STAT3 and diffuse large B-cell lymphoma: To develop a system to test functionality of the four STAT3 variants, we used two representative ABC DLBCL cell lines, OCI-Ly10 and HBL1, in which high activity of STAT3 is driven by the autocrine cytokines IL-6 or IL-10 and promotes cell survival and proliferation.6, 11, 24 The GCB cell line OCI-Ly19 with no constitutive STAT3 activation served as a control.