LEF1 and acute lymphoblastic leukemia: In fact deletions and mutations in LEF1 that inactivate its expression has been found in T-ALL [239], and more recently loss of TCF1 has been reported in a subset of pediatric T-ALL, the ETP subgroup, in which two patients were found to have deletions of Transcription factor 7 (TCF7) [the gene encoding TCF1] [237].