Established from bone marrow cells of an 11-year-old girl with T cell acute lymphoblastic leukemia (T-ALL) in relapse; cell lines BE-13 and PEER show identical DNA fingerprints and hence share common origin, presumably due to cross-contamination; however, their diploid and tetraploid karyotypes indicative of earlier and later passage numbers, respectively, suggest that BE-13 is derived from PEER, rather than vice-versa; carries NUP214-ABL1 fusion gene