Regulatory T cells have been identified as a target of PI3K p110δ inhibitors, and targeting p110δ signalling in these cells increases anti-tumour immune responses by releasing cytotoxic CD8+ T cells from Treg control [36, 37] even though lack of p110δ signalling also resulted in decreased CD8+ T cell expression of activation marker CD44 as well as granzyme B and perforin. Here, PRF1 is linked to neoplasm.