STAT5B and mantle cell lymphoma: Activated JAK/STAT signaling (especially phosphorylation of STAT3 and STAT5, which activates downstream effector genes to promote cell survival and inflammatory responses) is a characteristic feature of MPNs.31 To gain insights into the mechanisms by which MCL affects MPNs, we performed WB analysis to determine whether MCL can suppress STAT3/5 phosphorylation.