T cell acute lymphoblastic leukemia (T-ALL) frequently involves aberrant expression of TAL1 and LMO2, oncogenic members of the TAL1 transcriptional complex. Transcriptional activity of the TAL1-complex is thought to have a pivotal role in the transformation of thymocytes, and is associated with a differentiation block and self-renewal. The transcription factor FOXP3 was recently described to be expressed in a variety of malignancies including T-ALL. Veerle Fleskens' study, performed while a PhD student in the Coffer Lab, provides initial evidence for a novel role of FOXP3 as a tumor suppressor in T-ALL, through modulation of TAL1 transcriptional activity. This work has been accepted for publication in Oncogene.