Page 280 - Haematologica Vol. 109 - July 2024

LETTER TO THE EDITOR AB
CDE
FGH
Figure 3. Proteogenomic profiling detects BLK as a marker of TCF3::PBX1+ B-cell acute lymphoblastic leukemia targetable by the selective BLK inhibitor BLK-IN-2. (A) The volcano plot presents significantly (red) or non-significantly (grey) dysregulated proteins in TCF3::PBX1+ (left) or TCF3::HLF+ (right) leukemias. BLK is the most significantly dysregulated protein for the TCF3::PBX1+ subtype (minimal log2 fold change of ±1 and significance level of P<0.05 as cutoffs). (B) Gene expression data of human patient samples is derived from data sets available at the R2: genomics analysis and visualization platform (http://r2.amc.nl). Dot plot presents PBX1 and BLK expression in healthy controls (black), TCF3::PBX1+ (orange) and other unstratified leukemic samples (grey). Data of the Mixed Leukemia - MILE - 2004 - MAS5.0 - u133p2 study8 is shown. Three further studies are presented in the Online Supplemen- tary Figure S1D-F. (C,D) BLK RNA expression in TCF3::HLF+ (N=5) and TCF3::PBX1+ (N=5) B-ALL at the time of diagnosis (C) and after transplantation into NSG mice (TCF3::HLF+: N=22; TCF3::PBX1+: N=8). (D). Data is derived from our previous study.2 In order to de- termine differential expression, non-parametric Mann-Whitney t test (two-tailed) was used. (E) Dose-response curves for BLK-IN-2 show a differential response of TCF3::HLF+ (red) versus TCF3::PBX1+ (orange) leukemic cells. (F-H) Synergy drug screening of BLK-IN-2 and Ixabepilone reveals a strong synergistic effect in TCF3::PBX1+ cell lines, while no such effect is detected in the TCF3::HLF+ cell line HAL-01. Representative synergy plots of 3 independent experiments are shown. Drug concentration ranges were chosen accord- ing to the predetermined half-maximal inhibitory concentration (IC50) values of each cell line (RCH-ACV. and 697: 5-500 nM BLK-IN-2, 0.25-25 nM ixabepilone; HAL-01: 0.25-25 μM BLK-IN-2, 5-500 nM ixabepilone). Dimethyl sulfoxide (DMSO) was used as a negative control. ZIP synergy score analysis was conducted using the synergyfinder package version 3.0.14 with additional baseline correction.
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