Apoptosis and the Extrinsic Pathway

Apoptosis can be activated extrinsically by both the TNF and Fas pathways. Ligands can bind to either the TNF receptor or the Fas receptor, which have different downstream elements. In the TNF pathway, binding of the TNF-alpha ligand to receptor 1 activates caspases via death domains. TNF-alpha binding can also lead to the activation of transcription factors that are expressed in apoptosis and the inflammatory response. In the Fas pathway, the binding of the Fas ligand forms the death inducing signaling complex, which includes caspases. The formation of this complex also activates a positive feedback loop that keeps the apoptotic process moving forwards. Understanding how apoptosis works both extrinsically and intrinsically is crucial to developing targeted cancer treatments that can induce these pathways in tumors.