FAS and neoplasm: BiTEs can potentially overcome this as studies have found that while BiTEs only activate T-cells in the presence of TAA-positive tumor cells, cytokines released locally by BiTE-activated T-cells, such as TNF-α, IFN-γ, and FAS ligand seem to upregulate receptors such as intercellular adhesion molecule-1 (ICAM-1) and FAS on TAA-negative cells.