gastric cancer, and lung cancer [22].