PRF1 and cancer: A number of possibilities exist: their elimination from the tumor microenvironment, blocking their ability to produce a number of immune-suppressive/immune-altering molecules such as adenosine, PGE2, perforin, and granzyme B, targeting anti-apoptotic pathways, disrupting their ability to proliferate and or persist in tumors, etc. The list is not conclusive as our understanding continues to expand about the nature of Treg cells that prevail in different cancer types.