Aberrant activation of the Wnt pathway plays a pathogenetic role in various tumors and has been associated with adverse outcome in acute lymphoblastic leukemia (ALL). LEF1, a key mediator of Wnt signaling, has been linked to leukemic transformation, and recurrent mutations of LEF1 have been identified in pediatric T-ALL. Here we evaluated the prognostic significance of LEF1 expression in B-precursor ALL patients. LEF1 expression was determined by quantitative real-time RT-PCR in 282 adult Bprecursor ALL patients treated on 06/99 and 07/03 GMALL trials. Patients were grouped into quartiles (Q1-Q4) according to LEF1 expression levels (LEF1 high, Q4; n ؍ 71; LEF1 low, Q1-Q3; n ؍ 211). Patients with high LEF1 expression had a significantly shorter relapse-free survival (RFS) compared with low LEF1 expressers (5-year RFS: LEF1 high, 27%; LEF1 low, 47%; P ؍ .05). Importantly, high LEF1 expression was also associated with inferior RFS in standard-risk patients and was independently predictive for RFS (P ؍ .
IntroductionLong-term outcome of most adult patients with B-precursor acute lymphoblastic leukemia (ALL) remains unsatisfactory, although intensified therapy regimens have resulted in high complete remission (CR) rates. 1,2 During the last decade, overall survival (OS) of adult ALL patients has primarily been improved by risk-adapted treatment stratification based on clinical and molecular risk factors and by the use of tyrosine kinase inhibitors in BCR-ABL-positive patients. In the large, heterogeneous group of standard-risk patients without established risk factors, the relapse rate is still approximately 40% to 50% and not predictable with pretreatment markers. 3,4 Prospective evaluation of minimal residual disease (MRD) has improved individual risk assessment of standard-risk patients; however, the identification of new prognostic factors is of particular interest for this subgroup of ALL. Moreover, characterization of aberrant signaling pathways with prognostic relevance in standard-risk B-precursor ALL might elucidate molecular mechanisms of therapy resistance and may help to develop novel targeted therapies for these patients.Lymphoid enhancer factor 1 (LEF1) is a member of the LEF/T-cell factor family of transcription factors and a key mediator of the canonical Wingless-type (Wnt) pathway. 5 Wnt activation results in the accumulation of -catenin, which translocates to the nucleus and forms a complex with LEF/T-cell factor DNA binding proteins, thereby enhancing the transcription of target genes. Wnt downstream target genes (eg, MYC, CCND1) are involved in the regulation of central cellular processes, such as differentiation, cell cycle, proliferation, and survival. 6 Activation of the Wnt pathway has been implicated in leukemic transformation 7-9 and was shown to promote proliferation and survival of leukemic cells in vitro. [9][10][11] In ALL patients, a frequent down-regulation of Wnt antagonists sFRP1, sFRP2, sFRP4, sFRP5, WIF1, DKK3, and HDPR1 by promoter hypermethylation has been observed. 12 T...