Similarly, FAT1 function was assessed in TCF3-PBX1 positive ALL cell lines (PreB697 and MHH CALL3), which express FAT1 and exhibit low FAT1 methylation (as seen in TCF3-PBX1 primary samples), as well as a control TCF3-PBX1-negative line REH, in which the FAT1 gene is hypermethylated and not expressed. The gene discussed is PBX1; the disease is acute lymphoblastic leukemia.