MAP4K4 and Kaposi's sarcoma: For example, extracellular signal-regulated kinase (ERK), Jun N-terminal kinase (JNK) and p38 are involved in KSHV reactivation [4, 25–27, 40].Interestingly, MAP4K4, containing the let-7 targeting site in its 3’UTR, is highly expressed in KS tumors compared to adjacent normal tissues.