To investigate whether mutations in the reported repressive STAT5 TFBS located in the promoter region of MEF2C were implicated in T-cell leukemia, we performed sequence analyses of a 750 bp stretch in seven selected T-ALL cell lines (CCRF-CEM, JURKAT, MOLT-16, LOUCY, PEER, PER-117, RPMI-8402). The gene discussed is MEF2C; the disease is acute lymphoblastic leukemia.