PBX1 and neoplasm: We speculate that the T-progenitor neoplasms that occasionally develop in mice transplanted with E2A-PBX1-transduced bone marrow cells may be explicable based on the relatively greater ability of E2A-PBX1-expressing progenitors to penetrate into the pool of committed T- relative to B-lymphoid progenitors (compare Fig 1A and 1C)[5].