Complement factor C9 functions in targeting and eliminating extracellular bacteria; Perforin-1 is tasked with dealing with intracellular viruses and cancer cells; and Perforin-2 can eradicate both intra- and extracellular bacteria (Cullen and Martin, 2008; McCormack et al., 2013; Podack and Munson, 2016; Liu and Lieberman, 2020). Here, PRF1 is linked to cancer.