Low ERG and BAALC Expression Identifies a New Subgroup of Adult Acute T-Lymphoblastic Leukemia With a Highly Favorable Outcome

Abstract

Expression of the genes ERG (v-ets erythroblastosis virus E26 oncogene homolog) and BAALC (brain and acute leukemia, cytoplasmic) shows similarity during hematopoietic maturation and predicts outcome in acute myeloid leukemia. We hypothesized that like ERG, BAALC expression might be of prognostic significance in acute T-lymphoblastic leukemia (T-ALL) and that ERG and BAALC expression together would better identify the patient's risk profile. ERG and BAALC mRNA expression were determined by real-time reverse transcriptase polymerase chain reaction in 153 adults with T-ALL. Patients were designated low or high ERG expressers and low or high BAALC expressers. High BAALC expression correlated with a higher frequency of early T-ALL (P < .0001), CD34 positivity (P < .0001), coexpression of myeloid markers (P = .0001), and high ERG expression (P = .03). High BAALC compared with low BAALC patients had an inferior relapse-free survival (RFS; P = .0008) and overall survival (OS; P = .0001). In contrast, patients with low expression of both ERG and BAALC (representing 41% of all T-ALL patients) had the most favorable outcome (P < .0001; 4-year RFS: low ERG/low BAALC 81%; P < .0001; 4-year OS: low ERG/low BAALC 69%). On multivariable analysis, low ERG/low BAALC expression was of independent favorable prognostic significance (RFS, P = .001; OS, P = .003). Low expression of both ERG and BAALC identifies T-ALL patients with a distinctly favorable long-term outcome.