MAPK8 and leukemia: The effect of shikonin on U937 cells was also confirmed in another leukemia cell lines (Molt4, Jurkat, multidrug-resistant CEM/ADR5000 and CCRF-CEM), where shikonin also known to prevent c-MYC expression and affected phosphorylation of SAPK/JNK, ERK1/2 and AKT.