STING1 and colon carcinoma: To directly measure the percentage of apoptotic cells in the population without previous laser exposure stress, HCT116 human colon carcinoma cells transfected for NET23/STING with GFP fused at either the N- or C-terminus were fixed, stained with propidium iodide (PI) to measure all dying cells (PI only stains when the plasma membrane has been compromised) and annexin V for cells engaging early phases of defined apoptosis pathways, and analyzed by flow cytometry.