Functional analysis of the proapoptotic activity of putative FOXP1 targets. (A-B) U-2932 cells were transfected with the indicated expression plasmids and analyzed with respect to cell viability and apoptosis 48h later. Cell viability was determined by CellTiter Blue assay (A) and apoptosis was assessed by Annexin V staining (B). Red indicates target genes that reduce cell viability by >50% upon ectopic expression, compared with the empty vector control. Data are shown as means of 1 or 2 (+SEM) experiments; note that the same batch of transfection reagents was used throughout, every cDNA was expressed under the same promoter, and the same batch of transfected cells was used for the CellTiter Blue and apoptosis assays. (C-F) FOXP1 and S1PR2 expression in tumors from 2 patient cohorts consisting of 350 DLBCL patients²³  (C-D) and 496 DLBCL patients¹⁴  (E-F), which were further stratified based on ABC vs GCB subtype. ***P < .001 (2-tailed Mann-Whitney U test). Data sets were analyzed using R software or the R2 microarray analysis and visualization platform (http://r2.amc.nl). (G) S1PR2 and FOXP1_6 expression levels were determined in DLBCL cell lines by qRT-PCR (normalized to ACTIN). Red dots indicate ABC-type and green dots GCB-type cell lines. The correlation coefficient was calculated for the ABC cell lines only. (H) Expression levels of FOXP1 and S1PR2 during B-cell development were determined using publicly available data from Genomicscape.²⁴  The number in brackets denotes the number of samples analyzed per B-cell developmental stage.