PPP4R1 and lung cancer: Our results showed that there was an increase in PP4R2 but not PP4R1 co-immunoprecipitated with phospho-IKKα/βS176/180 during the late phase, whereas PP4 R3α/β and PP4R4 did not interact with phospho-IKKα/βS176/180 in lung cancer cells (Figure 1C).