Tumor necrosis factor (TNF) is the earliest discovered cytokine that can cause hemorrhagic necrosis of tumor tissue cells, mainly secreted by macrophages and fat cells in adipose tissue. It is named because it can directly kill tumor cells in vivo and in vitro. According to their source and structure, they are mainly divided into TNF-α and TNF-β. TNF-α is mainly produced by activated mononuclear-macrophages and various other cells. Large doses of TNF-α can cause cachexia, and patients show progressive weight loss, so TNF-α is also known as cachexia.