MAPK1 and primary effusion lymphoma: For those host signaling transduction kinases which have been found essential for the survival and pathogenesis of PEL [11], [12], [32]–[34], solid tumor tissues displayed lower phosphorylation of MAPK-ERK and mTOR, while no significant change found in the phosphorylation of Akt, MET, B-Raf and MAPK-p38 kinases than those within ascites cells from the same mice (Fig. 6C).