We performed western blotting and RT-PCR assays on three ABC-DLBCL cell lines (Ly3, Ly10, and SUDHL-2)13, 26,Tam et al.27, one xenograft sample from a patient with ABC-DLBCL (identified as RJ-Lym1) (Supplementary Fig. 1a), one multiple myeloma (MM) cell line (U266), and six cell lines that represent other types of B-cell lymphoma to screen for unstable mutants of Blimp-1 proteins. This evidence concerns the gene PRDM1 and diffuse large B-cell lymphoma.