Figure 5: Tumours from Sca1-Bcl6^floxed mice resemble post-GCB cells.

(a) Differential gene expression analysis of tumour-bearing spleens of four Sca1-Bcl6^floxed mice compared with spleens from four WT mice show significant differences. These differences include genes that are involved in B-cell signalling and cell cycle regulation. (b) GSEA identified no significant repression or derepression of Bcl6 target genes in Sca1-Bcl6^floxed tumour-bearing spleens compared with spleens from WT mice (GSEA FDR=1.000). This is in line with what is observed in human DLBCL that possess amplification of the BCL6 coding region. (c) Analysis of differentially expressed genes in Sca1-Bcl6^floxed tumour-bearing spleens with relation to gene expression signatures of normal murine B-cell differentiation including Pro/pre-B, transitional (Trans.) B-cells, follicular and marginal zone (Foll./MZ) B-cells, GCB cells, plasmablasts (P.blast) and plasma cells (P. cell). This shows significant enrichment of the normal plasmablast signature (hypergeometric enrichment P value =0.028, FDR=0.17). Red line represents a hypergeometric enrichment P value of 0.05. (d) Tumours from Sca1-Bcl6^floxed mice show increased expression of transcription factors that are associated with post-germinal centre stages of B-cell differentiation. Box plots represent the mean ± the interquartile range with whiskers extending to the minimum and maximum value. (e) Immunohistochemical staining shows negative expression of the germinal centre marker peanut agglutinin (PNA), but positive staining for the post-germinal centre transcription factor Irf4, and the ABC-like DLBCL marker FoxP1. Images are representative of ≥3 replicates. All panels are × 60, scale bar, 100 μm.