Differences in HES1 and PARP1 expression in B-ALL and T-ALL and the PARP1/HES1 ratio. Gene expression profiling was performed with U133A microarrays (Affymetrix) for 206 pediatric ALL patient samples (34 T-ALL, 172 B-ALL; see supplemental Figure 2). (A) Relative expression levels displayed with box-whisker quartile plots show higher levels of HES1 expression in T-ALL compared with multiple subgroups of B-ALL (P = 2.3 × 10−20, LIMMA; FDR = 1.4 × 10−18). (B) Expression data show that T-ALL samples express lowers levels of PARP1 than all B-ALL subgroups (P = 4.5 × 10−19, LIMMA; FDR = 2.3 × 10−17). Of note, the TCF3-PBX1 B-ALL subgroup expresses particularly high levels of PARP1 among B-ALL subgroups (P = 2.7 × 10−37, analysis of variance; FDR = 5.9 × 10−33). (C) Expression data were normalized to the combined B-ALL samples, and relative levels of HES1, PARP1, and a PARP1/HES1 ratio are shown. Note high HES1, low PARP1, and thus a low PARP1/HES1 ratio for T-ALL compared with B-ALL subgroups and combined B-ALL samples (P = 2.9 × 10−11, LIMMA). (D) Ratios of raw expression values for T-ALL and B-ALL samples (P < .0001). MLL indicates mixed-lineage leukemia; Ph+, Philadelphia chromosome (error bars represent ± 1 SD).
