Abnormal expression of FLI1 protein is an adverse prognostic factor in acute myeloid leukemia

Friend leukemia virus integration 1 (FLI1), an Ets transcription factor family member, is linked to acute myelogenous leukemia (AML) by chromosomal events at the FLI1 locus, but the biologic impact of FLI1 expression on AML is unknown. FLI1 protein expression was measured in 511 newly diagnosed AML patients. Expression was similar in peripheral blood (PB) and BM and higher at diagnosis than at relapse (P ∇ .02). Compared with normal CD34⁺ cells, expression in AML was above or below normal in 32% and 5% of patients, respectively. Levels were negatively correlated with an antecedent hematologic disorder (P ∇ .002) but not with age or cytogenetics. Mutated NPM1 (P ∇ .0007) or FLT3-ITD (P < .02) had higher expression. FLI1 levels were negatively correlated with 10 of 195 proteins associated with proliferation and stromal interaction, and positively correlated (R > 0.3) with 19 others. The FLI1 level was not predictive of remission attainment, but patients with low or high FLI1 expression had shorter remission duration (22.6 and 40.3 vs 51.1 weeks, respectively; P ∇ .01) and overall survival (45.2 and 35.4 vs 59.4 weeks, respectively; P ∇ .03). High FLI1 levels were adverse in univariate and multivariate analysis. FLI1 expression is frequently abnormal and prognostically adverse in AML. FLI1 and/or its response genes may be therapeutically targetable to interfere with AML cell biology.