STAT3 and plasma cell myeloma: IL-6 is known to induce STAT3-Tyr705 phosphorylation by JAKs, especially JAK2, in the two myeloma cells, and HEL 92.1.7 cells have a constitutively active JAK2(V617F) mutation and thus a constitutively activated (Tyr705-phosphorylated) STAT3 without IL-6; PP also potently inhibited both IL6-dependent and constitutive STAT3-Tyr705 phosphorylation (Harada et al., 2012).