How do I induce apoptosis in cell culture?

Apoptosis can be triggered in cell cultures through two main pathways: intrinsic and extrinsic. 

The intrinsic pathway is activated by internal stress or damage to the cell's DNA. Several triggers can initiate this pathway like withdrawing growth factors from the cell culture media, applying cellular stress or exposing cells to UV light. UV light can damage DNA by inducing thymine base dimers, while removing growth factors or increasing osmotic or metabolic stress can increase the production of reactive oxygen species (ROS). 

The external pathway is triggered by external signals that bind to specific receptors on the cell surface. To activate the extrinsic apoptosis pathway, introduce ligands such as cytokines or other molecules that bind to death receptors on the cell surface (e.g. TNF-alpha or TRAIL). Additionally, apply specific receptor agonists that are designed to activate these death receptors directly. Upon binding, these receptors form clusters and attract adaptor proteins (e.g. FADD) and pro-caspases (e.g. -8 and -10) to initiate the apoptosis cascade.