Fig. 3: Bcl-2 and Mcl-1 are mutually exclusively expressed and functionally redundant in DLBCL.
a Bcl-2, Bcl-XL, and Mcl-1 expression of the indicated cell lines as determined by Western blotting; tubulin expression served as loading control. Note that the Bcl-2 western blot is the same as shown in Fig. 2a, and is included again here to facilitate the comparison. b MCL1 and BCL2L1 gene expression of 206 DLBCL cases available through TCGA, stratified based on genetic subtype as assigned by Schmitz et al. [10]. The global p value was determined by Kruskal–Wallis test, and pairwise p-values by Mann–Whitney-Wilcoxon test. c Inverse correlation of MCL1 and BCL2 expression, and of BCL2L1 and BCL2 expression, of the 206 cases shown in b. d, e Mcl-1 and Bcl-2 expression, as determined by immunohistochemistry of 137 DLBCL patients. Representative pairs of stainings are shown in d for two cases, of whom one (patient 1) was Mcl-1-positive and Bcl-2-negative, and one (patient 2) was Mcl-1-negative and Bcl-2-positive (scale bar, 100 μm). The fraction (in %) of Mcl-1-positive among all Bcl-2-negative and -positive cases is shown in e, with absolute numbers listed above the respective graphs. The cutoffs for assigning Bcl-2 and Mcl-1 positivity were >70% and >30% of tumor cells, respectively. The inverse correlation (correlation coefficient: −0.161) is statistically significant as determined by Spearman correlation. f Viability as assessed by TMRE staining for mitochondrial membrane potential of the indicated cell lines, after 48 h of exposure to 40 nM venetoclax and/or to 1 μM S63845, an Mcl-1 inhibitor. The Mcl-1 and Bcl-2 expression of each cell line is annotated below the respective graphs on a scale from − to +++. Data in f are pooled from two and up to three independent experiments and plotted as means ± standard deviation. TMRE labels live cells with intact mitochondrial membrane potential; TMRE-negative cells are considered apoptotic.
