FAS and neoplasm: During the elimination phase, the balance is tipped towards anti-tumor immunity [19] due to the increased expression of neo-antigens in combination with the high frequency of major histocompatibility complex (MHC) class I molecules on the surface of tumor cells and the existence of apoptosis-inducing agents (perforin, granzymes, Fas, and tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) receptors) as well as anti-tumor factors, interferon (IFN)-α/β/γ, interleukin (IL)-1, IL-12, and tumor necrosis factor-alpha (TNF-α).